Re: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Ron Wright, C'mon Ron, I asked to get a feel for the references used in your explanation of how coax has a lower freq limit, not a compilation of your library collection. It appears that when you get a specific question you cannot provide an answer to, you go into a rambling dialog about unrelated and useless subjects. How about sticking to the subject at hand without the superfluous, nonessential, redundant, fluff. I get the feeling that when you get a direct question you cannot or are unable to provide an answer to, you meander into an unrelated direction to distract the person asking. Or to get them to go away in disgust. From what I can see about the tough questions you are asked, your answers possibly lack any substance or credibility, and may even border on being defective. How about it now, just provide the books or technical references you have to buttress your comments so I can look in them also to see how you arrived at your conclusions. I too have an extensive library of technical documents and some of the ones you have mentioned and I'm interested in furthering my knowledge, If you cannot or will not provide the references, I will understand. Your credibility in the technical responses provided with reference to coax having a low freq cutoff will have just evaporated. What do you say Ron? Can you support your utterances with references? Or am I and all the others reading this dialog, are to believe you're just puffing? Again. 73 Allan Crites WA9ZZU Ron Wright <[EMAIL PROTECTED]> wrote: Allan, Well I think most on here do not quote their sources for many got info long time ago and from many sources. If you want a list of some of what I got...well ok: Reference Data for Radio Engineers, ITT (have had about 30 years so probably should update, but still the RF stuff is pretty good...also very good quick reference book). Antenna Analysis by Wolff (need to know Calculus for this one) Electronic Engineers Handbook, Fink (is very popular) Handbook of Engineering Fundamentals, Eshbach (got at garage sell for $2, about 1500 pages) Information Transmission Modulation , and Noise, Schwartz (was my college EE text book on information theory...had great professor. This give real good analyas of modulations such as TDMA, etc. Mostly uses Fourier Transform). Have about 50 others along with many not related to electronics, but Physics and Cheminstry and a bunch of other stuff. Also lots on transistor and ones I really like data books giving all that technical stuff on parts like ICs. I even still have a tube manual and a tube checker. Will not do many sweep tubes so cannot help you with a CB amp. However, I find most of these are good for reference. The real fun is coming up with stuff on ones own and maybe using reference for some of it. Einstin once said one does not have to remember much as long as one knows where to go and get it, hi. Of course with the internet books are kinda loosing out, but still fun to look at well the ones with lots of pictures. I hope you enjoyed this as much as I. 73, ron, n9ee/r >From: allan crites <[EMAIL PROTECTED]> >Date: 2007/09/03 Mon PM 04:09:58 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >Duplexers > >Ron , Aw c'mon Ron, dig out those equations from your library so we can all >see where you're comming from. That way we can get an idea how much reference >materials you really have and who and what they are. And just because your >name is Wright doen't mean you're "right" all the time. Jesse also doesn't >ever bother to quote the sources for his statements. I'm begining to wonder if >you as well as he have any.  73 Allan Crites WA9ZZU > >Ron Wright <[EMAIL PROTECTED]> wrote: Gary, > >I gave the reason for the statement...measured with HP piece of test >equipment. Was quick and to the point. > >I did not think I had to dig into my libary and dig out the equations. Same >with stating an SWR...thought most would take a reading from a meter and not >having to give the equations. > >I did not see you giving your basis for rejecting the statement, but then >again I really did not expect it, hi. > >73, ron, n9ee/r > >>From: Gary Schafer <[EMAIL PROTECTED]> >>Date: 2007/09/02 Sun PM 08:29:08 CDT >>To: Repeater-Builder@yahoogroups.com >>Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> >>But it is your statement. >> >>73 >>Gary K4FMX >> >>> -Original Message- >>> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >>> [EMAIL PROTECTED] On Behalf Of Ron Wright >>> Sent: Sunday, September 02, 2007 6:46 AM >
Re: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Allan, Well I think most on here do not quote their sources for many got info long time ago and from many sources. If you want a list of some of what I got...well ok: Reference Data for Radio Engineers, ITT (have had about 30 years so probably should update, but still the RF stuff is pretty good...also very good quick reference book). Antenna Analysis by Wolff (need to know Calculus for this one) Electronic Engineers Handbook, Fink (is very popular) Handbook of Engineering Fundamentals, Eshbach (got at garage sell for $2, about 1500 pages) Information Transmission Modulation , and Noise, Schwartz (was my college EE text book on information theory...had great professor. This give real good analyas of modulations such as TDMA, etc. Mostly uses Fourier Transform). Have about 50 others along with many not related to electronics, but Physics and Cheminstry and a bunch of other stuff. Also lots on transistor and ones I really like data books giving all that technical stuff on parts like ICs. I even still have a tube manual and a tube checker. Will not do many sweep tubes so cannot help you with a CB amp. However, I find most of these are good for reference. The real fun is coming up with stuff on ones own and maybe using reference for some of it. Einstin once said one does not have to remember much as long as one knows where to go and get it, hi. Of course with the internet books are kinda loosing out, but still fun to look at well the ones with lots of pictures. I hope you enjoyed this as much as I. 73, ron, n9ee/r >From: allan crites <[EMAIL PROTECTED]> >Date: 2007/09/03 Mon PM 04:09:58 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >Duplexers > >Ron , Aw c'mon Ron, dig out those equations from your library so we can all >see where you're comming from. That way we can get an idea how much reference >materials you really have and who and what they are. And just because your >name is Wright doen't mean you're "right" all the time. Jesse also doesn't >ever bother to quote the sources for his statements. I'm begining to wonder if >you as well as he have any.  73 Allan Crites WA9ZZU > >Ron Wright <[EMAIL PROTECTED]> wrote: Gary, > >I gave the reason for the statement...measured with HP piece of test >equipment. Was quick and to the point. > >I did not think I had to dig into my libary and dig out the equations. Same >with stating an SWR...thought most would take a reading from a meter and not >having to give the equations. > >I did not see you giving your basis for rejecting the statement, but then >again I really did not expect it, hi. > >73, ron, n9ee/r > >>From: Gary Schafer <[EMAIL PROTECTED]> >>Date: 2007/09/02 Sun PM 08:29:08 CDT >>To: Repeater-Builder@yahoogroups.com >>Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> >>But it is your statement. >> >>73 >>Gary K4FMX >> >>> -Original Message- >>> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >>> [EMAIL PROTECTED] On Behalf Of Ron Wright >>> Sent: Sunday, September 02, 2007 6:46 AM >>> To: Repeater-Builder@yahoogroups.com >>> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >>> Duplexers >>> >>> Gary, >>> >>> I don't know. Why don't you tell us. >>> >>> I don't know why gravity will pull me to the ground real fast if I jump >>> off a bridge, but I have all the faith in the world it will. Einstin >>> tried to explain it, but died before he got the results. >>> >>> Taking the word of good test equipment is a good engineering approach. >>> Doing the math, I am sure I have here somewhere, and I am sure the >>> defferential equations would take a while probably starting with >>> Maxwell's, but as with gravity if you know it does what it does I use it. >>> >>> These discussions can at times go no where, hi. >>> >>> 73, ron, n9ee/r >>> >>> >>> >>> >From: Gary Schafer <[EMAIL PROTECTED]> >>> >Date: 2007/09/01 Sat PM 08:48:03 CDT >>> >To: Repeater-Builder@yahoogroups.com >>> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >>> >>> > >>> >Ron, >>> > >>> >Maybe you could tell us why coax cable has a lower frequency limit? You >>> >claim that it does but have not explained why or how. >>> > >>> >Why does the impedan
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
er www.microwaves101.com On 9/3/07, Jesse Lloyd <[EMAIL PROTECTED]> wrote: > > Sure I suppose... Electronic Communications Systems Fundamentals Through > Advanced - Fourth Edition. Page 319. > > Also I went to microwave101.com for some more info. > > Curious why your so interested in the sources, I'm not lying I swear! > > Jesse > > On 9/3/07, allan crites <[EMAIL PROTECTED]> wrote: > > > > Jesse, > > I find six titles by Tomasi with "Electronic Communications systems " in > > them.Could you be a bit more specific? And could you specify the pages > > where you found the information you used? And could you provide the > > information from which google searches? > > I'm interested in your sources. > > > > 73 Allan Crites WA9ZZU > > > > *Jesse Lloyd < [EMAIL PROTECTED]>* wrote: > > > > My source was "Electronic Communications Systems" by Wayne Tomasi from > > DeVry. Copyright 1998. Its my old collage text. Also I grabbed additional > > information from google searches. > > > > Jesse > > > > > > On 9/3/07, allan crites < [EMAIL PROTECTED]> wrote: > > > > > >Ron , > > > Aw c'mon Ron, dig out those equations from your library so we can all > > > see where you're comming from. That way we can get an idea how much > > > reference materials you really have and who and what they are. And just > > > because your name is Wright doen't mean you're "right" all the time. Jesse > > > also doesn't ever bother to quote the sources for his statements. I'm > > > begining to wonder if you as well as he have any. > > > > > > 73 Allan Crites WA9ZZU > > > > > > *Ron Wright < [EMAIL PROTECTED] >* wrote: > > > > > > Gary, > > > > > > I gave the reason for the statement...measured with HP piece of test > > > equipment. Was quick and to the point. > > > > > > I did not think I had to dig into my libary and dig out the equations. > > > Same with stating an SWR...thought most would take a reading from a meter > > > and not having to give the equations. > > > > > > I did not see you giving your basis for rejecting the statement, but > > > then again I really did not expect it, hi. > > > > > > 73, ron, n9ee/r > > > > > > >From: Gary Schafer < [EMAIL PROTECTED] > > > > >Date: 2007/09/02 Sun PM 08:29:08 CDT > > > >To: Repeater-Builder@yahoogroups.com > > > >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > > > Duplexers > > > > > > > > > > >But it is your statement. > > > > > > > >73 > > > >Gary K4FMX > > > > > > > >> -Original Message- > > > >> From: > > > >> Repeater-Builder@yahoogroups.com[mailto:Repeater- > > > >> [EMAIL PROTECTED] ] On Behalf Of > > > Ron Wright > > > >> Sent: Sunday, September 02, 2007 6:46 AM > > > >> To: > > > >> Repeater-Builder@yahoogroups.com > > > >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > > > > > > >> Duplexers > > > >> > > > >> Gary, > > > >> > > > >> I don't know. Why don't you tell us. > > > >> > > > >> I don't know why gravity will pull me to the ground real fast if I > > > jump > > > >> off a bridge, but I have all the faith in the world it will. > > > Einstin > > > >> tried to explain it, but died before he got the results. > > > >> > > > >> Taking the word of good test equipment is a good engineering > > > approach. > > > >> Doing the math, I am sure I have here somewhere, and I am sure the > > > >> defferential equations would take a while probably starting with > > > >> Maxwell's, but as with gravity if you know it does what it does I > > > use it. > > > >> > > > >> These discussions can at times go no where, hi. > > > >> > > > >> 73, ron, n9ee/r > > > >> > > > >> > > > >> > > > >> >From: Gary Schafer < [EMAIL PROTECTED] > > > > > > > >> >Date: 2007/09/01 Sat PM 08:48:03 CDT > > > >> >To: > > > >> >Repeater-Bu
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Sure I suppose... Electronic Communications Systems Fundamentals Through Advanced - Fourth Edition. Page 319. Also I went to microwave101.com for some more info. Curious why your so interested in the sources, I'm not lying I swear! Jesse On 9/3/07, allan crites <[EMAIL PROTECTED]> wrote: > > Jesse, > I find six titles by Tomasi with "Electronic Communications systems " in > them.Could you be a bit more specific? And could you specify the pages > where you found the information you used? And could you provide the > information from which google searches? > I'm interested in your sources. > > 73 Allan Crites WA9ZZU > > *Jesse Lloyd <[EMAIL PROTECTED]>* wrote: > > My source was "Electronic Communications Systems" by Wayne Tomasi from > DeVry. Copyright 1998. Its my old collage text. Also I grabbed additional > information from google searches. > > Jesse > > > On 9/3/07, allan crites <[EMAIL PROTECTED]> wrote: > > > >Ron , > > Aw c'mon Ron, dig out those equations from your library so we can all > > see where you're comming from. That way we can get an idea how much > > reference materials you really have and who and what they are. And just > > because your name is Wright doen't mean you're "right" all the time. Jesse > > also doesn't ever bother to quote the sources for his statements. I'm > > begining to wonder if you as well as he have any. > > > > 73 Allan Crites WA9ZZU > > > > *Ron Wright <[EMAIL PROTECTED] >* wrote: > > > > Gary, > > > > I gave the reason for the statement...measured with HP piece of test > > equipment. Was quick and to the point. > > > > I did not think I had to dig into my libary and dig out the equations. > > Same with stating an SWR...thought most would take a reading from a meter > > and not having to give the equations. > > > > I did not see you giving your basis for rejecting the statement, but > > then again I really did not expect it, hi. > > > > 73, ron, n9ee/r > > > > >From: Gary Schafer < [EMAIL PROTECTED] > > > >Date: 2007/09/02 Sun PM 08:29:08 CDT > > >To: Repeater-Builder@yahoogroups.com > > >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > > Duplexers > > > > > > > >But it is your statement. > > > > > >73 > > >Gary K4FMX > > > > > >> -Original Message- > > >> From: > > >> Repeater-Builder@yahoogroups.com[mailto:Repeater- > > >> [EMAIL PROTECTED] ] On Behalf Of Ron > > Wright > > >> Sent: Sunday, September 02, 2007 6:46 AM > > >> To: Repeater-Builder@yahoogroups.com > > >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > > >> Duplexers > > >> > > >> Gary, > > >> > > >> I don't know. Why don't you tell us. > > >> > > >> I don't know why gravity will pull me to the ground real fast if I > > jump > > >> off a bridge, but I have all the faith in the world it will. Einstin > > >> tried to explain it, but died before he got the results. > > >> > > >> Taking the word of good test equipment is a good engineering > > approach. > > >> Doing the math, I am sure I have here somewhere, and I am sure the > > >> defferential equations would take a while probably starting with > > >> Maxwell's, but as with gravity if you know it does what it does I use > > it. > > >> > > >> These discussions can at times go no where, hi. > > >> > > >> 73, ron, n9ee/r > > >> > > >> > > >> > > >> >From: Gary Schafer < [EMAIL PROTECTED] > > > > > >> >Date: 2007/09/01 Sat PM 08:48:03 CDT > > >> >To: Repeater-Builder@yahoogroups.com > > >> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > > Duplexers > > >> > > >> > > > >> >Ron, > > >> > > > >> >Maybe you could tell us why coax cable has a lower frequency limit? > > You > > >> >claim that it does but have not explained why or how. > > >> > > > >> >Why does the impedance change significantly at lower frequencies? > > >> > > > >> >73 > > >> >Gary K4FMX > > >> > > > >> >> -Original Message- > >
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Jesse, I find six titles by Tomasi with "Electronic Communications systems " in them.Could you be a bit more specific? And could you specify the pages where you found the information you used? And could you provide the information from which google searches? I'm interested in your sources. 73 Allan Crites WA9ZZU Jesse Lloyd <[EMAIL PROTECTED]> wrote: My source was "Electronic Communications Systems" by Wayne Tomasi from DeVry. Copyright 1998. Its my old collage text. Also I grabbed additional information from google searches. Jesse On 9/3/07, allan crites <[EMAIL PROTECTED]> wrote: Ron , Aw c'mon Ron, dig out those equations from your library so we can all see where you're comming from. That way we can get an idea how much reference materials you really have and who and what they are. And just because your name is Wright doen't mean you're "right" all the time. Jesse also doesn't ever bother to quote the sources for his statements. I'm begining to wonder if you as well as he have any. 73 Allan Crites WA9ZZU Ron Wright <[EMAIL PROTECTED] > wrote: Gary, I gave the reason for the statement...measured with HP piece of test equipment. Was quick and to the point. I did not think I had to dig into my libary and dig out the equations. Same with stating an SWR...thought most would take a reading from a meter and not having to give the equations. I did not see you giving your basis for rejecting the statement, but then again I really did not expect it, hi. 73, ron, n9ee/r >From: Gary Schafer < [EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 08:29:08 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >But it is your statement. > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto: Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Sunday, September 02, 2007 6:46 AM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> Gary, >> >> I don't know. Why don't you tell us. >> >> I don't know why gravity will pull me to the ground real fast if I jump >> off a bridge, but I have all the faith in the world it will. Einstin >> tried to explain it, but died before he got the results. >> >> Taking the word of good test equipment is a good engineering approach. >> Doing the math, I am sure I have here somewhere, and I am sure the >> defferential equations would take a while probably starting with >> Maxwell's, but as with gravity if you know it does what it does I use it. >> >> These discussions can at times go no where, hi. >> >> 73, ron, n9ee/r >> >> >> >> >From: Gary Schafer < [EMAIL PROTECTED]> >> >Date: 2007/09/01 Sat PM 08:48:03 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> > >> >Ron, >> > >> >Maybe you could tell us why coax cable has a lower frequency limit? You >> >claim that it does but have not explained why or how. >> > >> >Why does the impedance change significantly at lower frequencies? >> > >> >73 >> >Gary K4FMX >> > >> >> -Original Message- >> >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> >> Sent: Saturday, September 01, 2007 8:49 AM >> >> To: Repeater-Builder@yahoogroups.com >> >> Subject: Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> >> >> Gary, >> >> >> >> Yes the HP meter was spec'd to go below below 0.5 MHz, it went down to >> 100 >> >> kHz. >> >> >> >> I don't know where the confusion is...all coax and feedline has a upper >> >> and lower freq limit. Might try to learn something about this. >> >> >> >> I know about low freq RF. Worked on a Navy program that used 18 kHz, a >> >> C130 aircraft with 30,000 ft of wire hung out the back as a platform to >> >> talk to surmerged submarines. Ran over 250 kW. It was called TACMO. >> Due >> >> to the weight the wings kept falling off...well they were continously >> >> inspected and replaced before they fell off, but the aircraft was >> >> deffinitly over lo
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
My source was "Electronic Communications Systems" by Wayne Tomasi from DeVry. Copyright 1998. Its my old collage text. Also I grabbed additional information from google searches. Jesse On 9/3/07, allan crites <[EMAIL PROTECTED]> wrote: > > Ron , > Aw c'mon Ron, dig out those equations from your library so we can all see > where you're comming from. That way we can get an idea how much reference > materials you really have and who and what they are. And just because your > name is Wright doen't mean you're "right" all the time. Jesse also doesn't > ever bother to quote the sources for his statements. I'm begining to wonder > if you as well as he have any. > > 73 Allan Crites WA9ZZU > > *Ron Wright <[EMAIL PROTECTED]>* wrote: > > Gary, > > I gave the reason for the statement...measured with HP piece of test > equipment. Was quick and to the point. > > I did not think I had to dig into my libary and dig out the equations. > Same with stating an SWR...thought most would take a reading from a meter > and not having to give the equations. > > I did not see you giving your basis for rejecting the statement, but then > again I really did not expect it, hi. > > 73, ron, n9ee/r > > >From: Gary Schafer <[EMAIL PROTECTED] > > >Date: 2007/09/02 Sun PM 08:29:08 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > > > >But it is your statement. > > > >73 > >Gary K4FMX > > > >> -Original Message- > >> From: > >> Repeater-Builder@yahoogroups.com[mailto: > Repeater- > >> [EMAIL PROTECTED] ] On Behalf Of Ron > Wright > >> Sent: Sunday, September 02, 2007 6:46 AM > >> To: Repeater-Builder@yahoogroups.com > >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > >> Duplexers > >> > >> Gary, > >> > >> I don't know. Why don't you tell us. > >> > >> I don't know why gravity will pull me to the ground real fast if I jump > >> off a bridge, but I have all the faith in the world it will. Einstin > >> tried to explain it, but died before he got the results. > >> > >> Taking the word of good test equipment is a good engineering approach. > >> Doing the math, I am sure I have here somewhere, and I am sure the > >> defferential equations would take a while probably starting with > >> Maxwell's, but as with gravity if you know it does what it does I use > it. > >> > >> These discussions can at times go no where, hi. > >> > >> 73, ron, n9ee/r > >> > >> > >> > >> >From: Gary Schafer <[EMAIL PROTECTED] > > >> >Date: 2007/09/01 Sat PM 08:48:03 CDT > >> >To: Repeater-Builder@yahoogroups.com > >> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > >> > >> > > >> >Ron, > >> > > >> >Maybe you could tell us why coax cable has a lower frequency limit? > You > >> >claim that it does but have not explained why or how. > >> > > >> >Why does the impedance change significantly at lower frequencies? > >> > > >> >73 > >> >Gary K4FMX > >> > > >> >> -Original Message- > >> >> From: > >> >> Repeater-Builder@yahoogroups.com[mailto: > Repeater- > >> >> [EMAIL PROTECTED] ] On Behalf Of > Ron Wright > >> >> Sent: Saturday, September 01, 2007 8:49 AM > >> >> To: Repeater-Builder@yahoogroups.com > >> >> Subject: Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > >> Duplexers > >> >> > >> >> Gary, > >> >> > >> >> Yes the HP meter was spec'd to go below below 0.5 MHz, it went down > to > >> 100 > >> >> kHz. > >> >> > >> >> I don't know where the confusion is...all coax and feedline has a > upper > >> >> and lower freq limit. Might try to learn something about this. > >> >> > >> >> I know about low freq RF. Worked on a Navy program that used 18 kHz, > a > >> >> C130 aircraft with 30,000 ft of wire hung out the back as a platform > to > >> >> talk to surmerged submarines. Ran over 250 kW. It was called TACMO. > >> Due > >> >> to the weight the wings kept falling off...well they
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Ron , Aw c'mon Ron, dig out those equations from your library so we can all see where you're comming from. That way we can get an idea how much reference materials you really have and who and what they are. And just because your name is Wright doen't mean you're "right" all the time. Jesse also doesn't ever bother to quote the sources for his statements. I'm begining to wonder if you as well as he have any. 73 Allan Crites WA9ZZU Ron Wright <[EMAIL PROTECTED]> wrote: Gary, I gave the reason for the statement...measured with HP piece of test equipment. Was quick and to the point. I did not think I had to dig into my libary and dig out the equations. Same with stating an SWR...thought most would take a reading from a meter and not having to give the equations. I did not see you giving your basis for rejecting the statement, but then again I really did not expect it, hi. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 08:29:08 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >But it is your statement. > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Sunday, September 02, 2007 6:46 AM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> Gary, >> >> I don't know. Why don't you tell us. >> >> I don't know why gravity will pull me to the ground real fast if I jump >> off a bridge, but I have all the faith in the world it will. Einstin >> tried to explain it, but died before he got the results. >> >> Taking the word of good test equipment is a good engineering approach. >> Doing the math, I am sure I have here somewhere, and I am sure the >> defferential equations would take a while probably starting with >> Maxwell's, but as with gravity if you know it does what it does I use it. >> >> These discussions can at times go no where, hi. >> >> 73, ron, n9ee/r >> >> >> >> >From: Gary Schafer <[EMAIL PROTECTED]> >> >Date: 2007/09/01 Sat PM 08:48:03 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> > >> >Ron, >> > >> >Maybe you could tell us why coax cable has a lower frequency limit? You >> >claim that it does but have not explained why or how. >> > >> >Why does the impedance change significantly at lower frequencies? >> > >> >73 >> >Gary K4FMX >> > >> >> -Original Message- >> >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> >> Sent: Saturday, September 01, 2007 8:49 AM >> >> To: Repeater-Builder@yahoogroups.com >> >> Subject: Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> >> >> Gary, >> >> >> >> Yes the HP meter was spec'd to go below below 0.5 MHz, it went down to >> 100 >> >> kHz. >> >> >> >> I don't know where the confusion is...all coax and feedline has a upper >> >> and lower freq limit. Might try to learn something about this. >> >> >> >> I know about low freq RF. Worked on a Navy program that used 18 kHz, a >> >> C130 aircraft with 30,000 ft of wire hung out the back as a platform to >> >> talk to surmerged submarines. Ran over 250 kW. It was called TACMO. >> Due >> >> to the weight the wings kept falling off...well they were continously >> >> inspected and replaced before they fell off, but the aircraft was >> >> deffinitly over loaded. Had generators on all 4 engines to get the >> power >> >> they needed. Now that was a repeater. >> >> >> >> However, AC power distribution is not trying to radiate power, but >> >> transfer it with widly varing loads. Totally different engineering. >> >> >> >> At low frequencies such as 1 kHz little radiation takes place. Far >> less >> >> at 60 Hz. The EMF returns to the radiator, wire, before the next cycle >> >> can force it out. This is a problem in some applications, but since >> most >> >> do not want radiation it is not. >> >> >> >>
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Hahaha a audiophiles... can sell them anything no need for real physics, just tell them that this device will make things sound better, back it up with a BS statment that doesn't apply, and charge them 100 bux. On 9/3/07, Jeff DePolo <[EMAIL PROTECTED]> wrote: > > > > One can see there becomes a point where the coax will not > > look like coax at low frequencies or atleast have a > > characteristic impedance of something other than it normal value. > > Most of this is true (although I don't know what you mean by "coax will > not > look like coax"), and I already acknowledged in a previous post that at > sufficiently low frequencies and sufficiently short cable lengths (in > terms > of a fraction of a wavelength) that you may measure effects that seem to > conflict with what you would expect to happen at higher frequencies and > longer cable lengths. That's not what we're arguing. Or at least that's > not what I'm arguing. > > I specifically was addressing your statement that all coax has a > low-frequency cutoff, which it does NOT. Will a transmission line behave > identically at all frequencies? Of course not, that's not new news, there > are many things that affect a cable's behavior as frequency is varied. > > To put this to bed once and for all, can we at least agree that coax does > not have a low-frequency cutoff? I'm sure there will be many audiophiles > that will be happy to hear that their gold-plated oxygen-free litz-wire > triple-shielded phono cables that they paid $100 for will continue to work > into the subaudible range if we can just acknowledge this fact and move > on. > > --- Jeff > > >
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> One can see there becomes a point where the coax will not > look like coax at low frequencies or atleast have a > characteristic impedance of something other than it normal value. Most of this is true (although I don't know what you mean by "coax will not look like coax"), and I already acknowledged in a previous post that at sufficiently low frequencies and sufficiently short cable lengths (in terms of a fraction of a wavelength) that you may measure effects that seem to conflict with what you would expect to happen at higher frequencies and longer cable lengths. That's not what we're arguing. Or at least that's not what I'm arguing. I specifically was addressing your statement that all coax has a low-frequency cutoff, which it does NOT. Will a transmission line behave identically at all frequencies? Of course not, that's not new news, there are many things that affect a cable's behavior as frequency is varied. To put this to bed once and for all, can we at least agree that coax does not have a low-frequency cutoff? I'm sure there will be many audiophiles that will be happy to hear that their gold-plated oxygen-free litz-wire triple-shielded phono cables that they paid $100 for will continue to work into the subaudible range if we can just acknowledge this fact and move on. --- Jeff
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Gary, I gave the reason for the statement...measured with HP piece of test equipment. Was quick and to the point. I did not think I had to dig into my libary and dig out the equations. Same with stating an SWR...thought most would take a reading from a meter and not having to give the equations. I did not see you giving your basis for rejecting the statement, but then again I really did not expect it, hi. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 08:29:08 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >But it is your statement. > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Sunday, September 02, 2007 6:46 AM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> Gary, >> >> I don't know. Why don't you tell us. >> >> I don't know why gravity will pull me to the ground real fast if I jump >> off a bridge, but I have all the faith in the world it will. Einstin >> tried to explain it, but died before he got the results. >> >> Taking the word of good test equipment is a good engineering approach. >> Doing the math, I am sure I have here somewhere, and I am sure the >> defferential equations would take a while probably starting with >> Maxwell's, but as with gravity if you know it does what it does I use it. >> >> These discussions can at times go no where, hi. >> >> 73, ron, n9ee/r >> >> >> >> >From: Gary Schafer <[EMAIL PROTECTED]> >> >Date: 2007/09/01 Sat PM 08:48:03 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> > >> >Ron, >> > >> >Maybe you could tell us why coax cable has a lower frequency limit? You >> >claim that it does but have not explained why or how. >> > >> >Why does the impedance change significantly at lower frequencies? >> > >> >73 >> >Gary K4FMX >> > >> >> -Original Message- >> >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> >> Sent: Saturday, September 01, 2007 8:49 AM >> >> To: Repeater-Builder@yahoogroups.com >> >> Subject: Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> >> >> Gary, >> >> >> >> Yes the HP meter was spec'd to go below below 0.5 MHz, it went down to >> 100 >> >> kHz. >> >> >> >> I don't know where the confusion is...all coax and feedline has a upper >> >> and lower freq limit. Might try to learn something about this. >> >> >> >> I know about low freq RF. Worked on a Navy program that used 18 kHz, a >> >> C130 aircraft with 30,000 ft of wire hung out the back as a platform to >> >> talk to surmerged submarines. Ran over 250 kW. It was called TACMO. >> Due >> >> to the weight the wings kept falling off...well they were continously >> >> inspected and replaced before they fell off, but the aircraft was >> >> deffinitly over loaded. Had generators on all 4 engines to get the >> power >> >> they needed. Now that was a repeater. >> >> >> >> However, AC power distribution is not trying to radiate power, but >> >> transfer it with widly varing loads. Totally different engineering. >> >> >> >> At low frequencies such as 1 kHz little radiation takes place. Far >> less >> >> at 60 Hz. The EMF returns to the radiator, wire, before the next cycle >> >> can force it out. This is a problem in some applications, but since >> most >> >> do not want radiation it is not. >> >> >> >> 73, ron, n9ee/r >> >> >> >> >> >> >> >> >> >> >From: Gary Schafer <[EMAIL PROTECTED]> >> >> >Date: 2007/08/31 Fri PM 05:59:28 CDT >> >> >To: Repeater-Builder@yahoogroups.com >> >> >Subject: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> >> >> > >> >> >Are you sure that the impedance meter you used was speced for >> operation
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This could be correct in that say a 50 Ohm coax at 10 MHz would be say 120 Ohms at 100 kHz or 90 Ohms at 50 kHz...freq dependent. There is still L and C. However, this would have to be for a specific design or application. It would affect wideband stuff like video and it does. I guess one could build different loads seperated by filters...not me, hi. As I said in the beginning coax has a upper and lower limit as far as characteristic impedance. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 08:41:54 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >Duplexers > >I was wondering when someone was going to dredge that up from the Beldon >papers. Good going Jesse. >But that still doesn't mean or show that coax cable has a low frequency >cutoff or that it stops looking like or acting like a coax cable at low >frequencies. It tells us that other factors come into play at low >frequencies. > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Jesse Lloyd >> Sent: Sunday, September 02, 2007 12:38 PM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> Ok. Coax doesn't have an impedance at DC it has a resistance. >> >> Coax impedance is found by: >> Zo = sqrt [ (R +j 2 pi f L ) / (G + j 2 pi f c) ] >> >> where: >> f is frequency >> L is inductance >> C is capacitance >> R is the resistance >> G is shunt conductance in mhos caused by the dielectric >> j is of course the imaginary number >> >> At extreamly low frequencies 2 pi f L and 2 pi F c are small compared >> to R and G, >> So you can now rewight as: >> >> Zo= sqrt (R/G) >> >> once f gets large enough, R and G can be neglected so the equation then >> is: >> >> Zo= sqrt [j 2pi f L / j 2pi f L) >> >> or Zo = sqrt (L/C) >> >> >> So as you can see the equation for transmission lines involves f, >> therefor f does have an effect on imedance... Ron's right. >> >> >> Jesse >> >> >> On 9/2/07, Ron Wright <[EMAIL PROTECTED]> wrote: >> > >> > >> > >> > >> > >> > >> > Jeff, >> > >> > Impedance refers to both R and X, resistance and reactance. Impedance >> affects all current flow, DC and AC. X affects AC only. >> > >> > Yes DC is steady state. Guess you can get the simple stuff. >> > >> > No a coax will not function the same at 5 Hz as it does at 2 meters. >> > >> > Evidently you have not had the previledge of working with equipment or >> engineers that allows one to look at some of these issues. >> > >> > Oh well. >> > >> > 73, ron, n9ee/r >> > >> > >From: Jeff DePolo <[EMAIL PROTECTED]> >> > >Date: 2007/09/02 Sun AM 09:01:03 CDT >> > >To: Repeater-Builder@yahoogroups.com >> > >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> > >> > >> > > >> > >> >> > >> The question is way off base. No one said one cannot carry >> > >> DC or any other signal on coax. The question was what was >> > >> the impedance of a coax at given frequencies. >> > > >> > >You said coax has a low-frequency cutoff. I'm asking about that >> > >specifically. I didn't ask about about impedance. >> > > >> > >> At DC I can guarantee you RG59 is not 75 Ohms unless you got >> > >> enough to get enough R and this is totally another >> > >> discussion. >> > > >> > >Under steady-state conditions, yes, you'd be right. >> > > >> > >> At DC, I would think you would agree one will not see >> > >> RG59 being 75 Ohm at DC. >> > > >> > >At steady-state DC, there's no such thing as impedance, there's only >> > >resistance. By definition, impedance is the opposition to a varying >> > >electric current, i.e. it only applies when we're talking about AC. >> > > >> > >> The same can be said at 1 Hz or 2 >> > >> Hz or 5 Hz...etc. >> > > >> > >No, it can'
Re: RE: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
>From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 09:07:18 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >Duplexers > > >Isnât it interesting to note thatthe impedance goes UP at low frequencies >but not by leaps and bounds. It goes up for the impedance is now more related to R and series L with the parallel C having little affect. The cable now is in series with the load. This is why we use transmission lines so as not to be part of the load, but to transfer power. > >However you didnât say if the âRâresistance in the equations is DC >resistance or AC resistance? The R is both AC and DC although skin effect can produce more R at higher frequency, but not much at 100 kHz. The beauty of R...same all the time unless one gets too much I then the R changes and sometimes get smoke. > >If you also look in those Beldon papersyou will see that the âcharacteristic >impedanceâ of coax is not aspecific number but rather an average number. The >impedance swings all over theplace with change in frequency. There are many >high and low swings in impedanceat specific frequencies. If you got characteristic impedance or just impedance swinging all over the place you got a problem. One does see slight bumps in cables like the big water pipe with flange connections due to they are most often air with donut type insulator. These insulators form a defferent dielectric and give some slight difference in characteristic impedance. When running 10s of kW they become a factor so applications like TV stations order specific lengths of this coax to null out these bumps. A continous length of hardline will have consistant impedance. I guess we were talking about wheather coax has a lower freq limit. > >At low frequencies (or most any frequency)a coax cable does not start to >exhibit coax cable (transmission line) propertiesuntil the length of the cable >approaches 1/10 wavelength. Yes this means thatwith most common lengths of >cable at audio frequencies for example, a piece ofcoax cable only looks like a >piece of shielded cable with capacitance acrossit. But lengthen that same >cable with the same frequency to 1/10 wave length ormore and the cable now >looks like a transmission line. >This same thing happens with powerdistribution lines. The long lines are >transmission lines (appropriately named)and suffer from the same problems as >any other transmission line includingstanding waves. > >73 >Gary K4FMX > > >From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of >Jesse Lloyd >Sent: Sunday, September 02, 20074:10 PM >To: Repeater-Builder@yahoogroups.com >Subject: Re: RE: RE: RE: RE: RE:RE: RE: Re: Re: RE: [Repeater-Builder] Re: >Duplexers > >So to plug some numbersin: > >Say you have a cable with the following specs (50 ohm cable) >Capacitance of 100.3 pF/m >Inducatance of 251 nH/m >Resistane of 0.164 ohms/m >Shunt conductance of 12.8 mS/m > > >Zo = sqrt [ (R + j 2 pi f L ) / (G  + j 2 pi f C ) ] > > >at 100 Hz= 113 ohms > >at 1 Khz= 111 ohms > >at 10 Khz= 97 ohms > >at 100 Khz= 65 ohms > >at 1 Mhz= 52 ohms > >at 100 Mhz= 50 ohms > >at 1 Ghz= 50 ohms > >Proved.com > >Jesse > > > >On 9/2/07, RonWright <[EMAIL PROTECTED]>wrote: >Jeff, > >I have plenty of text books here, oh well. All refer to impedance as Z >andZ=R+jX or Z = magnitude and phase angle. A 500 Ohm resistor has an >impedance of500 Ohms or 500+j0 or 500 0 deg phase. > >I think in Jesse's and my last posting you might see about the low and >highfreq differences in coax. Maybe not. > >Oh well. Good discussion. > >73, ron, n9ee/r > >>From: Jeff DePolo <[EMAIL PROTECTED]> >>Date: 2007/09/02 Sun PM 12:12:51 CDT >>To: Repeater-Builder@yahoogroups.com >>Subject: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] >>Re:Duplexers > >> >>> Impedance refers to both R and X, resistance andreactance. Impedance >>affects all current flow, DC and AC. X affects AC only. >> >>Impedance is specific to AC. There's no such thing asimpedance at DC, only >>resistance. Look up in the definition of impedance in anyengineering text >>and you'll find that it only applies to AC. >> >>A cable's characteristic impedance is determined by the ratioof E to I when >>there are no reflections on the line. Reflections can onlyexist when the >>current being carried is varying, i.e. an AC waveform. >> >>A coaxial cable that has a 75 ohm characteristic impedancewill conduct >>ste
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The equation is for characteristic impedance which means a line of infinite length or one that is terminated with a resistive load equalling the impedance of the transmission line. An interesting note, twisted pair telco lines are about 600 ohms at baseband levels but are 120 ohms at DSL frequencies. Cat 5 has a impedance of 100 ohms if I can remember right. Impedance is given by belden as "nominal impedance" which means the impedance of the cable at frequencies where Zo doesn't change (much) ie frequencies above 5 Mhz-ish. You'll notice that the characteristic impedance flat lines at after a certain point if you plot the function on a graph. I cant see a reason why the characteristic impedance of the cable would change when you start getting into high frequencies. Skin effect maybe, but the increased resistance will still would be negligible compared to 2 pi F L. The real problem here is the definition of cutoff i suppose... it can mean either loss, impedance mismatch or both. Also cutoff is really a critical frequency rather than a gradual curve. Therefor the is no real low frequency cutoff, only a gradual curve that is impedance related (not loss related). For high frequencies there is a gradual curve and a cutoff frequency like Gary said. The gradual curve is cable loss. The "High frequency cutoff" is the point where the size of the cable reaches that of TE0 (waveguide). The cutoff wavelength is: pi [ ( D + d ) / 2 ] This is for air dielectric. With something other than air, equations starts getting messy... what happens is that wavelength gets shorter thus frequency goes up... but there is still a cutoff frequency. Jesse On 9/2/07, Gary Schafer <[EMAIL PROTECTED]> wrote: > >Correction to below: Change the word "frequency" to wavelength. It > should read; > > > > There is no "high frequency cutoff" but as the spacing of the center > conductor and shield gets larger compared to WAVELENGTH a point is reached > where the propagation mode of the cable changes and other modes come into > play (where multiple propagation modes exist) and the multiple modes can > interfere with each other causing partial cancellations. This causes > additional losses. > > > > > > There is no "high frequency cutoff" but as the spacing of the center > conductor and shield gets larger compared to frequency a point is reached > where the propagation mode of the cable changes and other modes come into > play (where multiple propagation modes exist) and the multiple modes can > interfere with each other causing partial cancellations. This causes > additional losses. > > > > 73 > > Gary K4FMX > > >
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Correction to below: Change the word "frequency" to wavelength. It should read; There is no "high frequency cutoff" but as the spacing of the center conductor and shield gets larger compared to WAVELENGTH a point is reached where the propagation mode of the cable changes and other modes come into play (where multiple propagation modes exist) and the multiple modes can interfere with each other causing partial cancellations. This causes additional losses. There is no "high frequency cutoff" but as the spacing of the center conductor and shield gets larger compared to frequency a point is reached where the propagation mode of the cable changes and other modes come into play (where multiple propagation modes exist) and the multiple modes can interfere with each other causing partial cancellations. This causes additional losses. 73 Gary K4FMX
RE: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Isn't it interesting to note that the impedance goes UP at low frequencies but not by leaps and bounds. However you didn't say if the "R" resistance in the equations is DC resistance or AC resistance? If you also look in those Beldon papers you will see that the "characteristic impedance" of coax is not a specific number but rather an average number. The impedance swings all over the place with change in frequency. There are many high and low swings in impedance at specific frequencies. At low frequencies (or most any frequency) a coax cable does not start to exhibit coax cable (transmission line) properties until the length of the cable approaches 1/10 wavelength. Yes this means that with most common lengths of cable at audio frequencies for example, a piece of coax cable only looks like a piece of shielded cable with capacitance across it. But lengthen that same cable with the same frequency to 1/10 wave length or more and the cable now looks like a transmission line. This same thing happens with power distribution lines. The long lines are transmission lines (appropriately named) and suffer from the same problems as any other transmission line including standing waves. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Sunday, September 02, 2007 4:10 PM To: Repeater-Builder@yahoogroups.com Subject: Re: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers So to plug some numbers in: Say you have a cable with the following specs (50 ohm cable) Capacitance of 100.3 pF/m Inducatance of 251 nH/m Resistane of 0.164 ohms/m Shunt conductance of 12.8 mS/m Zo = sqrt [ (R + j 2 pi f L ) / (G + j 2 pi f C ) ] at 100 Hz= 113 ohms at 1 Khz= 111 ohms at 10 Khz= 97 ohms at 100 Khz= 65 ohms at 1 Mhz= 52 ohms at 100 Mhz= 50 ohms at 1 Ghz= 50 ohms Proved.com Jesse On 9/2/07, Ron Wright <[EMAIL PROTECTED]> wrote: Jeff, I have plenty of text books here, oh well. All refer to impedance as Z and Z=R+jX or Z = magnitude and phase angle. A 500 Ohm resistor has an impedance of 500 Ohms or 500+j0 or 500 0 deg phase. I think in Jesse's and my last posting you might see about the low and high freq differences in coax. Maybe not. Oh well. Good discussion. 73, ron, n9ee/r >From: Jeff DePolo <[EMAIL PROTECTED] <mailto:jeff%40depolo.net> > >Date: 2007/09/02 Sun PM 12:12:51 CDT >To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> >Subject: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> Impedance refers to both R and X, resistance and reactance. Impedance >affects all current flow, DC and AC. X affects AC only. > >Impedance is specific to AC. There's no such thing as impedance at DC, only >resistance. Look up in the definition of impedance in any engineering text >and you'll find that it only applies to AC. > >A cable's characteristic impedance is determined by the ratio of E to I when >there are no reflections on the line. Reflections can only exist when the >current being carried is varying, i.e. an AC waveform. > >A coaxial cable that has a 75 ohm characteristic impedance will conduct >steady-state DC at any E to I ratio, and will do so without reflection. The >cable does not perform any transformation regardless of the load, unlike the >AC case. > >> No a coax will not function the same at 5 Hz as it does at 2 meters. > >Why not? > >> Evidently you have not had the previledge of working with >> equipment or engineers that allows one to look at some of >> these issues. > >Oh, I think have... > --- Jeff > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
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My reply was a tongue in cheek reply to try and inspire some explanations rather than the "just because it is" kind. You are correct about steady state DC. Just food for thought In order to get to that steady state at the far end of the cable you must first apply the DC at the opposite end. It takes time for that DC signal to reach the other end and that time will be the velocity factor of the cable. After that you have steady state DC. Upper frequency roll off of coax cable is mainly a function of the AC resistance (caused by skin effect) of the center conductor. Dielectric loss comes into play above VHF frequencies. Larger diameter coax has less loss because it has a larger center conductor with less AC resistance. During propagation of a signal down a coax line the energy is swapped between the magnetic and electric fields in the cable. I.e. The capacitor charges and discharges into the inductor and back again. Inductive and capacitive reactances have nothing to do with loss. There is no "high frequency cutoff" but as the spacing of the center conductor and shield gets larger compared to frequency a point is reached where the propagation mode of the cable changes and other modes come into play (where multiple propagation modes exist) and the multiple modes can interfere with each other causing partial cancellations. This causes additional losses. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff Condit Sent: Saturday, September 01, 2007 10:24 PM To: Repeater-Builder@yahoogroups.com Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers Hi all! If a piece of coax is sitting at ground and you suddenly attach a battery (DC) across it, you're really talking about a step function change in voltage which carries a wide spectrum of high frequencies The 'change' propagates down the coax at near the speed of light as expected. True DC, on the other hand, means nothing is changing. Everything is constant forever. In this case speed of propagation is a moot point. Regarding the upper frequency rolloff its pretty easy to see how it comes about. Current flowing in a straight wire give rise to a magnetic field around it. Since it takes energy to create the field and whe the field collapses it returns the energy, we're talking about series inductance. Yes, the central conductor of a piece of coax exhibits a certain number of nH per inch. It also has parallel capacitance to the outer braid or cylinder in terms of pF per inch. As frequencies increase the series inductive impedance increases which tends to block the series flow. Simultaneously, as frequencies increase the parallel capacitive impedance decreases tending to shunt the flow to the shield. The combination of these two effects are what gives rise to the high frequency rolloff characteristics. Larger diameter coax has less capacitance per inch and so has less rolloff for a given frequency. There is one other effect that also causes rolloff at even higher frequencies, and that is increased dielectric loss. Hope this helps. - Original Message - From: Gary Schafer <mailto:[EMAIL PROTECTED]> To: Repeater-Builder@yahoogroups.com Sent: Saturday, September 01, 2007 6:58 PM Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers How do you know it is not 75 ohms at DC? How long do you think it will take for the DC signal to reach the other end of the coax if it is applied at one end? Will it be at the speed of light? 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@ <mailto:Repeater-Builder@yahoogroups.com> yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> .com] On Behalf Of Ron Wright > Sent: Saturday, September 01, 2007 8:02 PM > To: Repeater-Builder@ <mailto:Repeater-Builder%40yahoogroups.com> yahoogroups.com > Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > Jeff, > > The question is way off base. No one said one cannot carry DC or any > other signal on coax. The question was what was the impedance of a coax > at given frequencies. > > At DC I can guarantee you RG59 is not 75 Ohms unless you got enough to get > enough R and this is totally another discussion. I would think you would > agree one will not see RG59 being 75 Ohm at DC. The same can be said at 1 > Hz or 2 Hz or 5 Hz...etc. There is a point at which it starts to > propergate and does look like 75 Ohms. I think you might understand this. > > 73, ron, n9ee/r > > > > > >From: Jeff DePolo <[EMAIL PROTECTED] <mailto:jeff%40depolo.net> net> > >Date: 2007/09/01 Sat PM 01:18:35 CDT > >To: Repeater-Builder@ <mailto:Repeater-Builder%40yahoogroups.com> yahoogroups.com
RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
I was wondering when someone was going to dredge that up from the Beldon papers. Good going Jesse. But that still doesn't mean or show that coax cable has a low frequency cutoff or that it stops looking like or acting like a coax cable at low frequencies. It tells us that other factors come into play at low frequencies. 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Jesse Lloyd > Sent: Sunday, September 02, 2007 12:38 PM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > Ok. Coax doesn't have an impedance at DC it has a resistance. > > Coax impedance is found by: > Zo = sqrt [ (R +j 2 pi f L ) / (G + j 2 pi f c) ] > > where: > f is frequency > L is inductance > C is capacitance > R is the resistance > G is shunt conductance in mhos caused by the dielectric > j is of course the imaginary number > > At extreamly low frequencies 2 pi f L and 2 pi F c are small compared > to R and G, > So you can now rewight as: > > Zo= sqrt (R/G) > > once f gets large enough, R and G can be neglected so the equation then > is: > > Zo= sqrt [j 2pi f L / j 2pi f L) > > or Zo = sqrt (L/C) > > > So as you can see the equation for transmission lines involves f, > therefor f does have an effect on imedance... Ron's right. > > > Jesse > > > On 9/2/07, Ron Wright <[EMAIL PROTECTED]> wrote: > > > > > > > > > > > > > > Jeff, > > > > Impedance refers to both R and X, resistance and reactance. Impedance > affects all current flow, DC and AC. X affects AC only. > > > > Yes DC is steady state. Guess you can get the simple stuff. > > > > No a coax will not function the same at 5 Hz as it does at 2 meters. > > > > Evidently you have not had the previledge of working with equipment or > engineers that allows one to look at some of these issues. > > > > Oh well. > > > > 73, ron, n9ee/r > > > > >From: Jeff DePolo <[EMAIL PROTECTED]> > > >Date: 2007/09/02 Sun AM 09:01:03 CDT > > >To: Repeater-Builder@yahoogroups.com > > >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > > > > > > > > >> > > >> The question is way off base. No one said one cannot carry > > >> DC or any other signal on coax. The question was what was > > >> the impedance of a coax at given frequencies. > > > > > >You said coax has a low-frequency cutoff. I'm asking about that > > >specifically. I didn't ask about about impedance. > > > > > >> At DC I can guarantee you RG59 is not 75 Ohms unless you got > > >> enough to get enough R and this is totally another > > >> discussion. > > > > > >Under steady-state conditions, yes, you'd be right. > > > > > >> At DC, I would think you would agree one will not see > > >> RG59 being 75 Ohm at DC. > > > > > >At steady-state DC, there's no such thing as impedance, there's only > > >resistance. By definition, impedance is the opposition to a varying > > >electric current, i.e. it only applies when we're talking about AC. > > > > > >> The same can be said at 1 Hz or 2 > > >> Hz or 5 Hz...etc. > > > > > >No, it can't. If you had a piece of cable long enough, it would > behave the > > >same way at 5 Hz as would a 100 foot piece of cable on 2m. > > > > > >> There is a point at which it starts to > > >> propergate and does look like 75 Ohms. I think you might > > >> understand this. > > > > > >I'm not trying to rake you over the coals Ron, but I *am* trying to > prove a > > >point: there is no low-frequency cutoff for coaxial cable, period. > You may > > >experience (or even measure) behavior at very low frequencies when the > cable > > >is a small fraction of an electrical wavelength that might make you > want to > > >think otherwise, but it's not due to transmission line theory, math, > or > > >physics breaking down at some low-frequency cutoff. > > > > > > --- Jeff > > > > > > > > > > Ron Wright, N9EE > > 727-376-6575 > > MICRO COMPUTER CONCEPTS > > Owner 146.64 repeater Tampa Bay, FL > > No tone, all are welcome. > > > > > > > > > > > > > > Yahoo! Groups Links > > >
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Yes Ron, a tongue in cheek reply, but not entirely. 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Sunday, September 02, 2007 6:40 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > Gary, > > Now I know you are kidding, hi. > > 73, ron, n9ee/r > > > > From: Gary Schafer <[EMAIL PROTECTED]> > >Date: 2007/09/01 Sat PM 08:58:13 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > > > >How do you know it is not 75 ohms at DC? > >How long do you think it will take for the DC signal to reach the other > end > >of the coax if it is applied at one end? Will it be at the speed of > light? > > > >73 > >Gary K4FMX > > > >> -Original Message- > >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > >> [EMAIL PROTECTED] On Behalf Of Ron Wright > >> Sent: Saturday, September 01, 2007 8:02 PM > >> To: Repeater-Builder@yahoogroups.com > >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > >> Duplexers > >> > >> Jeff, > >> > >> The question is way off base. No one said one cannot carry DC or any > >> other signal on coax. The question was what was the impedance of a > coax > >> at given frequencies. > >> > >> At DC I can guarantee you RG59 is not 75 Ohms unless you got enough to > get > >> enough R and this is totally another discussion. I would think you > would > >> agree one will not see RG59 being 75 Ohm at DC. The same can be said > at 1 > >> Hz or 2 Hz or 5 Hz...etc. There is a point at which it starts to > >> propergate and does look like 75 Ohms. I think you might understand > this. > >> > >> 73, ron, n9ee/r > >> > >> > >> > >> > >> >From: Jeff DePolo <[EMAIL PROTECTED]> > >> >Date: 2007/09/01 Sat PM 01:18:35 CDT > >> >To: Repeater-Builder@yahoogroups.com > >> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > >> > >> > > >> >> I don't know where the confusion is...all coax and feedline > >> >> has a upper and lower freq limit. Might try to learn > >> >> something about this. > >> > > >> >If what you say is true, can you tell me, using sound engineering and > >> math, > >> >why you can carry DC on coax if it has a low-frequency cutoff? > >> > > >> > --- Jeff > >> > > >> > > >> > >> > >> Ron Wright, N9EE > >> 727-376-6575 > >> MICRO COMPUTER CONCEPTS > >> Owner 146.64 repeater Tampa Bay, FL > >> No tone, all are welcome. > >> > >> > >> > >> > >> > >> > >> > >> Yahoo! Groups Links > >> > >> > >> > > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > > > > > > > Yahoo! Groups Links > > >
RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
But it is your statement. 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Sunday, September 02, 2007 6:46 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > Gary, > > I don't know. Why don't you tell us. > > I don't know why gravity will pull me to the ground real fast if I jump > off a bridge, but I have all the faith in the world it will. Einstin > tried to explain it, but died before he got the results. > > Taking the word of good test equipment is a good engineering approach. > Doing the math, I am sure I have here somewhere, and I am sure the > defferential equations would take a while probably starting with > Maxwell's, but as with gravity if you know it does what it does I use it. > > These discussions can at times go no where, hi. > > 73, ron, n9ee/r > > > > >From: Gary Schafer <[EMAIL PROTECTED]> > >Date: 2007/09/01 Sat PM 08:48:03 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > >Ron, > > > >Maybe you could tell us why coax cable has a lower frequency limit? You > >claim that it does but have not explained why or how. > > > >Why does the impedance change significantly at lower frequencies? > > > >73 > >Gary K4FMX > > > >> -Original Message- > >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > >> [EMAIL PROTECTED] On Behalf Of Ron Wright > >> Sent: Saturday, September 01, 2007 8:49 AM > >> To: Repeater-Builder@yahoogroups.com > >> Subject: Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > >> > >> Gary, > >> > >> Yes the HP meter was spec'd to go below below 0.5 MHz, it went down to > 100 > >> kHz. > >> > >> I don't know where the confusion is...all coax and feedline has a upper > >> and lower freq limit. Might try to learn something about this. > >> > >> I know about low freq RF. Worked on a Navy program that used 18 kHz, a > >> C130 aircraft with 30,000 ft of wire hung out the back as a platform to > >> talk to surmerged submarines. Ran over 250 kW. It was called TACMO. > Due > >> to the weight the wings kept falling off...well they were continously > >> inspected and replaced before they fell off, but the aircraft was > >> deffinitly over loaded. Had generators on all 4 engines to get the > power > >> they needed. Now that was a repeater. > >> > >> However, AC power distribution is not trying to radiate power, but > >> transfer it with widly varing loads. Totally different engineering. > >> > >> At low frequencies such as 1 kHz little radiation takes place. Far > less > >> at 60 Hz. The EMF returns to the radiator, wire, before the next cycle > >> can force it out. This is a problem in some applications, but since > most > >> do not want radiation it is not. > >> > >> 73, ron, n9ee/r > >> > >> > >> > >> > >> >From: Gary Schafer <[EMAIL PROTECTED]> > >> >Date: 2007/08/31 Fri PM 05:59:28 CDT > >> >To: Repeater-Builder@yahoogroups.com > >> >Subject: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> > >> > > >> >Are you sure that the impedance meter you used was speced for > operation > >> >below .5 MHz? > >> > > >> >Yes all capacitors have inductance. Lead length is particularly a > >> problem. > >> > > >> >15 KHz can be treated as RF or audio it all depends on what transducer > >> you > >> >are using it to couple it with. Use a speaker and it is audio. Use an > >> >antenna it is RF. All RF propagates the same on a transmission line. > 15 > >> KHz > >> >or even 1 KHz propagates as RF just like any RF signal does through > the > >> air > >> >and even thru the ground as in the case of low frequencies. Read about > >> what > >> >some of the VLF guys are doing. > >> > > >> >On a video cable remove the termination on the far end of the cable > and > >> look > >> >at the reflected energy. It has the same effect at those frequencies > as > >> it > >> >does at HF or VHF. > >> > > >
Re: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
So to plug some numbers in: Say you have a cable with the following specs (50 ohm cable) Capacitance of 100.3 pF/m Inducatance of 251 nH/m Resistane of 0.164 ohms/m Shunt conductance of 12.8 mS/m Zo = sqrt [ (R + j 2 pi f L ) / (G + j 2 pi f C ) ] at 100 Hz= 113 ohms at 1 Khz= 111 ohms at 10 Khz= 97 ohms at 100 Khz= 65 ohms at 1 Mhz= 52 ohms at 100 Mhz= 50 ohms at 1 Ghz= 50 ohms Proved.com Jesse On 9/2/07, Ron Wright <[EMAIL PROTECTED]> wrote: > > Jeff, > > I have plenty of text books here, oh well. All refer to impedance as Z and > Z=R+jX or Z = magnitude and phase angle. A 500 Ohm resistor has an impedance > of 500 Ohms or 500+j0 or 500 0 deg phase. > > I think in Jesse's and my last posting you might see about the low and > high freq differences in coax. Maybe not. > > Oh well. Good discussion. > > 73, ron, n9ee/r > > >From: Jeff DePolo <[EMAIL PROTECTED] > > >Date: 2007/09/02 Sun PM 12:12:51 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > > > >> Impedance refers to both R and X, resistance and reactance. Impedance > >affects all current flow, DC and AC. X affects AC only. > > > >Impedance is specific to AC. There's no such thing as impedance at DC, > only > >resistance. Look up in the definition of impedance in any engineering > text > >and you'll find that it only applies to AC. > > > >A cable's characteristic impedance is determined by the ratio of E to I > when > >there are no reflections on the line. Reflections can only exist when the > >current being carried is varying, i.e. an AC waveform. > > > >A coaxial cable that has a 75 ohm characteristic impedance will conduct > >steady-state DC at any E to I ratio, and will do so without reflection. > The > >cable does not perform any transformation regardless of the load, unlike > the > >AC case. > > > >> No a coax will not function the same at 5 Hz as it does at 2 meters. > > > >Why not? > > > >> Evidently you have not had the previledge of working with > >> equipment or engineers that allows one to look at some of > >> these issues. > > > >Oh, I think have... > > --- Jeff > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > >
Re: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Jeff, I have plenty of text books here, oh well. All refer to impedance as Z and Z=R+jX or Z = magnitude and phase angle. A 500 Ohm resistor has an impedance of 500 Ohms or 500+j0 or 500 0 deg phase. I think in Jesse's and my last posting you might see about the low and high freq differences in coax. Maybe not. Oh well. Good discussion. 73, ron, n9ee/r >From: Jeff DePolo <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 12:12:51 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >Duplexers > >> Impedance refers to both R and X, resistance and reactance. Impedance >affects all current flow, DC and AC. X affects AC only. > >Impedance is specific to AC. There's no such thing as impedance at DC, only >resistance. Look up in the definition of impedance in any engineering text >and you'll find that it only applies to AC. > >A cable's characteristic impedance is determined by the ratio of E to I when >there are no reflections on the line. Reflections can only exist when the >current being carried is varying, i.e. an AC waveform. > >A coaxial cable that has a 75 ohm characteristic impedance will conduct >steady-state DC at any E to I ratio, and will do so without reflection. The >cable does not perform any transformation regardless of the load, unlike the >AC case. > >> No a coax will not function the same at 5 Hz as it does at 2 meters. > >Why not? > >> Evidently you have not had the previledge of working with >> equipment or engineers that allows one to look at some of >> these issues. > >Oh, I think have... > --- Jeff > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Jesse, You got it, well said. If you take a simple 100 ft piece of 1/4" superflex a typical value for its C=2400pf, L=6 uH and R=570 Ohm. At 5 Hz the Ls and Cs mean little compared to the R. At 10 MHz Ls and Cs mean a lot compared to the R. One can see there becomes a point where the coax will not look like coax at low frequencies or atleast have a characteristic impedance of something other than it normal value. I did this about 30 years ago for RG59, but cannot remember the numbers for some reason, hi. 73, ron, n9ee/r From: Jesse Lloyd <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun PM 12:38:28 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >Duplexers > >Ok. Coax doesn't have an impedance at DC it has a resistance. > >Coax impedance is found by: > Zo = sqrt [ (R +j 2 pi f L ) / (G + j 2 pi f c) ] > >where: >f is frequency >L is inductance >C is capacitance >R is the resistance >G is shunt conductance in mhos caused by the dielectric >j is of course the imaginary number > >At extreamly low frequencies 2 pi f L and 2 pi F c are small compared >to R and G, >So you can now rewight as: > >Zo= sqrt (R/G) > >once f gets large enough, R and G can be neglected so the equation then is: > >Zo= sqrt [j 2pi f L / j 2pi f L) > >or Zo = sqrt (L/C) > >So as you can see the equation for transmission lines involves f, >therefor f does have an effect on imedance... Ron's right. > >Jesse > >On 9/2/07, Ron Wright <[EMAIL PROTECTED]> wrote: >> >> >> >> >> >> >> Jeff, >> >> Impedance refers to both R and X, resistance and reactance. Impedance >> affects all current flow, DC and AC. X affects AC only. >> >> Yes DC is steady state. Guess you can get the simple stuff. >> >> No a coax will not function the same at 5 Hz as it does at 2 meters. >> >> Evidently you have not had the previledge of working with equipment or >> engineers that allows one to look at some of these issues. >> >> Oh well. >> >> 73, ron, n9ee/r >> >> >From: Jeff DePolo <[EMAIL PROTECTED]> >> >Date: 2007/09/02 Sun AM 09:01:03 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> >> > >> >> >> >> The question is way off base. No one said one cannot carry >> >> DC or any other signal on coax. The question was what was >> >> the impedance of a coax at given frequencies. >> > >> >You said coax has a low-frequency cutoff. I'm asking about that >> >specifically. I didn't ask about about impedance. >> > >> >> At DC I can guarantee you RG59 is not 75 Ohms unless you got >> >> enough to get enough R and this is totally another >> >> discussion. >> > >> >Under steady-state conditions, yes, you'd be right. >> > >> >> At DC, I would think you would agree one will not see >> >> RG59 being 75 Ohm at DC. >> > >> >At steady-state DC, there's no such thing as impedance, there's only >> >resistance. By definition, impedance is the opposition to a varying >> >electric current, i.e. it only applies when we're talking about AC. >> > >> >> The same can be said at 1 Hz or 2 >> >> Hz or 5 Hz...etc. >> > >> >No, it can't. If you had a piece of cable long enough, it would behave the >> >same way at 5 Hz as would a 100 foot piece of cable on 2m. >> > >> >> There is a point at which it starts to >> >> propergate and does look like 75 Ohms. I think you might >> >> understand this. >> > >> >I'm not trying to rake you over the coals Ron, but I *am* trying to prove a >> >point: there is no low-frequency cutoff for coaxial cable, period. You may >> >experience (or even measure) behavior at very low frequencies when the >> cable >> >is a small fraction of an electrical wavelength that might make you want to >> >think otherwise, but it's not due to transmission line theory, math, or >> >physics breaking down at some low-frequency cutoff. >> > >> > --- Jeff >> > >> > >> >> Ron Wright, N9EE >> 727-376-6575 >> MICRO COMPUTER CONCEPTS >> Owner 146.64 repeater Tampa Bay, FL >> No tone, all are welcome. >> >> >> >> > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Ok. Coax doesn't have an impedance at DC it has a resistance. Coax impedance is found by: Zo = sqrt [ (R +j 2 pi f L ) / (G + j 2 pi f c) ] where: f is frequency L is inductance C is capacitance R is the resistance G is shunt conductance in mhos caused by the dielectric j is of course the imaginary number At extreamly low frequencies 2 pi f L and 2 pi F c are small compared to R and G, So you can now rewight as: Zo= sqrt (R/G) once f gets large enough, R and G can be neglected so the equation then is: Zo= sqrt [j 2pi f L / j 2pi f L) or Zo = sqrt (L/C) So as you can see the equation for transmission lines involves f, therefor f does have an effect on imedance... Ron's right. Jesse On 9/2/07, Ron Wright <[EMAIL PROTECTED]> wrote: > > > > > > > Jeff, > > Impedance refers to both R and X, resistance and reactance. Impedance > affects all current flow, DC and AC. X affects AC only. > > Yes DC is steady state. Guess you can get the simple stuff. > > No a coax will not function the same at 5 Hz as it does at 2 meters. > > Evidently you have not had the previledge of working with equipment or > engineers that allows one to look at some of these issues. > > Oh well. > > 73, ron, n9ee/r > > >From: Jeff DePolo <[EMAIL PROTECTED]> > >Date: 2007/09/02 Sun AM 09:01:03 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > > > > >> > >> The question is way off base. No one said one cannot carry > >> DC or any other signal on coax. The question was what was > >> the impedance of a coax at given frequencies. > > > >You said coax has a low-frequency cutoff. I'm asking about that > >specifically. I didn't ask about about impedance. > > > >> At DC I can guarantee you RG59 is not 75 Ohms unless you got > >> enough to get enough R and this is totally another > >> discussion. > > > >Under steady-state conditions, yes, you'd be right. > > > >> At DC, I would think you would agree one will not see > >> RG59 being 75 Ohm at DC. > > > >At steady-state DC, there's no such thing as impedance, there's only > >resistance. By definition, impedance is the opposition to a varying > >electric current, i.e. it only applies when we're talking about AC. > > > >> The same can be said at 1 Hz or 2 > >> Hz or 5 Hz...etc. > > > >No, it can't. If you had a piece of cable long enough, it would behave the > >same way at 5 Hz as would a 100 foot piece of cable on 2m. > > > >> There is a point at which it starts to > >> propergate and does look like 75 Ohms. I think you might > >> understand this. > > > >I'm not trying to rake you over the coals Ron, but I *am* trying to prove a > >point: there is no low-frequency cutoff for coaxial cable, period. You may > >experience (or even measure) behavior at very low frequencies when the cable > >is a small fraction of an electrical wavelength that might make you want to > >think otherwise, but it's not due to transmission line theory, math, or > >physics breaking down at some low-frequency cutoff. > > > >--- Jeff > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > > >
RE: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> Impedance refers to both R and X, resistance and reactance. Impedance affects all current flow, DC and AC. X affects AC only. Impedance is specific to AC. There's no such thing as impedance at DC, only resistance. Look up in the definition of impedance in any engineering text and you'll find that it only applies to AC. A cable's characteristic impedance is determined by the ratio of E to I when there are no reflections on the line. Reflections can only exist when the current being carried is varying, i.e. an AC waveform. A coaxial cable that has a 75 ohm characteristic impedance will conduct steady-state DC at any E to I ratio, and will do so without reflection. The cable does not perform any transformation regardless of the load, unlike the AC case. > No a coax will not function the same at 5 Hz as it does at 2 meters. Why not? > Evidently you have not had the previledge of working with > equipment or engineers that allows one to look at some of > these issues. Oh, I think have... --- Jeff
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Jeff, Impedance refers to both R and X, resistance and reactance. Impedance affects all current flow, DC and AC. X affects AC only. Yes DC is steady state. Guess you can get the simple stuff. No a coax will not function the same at 5 Hz as it does at 2 meters. Evidently you have not had the previledge of working with equipment or engineers that allows one to look at some of these issues. Oh well. 73, ron, n9ee/r >From: Jeff DePolo <[EMAIL PROTECTED]> >Date: 2007/09/02 Sun AM 09:01:03 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> >> The question is way off base. No one said one cannot carry >> DC or any other signal on coax. The question was what was >> the impedance of a coax at given frequencies. > >You said coax has a low-frequency cutoff. I'm asking about that >specifically. I didn't ask about about impedance. > >> At DC I can guarantee you RG59 is not 75 Ohms unless you got >> enough to get enough R and this is totally another >> discussion. > >Under steady-state conditions, yes, you'd be right. > >> At DC, I would think you would agree one will not see >> RG59 being 75 Ohm at DC. > >At steady-state DC, there's no such thing as impedance, there's only >resistance. By definition, impedance is the opposition to a varying >electric current, i.e. it only applies when we're talking about AC. > >> The same can be said at 1 Hz or 2 >> Hz or 5 Hz...etc. > >No, it can't. If you had a piece of cable long enough, it would behave the >same way at 5 Hz as would a 100 foot piece of cable on 2m. > >> There is a point at which it starts to >> propergate and does look like 75 Ohms. I think you might >> understand this. > >I'm not trying to rake you over the coals Ron, but I *am* trying to prove a >point: there is no low-frequency cutoff for coaxial cable, period. You may >experience (or even measure) behavior at very low frequencies when the cable >is a small fraction of an electrical wavelength that might make you want to >think otherwise, but it's not due to transmission line theory, math, or >physics breaking down at some low-frequency cutoff. > > --- Jeff > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> > The question is way off base. No one said one cannot carry > DC or any other signal on coax. The question was what was > the impedance of a coax at given frequencies. You said coax has a low-frequency cutoff. I'm asking about that specifically. I didn't ask about about impedance. > At DC I can guarantee you RG59 is not 75 Ohms unless you got > enough to get enough R and this is totally another > discussion. Under steady-state conditions, yes, you'd be right. > At DC, I would think you would agree one will not see > RG59 being 75 Ohm at DC. At steady-state DC, there's no such thing as impedance, there's only resistance. By definition, impedance is the opposition to a varying electric current, i.e. it only applies when we're talking about AC. > The same can be said at 1 Hz or 2 > Hz or 5 Hz...etc. No, it can't. If you had a piece of cable long enough, it would behave the same way at 5 Hz as would a 100 foot piece of cable on 2m. > There is a point at which it starts to > propergate and does look like 75 Ohms. I think you might > understand this. I'm not trying to rake you over the coals Ron, but I *am* trying to prove a point: there is no low-frequency cutoff for coaxial cable, period. You may experience (or even measure) behavior at very low frequencies when the cable is a small fraction of an electrical wavelength that might make you want to think otherwise, but it's not due to transmission line theory, math, or physics breaking down at some low-frequency cutoff. --- Jeff
Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Gary, I don't know. Why don't you tell us. I don't know why gravity will pull me to the ground real fast if I jump off a bridge, but I have all the faith in the world it will. Einstin tried to explain it, but died before he got the results. Taking the word of good test equipment is a good engineering approach. Doing the math, I am sure I have here somewhere, and I am sure the defferential equations would take a while probably starting with Maxwell's, but as with gravity if you know it does what it does I use it. These discussions can at times go no where, hi. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/09/01 Sat PM 08:48:03 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >Ron, > >Maybe you could tell us why coax cable has a lower frequency limit? You >claim that it does but have not explained why or how. > >Why does the impedance change significantly at lower frequencies? > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Saturday, September 01, 2007 8:49 AM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> Gary, >> >> Yes the HP meter was spec'd to go below below 0.5 MHz, it went down to 100 >> kHz. >> >> I don't know where the confusion is...all coax and feedline has a upper >> and lower freq limit. Might try to learn something about this. >> >> I know about low freq RF. Worked on a Navy program that used 18 kHz, a >> C130 aircraft with 30,000 ft of wire hung out the back as a platform to >> talk to surmerged submarines. Ran over 250 kW. It was called TACMO. Due >> to the weight the wings kept falling off...well they were continously >> inspected and replaced before they fell off, but the aircraft was >> deffinitly over loaded. Had generators on all 4 engines to get the power >> they needed. Now that was a repeater. >> >> However, AC power distribution is not trying to radiate power, but >> transfer it with widly varing loads. Totally different engineering. >> >> At low frequencies such as 1 kHz little radiation takes place. Far less >> at 60 Hz. The EMF returns to the radiator, wire, before the next cycle >> can force it out. This is a problem in some applications, but since most >> do not want radiation it is not. >> >> 73, ron, n9ee/r >> >> >> >> >> >From: Gary Schafer <[EMAIL PROTECTED]> >> >Date: 2007/08/31 Fri PM 05:59:28 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> > >> >Are you sure that the impedance meter you used was speced for operation >> >below .5 MHz? >> > >> >Yes all capacitors have inductance. Lead length is particularly a >> problem. >> > >> >15 KHz can be treated as RF or audio it all depends on what transducer >> you >> >are using it to couple it with. Use a speaker and it is audio. Use an >> >antenna it is RF. All RF propagates the same on a transmission line. 15 >> KHz >> >or even 1 KHz propagates as RF just like any RF signal does through the >> air >> >and even thru the ground as in the case of low frequencies. Read about >> what >> >some of the VLF guys are doing. >> > >> >On a video cable remove the termination on the far end of the cable and >> look >> >at the reflected energy. It has the same effect at those frequencies as >> it >> >does at HF or VHF. >> > >> >Yes long runs of video cable can be a problem. Long runs of cable in the >> >catv industry have the same problems of frequency roll off. They call it >> >"tilt" and their amplifiers have compensation for cable attenuation in >> order >> >to make the system "flat". >> > >> >I have an HP signal level meter that measures RF from 10 Hz to 30 MHz. I >> can >> >feed an audio oscillator set to 1 KHz or 1 MHz into the same input as I >> feed >> >a 1 MHz RF generator into. The signal level meter handles it the same. >> Only >> >difference is the output impedance of the audio oscillator is 600 ohms >> >rather than 50 ohms. The instrument doesn't know or care if we want to >> call >> >it audio or RF. As far as it is concerned i
Re: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Gary, Now I know you are kidding, hi. 73, ron, n9ee/r From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/09/01 Sat PM 08:58:13 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >How do you know it is not 75 ohms at DC? >How long do you think it will take for the DC signal to reach the other end >of the coax if it is applied at one end? Will it be at the speed of light? > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Saturday, September 01, 2007 8:02 PM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: >> Duplexers >> >> Jeff, >> >> The question is way off base. No one said one cannot carry DC or any >> other signal on coax. The question was what was the impedance of a coax >> at given frequencies. >> >> At DC I can guarantee you RG59 is not 75 Ohms unless you got enough to get >> enough R and this is totally another discussion. I would think you would >> agree one will not see RG59 being 75 Ohm at DC. The same can be said at 1 >> Hz or 2 Hz or 5 Hz...etc. There is a point at which it starts to >> propergate and does look like 75 Ohms. I think you might understand this. >> >> 73, ron, n9ee/r >> >> >> >> >> >From: Jeff DePolo <[EMAIL PROTECTED]> >> >Date: 2007/09/01 Sat PM 01:18:35 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> > >> >> I don't know where the confusion is...all coax and feedline >> >> has a upper and lower freq limit. Might try to learn >> >> something about this. >> > >> >If what you say is true, can you tell me, using sound engineering and >> math, >> >why you can carry DC on coax if it has a low-frequency cutoff? >> > >> >--- Jeff >> > >> > >> >> >> Ron Wright, N9EE >> 727-376-6575 >> MICRO COMPUTER CONCEPTS >> Owner 146.64 repeater Tampa Bay, FL >> No tone, all are welcome. >> >> >> >> >> >> >> >> Yahoo! Groups Links >> >> >> > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Hi all! If a piece of coax is sitting at ground and you suddenly attach a battery (DC) across it, you're really talking about a step function change in voltage which carries a wide spectrum of high frequencies The 'change' propagates down the coax at near the speed of light as expected. True DC, on the other hand, means nothing is changing. Everything is constant forever. In this case speed of propagation is a moot point. Regarding the upper frequency rolloff its pretty easy to see how it comes about. Current flowing in a straight wire give rise to a magnetic field around it. Since it takes energy to create the field and whe the field collapses it returns the energy, we're talking about series inductance. Yes, the central conductor of a piece of coax exhibits a certain number of nH per inch. It also has parallel capacitance to the outer braid or cylinder in terms of pF per inch. As frequencies increase the series inductive impedance increases which tends to block the series flow. Simultaneously, as frequencies increase the parallel capacitive impedance decreases tending to shunt the flow to the shield. The combination of these two effects are what gives rise to the high frequency rolloff characteristics. Larger diameter coax has less capacitance per inch and so has less rolloff for a given frequency. There is one other effect that also causes rolloff at even higher frequencies, and that is increased dielectric loss. Hope this helps. - Original Message - From: Gary Schafer To: Repeater-Builder@yahoogroups.com Sent: Saturday, September 01, 2007 6:58 PM Subject: RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers How do you know it is not 75 ohms at DC? How long do you think it will take for the DC signal to reach the other end of the coax if it is applied at one end? Will it be at the speed of light? 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Saturday, September 01, 2007 8:02 PM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > Jeff, > > The question is way off base. No one said one cannot carry DC or any > other signal on coax. The question was what was the impedance of a coax > at given frequencies. > > At DC I can guarantee you RG59 is not 75 Ohms unless you got enough to get > enough R and this is totally another discussion. I would think you would > agree one will not see RG59 being 75 Ohm at DC. The same can be said at 1 > Hz or 2 Hz or 5 Hz...etc. There is a point at which it starts to > propergate and does look like 75 Ohms. I think you might understand this. > > 73, ron, n9ee/r > > > > > >From: Jeff DePolo <[EMAIL PROTECTED]> > >Date: 2007/09/01 Sat PM 01:18:35 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > >> I don't know where the confusion is...all coax and feedline > >> has a upper and lower freq limit. Might try to learn > >> something about this. > > > >If what you say is true, can you tell me, using sound engineering and > math, > >why you can carry DC on coax if it has a low-frequency cutoff? > > > > --- Jeff > > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > > > > > > > Yahoo! Groups Links > > > -- No virus found in this incoming message. Checked by AVG. Version: 7.5.485 / Virus Database: 269.13.1/982 - Release Date: 8/31/2007 5:21 PM
RE: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
How do you know it is not 75 ohms at DC? How long do you think it will take for the DC signal to reach the other end of the coax if it is applied at one end? Will it be at the speed of light? 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Saturday, September 01, 2007 8:02 PM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: > Duplexers > > Jeff, > > The question is way off base. No one said one cannot carry DC or any > other signal on coax. The question was what was the impedance of a coax > at given frequencies. > > At DC I can guarantee you RG59 is not 75 Ohms unless you got enough to get > enough R and this is totally another discussion. I would think you would > agree one will not see RG59 being 75 Ohm at DC. The same can be said at 1 > Hz or 2 Hz or 5 Hz...etc. There is a point at which it starts to > propergate and does look like 75 Ohms. I think you might understand this. > > 73, ron, n9ee/r > > > > > >From: Jeff DePolo <[EMAIL PROTECTED]> > >Date: 2007/09/01 Sat PM 01:18:35 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > >> I don't know where the confusion is...all coax and feedline > >> has a upper and lower freq limit. Might try to learn > >> something about this. > > > >If what you say is true, can you tell me, using sound engineering and > math, > >why you can carry DC on coax if it has a low-frequency cutoff? > > > > --- Jeff > > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > > > > > > > Yahoo! Groups Links > > >
RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Ron, Maybe you could tell us why coax cable has a lower frequency limit? You claim that it does but have not explained why or how. Why does the impedance change significantly at lower frequencies? 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Saturday, September 01, 2007 8:49 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > Gary, > > Yes the HP meter was spec'd to go below below 0.5 MHz, it went down to 100 > kHz. > > I don't know where the confusion is...all coax and feedline has a upper > and lower freq limit. Might try to learn something about this. > > I know about low freq RF. Worked on a Navy program that used 18 kHz, a > C130 aircraft with 30,000 ft of wire hung out the back as a platform to > talk to surmerged submarines. Ran over 250 kW. It was called TACMO. Due > to the weight the wings kept falling off...well they were continously > inspected and replaced before they fell off, but the aircraft was > deffinitly over loaded. Had generators on all 4 engines to get the power > they needed. Now that was a repeater. > > However, AC power distribution is not trying to radiate power, but > transfer it with widly varing loads. Totally different engineering. > > At low frequencies such as 1 kHz little radiation takes place. Far less > at 60 Hz. The EMF returns to the radiator, wire, before the next cycle > can force it out. This is a problem in some applications, but since most > do not want radiation it is not. > > 73, ron, n9ee/r > > > > > >From: Gary Schafer <[EMAIL PROTECTED]> > >Date: 2007/08/31 Fri PM 05:59:28 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > >Are you sure that the impedance meter you used was speced for operation > >below .5 MHz? > > > >Yes all capacitors have inductance. Lead length is particularly a > problem. > > > >15 KHz can be treated as RF or audio it all depends on what transducer > you > >are using it to couple it with. Use a speaker and it is audio. Use an > >antenna it is RF. All RF propagates the same on a transmission line. 15 > KHz > >or even 1 KHz propagates as RF just like any RF signal does through the > air > >and even thru the ground as in the case of low frequencies. Read about > what > >some of the VLF guys are doing. > > > >On a video cable remove the termination on the far end of the cable and > look > >at the reflected energy. It has the same effect at those frequencies as > it > >does at HF or VHF. > > > >Yes long runs of video cable can be a problem. Long runs of cable in the > >catv industry have the same problems of frequency roll off. They call it > >"tilt" and their amplifiers have compensation for cable attenuation in > order > >to make the system "flat". > > > >I have an HP signal level meter that measures RF from 10 Hz to 30 MHz. I > can > >feed an audio oscillator set to 1 KHz or 1 MHz into the same input as I > feed > >a 1 MHz RF generator into. The signal level meter handles it the same. > Only > >difference is the output impedance of the audio oscillator is 600 ohms > >rather than 50 ohms. The instrument doesn't know or care if we want to > call > >it audio or RF. As far as it is concerned it treats it as RF. > > > >I have an audio amplifier that has just about a flat response from around > 5 > >Hz to 1 MHz. Is that an audio amplifier or an RF amplifier? :>) > > > >73 > >Gary K4FMX > > > >> -Original Message- > >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > >> [EMAIL PROTECTED] On Behalf Of Ron Wright > >> Sent: Friday, August 31, 2007 7:12 AM > >> To: Repeater-Builder@yahoogroups.com > >> Subject: Re: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> > >> Gary, > >> > >> To measure the impedance of the RG59 I used an HP impedence meter which > >> displayed Z and phase. I use to use it to determine where caps became > >> resonant as a demo for many caps look inductive above a given freq. > Mica > >> caps did pretty good, but still hard to find a cap at 1000 pf that was > a > >> cap above 25 MHz. These become issues in bypass caps and also for > >> resonant circuits trying to get higher Qs where the C is large. > >> > >> In a good lab one often ha
Re: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Jeff, The question is way off base. No one said one cannot carry DC or any other signal on coax. The question was what was the impedance of a coax at given frequencies. At DC I can guarantee you RG59 is not 75 Ohms unless you got enough to get enough R and this is totally another discussion. I would think you would agree one will not see RG59 being 75 Ohm at DC. The same can be said at 1 Hz or 2 Hz or 5 Hz...etc. There is a point at which it starts to propergate and does look like 75 Ohms. I think you might understand this. 73, ron, n9ee/r >From: Jeff DePolo <[EMAIL PROTECTED]> >Date: 2007/09/01 Sat PM 01:18:35 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> I don't know where the confusion is...all coax and feedline >> has a upper and lower freq limit. Might try to learn >> something about this. > >If what you say is true, can you tell me, using sound engineering and math, >why you can carry DC on coax if it has a low-frequency cutoff? > > --- Jeff > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> I don't know where the confusion is...all coax and feedline > has a upper and lower freq limit. Might try to learn > something about this. If what you say is true, can you tell me, using sound engineering and math, why you can carry DC on coax if it has a low-frequency cutoff? --- Jeff
Re: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Gary, Yes the HP meter was spec'd to go below below 0.5 MHz, it went down to 100 kHz. I don't know where the confusion is...all coax and feedline has a upper and lower freq limit. Might try to learn something about this. I know about low freq RF. Worked on a Navy program that used 18 kHz, a C130 aircraft with 30,000 ft of wire hung out the back as a platform to talk to surmerged submarines. Ran over 250 kW. It was called TACMO. Due to the weight the wings kept falling off...well they were continously inspected and replaced before they fell off, but the aircraft was deffinitly over loaded. Had generators on all 4 engines to get the power they needed. Now that was a repeater. However, AC power distribution is not trying to radiate power, but transfer it with widly varing loads. Totally different engineering. At low frequencies such as 1 kHz little radiation takes place. Far less at 60 Hz. The EMF returns to the radiator, wire, before the next cycle can force it out. This is a problem in some applications, but since most do not want radiation it is not. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/08/31 Fri PM 05:59:28 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >Are you sure that the impedance meter you used was speced for operation >below .5 MHz? > >Yes all capacitors have inductance. Lead length is particularly a problem. > >15 KHz can be treated as RF or audio it all depends on what transducer you >are using it to couple it with. Use a speaker and it is audio. Use an >antenna it is RF. All RF propagates the same on a transmission line. 15 KHz >or even 1 KHz propagates as RF just like any RF signal does through the air >and even thru the ground as in the case of low frequencies. Read about what >some of the VLF guys are doing. > >On a video cable remove the termination on the far end of the cable and look >at the reflected energy. It has the same effect at those frequencies as it >does at HF or VHF. > >Yes long runs of video cable can be a problem. Long runs of cable in the >catv industry have the same problems of frequency roll off. They call it >"tilt" and their amplifiers have compensation for cable attenuation in order >to make the system "flat". > >I have an HP signal level meter that measures RF from 10 Hz to 30 MHz. I can >feed an audio oscillator set to 1 KHz or 1 MHz into the same input as I feed >a 1 MHz RF generator into. The signal level meter handles it the same. Only >difference is the output impedance of the audio oscillator is 600 ohms >rather than 50 ohms. The instrument doesn't know or care if we want to call >it audio or RF. As far as it is concerned it treats it as RF. > >I have an audio amplifier that has just about a flat response from around 5 >Hz to 1 MHz. Is that an audio amplifier or an RF amplifier? :>) > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Friday, August 31, 2007 7:12 AM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> Gary, >> >> To measure the impedance of the RG59 I used an HP impedence meter which >> displayed Z and phase. I use to use it to determine where caps became >> resonant as a demo for many caps look inductive above a given freq. Mica >> caps did pretty good, but still hard to find a cap at 1000 pf that was a >> cap above 25 MHz. These become issues in bypass caps and also for >> resonant circuits trying to get higher Qs where the C is large. >> >> In a good lab one often has tons of test equipment for making >> measurements, even spectrum anal that go down to tenths of Hz and to many >> GHz. I've had the previdlege of working in such places and some was for >> my use in my work. >> >> I know RG59 is a most commonly used cable in video. However, one does not >> have to go far before it really affects video especially color where the >> phase is so important. Also the syncs get torn up so bad monitors loose >> sync on the veritical retrace and a portion of the picture is torn at the >> top. Many manufactures make line amps that not only compenstate for loss, >> but varied freq response and some for sync...the better ones do sync also. >> The vertical sync is at about 60 Hz and horiz at 15734 Hz which is in the >> audio freq where the signal is not really propergating like in RF. Many >> things change. Of course for a run of couple hundred feet this is not a >> problem, bu
RE: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Are you sure that the impedance meter you used was speced for operation below .5 MHz? Yes all capacitors have inductance. Lead length is particularly a problem. 15 KHz can be treated as RF or audio it all depends on what transducer you are using it to couple it with. Use a speaker and it is audio. Use an antenna it is RF. All RF propagates the same on a transmission line. 15 KHz or even 1 KHz propagates as RF just like any RF signal does through the air and even thru the ground as in the case of low frequencies. Read about what some of the VLF guys are doing. On a video cable remove the termination on the far end of the cable and look at the reflected energy. It has the same effect at those frequencies as it does at HF or VHF. Yes long runs of video cable can be a problem. Long runs of cable in the catv industry have the same problems of frequency roll off. They call it "tilt" and their amplifiers have compensation for cable attenuation in order to make the system "flat". I have an HP signal level meter that measures RF from 10 Hz to 30 MHz. I can feed an audio oscillator set to 1 KHz or 1 MHz into the same input as I feed a 1 MHz RF generator into. The signal level meter handles it the same. Only difference is the output impedance of the audio oscillator is 600 ohms rather than 50 ohms. The instrument doesn't know or care if we want to call it audio or RF. As far as it is concerned it treats it as RF. I have an audio amplifier that has just about a flat response from around 5 Hz to 1 MHz. Is that an audio amplifier or an RF amplifier? :>) 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Friday, August 31, 2007 7:12 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > Gary, > > To measure the impedance of the RG59 I used an HP impedence meter which > displayed Z and phase. I use to use it to determine where caps became > resonant as a demo for many caps look inductive above a given freq. Mica > caps did pretty good, but still hard to find a cap at 1000 pf that was a > cap above 25 MHz. These become issues in bypass caps and also for > resonant circuits trying to get higher Qs where the C is large. > > In a good lab one often has tons of test equipment for making > measurements, even spectrum anal that go down to tenths of Hz and to many > GHz. I've had the previdlege of working in such places and some was for > my use in my work. > > I know RG59 is a most commonly used cable in video. However, one does not > have to go far before it really affects video especially color where the > phase is so important. Also the syncs get torn up so bad monitors loose > sync on the veritical retrace and a portion of the picture is torn at the > top. Many manufactures make line amps that not only compenstate for loss, > but varied freq response and some for sync...the better ones do sync also. > The vertical sync is at about 60 Hz and horiz at 15734 Hz which is in the > audio freq where the signal is not really propergating like in RF. Many > things change. Of course for a run of couple hundred feet this is not a > problem, but long runs it becomes one. > > 73, ron, n9ee/r > > > > >From: Gary Schafer <[EMAIL PROTECTED]> > >Date: 2007/08/30 Thu PM 07:39:21 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > >I wonder what you were using to measure the impedance of the cable with > >below .5 MHz? > >Some cable especially rg59 types have copper clad steel center > conductors. > >If the copper clad is very thin low frequencies can penetrate the copper > >clad and get into the steel where the loss can go up substantially. If > you > >are using that cable to transform an impedance the additional lose can > make > >the impedance transformation something other than expected. The impedance > >will be closer to the characteristic impedance of the cable rather than > the > >expected transformation impedance. > >But to have the characteristic impedance fall apart at .5 MHz would be a > >mystery. 75 ohm cable is used extensively in video base band applications > >where flat low frequency response is needed. > > > >73 > >Gary K4FMX > > > >> -Original Message- > >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > >> [EMAIL PROTECTED] On Behalf Of Ron Wright > >> Sent: Thursday, August 30, 2007 10:48 AM > >> To: Repeater-Builder@yahoogroups.com > >> Subject: Re: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Re: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Gary, To measure the impedance of the RG59 I used an HP impedence meter which displayed Z and phase. I use to use it to determine where caps became resonant as a demo for many caps look inductive above a given freq. Mica caps did pretty good, but still hard to find a cap at 1000 pf that was a cap above 25 MHz. These become issues in bypass caps and also for resonant circuits trying to get higher Qs where the C is large. In a good lab one often has tons of test equipment for making measurements, even spectrum anal that go down to tenths of Hz and to many GHz. I've had the previdlege of working in such places and some was for my use in my work. I know RG59 is a most commonly used cable in video. However, one does not have to go far before it really affects video especially color where the phase is so important. Also the syncs get torn up so bad monitors loose sync on the veritical retrace and a portion of the picture is torn at the top. Many manufactures make line amps that not only compenstate for loss, but varied freq response and some for sync...the better ones do sync also. The vertical sync is at about 60 Hz and horiz at 15734 Hz which is in the audio freq where the signal is not really propergating like in RF. Many things change. Of course for a run of couple hundred feet this is not a problem, but long runs it becomes one. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/08/30 Thu PM 07:39:21 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >I wonder what you were using to measure the impedance of the cable with >below .5 MHz? >Some cable especially rg59 types have copper clad steel center conductors. >If the copper clad is very thin low frequencies can penetrate the copper >clad and get into the steel where the loss can go up substantially. If you >are using that cable to transform an impedance the additional lose can make >the impedance transformation something other than expected. The impedance >will be closer to the characteristic impedance of the cable rather than the >expected transformation impedance. >But to have the characteristic impedance fall apart at .5 MHz would be a >mystery. 75 ohm cable is used extensively in video base band applications >where flat low frequency response is needed. > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Thursday, August 30, 2007 10:48 AM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> Gary, >> >> I've measured RG59 cable terminated into a 75 Ohm resistive load with a >> variable freq impedance meter. We found the coax stopped being 75 Ohms >> below about 0.5 MHz. The cable manufacture also verified this. Other >> engineers in our department knew of this as well. >> >> We were designing security systems using video and the vertical and >> harizonal sync signals became very distored over long, 2500 ft. RG59 >> cables and this was the major reason. We had to design circuits that >> corrected this, but the cable had the problem. >> >> I am sure different RG59 cables have different low freq bandwidths. RG11 >> would also be different as well as cable TV cable. >> >> All coax has a lower and upper frequency range. Since we deal with radio >> this is not much of a factor until one gets real low or GHz levels. >> >> Coax also has the problem of a upper freq limit due to it's outer shield >> becomes large enough to act as wave guide. One will see upper freq specs >> will be lower the larger cable. >> >> 73, ron, n9ee/r >> >> >> >> >From: Gary Schafer <[EMAIL PROTECTED]> >> >Date: 2007/08/29 Wed PM 09:23:57 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> >> >As far as bandwidth goes,,, where do you get this .5 MHz for rg59 cable >> as a >> >lower limit? >> > >> >Open wire lines begin to radiate as frequency is increased to the point >> >where the line spacing becomes an appreciable portion of a wave length >> due >> >to the time it takes for propagation of fields between wires. >> > >> >73 >> >Gary K4FMX >> > >> >> >> Ron Wright, N9EE >> 727-376-6575 >> MICRO COMPUTER CONCEPTS >> Owner 146.64 repeater Tampa Bay, FL >> No tone, all are welcome. >> >> >> >> >> >> >> >> Yahoo! Groups Links >> >> >> > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
I wonder what you were using to measure the impedance of the cable with below .5 MHz? Some cable especially rg59 types have copper clad steel center conductors. If the copper clad is very thin low frequencies can penetrate the copper clad and get into the steel where the loss can go up substantially. If you are using that cable to transform an impedance the additional lose can make the impedance transformation something other than expected. The impedance will be closer to the characteristic impedance of the cable rather than the expected transformation impedance. But to have the characteristic impedance fall apart at .5 MHz would be a mystery. 75 ohm cable is used extensively in video base band applications where flat low frequency response is needed. 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Thursday, August 30, 2007 10:48 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > Gary, > > I've measured RG59 cable terminated into a 75 Ohm resistive load with a > variable freq impedance meter. We found the coax stopped being 75 Ohms > below about 0.5 MHz. The cable manufacture also verified this. Other > engineers in our department knew of this as well. > > We were designing security systems using video and the vertical and > harizonal sync signals became very distored over long, 2500 ft. RG59 > cables and this was the major reason. We had to design circuits that > corrected this, but the cable had the problem. > > I am sure different RG59 cables have different low freq bandwidths. RG11 > would also be different as well as cable TV cable. > > All coax has a lower and upper frequency range. Since we deal with radio > this is not much of a factor until one gets real low or GHz levels. > > Coax also has the problem of a upper freq limit due to it's outer shield > becomes large enough to act as wave guide. One will see upper freq specs > will be lower the larger cable. > > 73, ron, n9ee/r > > > > >From: Gary Schafer <[EMAIL PROTECTED]> > >Date: 2007/08/29 Wed PM 09:23:57 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > >As far as bandwidth goes,,, where do you get this .5 MHz for rg59 cable > as a > >lower limit? > > > >Open wire lines begin to radiate as frequency is increased to the point > >where the line spacing becomes an appreciable portion of a wave length > due > >to the time it takes for propagation of fields between wires. > > > >73 > >Gary K4FMX > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > > > > > > > Yahoo! Groups Links > > >
RE: RE: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Hi Ron, Think about what goes on in power and RF transmission. Radiation is a problem in power distribution just like it is in RF. Propagation down the line is a concern in power distribution the same as RF. If you compare 160 meter transmitter/tuner L and C values to those of values used at 2 meters there is a large difference there also. Power distribution is just a lower frequency. Standing waves on power distribution lines are just as important as those on RF lines. Standing waves on power distribution produce hot spots in lines just like RF does. The only difference is the wave length is much longer at 60 Hz and you need to travel a much greater distance to see the effects but the effect are the same. 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Thursday, August 30, 2007 10:54 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > Gary, > > AC power line transmission theory is very different than RF. In RF > radiation and propagation down the line follows a much different science. > Also in AC lines the load is continously changing and at 60 Hz it takes > large Ls and Cs to make much difference. AC power is more concerned with > power factor than radiation. This can lead to more voltage and current, > at the same time, out than at the source. > > There are some concerns of very long grid lines with transmission, but > plays a much less factor than at RF. > > 73, ron, n9ee/r > > > > > >From: Gary Schafer <[EMAIL PROTECTED]> > >Date: 2007/08/29 Wed PM 09:03:50 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > >Transmission line theory is transmission line theory. It doesn't matter > what > >the frequency is it all works the same. Power line transmission engineers > >worry about the same things in power transmission as do RF engineers. > Only > >the wavelength is different. > > > >> IR drops in feed lines is much less than a factor than the > LC/dielectric > >> type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz > >> will have radically different losses yet both have the same I and V and > R. > >> > > > >A feed line at 10 MHz has a totally different R loss than the same feed > line > >used at 1000 MHz. It does NOT have the same R at different frequencies. > It > >has the same "Z" (surge or characteristic impedance) at all frequencies > but > >not the same series resistance R. The resistance increases because of > skin > >effect the higher the frequency is. This is where loss comes from. > > > >73 > >Gary K4FMX > > > >> -Original Message- > >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > >> [EMAIL PROTECTED] On Behalf Of Ron Wright > >> Sent: Wednesday, August 29, 2007 9:32 AM > >> To: Repeater-Builder@yahoogroups.com > >> Subject: Re: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> > >> Ralph, > >> > >> Transmission line theory for RF and AC power is totally different. In > AC > >> power lines little is paid attention to as for transmission except for > R > >> losses and power factor. Yes up the voltage/lower the current and the > IR > >> loss goes down. > >> > >> For RF this is totally different for the RF propergatesdown the line, > not > >> just passes as voltage and currents. This is why feedlines have > specific > >> impedances and loads used. > >> > >> One can have any impedance of coax or twin feeds one wants...that is if > >> you have the material and space for it. One can get off the shelf 75 > Ohm > >> twin lead. Using 50 or 75 Ohm has more to do with stability especially > at > >> RF. > >> > >> IR drops in feedlines is much less than a factor than the LC/dielectric > >> type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz > >> will have radically different losses yet both have the same I and V and > R. > >> > >> 73, ron, n9ee/r > >> > >> > >> > >> > >> >From: Ralph Mowery <[EMAIL PROTECTED]> > >> >Date: 2007/08/27 Mon AM 09:20:07 CDT > >> >To: Repeater-Builder@yahoogroups.com > >> >Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> > >> > > >> > > >> >--- Ron Wright <[EMAIL PROTECTED]
RE: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of Ron Wright Sent: Thursday, August 30, 2007 11:48 AM To: Repeater-Builder@yahoogroups.com Subject: Re: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers Gary, Coax also has the problem of a upper freq limit due to it's outer shield becomes large enough to act as wave guide. One will see upper freq specs will be lower the larger cable. 73, ron, n9ee/r Recent Activity a.. 14New Members b.. 3New Files Visit Your Group Share Photos Put your favorite photos and more online. Yoga Resources on Yahoo! Groups Take the stress out of your life. Endurance Zone on Yahoo! Groups Communities about higher endurance. . Yep, try 2.4ghz ATV using 1-7/8" heliax... not a happy combo.. LOL! 73 Mike Perryman www.k5jmp.us
Re: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Gary, I've measured RG59 cable terminated into a 75 Ohm resistive load with a variable freq impedance meter. We found the coax stopped being 75 Ohms below about 0.5 MHz. The cable manufacture also verified this. Other engineers in our department knew of this as well. We were designing security systems using video and the vertical and harizonal sync signals became very distored over long, 2500 ft. RG59 cables and this was the major reason. We had to design circuits that corrected this, but the cable had the problem. I am sure different RG59 cables have different low freq bandwidths. RG11 would also be different as well as cable TV cable. All coax has a lower and upper frequency range. Since we deal with radio this is not much of a factor until one gets real low or GHz levels. Coax also has the problem of a upper freq limit due to it's outer shield becomes large enough to act as wave guide. One will see upper freq specs will be lower the larger cable. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/08/29 Wed PM 09:23:57 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers >As far as bandwidth goes,,, where do you get this .5 MHz for rg59 cable as a >lower limit? > >Open wire lines begin to radiate as frequency is increased to the point >where the line spacing becomes an appreciable portion of a wave length due >to the time it takes for propagation of fields between wires. > >73 >Gary K4FMX > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: RE: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Gary, AC power line transmission theory is very different than RF. In RF radiation and propagation down the line follows a much different science. Also in AC lines the load is continously changing and at 60 Hz it takes large Ls and Cs to make much difference. AC power is more concerned with power factor than radiation. This can lead to more voltage and current, at the same time, out than at the source. There are some concerns of very long grid lines with transmission, but plays a much less factor than at RF. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/08/29 Wed PM 09:03:50 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >Transmission line theory is transmission line theory. It doesn't matter what >the frequency is it all works the same. Power line transmission engineers >worry about the same things in power transmission as do RF engineers. Only >the wavelength is different. > >> IR drops in feed lines is much less than a factor than the LC/dielectric >> type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz >> will have radically different losses yet both have the same I and V and R. >> > >A feed line at 10 MHz has a totally different R loss than the same feed line >used at 1000 MHz. It does NOT have the same R at different frequencies. It >has the same "Z" (surge or characteristic impedance) at all frequencies but >not the same series resistance R. The resistance increases because of skin >effect the higher the frequency is. This is where loss comes from. > >73 >Gary K4FMX > >> -Original Message- >> From: Repeater-Builder@yahoogroups.com [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Wednesday, August 29, 2007 9:32 AM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> Ralph, >> >> Transmission line theory for RF and AC power is totally different. In AC >> power lines little is paid attention to as for transmission except for R >> losses and power factor. Yes up the voltage/lower the current and the IR >> loss goes down. >> >> For RF this is totally different for the RF propergatesdown the line, not >> just passes as voltage and currents. This is why feedlines have specific >> impedances and loads used. >> >> One can have any impedance of coax or twin feeds one wants...that is if >> you have the material and space for it. One can get off the shelf 75 Ohm >> twin lead. Using 50 or 75 Ohm has more to do with stability especially at >> RF. >> >> IR drops in feedlines is much less than a factor than the LC/dielectric >> type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz >> will have radically different losses yet both have the same I and V and R. >> >> 73, ron, n9ee/r >> >> >> >> >> >From: Ralph Mowery <[EMAIL PROTECTED]> >> >Date: 2007/08/27 Mon AM 09:20:07 CDT >> >To: Repeater-Builder@yahoogroups.com >> >Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers >> >> > >> > >> >--- Ron Wright <[EMAIL PROTECTED]> wrote: >> > >> >> Jesse, >> >> >> >> Then why do twin feeders have much less loss than >> >> coax??? Skin affect is even more of a factor there >> >> due to the differences in the area of the outer >> >> shield in coax vs the twin feeders wire. >> >> >> >> Maybe it is because of the larger C coupling in the >> >> coax due to the larger surface area of the shield. >> >> Coax has a lower R even with skin effect than twin >> >> line feeders. >> >> >> >> Skin affect is a factor, but a small one compared to >> >> the LC factor. >> >> >> >> 73, ron, n9ee/r >> >> >> > >> >It is not open wire or coax that determins the power >> >loss. It is the impedance of the line and the size of >> >the conductors for frequencies up to 1000 Mhz or so. >> > >> >To transfer 1000 watts of power , the voltage will be >> >higher and the current lower in most prectical open >> >wire lines. That is because the impedance will be >> >around 300 to 600 ohms. Coax is usually 50 or 70 >> >ohms. To get 1000 watts of power through that >> >impedance line it requires less voltage and more >> >current. >> > >> >This is the principal of regular 60 hz power line &
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
You can not measure R with an ohmmeter either. R is the AC resistance of the wires in the line and must be measured at the operating frequency. Note that AC resistance is a different thing than impedance. AC resistance is the result of skin effect losses in a wire. Skin effect is the result of eddy currents within a conductor causing cancellations in current flow below the surface of the conductor so less depth of the conductor is effective in carrying the current thus the thinner surface available to carry current. The thin surface gets thinner as frequency is increased. This thinner surface has higher resistance the higher the frequency applied to the conductor. Thus the term AC resistance. It is the measure of resistance to an AC signal. Much different than DC resistance of the same conductor. As far as bandwidth goes,,, where do you get this .5 MHz for rg59 cable as a lower limit? Open wire lines begin to radiate as frequency is increased to the point where the line spacing becomes an appreciable portion of a wave length due to the time it takes for propagation of fields between wires. 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Wednesday, August 29, 2007 9:37 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > The 300 Ohm or 50 Ohm is not part of the R in IR losses. The 300 and 50 > are the characteristic impedances of the line and not the R values. One > cannot measure the chartistic impedance using an Ohm meter...the R one can > and it will most often be very low. > > Also the characteristic impedance of a transmission line has a bandwidth. > Typical RG59 has a lower freq at being 75 Ohms of about 0.5 MHz. Larger > lines have lower high freq limits mainly because they start to look like > wave guide. Increasing the feedline size say at 100 GHz might actually > increase the losses. > > I think we are getting somewhat confused here,hi. > > 73, ron, n9ee/r > > > > >From: Jeff DePolo <[EMAIL PROTECTED]> > >Date: 2007/08/27 Mon AM 08:55:41 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > >> Jesse, > >> > >> Then why do twin feeders have much less loss than coax??? > >> Skin affect is even more of a factor there due to the > >> differences in the area of the outer shield in coax vs the > >> twin feeders wire. > > > >The current in a 50 ohm cable is higher as compared to a 300 ohm cable > for a > >given power (by a factor of the sqrt(300/50), or about 2.5) . Power lost > >due to I2R losses vary in proportion to the square of the current > >(obviously), so for a given effective resistance in the conductors, a 50 > ohm > >cable would have 6 times greater I2R losses than a 300 ohm cable. > > > >But like Ron said, the conductor sizes are typically smaller in a 300 ohm > >twin lead cable (as compared to, say, 7/8" Heliax), so at some point you > >start getting into comparing apples and oranges... > > > >> Maybe it is because of the larger C coupling in the coax due > >> to the larger surface area of the shield. Coax has a lower R > >> even with skin effect than twin line feeders. > > > >Again, it depends on the size of the conductors. It's not a valid > statement > >that "all 300 ohm balanced lines have lower loss than 50 ohm coax". But > if > >you want to compare the two cables at approximately the same size (say, > the > >diameter of the coax is equal to the width of the twin-lead), then the > >balanced line is probably going to be the winner in the loss department > at > >VHF. > > > >> Skin affect is a factor, but a small one compared to the LC factor. > > > >Please define "the LC factor". > > > > --- Jeff > > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > > > > > > > Yahoo! Groups Links > > >
RE: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Transmission line theory is transmission line theory. It doesn't matter what the frequency is it all works the same. Power line transmission engineers worry about the same things in power transmission as do RF engineers. Only the wavelength is different. > IR drops in feed lines is much less than a factor than the LC/dielectric > type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz > will have radically different losses yet both have the same I and V and R. > A feed line at 10 MHz has a totally different R loss than the same feed line used at 1000 MHz. It does NOT have the same R at different frequencies. It has the same "Z" (surge or characteristic impedance) at all frequencies but not the same series resistance R. The resistance increases because of skin effect the higher the frequency is. This is where loss comes from. 73 Gary K4FMX > -Original Message- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Wednesday, August 29, 2007 9:32 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > Ralph, > > Transmission line theory for RF and AC power is totally different. In AC > power lines little is paid attention to as for transmission except for R > losses and power factor. Yes up the voltage/lower the current and the IR > loss goes down. > > For RF this is totally different for the RF propergatesdown the line, not > just passes as voltage and currents. This is why feedlines have specific > impedances and loads used. > > One can have any impedance of coax or twin feeds one wants...that is if > you have the material and space for it. One can get off the shelf 75 Ohm > twin lead. Using 50 or 75 Ohm has more to do with stability especially at > RF. > > IR drops in feedlines is much less than a factor than the LC/dielectric > type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz > will have radically different losses yet both have the same I and V and R. > > 73, ron, n9ee/r > > > > > >From: Ralph Mowery <[EMAIL PROTECTED]> > >Date: 2007/08/27 Mon AM 09:20:07 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > > > >--- Ron Wright <[EMAIL PROTECTED]> wrote: > > > >> Jesse, > >> > >> Then why do twin feeders have much less loss than > >> coax??? Skin affect is even more of a factor there > >> due to the differences in the area of the outer > >> shield in coax vs the twin feeders wire. > >> > >> Maybe it is because of the larger C coupling in the > >> coax due to the larger surface area of the shield. > >> Coax has a lower R even with skin effect than twin > >> line feeders. > >> > >> Skin affect is a factor, but a small one compared to > >> the LC factor. > >> > >> 73, ron, n9ee/r > >> > > > >It is not open wire or coax that determins the power > >loss. It is the impedance of the line and the size of > >the conductors for frequencies up to 1000 Mhz or so. > > > >To transfer 1000 watts of power , the voltage will be > >higher and the current lower in most prectical open > >wire lines. That is because the impedance will be > >around 300 to 600 ohms. Coax is usually 50 or 70 > >ohms. To get 1000 watts of power through that > >impedance line it requires less voltage and more > >current. > > > >This is the principal of regular 60 hz power line > >transmission. Up the voltage to a few hundred > >thousand volts and the current will go down. This > >lowers the losses. > > > >I don't care to take time to do the calculations, but > >if you take some small guage wire (say # 20) and > >space it close to make about 200 ohms line and figuer > >the loss, it may be higher than some 1 inch or even > >1/2 inch hardline. > > > >At frequencies below around 1000 Mhz the major loss is > >the IsqR loss in all lines. Radiation is a very small > >part. In coax there is a point in which the current > >on the shield is not flowing but jumping from point to > >point where the shield wires cross. This causes some > >resistance. That is partly why the foil shielded coax > >and hardline is lower in loss than regular coax. > > > >__ > >Be a better Heartthrob. Get better relationship answers from someone who > knows. Yahoo! Answers - Check it out. > >http://answers.yahoo.com/dir/?link=list&sid=396545433 > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > > > > > > > Yahoo! Groups Links > > >
Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
I hope your printer has a lot of paper Randy, This will be the 61st message sent :) Jesse On 8/29/07, R. K. Brumback <[EMAIL PROTECTED]> wrote: > >Quote*: "**If there weren't resistors in there too, transmission lines > would have no loss."* > > > > Yes, with a perfect Z, resistance would be the only math to do for loss. > But it is never perfect as even FM has a changing frequency and we use a > broad range of frequencies. I have enjoyed this thread so much I am > printing it out and re-reading it to get more knowledge. I tip my hat and > bow deeply in your direction. > > Randy > > W4CPT > > > > Original Message- > *From:* Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] > ups.com] *On Behalf Of *Jeff DePolo > *Sent:* Wednesday, August 29, 2007 11:28 AM > *To:* Repeater-Builder@yahoogroups.com > *Subject:* RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > > > > >There's a capacitor hidden in in my coax? Where? I can't > > find it, and now > > >I've ruined my cable looking for it :-) > > > > > > > Yep, whenever one has two conductors with spacing between > > them you got a cap. For a cap in coax might try looking for > > the conductors of center and shield...looks like 2 conductors > > seperated to me, hi. Yep there are caps in that coax. > > It was a joke... > > > That is what makes a feedline...parrallel caps and series > > inductors. They determine the coax or any other feedline > > characterist impedance. > > You forgot the resistors that are in series with the inductors and caps > (in > real-world transmission lines). If there weren't resistors in there too, > transmissions lines would have no loss. > > --- Jeff > > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 > 12:00 AM > > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 > 12:00 AM > > >
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Quote: “If there weren't resistors in there too, transmission lines would have no loss.” Yes, with a perfect Z, resistance would be the only math to do for loss. But it is never perfect as even FM has a changing frequency and we use a broad range of frequencies. I have enjoyed this thread so much I am printing it out and re-reading it to get more knowledge. I tip my hat and bow deeply in your direction. Randy W4CPT Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Wednesday, August 29, 2007 11:28 AM To: Repeater-Builder@yahoogroups.com Subject: RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >There's a capacitor hidden in in my coax? Where? I can't > find it, and now > >I've ruined my cable looking for it :-) > > > > Yep, whenever one has two conductors with spacing between > them you got a cap. For a cap in coax might try looking for > the conductors of center and shield...looks like 2 conductors > seperated to me, hi. Yep there are caps in that coax. It was a joke... > That is what makes a feedline...parralle-l caps and series > inductors. They determine the coax or any other feedline > characterist impedance. You forgot the resistors that are in series with the inductors and caps (in real-world transmission lines). If there weren't resistors in there too, transmissions lines would have no loss. --- Jeff No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> The 300 Ohm or 50 Ohm is not part of the R in IR losses. No, but the Z (300 or 50 or whatever) is what determines the *I* for a given amount of power. The actual losses are due to that I squared, and the R of the conductors themselves. Z is impedance. R is resistance. > I think we are getting somewhat confused here,hi. I'm not, at least not yet, but it's still early in the day. --- Jeff
RE: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> >There's a capacitor hidden in in my coax? Where? I can't > find it, and now > >I've ruined my cable looking for it :-) > > > > Yep, whenever one has two conductors with spacing between > them you got a cap. For a cap in coax might try looking for > the conductors of center and shield...looks like 2 conductors > seperated to me, hi. Yep there are caps in that coax. It was a joke... > That is what makes a feedline...parrallel caps and series > inductors. They determine the coax or any other feedline > characterist impedance. You forgot the resistors that are in series with the inductors and caps (in real-world transmission lines). If there weren't resistors in there too, transmissions lines would have no loss. --- Jeff
Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
The 300 Ohm or 50 Ohm is not part of the R in IR losses. The 300 and 50 are the characteristic impedances of the line and not the R values. One cannot measure the chartistic impedance using an Ohm meter...the R one can and it will most often be very low. Also the characteristic impedance of a transmission line has a bandwidth. Typical RG59 has a lower freq at being 75 Ohms of about 0.5 MHz. Larger lines have lower high freq limits mainly because they start to look like wave guide. Increasing the feedline size say at 100 GHz might actually increase the losses. I think we are getting somewhat confused here,hi. 73, ron, n9ee/r >From: Jeff DePolo <[EMAIL PROTECTED]> >Date: 2007/08/27 Mon AM 08:55:41 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >> Jesse, >> >> Then why do twin feeders have much less loss than coax??? >> Skin affect is even more of a factor there due to the >> differences in the area of the outer shield in coax vs the >> twin feeders wire. > >The current in a 50 ohm cable is higher as compared to a 300 ohm cable for a >given power (by a factor of the sqrt(300/50), or about 2.5) . Power lost >due to I2R losses vary in proportion to the square of the current >(obviously), so for a given effective resistance in the conductors, a 50 ohm >cable would have 6 times greater I2R losses than a 300 ohm cable. > >But like Ron said, the conductor sizes are typically smaller in a 300 ohm >twin lead cable (as compared to, say, 7/8" Heliax), so at some point you >start getting into comparing apples and oranges... > >> Maybe it is because of the larger C coupling in the coax due >> to the larger surface area of the shield. Coax has a lower R >> even with skin effect than twin line feeders. > >Again, it depends on the size of the conductors. It's not a valid statement >that "all 300 ohm balanced lines have lower loss than 50 ohm coax". But if >you want to compare the two cables at approximately the same size (say, the >diameter of the coax is equal to the width of the twin-lead), then the >balanced line is probably going to be the winner in the loss department at >VHF. > >> Skin affect is a factor, but a small one compared to the LC factor. > >Please define "the LC factor". > > --- Jeff > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Ralph, Transmission line theory for RF and AC power is totally different. In AC power lines little is paid attention to as for transmission except for R losses and power factor. Yes up the voltage/lower the current and the IR loss goes down. For RF this is totally different for the RF propergatesdown the line, not just passes as voltage and currents. This is why feedlines have specific impedances and loads used. One can have any impedance of coax or twin feeds one wants...that is if you have the material and space for it. One can get off the shelf 75 Ohm twin lead. Using 50 or 75 Ohm has more to do with stability especially at RF. IR drops in feedlines is much less than a factor than the LC/dielectric type losses. Again frequency shows this. 100 W at 10 MHz and 1000 MHz will have radically different losses yet both have the same I and V and R. 73, ron, n9ee/r >From: Ralph Mowery <[EMAIL PROTECTED]> >Date: 2007/08/27 Mon AM 09:20:07 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers > > >--- Ron Wright <[EMAIL PROTECTED]> wrote: > >> Jesse, >> >> Then why do twin feeders have much less loss than >> coax??? Skin affect is even more of a factor there >> due to the differences in the area of the outer >> shield in coax vs the twin feeders wire. >> >> Maybe it is because of the larger C coupling in the >> coax due to the larger surface area of the shield. >> Coax has a lower R even with skin effect than twin >> line feeders. >> >> Skin affect is a factor, but a small one compared to >> the LC factor. >> >> 73, ron, n9ee/r >> > >It is not open wire or coax that determins the power >loss. It is the impedance of the line and the size of >the conductors for frequencies up to 1000 Mhz or so. > >To transfer 1000 watts of power , the voltage will be >higher and the current lower in most prectical open >wire lines. That is because the impedance will be >around 300 to 600 ohms. Coax is usually 50 or 70 >ohms. To get 1000 watts of power through that >impedance line it requires less voltage and more >current. > >This is the principal of regular 60 hz power line >transmission. Up the voltage to a few hundred >thousand volts and the current will go down. This >lowers the losses. > >I don't care to take time to do the calculations, but >if you take some small guage wire (say # 20) and >space it close to make about 200 ohms line and figuer >the loss, it may be higher than some 1 inch or even >1/2 inch hardline. > >At frequencies below around 1000 Mhz the major loss is >the IsqR loss in all lines. Radiation is a very small >part. In coax there is a point in which the current >on the shield is not flowing but jumping from point to >point where the shield wires cross. This causes some >resistance. That is partly why the foil shielded coax >and hardline is lower in loss than regular coax. > >__ >Be a better Heartthrob. Get better relationship answers from someone who >knows. Yahoo! Answers - Check it out. >http://answers.yahoo.com/dir/?link=list&sid=396545433 > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
>From: Jeff DePolo <[EMAIL PROTECTED]> >Date: 2007/08/27 Mon PM 01:57:13 CDT > >There's a capacitor hidden in in my coax? Where? I can't find it, and now >I've ruined my cable looking for it :-) > Yep, whenever one has two conductors with spacing between them you got a cap. For a cap in coax might try looking for the conductors of center and shield...looks like 2 conductors seperated to me, hi. Yep there are caps in that coax. That is what makes a feedline...parrallel caps and series inductors. They determine the coax or any other feedline characterist impedance. 73, ron, n9ee/r Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Ok let's compare open wire line to coax. Assuming the same resistive loss in open wire line as that of a coax cable (same size center conductor as open wire line) we have the following: 200 watts into a 50 ohm line impedance will have a current of 2 amps. I squared R = 2x2=4x50 = 200 watts. Now if we put that same 200 watts into a 600 ohm open wire line we have a current of only .577 amps. .577x.577=.333x600 = 199.75 rounded to 200 watts. Notice how much less the current is. If our lines have a resistance of say 10 ohms the 50 ohm line at 2 amps will have a loss of 2x2=4x10 or 40 watts. (I just picked 10 ohms as an arbitrary loss resistance) With the open wire line with a current of .577 amps we will have a loss of .577x.577=.333x10 = 3.33 watts. Quite a difference in loss by just changing the impedance of the line! All because of less current! You can go to quite a bit of a smaller conductor in an open wire line than in coax and still be ahead of the losses. The ARRL handbook has a graph showing the relative losses of different coax cables compared to open wire line. The major factor in coax line impedance is the ratio of the center conductor size to that of the shield. The dielectric material does play a part but not near as much as the diameter ratios. Skin effect is the major contributor to line loss up to UHF. Skin effect is the cause of the resistance in the conductors in the line. It has nothing to do with the surge impedance of the line. Dielectric loss contributes very little to loss below UHF. Above that if does become a major factor. As frequency goes up so does skin effect loss. The surface of the conductor becomes thinner as far as RF goes with increased frequency as the RF does not penetrate as deeply. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 11:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers The whole problem here is the comparison between high impedance twin lead and low impedance coax. Is the difference of impedance really coax attenuation? If you kept I equal between twin lead and coax who would win? Also impedance shouldn't change because of frequency (with the exception of extreme situations). Its not C which defines the impedance of a cable its RLC and Shunt conductance. Skin effect has attenuation which increases with the square root of the frequency, so at higher frequencies it becomes less. Dielectric loss is directly proportional to frequency as you go up in frequency at some point it becomes the major factor of coax loss. Dielectric loss is because of the capacitor in the cable, not the capacitance. All capacitors have loss, this is the dielectric loss. It has to do with the dielectric material in the cable, air being one of the best. Jesse On 8/27/07, Ralph Mowery <[EMAIL PROTECTED]> wrote: --- Ron Wright <[EMAIL PROTECTED] <mailto:mccrpt%40verizon.net> > wrote: > Jesse, > > Then why do twin feeders have much less loss than > coax??? Skin affect is even more of a factor there > due to the differences in the area of the outer > shield in coax vs the twin feeders wire. > > Maybe it is because of the larger C coupling in the > coax due to the larger surface area of the shield. > Coax has a lower R even with skin effect than twin > line feeders. > > Skin affect is a factor, but a small one compared to > the LC factor. > > 73, ron, n9ee/r > It is not open wire or coax that determins the power loss. It is the impedance of the line and the size of the conductors for frequencies up to 1000 Mhz or so. To transfer 1000 watts of power , the voltage will be higher and the current lower in most prectical open wire lines. That is because the impedance will be around 300 to 600 ohms. Coax is usually 50 or 70 ohms. To get 1000 watts of power through that impedance line it requires less voltage and more current. This is the principal of regular 60 hz power line transmission. Up the voltage to a few hundred thousand volts and the current will go down. This lowers the losses. I don't care to take time to do the calculations, but if you take some small guage wire (say # 20) and space it close to make about 200 ohms line and figuer the loss, it may be higher than some 1 inch or even 1/2 inch hardline. At frequencies below around 1000 Mhz the major loss is the IsqR loss in all lines. Radiation is a very small part. In coax there is a point in which the current on the shield is not flowing but jumping from point to point where the shield wires cross. This causes some resistance. That is partly why the foil shielded coax and hardline is lower in loss than regular coax. __ Be a better Heartthrob. Get better relationship answ
RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
I forgot to mention in my last post that only considering the center conductor size in coax cable is necessary in these discussions of loss. The shield of the coax has many times the surface area of the center conductor and has much less resistive loss than the center conductor does. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 11:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers The whole problem here is the comparison between high impedance twin lead and low impedance coax. Is the difference of impedance really coax attenuation? If you kept I equal between twin lead and coax who would win? Also impedance shouldn't change because of frequency (with the exception of extreme situations). Its not C which defines the impedance of a cable its RLC and Shunt conductance. Skin effect has attenuation which increases with the square root of the frequency, so at higher frequencies it becomes less. Dielectric loss is directly proportional to frequency as you go up in frequency at some point it becomes the major factor of coax loss. Dielectric loss is because of the capacitor in the cable, not the capacitance. All capacitors have loss, this is the dielectric loss. It has to do with the dielectric material in the cable, air being one of the best. Jesse On 8/27/07, Ralph Mowery <[EMAIL PROTECTED]> wrote: --- Ron Wright <[EMAIL PROTECTED] <mailto:mccrpt%40verizon.net> > wrote: > Jesse, > > Then why do twin feeders have much less loss than > coax??? Skin affect is even more of a factor there > due to the differences in the area of the outer > shield in coax vs the twin feeders wire. > > Maybe it is because of the larger C coupling in the > coax due to the larger surface area of the shield. > Coax has a lower R even with skin effect than twin > line feeders. > > Skin affect is a factor, but a small one compared to > the LC factor. > > 73, ron, n9ee/r > It is not open wire or coax that determins the power loss. It is the impedance of the line and the size of the conductors for frequencies up to 1000 Mhz or so. To transfer 1000 watts of power , the voltage will be higher and the current lower in most prectical open wire lines. That is because the impedance will be around 300 to 600 ohms. Coax is usually 50 or 70 ohms. To get 1000 watts of power through that impedance line it requires less voltage and more current. This is the principal of regular 60 hz power line transmission. Up the voltage to a few hundred thousand volts and the current will go down. This lowers the losses. I don't care to take time to do the calculations, but if you take some small guage wire (say # 20) and space it close to make about 200 ohms line and figuer the loss, it may be higher than some 1 inch or even 1/2 inch hardline. At frequencies below around 1000 Mhz the major loss is the IsqR loss in all lines. Radiation is a very small part. In coax there is a point in which the current on the shield is not flowing but jumping from point to point where the shield wires cross. This causes some resistance. That is partly why the foil shielded coax and hardline is lower in loss than regular coax. __ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list <http://answers.yahoo.com/dir/?link=list&sid=396545433> &sid=396545433
RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> The whole problem here is the comparison between high > impedance twin lead and low impedance coax. Is the > difference of impedance really coax attenuation? Maybe I'm not understanding the question. In the most general terms, loss has no direct correlation to impedance because there are other parameters that affect loss aside from Z, including conductor sizes and dielectric materials. > If you kept > I equal between twin lead and coax who would win? If you kept I equal, then the Z would be equal too (assuming we're not changing power). Which cable (balanced vs unbalanced) would have less attenution depends primarily on the effective resistance of the conductors as a function of skin depth, at least at VHF/UHF with the kinds of dielectric we typically use in the field. Like I said before, you can't compare two cables based only on their characteristic Z; you have to consider the effective resistances at the frequency of interest as a function of conductor size and skin depth, and then added to that, the dielectric losses which contribute much less to the total attenuation. > Skin effect has attenuation which increases with the square > root of the frequency, so at higher frequencies it becomes > less. No, the attenution becomes MORE at higher frequencies, not less. > Dielectric loss is directly proportional to frequency > as you go up in frequency at some point it becomes the major > factor of coax loss. At VHF/UHF, dielectric loss is almost always less of an issue than ohmic losses except in the case of extremely poor dielectrics, and I don't know of any dielectric used today that would qualify as being "extremely poor". Maybe if the dielectric were made out of wood, play-doh, or Cherry Garcia ice cream the dielectric losses would dominate... :-) > Dielectric loss is because of the > capacitor in the cable, not the capacitance. There's a capacitor hidden in in my coax? Where? I can't find it, and now I've ruined my cable looking for it :-) > All capacitors > have loss, this is the dielectric loss. It has to do with > the dielectric material in the cable, air being one of the best. Capacitors also have ohmic (resistive) losses too; it's not all dielectric loss. Only "ideal" capacitors have neither dielectric nor resistive losses. All of the capacitors we deal with in the real world have both. --- Jeff
RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> It appears that the instant discussion has overlooked that > there are three factors in the attenuation of transmission > lines. They are the conductor losses, the dielectric losses, and > also the optimum ratio of b/a = 3.6 for a coaxial line, which > corresponds to a characteristic impedance of 77 ohms for a > line with air dielectric. > Obviously a solid dielectric coaxial or balanced transmission > line will have a higher loss than a line of foam or air dielectric. Yes, but it's also equally important to note that with solid polyethylene, a very common dielectric, minimum attenuation is Z=51 ohms. Coincidence? I think not! :-) --- Jeff
Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
The whole problem here is the comparison between high impedance twin lead and low impedance coax. Is the difference of impedance really coax attenuation? If you kept I equal between twin lead and coax who would win? Also impedance shouldn't change because of frequency (with the exception of extreme situations). Its not C which defines the impedance of a cable its RLC and Shunt conductance. Skin effect has attenuation which increases with the square root of the frequency, so at higher frequencies it becomes less. Dielectric loss is directly proportional to frequency as you go up in frequency at some point it becomes the major factor of coax loss. Dielectric loss is because of the capacitor in the cable, not the capacitance. All capacitors have loss, this is the dielectric loss. It has to do with the dielectric material in the cable, air being one of the best. Jesse On 8/27/07, Ralph Mowery <[EMAIL PROTECTED]> wrote: > > > --- Ron Wright <[EMAIL PROTECTED] > wrote: > > > Jesse, > > > > Then why do twin feeders have much less loss than > > coax??? Skin affect is even more of a factor there > > due to the differences in the area of the outer > > shield in coax vs the twin feeders wire. > > > > Maybe it is because of the larger C coupling in the > > coax due to the larger surface area of the shield. > > Coax has a lower R even with skin effect than twin > > line feeders. > > > > Skin affect is a factor, but a small one compared to > > the LC factor. > > > > 73, ron, n9ee/r > > > > It is not open wire or coax that determins the power > loss. It is the impedance of the line and the size of > the conductors for frequencies up to 1000 Mhz or so. > > To transfer 1000 watts of power , the voltage will be > higher and the current lower in most prectical open > wire lines. That is because the impedance will be > around 300 to 600 ohms. Coax is usually 50 or 70 > ohms. To get 1000 watts of power through that > impedance line it requires less voltage and more > current. > > This is the principal of regular 60 hz power line > transmission. Up the voltage to a few hundred > thousand volts and the current will go down. This > lowers the losses. > > I don't care to take time to do the calculations, but > if you take some small guage wire (say # 20) and > space it close to make about 200 ohms line and figuer > the loss, it may be higher than some 1 inch or even > 1/2 inch hardline. > > At frequencies below around 1000 Mhz the major loss is > the IsqR loss in all lines. Radiation is a very small > part. In coax there is a point in which the current > on the shield is not flowing but jumping from point to > point where the shield wires cross. This causes some > resistance. That is partly why the foil shielded coax > and hardline is lower in loss than regular coax. > > __ > Be a better Heartthrob. Get better relationship answers from someone who > knows. Yahoo! Answers - Check it out. > http://answers.yahoo.com/dir/?link=list&sid=396545433 > >
RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
It appears that the instant discussion has overlooked that there are three factors in the attenuation of transmission lines. They are the conductor losses, the dielectric losses, and also the optimum ratio of b/a = 3.6 for a coaxial line, which corresponds to a characteristic impedance of 77 ohms for a line with air dielectric. Obviously a solid dielectric coaxial or balanced transmission line will have a higher loss than a line of foam or air dielectric. A very complete discussion (without any high power math) of the attenuation of coaxial transmission lines which includes the losses in the resistivity of conductors and the attenuation resulting from dielectric losses is to be found in the publication Microwave Transmission Design Data by Theodore Moreno beginning on p.63 to p.66. There is also a graph showing the relationship of the various characteristics (attenuation, maximum resonant impedance, breakdown voltage, and power carrying capacity) of a coaxial transmission line plotted as functions of the ratio of radii of outer and inner conductors. I would suggest the respondents pursue this publication for additional information and end the speculation about attenuation in coaxial transmission lines that does not benefit the less informed readers of this group. Allan Crites WA9ZZU Jeff DePolo <[EMAIL PROTECTED]> wrote: > Jesse, > > Then why do twin feeders have much less loss than coax??? > Skin affect is even more of a factor there due to the > differences in the area of the outer shield in coax vs the > twin feeders wire. The current in a 50 ohm cable is higher as compared to a 300 ohm cable for a given power (by a factor of the sqrt(300/50), or about 2.5) . Power lost due to I2R losses vary in proportion to the square of the current (obviously), so for a given effective resistance in the conductors, a 50 ohm cable would have 6 times greater I2R losses than a 300 ohm cable. But like Ron said, the conductor sizes are typically smaller in a 300 ohm twin lead cable (as compared to, say, 7/8" Heliax), so at some point you start getting into comparing apples and oranges... > Maybe it is because of the larger C coupling in the coax due > to the larger surface area of the shield. Coax has a lower R > even with skin effect than twin line feeders. Again, it depends on the size of the conductors. It's not a valid statement that "all 300 ohm balanced lines have lower loss than 50 ohm coax". But if you want to compare the two cables at approximately the same size (say, the diameter of the coax is equal to the width of the twin-lead), then the balanced line is probably going to be the winner in the loss department at VHF. > Skin affect is a factor, but a small one compared to the LC factor. Please define "the LC factor". --- Jeff
Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
--- Ron Wright <[EMAIL PROTECTED]> wrote: > Jesse, > > Then why do twin feeders have much less loss than > coax??? Skin affect is even more of a factor there > due to the differences in the area of the outer > shield in coax vs the twin feeders wire. > > Maybe it is because of the larger C coupling in the > coax due to the larger surface area of the shield. > Coax has a lower R even with skin effect than twin > line feeders. > > Skin affect is a factor, but a small one compared to > the LC factor. > > 73, ron, n9ee/r > It is not open wire or coax that determins the power loss. It is the impedance of the line and the size of the conductors for frequencies up to 1000 Mhz or so. To transfer 1000 watts of power , the voltage will be higher and the current lower in most prectical open wire lines. That is because the impedance will be around 300 to 600 ohms. Coax is usually 50 or 70 ohms. To get 1000 watts of power through that impedance line it requires less voltage and more current. This is the principal of regular 60 hz power line transmission. Up the voltage to a few hundred thousand volts and the current will go down. This lowers the losses. I don't care to take time to do the calculations, but if you take some small guage wire (say # 20) and space it close to make about 200 ohms line and figuer the loss, it may be higher than some 1 inch or even 1/2 inch hardline. At frequencies below around 1000 Mhz the major loss is the IsqR loss in all lines. Radiation is a very small part. In coax there is a point in which the current on the shield is not flowing but jumping from point to point where the shield wires cross. This causes some resistance. That is partly why the foil shielded coax and hardline is lower in loss than regular coax. Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545433
RE: RE: Re: RE: [Repeater-Builder] Re: Duplexers
Gary's got it all right, though I take minor exception with one issue: > As the center conductor size is increasedin a cable the > shield must also be increased in order to maintain the > samecenter conductor to shield diameter ratio which maintains > the impedance. If thecenter conductor size was increased > without changing the outer conductor theimpedance of the > cable would be lower. The Z is determined by the ratio of the OD of the inner and ID of the outer AND the dielectric constant of the material between them. You can increase/decrease the size of one without changing the other as long as the dielectric constant changes to compensate to keep the Z the same. To wit: LMR-400 vs RG-8 solid poly. Ron - the higher in frequency you go, the less "skin depth" there is, ergo the more resistance there is. I2R losses almost always dominate at UHF and below for the kinds of coax we usually work with. Think about it this way. If at 6m the skin effect causes your center conductor to have the same effective cross-sectional area (due to the skin effect) as, say, 12 gauge wire, at 440 the same coax will have an effective cross-sectional area of something smaller, like 18 gauge wire. --- Jeff > -Original Message- > From: Repeater-Builder@yahoogroups.com > [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright > Sent: Monday, August 27, 2007 7:30 AM > To: Repeater-Builder@yahoogroups.com > Subject: Re: RE: Re: RE: [Repeater-Builder] Re: Duplexers > > Loss in feedline has lots more to do with the LC in the cable > than I^2R. If I^R were a major factor then frequency would > not have much say in the equation. Skin affect is a factor, > but then it would also be in twin feeder which have sufficent > less loss over coax which has a much larger LC factor. > > 73, ron, n9ee/r > > > > > >From: Gary Schafer <[EMAIL PROTECTED]> > >Date: 2007/08/26 Sun PM 08:47:29 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: RE: Re: RE: [Repeater-Builder] Re: Duplexers > > > > > > >Jesse is right about skin effect beinggreater at higher > frequencies on the same cable. But current will be less > alsoas resistance increases. Current is a function of > resistance for a given amountof power applied. > >Â > >Coax loss is mainly due to resistive lossup thru VHF. > Dielectric loss also starts to come into play as you get into > UHFand above. The higher the frequency the higher the > resistance is in the cableconductor due to skin effect. > >Â > >Losses due to radiation are very low andalmost immeasurable > in most cases. > >Â > >Open wire line will radiate very little ifit is properly > balanced even when SWR is very high. > >Â > >The reason open wire line has less lossthan coax cable is > that the impedance is generally higher. The higher > theimpedance the lower the current for a given amount of > power thus the lower theI squared R loss in the line. (Note > that the â??Râ? in I squared Rloss is talking about the > resistive loss in the cable and not the impedance ofthe cable) > >Â > >A 75 ohm coax cable with the sameapproximate size as a 50 > ohm cable will have lower loss than the 50 ohm cablebecause > of the lower current in the cable. (Less I squared R loss) > >Â > >In coax cable the loss is mainlydetermined by the center > conductor size/surface area. Current flow is veryshallow at > RF frequencies so it does not matter if center conductor is > solid ortubing. Tubing gets more economical with larger sizes. > >Â > >As the center conductor size is increasedin a cable the > shield must also be increased in order to maintain the > samecenter conductor to shield diameter ratio which maintains > the impedance. If thecenter conductor size was increased > without changing the outer conductor theimpedance of the > cable would be lower. > >Â > >Losses due to SWR on the line are due topart of the signal > being reflected and re-reflected and suffering > additionalresistive losses as it makes the second (and > multiple) trip up and down theline. This is not to be > confused with mis-match loss. > >Â > >Mis-match loss is not a loss attributableto cable loss but > it is a loss that comes about because the transmitter doesnot > see a flat 50 ohms and does not transfer full power because > the loading haschanged due to the impedance mis- match. This > type of loss is what is seen dueto poor connectors. Often > connector mis-match loss is confused with direct lossin the > connector. Direct loss produces heat as does all I squared R loss. > >Â > >73 > >G
RE: Re: Re: RE: [Repeater-Builder] Re: Duplexers
> Jesse, > > Then why do twin feeders have much less loss than coax??? > Skin affect is even more of a factor there due to the > differences in the area of the outer shield in coax vs the > twin feeders wire. The current in a 50 ohm cable is higher as compared to a 300 ohm cable for a given power (by a factor of the sqrt(300/50), or about 2.5) . Power lost due to I2R losses vary in proportion to the square of the current (obviously), so for a given effective resistance in the conductors, a 50 ohm cable would have 6 times greater I2R losses than a 300 ohm cable. But like Ron said, the conductor sizes are typically smaller in a 300 ohm twin lead cable (as compared to, say, 7/8" Heliax), so at some point you start getting into comparing apples and oranges... > Maybe it is because of the larger C coupling in the coax due > to the larger surface area of the shield. Coax has a lower R > even with skin effect than twin line feeders. Again, it depends on the size of the conductors. It's not a valid statement that "all 300 ohm balanced lines have lower loss than 50 ohm coax". But if you want to compare the two cables at approximately the same size (say, the diameter of the coax is equal to the width of the twin-lead), then the balanced line is probably going to be the winner in the loss department at VHF. > Skin affect is a factor, but a small one compared to the LC factor. Please define "the LC factor". --- Jeff
Re: Re: Re: RE: [Repeater-Builder] Re: Duplexers
Jesse, Then why do twin feeders have much less loss than coax??? Skin affect is even more of a factor there due to the differences in the area of the outer shield in coax vs the twin feeders wire. Maybe it is because of the larger C coupling in the coax due to the larger surface area of the shield. Coax has a lower R even with skin effect than twin line feeders. Skin affect is a factor, but a small one compared to the LC factor. 73, ron, n9ee/r >From: Jesse Lloyd <[EMAIL PROTECTED]> >Date: 2007/08/26 Sun PM 03:32:00 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: Re: RE: [Repeater-Builder] Re: Duplexers > >Well skin effect varies with frequency, there for the R is higher with >frequency. I is constant, but R is not, so your power lost will vary with >frequency because of I^2R and skin effect. This is why larger diameter solid >hardline has less loss than smaller. > > > >On 8/26/07, Ron Wright <[EMAIL PROTECTED]> wrote: >Jesse, > >You are correct and this is why some large coax have hollow tubing for the >inter conductor. Due to skin effect the current density on the outer part of >the conductor is higher. > >But if a coax has 10 watts with a said current at one freq and the same >current at a higher freq the losses will be different. This was my point. > >73, ron, n9ee/r > >>From: Jesse Lloyd <[EMAIL PROTECTED]> >>Date: 2007/08/26 Sun PM 02:34:41 CDT >>To: Repeater-Builder@yahoogroups.com >>Subject: Re: RE: [Repeater-Builder] Re: Duplexers > >> >>I^2R losses do change with frequency because of the skin effect. >> >> >> >>On 8/26/07, Ron Wright <[EMAIL PROTECTED]> wrote: >>Jeff, >> >>The low shield coverage is one reason I do not buy cables with pre-installed >>connectors unless I know the cable...not just because it says RG8 or whatever. >> >>I used a piece of 50 ft RS RG8 w/pre-installed connectors for a few years and >>finally cut it for other purposes and was so disappointed I had purchased >>such a cable with so little shield. >> >>Guess works for CB and Ham HF bands, but really not good for VHF/UHF. The >>same can be said for many PL259 connectors and adapters. >> >>73, ron, n9ee/r >> >>>From: Jeff DePolo <[EMAIL PROTECTED]> >>>Date: 2007/08/26 Sun PM 12:59:45 CDT >>>To: Repeater-Builder@yahoogroups.com >>>Subject: RE: [Repeater-Builder] Re: Duplexers >> >>> >>>Coax leakage is different than currents flowing on the shield though... >>> >>>I remember having some RG8 from Radio Shack with braid openings that you >>>could probably fit a pencil through. >>> >>>> Some of the cheaper coax brands have less than about 70% shielding >>>> making them pretty leaky to rf. It works just killer for adding a >>>> little extra signal horse-power to a carrier current broadcast >>>> station. Radiax without trying... >>> >>>You could run it up the tower and have a really long antenna. Lots of >>>capture area ;-) >>> >>> >> >>Ron Wright, N9EE >>727-376-6575 >>MICRO COMPUTER CONCEPTS >>Owner 146.64 repeater Tampa Bay, FL >>No tone, all are welcome. >> >> >> > >Ron Wright, N9EE >727-376-6575 >MICRO COMPUTER CONCEPTS >Owner 146.64 repeater Tampa Bay, FL >No tone, all are welcome. > > > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: RE: Re: RE: [Repeater-Builder] Re: Duplexers
Loss in feedline has lots more to do with the LC in the cable than I^2R. If I^R were a major factor then frequency would not have much say in the equation. Skin affect is a factor, but then it would also be in twin feeder which have sufficent less loss over coax which has a much larger LC factor. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/08/26 Sun PM 08:47:29 CDT >To: Repeater-Builder@yahoogroups.com >Subject: RE: Re: RE: [Repeater-Builder] Re: Duplexers > > >Jesse is right about skin effect beinggreater at higher frequencies on the >same cable. But current will be less alsoas resistance increases. Current is a >function of resistance for a given amountof power applied. > >Coax loss is mainly due to resistive lossup thru VHF. Dielectric loss also >starts to come into play as you get into UHFand above. The higher the >frequency the higher the resistance is in the cableconductor due to skin >effect. > >Losses due to radiation are very low andalmost immeasurable in most cases. > >Open wire line will radiate very little ifit is properly balanced even when >SWR is very high. > >The reason open wire line has less lossthan coax cable is that the impedance >is generally higher. The higher theimpedance the lower the current for a given >amount of power thus the lower theI squared R loss in the line. (Note that the >âRâ in I squared Rloss is talking about the resistive loss in the cable >and not the impedance ofthe cable) > >A 75 ohm coax cable with the sameapproximate size as a 50 ohm cable will have >lower loss than the 50 ohm cablebecause of the lower current in the cable. >(Less I squared R loss) > >In coax cable the loss is mainlydetermined by the center conductor >size/surface area. Current flow is veryshallow at RF frequencies so it does >not matter if center conductor is solid ortubing. Tubing gets more economical >with larger sizes. > >As the center conductor size is increasedin a cable the shield must also be >increased in order to maintain the samecenter conductor to shield diameter >ratio which maintains the impedance. If thecenter conductor size was increased >without changing the outer conductor theimpedance of the cable would be lower. > >Losses due to SWR on the line are due topart of the signal being reflected and >re-reflected and suffering additionalresistive losses as it makes the second >(and multiple) trip up and down theline. This is not to be confused with >mis-match loss. > >Mis-match loss is not a loss attributableto cable loss but it is a loss that >comes about because the transmitter doesnot see a flat 50 ohms and does not >transfer full power because the loading haschanged due to the impedance mis- >match. This type of loss is what is seen dueto poor connectors. Often >connector mis-match loss is confused with direct lossin the connector. Direct >loss produces heat as does all I squared R loss. > >73 >Gary K4FMX > > >From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of >Jesse Lloyd >Sent: Sunday, August 26, 2007 3:32PM >To: Repeater-Builder@yahoogroups.com >Subject: Re: Re: RE:[Repeater-Builder] Re: Duplexers > >Well skin effect varieswith frequency, there for the R is higher with >frequency. I is constant,but R is not, so your power lost will vary with >frequency because of I^2R andskin effect. This is why larger diameter solid >hardline has less lossthan smaller. > > > >On 8/26/07, RonWright <[EMAIL PROTECTED]>wrote: >Jesse, > >You are correct and this is why some large coax have hollow tubing for >theinter conductor. Due to skin effect the current density on the outer part >ofthe conductor is higher. > >But if a coax has 10 watts with a said current at one freq and the same >currentat a higher freq the losses will be different. This was my point. > >73, ron, n9ee/r > >>From: Jesse Lloyd <[EMAIL PROTECTED]> >>Date: 2007/08/26 Sun PM 02:34:41 CDT >>To: Repeater-Builder@yahoogroups.com >>Subject: Re: RE: [Repeater-Builder] Re: Duplexers > > >> >>I^2R losses do change with frequency because of the skineffect. >> >> >> >>On 8/26/07, Ron Wright <[EMAIL PROTECTED]>wrote: >>Jeff, >> >>The low shield coverage is one reason I do not buy cableswith pre-installed >>connectors unless I know the cable...not just because itsays RG8 or whatever. >> >>I used a piece of 50 ft RS RG8 w/pre-installed connectors fora few years and >>finally cut it for other purposes and was so disappointed I hadpurchased such >>a cable with so little shield. >> >>Guess works
RE: Re: RE: [Repeater-Builder] Re: Duplexers
Jesse is right about skin effect being greater at higher frequencies on the same cable. But current will be less also as resistance increases. Current is a function of resistance for a given amount of power applied. Coax loss is mainly due to resistive loss up thru VHF. Dielectric loss also starts to come into play as you get into UHF and above. The higher the frequency the higher the resistance is in the cable conductor due to skin effect. Losses due to radiation are very low and almost immeasurable in most cases. Open wire line will radiate very little if it is properly balanced even when SWR is very high. The reason open wire line has less loss than coax cable is that the impedance is generally higher. The higher the impedance the lower the current for a given amount of power thus the lower the I squared R loss in the line. (Note that the "R" in I squared R loss is talking about the resistive loss in the cable and not the impedance of the cable) A 75 ohm coax cable with the same approximate size as a 50 ohm cable will have lower loss than the 50 ohm cable because of the lower current in the cable. (Less I squared R loss) In coax cable the loss is mainly determined by the center conductor size/surface area. Current flow is very shallow at RF frequencies so it does not matter if center conductor is solid or tubing. Tubing gets more economical with larger sizes. As the center conductor size is increased in a cable the shield must also be increased in order to maintain the same center conductor to shield diameter ratio which maintains the impedance. If the center conductor size was increased without changing the outer conductor the impedance of the cable would be lower. Losses due to SWR on the line are due to part of the signal being reflected and re-reflected and suffering additional resistive losses as it makes the second (and multiple) trip up and down the line. This is not to be confused with mis-match loss. Mis-match loss is not a loss attributable to cable loss but it is a loss that comes about because the transmitter does not see a flat 50 ohms and does not transfer full power because the loading has changed due to the impedance mis- match. This type of loss is what is seen due to poor connectors. Often connector mis-match loss is confused with direct loss in the connector. Direct loss produces heat as does all I squared R loss. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Sunday, August 26, 2007 3:32 PM To: Repeater-Builder@yahoogroups.com Subject: Re: Re: RE: [Repeater-Builder] Re: Duplexers Well skin effect varies with frequency, there for the R is higher with frequency. I is constant, but R is not, so your power lost will vary with frequency because of I^2R and skin effect. This is why larger diameter solid hardline has less loss than smaller. On 8/26/07, Ron Wright <[EMAIL PROTECTED]> wrote: Jesse, You are correct and this is why some large coax have hollow tubing for the inter conductor. Due to skin effect the current density on the outer part of the conductor is higher. But if a coax has 10 watts with a said current at one freq and the same current at a higher freq the losses will be different. This was my point. 73, ron, n9ee/r >From: Jesse Lloyd <[EMAIL PROTECTED] <mailto:ve7lyd%40gmail.com> > >Date: 2007/08/26 Sun PM 02:34:41 CDT >To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> >Subject: Re: RE: [Repeater-Builder] Re: Duplexers > >I^2R losses do change with frequency because of the skin effect. > > > >On 8/26/07, Ron Wright <[EMAIL PROTECTED] <mailto:mccrpt%40verizon.net> > wrote: >Jeff, > >The low shield coverage is one reason I do not buy cables with pre-installed connectors unless I know the cable...not just because it says RG8 or whatever. > >I used a piece of 50 ft RS RG8 w/pre-installed connectors for a few years and finally cut it for other purposes and was so disappointed I had purchased such a cable with so little shield. > >Guess works for CB and Ham HF bands, but really not good for VHF/UHF. The same can be said for many PL259 connectors and adapters. > >73, ron, n9ee/r > >>From: Jeff DePolo <[EMAIL PROTECTED] <mailto:jeff%40depolo.net> > >>Date: 2007/08/26 Sun PM 12:59:45 CDT >>To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> >>Subject: RE: [Repeater-Builder] Re: Duplexers > >> >>Coax leakage is different than currents flowing on the shield though... >> >>I remember having some RG8 from Radio Shack with braid openings that you >>could probably fit a pencil through. >> >>> Some of the cheaper coax brands have less than about 70% shielding >>> making them pretty le
Re: Re: RE: [Repeater-Builder] Re: Duplexers
Well skin effect varies with frequency, there for the R is higher with frequency. I is constant, but R is not, so your power lost will vary with frequency because of I^2R and skin effect. This is why larger diameter solid hardline has less loss than smaller. On 8/26/07, Ron Wright <[EMAIL PROTECTED]> wrote: > > Jesse, > > You are correct and this is why some large coax have hollow tubing for the > inter conductor. Due to skin effect the current density on the outer part of > the conductor is higher. > > But if a coax has 10 watts with a said current at one freq and the same > current at a higher freq the losses will be different. This was my point. > > 73, ron, n9ee/r > > >From: Jesse Lloyd <[EMAIL PROTECTED] > > >Date: 2007/08/26 Sun PM 02:34:41 CDT > >To: Repeater-Builder@yahoogroups.com > >Subject: Re: RE: [Repeater-Builder] Re: Duplexers > > > > > >I^2R losses do change with frequency because of the skin effect. > > > > > > > >On 8/26/07, Ron Wright <[EMAIL PROTECTED] > wrote: > > >Jeff, > > > >The low shield coverage is one reason I do not buy cables with > pre-installed connectors unless I know the cable...not just because it says > RG8 or whatever. > > > >I used a piece of 50 ft RS RG8 w/pre-installed connectors for a few years > and finally cut it for other purposes and was so disappointed I had > purchased such a cable with so little shield. > > > >Guess works for CB and Ham HF bands, but really not good for VHF/UHF. The > same can be said for many PL259 connectors and adapters. > > > >73, ron, n9ee/r > > > >>From: Jeff DePolo <[EMAIL PROTECTED] > > >>Date: 2007/08/26 Sun PM 12:59:45 CDT > >>To: Repeater-Builder@yahoogroups.com > >>Subject: RE: [Repeater-Builder] Re: Duplexers > > > >> > >>Coax leakage is different than currents flowing on the shield though... > >> > >>I remember having some RG8 from Radio Shack with braid openings that you > >>could probably fit a pencil through. > >> > >>> Some of the cheaper coax brands have less than about 70% shielding > >>> making them pretty leaky to rf. It works just killer for adding a > >>> little extra signal horse-power to a carrier current broadcast > >>> station. Radiax without trying... > >> > >>You could run it up the tower and have a really long antenna. Lots of > >>capture area ;-) > >> > >> > > > >Ron Wright, N9EE > >727-376-6575 > >MICRO COMPUTER CONCEPTS > >Owner 146.64 repeater Tampa Bay, FL > >No tone, all are welcome. > > > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. > > >
Re: Re: RE: [Repeater-Builder] Re: Duplexers
Jesse, You are correct and this is why some large coax have hollow tubing for the inter conductor. Due to skin effect the current density on the outer part of the conductor is higher. But if a coax has 10 watts with a said current at one freq and the same current at a higher freq the losses will be different. This was my point. 73, ron, n9ee/r >From: Jesse Lloyd <[EMAIL PROTECTED]> >Date: 2007/08/26 Sun PM 02:34:41 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: RE: [Repeater-Builder] Re: Duplexers > >I^2R losses do change with frequency because of the skin effect. > > > >On 8/26/07, Ron Wright <[EMAIL PROTECTED]> wrote: >Jeff, > >The low shield coverage is one reason I do not buy cables with pre-installed >connectors unless I know the cable...not just because it says RG8 or whatever. > >I used a piece of 50 ft RS RG8 w/pre-installed connectors for a few years and >finally cut it for other purposes and was so disappointed I had purchased such >a cable with so little shield. > >Guess works for CB and Ham HF bands, but really not good for VHF/UHF. The >same can be said for many PL259 connectors and adapters. > >73, ron, n9ee/r > >>From: Jeff DePolo <[EMAIL PROTECTED]> >>Date: 2007/08/26 Sun PM 12:59:45 CDT >>To: Repeater-Builder@yahoogroups.com >>Subject: RE: [Repeater-Builder] Re: Duplexers > >> >>Coax leakage is different than currents flowing on the shield though... >> >>I remember having some RG8 from Radio Shack with braid openings that you >>could probably fit a pencil through. >> >>> Some of the cheaper coax brands have less than about 70% shielding >>> making them pretty leaky to rf. It works just killer for adding a >>> little extra signal horse-power to a carrier current broadcast >>> station. Radiax without trying... >> >>You could run it up the tower and have a really long antenna. Lots of >>capture area ;-) >> >> > >Ron Wright, N9EE >727-376-6575 >MICRO COMPUTER CONCEPTS >Owner 146.64 repeater Tampa Bay, FL >No tone, all are welcome. > > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
