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] <gaschafer%40comcast.net>> > >Date: 2007/09/02 Sun PM 08:29:08 CDT > >To: [email protected] <Repeater-Builder%40yahoogroups.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: > >> [email protected]<Repeater-Builder%40yahoogroups.com>[mailto: > Repeater- > >> [EMAIL PROTECTED] <Builder%40yahoogroups.com>] On Behalf Of Ron > Wright > >> Sent: Sunday, September 02, 2007 6:46 AM > >> To: [email protected]<Repeater-Builder%40yahoogroups.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] <gaschafer%40comcast.net>> > >> >Date: 2007/09/01 Sat PM 08:48:03 CDT > >> >To: [email protected]<Repeater-Builder%40yahoogroups.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: > >> >> [email protected]<Repeater-Builder%40yahoogroups.com>[mailto: > Repeater- > >> >> [EMAIL PROTECTED] <Builder%40yahoogroups.com>] On Behalf Of > Ron Wright > >> >> Sent: Saturday, September 01, 2007 8:49 AM > >> >> To: [email protected]<Repeater-Builder%40yahoogroups.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] <gaschafer%40comcast.net> > > > >> >> >Date: 2007/08/31 Fri PM 05:59:28 CDT > >> >> >To: > >> >> >[email protected]<Repeater-Builder%40yahoogroups.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: > >> >> >> [email protected]<Repeater-Builder%40yahoogroups.com>[mailto: > Repeater- > >> >> >> [EMAIL PROTECTED] <Builder%40yahoogroups.com>] On Behalf Of > Ron Wright > >> >> >> Sent: Friday, August 31, 2007 7:12 AM > >> >> >> To: > >> >> >> [email protected]<Repeater-Builder%40yahoogroups.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]<gaschafer%40comcast.net> > > > >> >> >> >Date: 2007/08/30 Thu PM 07:39:21 CDT > >> >> >> >To: > >> >> >> >[email protected]<Repeater-Builder%40yahoogroups.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: > >> >> >> >> [email protected]<Repeater-Builder%40yahoogroups.com>[mailto: > Repeater- > >> >> >> >> [EMAIL PROTECTED] <Builder%40yahoogroups.com>] On Behalf > Of Ron Wright > >> >> >> >> Sent: Thursday, August 30, 2007 10:48 AM > >> >> >> >> To: > >> >> >> >> [email protected]<Repeater-Builder%40yahoogroups.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]<gaschafer%40comcast.net> > > > >> >> >> >> >Date: 2007/08/29 Wed PM 09:23:57 CDT > >> >> >> >> >To: > >> >> >> >> >[email protected]<Repeater-Builder%40yahoogroups.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. > >> >> >> > >> >> >> > >> >> >> > >> >> >> > >> >> >> > >> >> >> > >> >> >> > >> >> >> 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 > >> >> > >> >> > >> >> > >> > > >> > > >> > >> > >> 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. > > > >
