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: [email protected]
>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] [mailto: Repeater-
>> [EMAIL PROTECTED] On Behalf Of Ron Wright
>> Sent: Sunday, September 02, 2007 6:46 AM
>> To: [email protected]
>> 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: [email protected]
>> >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] [mailto:Repeater-
>> >> [EMAIL PROTECTED] On Behalf Of Ron Wright
>> >> Sent: Saturday, September 01, 2007 8:49 AM
>> >> To: [email protected]
>> >> 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: [email protected]
>> >> >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] [mailto: Repeater-
>> >> >> [EMAIL PROTECTED] On Behalf Of Ron Wright
>> >> >> Sent: Friday, August 31, 2007 7:12 AM
>> >> >> To: [email protected]
>> >> >> 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: [email protected]
>> >> >> >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] [mailto: Repeater-
>> >> >> >> [EMAIL PROTECTED] On Behalf Of Ron Wright
>> >> >> >> Sent: Thursday, August 30, 2007 10:48 AM
>> >> >> >> To: [email protected]
>> >> >> >> 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: [email protected]
>> >> >> >> >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.
