In the end it is transferring power to the antenna that counts. Unless the
VSWR is awfully high and/or the line length is very long I think it is quite
stuffiest to put a tuning network at the station so the transmitter is happy
and then start sending. You most likely ( and the folks you contact) will
never know that your antenna is neither resonant nor matched at the
frequency you are operating -- and you signal will not be noticeably
impaired either.
Tod, KØTO
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Brown
> Sent: Tuesday, November 15, 2005 3:50 PM
> To: Tower Talk List
> Subject: Re: [TowerTalk] Understanding Antenna Impedance Measurements
>
> On Tue, 15 Nov 2005 15:38:28 -0700, Tod wrote:
>
> >Those values look like they are within about 2% of expected
> values for
> >the R and within 20% or so on the X. Is the analyzer accuracy any
> >better than that if there is NO coax between the load and
> the analyzer?
>
> What Jim Lux has shown by cranking the numbers is that when
> the VSWR is small, the effect of the transmission line is
> small. That would be true whether the line was a half wave or
> not. But when it's a half wave length, it has almost the
> effect of moving the analyzer to the antenna terminals AT
> THAT FREQUENCY.
> I say "almost" because the loss in the line will reduce the
> VSWR slightly (but VERY little on topband).
>
> Tom can tell you a lot more about analyzer errors. But
> consider this -- it isn't really possible to stick the
> analyzer at the antenna and read it without a very tall
> ladder, and your presence next to the analyzer will detune it
> a bit. There's also the interaction of the antenna with the
> coax. Other errors
> -- the analyzer has some finite input R and C. For small
> VSWR, neither mean much, especially at 2 MHz, but they sure
> do at higher frequencies and high VSWR. As I recall, W4EF
> said that the AEA CIA-HF has input Z on the order of 10-12K
> in parallel with 12 pF. That's an older box, and the new one
> may or may not be better.
>
> Jim K9YC
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers",
> "Wireless Weather Stations", and lot's more. Call Toll Free,
> 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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