"Reg Edwards" wrote in news:dmf4fr$4cu$1
@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com:


"Saandy wrote

you can't measure SWR.
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I am pleased you agree with me.

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You can CALCULATE the SWR using the formula.
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But of what use is the SWR it after you have calculated it?

To what transmission line does it apply? Where is it? What are the
locations of max-volts and min-volts? It does NOT apply to the line
between transmitter and antenna. I suggest it exists only in your
imagination. ;o)

Heh heh. I remember one time a friend of mine was wailing that his fancy
new outdoor 2m antenna wasn't working as good as the indoor mag-mount on
a pie plate that he had been using.

I asked about his installation and he informed me that the antenna was
properly installed and that the SWR was 1 to 1. So I inquired further.
He was using a bridge to measure reflected power at the transmitter. And
there really wasn't any. Then I asked him what he was using for
transmission line. Turns out it was about 75 feet of cheap RG58. So I
told him to take it off the antenna and see what the bridge said with no
antenna. It climbed all the way to 1.2 to 1. In short, the coax was
simply eating the power. Changing it out to better quality line proved
to be the answer there.

SWR is so overrated. I'm in the process of putting together a modest
balcony-based HF station. I'm much more interested in the efficiency of
loading coils than in actual SWR on the coax. A 3-to-1 SWR on coax is
meaningless at 80 meters. It adds only a fraction of a decibel to
losses, even in RG58. But your transmitter might not like the complex
load it is seeing at the end of that coax, hence the utility of a tuning
device. Back in the day, I used to just ignore such issues because my
transmitters had pretty good output tuning networks. But with the advent
of broadbanded solid state finals, it is necessary to match the radio to
the transmission line's complex input impedance.

--
Dave Oldridge+
ICQ 1800667