I agree that varying any one of the three parameters will result in
variation in received signal strength, assuming that VSWR affects
transmitter output (not always true). However, they are all independent
of the others. My comments are embedded below. Note that by Feedline
Loss, I am referring to the intrinsic loss of the line, not the absolute
power lost.
> > Gain is not VSWR is not Feedline Loss. They are three completely
> separate
> > issues. 73, Ward N0AX
>
> I'd like to try to simplify this for a non-engineer type such as I.
>
> 1. If there is feedline loss then less signal gets from the TX output to
> the antenna (and thus
> to the listener -- you).
> 2. If there is feedline loss then less signal gets from the antenna to the
> RX input (and thus
> to the listener -- me).
1 and 2 are the same statement, of course. The solution is to use a
lower-loss cable, whether or not you change antenna impedance or gain.
> 3. If there is high VSWR then less signal gets to the antenna because the
> TX (if solid state
> and circuit-protected) automatically lowers the power output.
This is a transmitter problem, not a gain/VSWR/feedline loss problem. The
solution is to use a tuner (also known as a "transmitter fooler") to allow
the transmitter to run at rated output power. This does not affect
feedline loss or line VSWR at all. As a matter of fact, by using the
tuner without changing the antenna gain or impedance, the absolute amount
of power lost in the line will *increase*, yet the received signal
strength will also increase! Hmmm...
> 4. If there is high VSWR then feedline loss may increase due to heating
> and radiation and
> thus less signal gets to the antenna and directed towards the intended
> receiver.
Nope, sorry. Heating does not occur to any meaningful degree except in
the most extreme cases. Feedline radiation only occurs because of
insufficient shield coverage (leakage) or RF currents flowing on the
outside of the shield. Neither has anything to do with any of the three
parameters in question.
> 5. The more gain the antenna has the more the TX signal is magnified
> (after adjustments
> measured in 1, 2, 3 & 4 above).
> 6. The more gain the antenna has the more the RX signal is magnified
> (after adjustments
> measured in 1 & 2 above).
Agreed. This is independent of VSWR and feedline loss, however.
> Do I finally have this clear? :-)
>
> Thanks & 73, DavidC AA1FA
>
Not really - I advise a trip to the store for an ARRL Antenna Book and a
copy of Walt Maxwell W2DU's "Reflections". Good reading in the ol' summer
hammock.
"The absorption is high,
and low bands ain't cookin'."
Sorry, Mr. Gershwin...
It's true that one component of a system can affect the performance of
others in the same system, but that doesn't mean that the two are
necessarily dependent on each other.
73, Ward N0AX
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