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Gary Schafer
 
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Default How to use a simple SWR meter and what it means to your VHF

On Fri, 21 Nov 2003 20:12:32 +0100, "Meindert Sprang"
wrote:

"Gary Schafer" wrote in message
.. .
You need to tune your tuner only to provide the proper impedance match
to your transmitter. A 50 ohm SWR bridge at the transmitter will tell
you when you have achieved that.

Swr on the feed line matters very little.

snip
If you have an antenna and a feed line that has a 3:1 SWR on it at the
transmitter end the transmitter will not perform properly. If you
place a matching device (tuner) between the transmitter and that feed
line and tune it so that the transmitter sees a pure 50 ohms, then the
transmitter is completely happy.

But the feed line still has that same 3:1 SWR on it. 25% reflected
power from the antenna.


You obviously don't understand how this works. The combination of antenna
and feedline presents a certain impedance at the end of the feedline. What
the tuner does is transform the 50 Ohm on the TX side to the impedance on
the feedline. And when this all matches, there is no SWR. Neither on the TX
side of the tuner, nor on the feedline side.

Meindert
pe1grv



Wann bet? :)

Try it some time. Tune the tuner so there is no SWR at the
transmitter. Then place the SWR meter between the tuner and the
transmission line. You will still see the same SWR that you started
with!

There is nothing you can do at the transmitter end of the transmission
line to change the impedance or the SWR on the transmission line. That
can only be done at the antenna end of the line.

Regards
Gary