Thread: SWR - wtf?
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Old June 27th 05, 11:31 PM
Frank Gilliland
 
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On Mon, 27 Jun 2005 13:48:34 -0400, "john d"
wrote in :

So ... I have an older CB - Cobra 21 LTD Classic with weather stns etc. ...
a 102" Shakespeare Antenna - 18' of cable - and this
http://cgi.ebay.com/ws/eBayISAPI.dll...tegory=48 699

(not advertising it just using it for the picture) ... Anyone know how to
use the Land Matic LM-50 ... it was pretty cheap like $16.00 Cdn I think - I
got it new but it didn't have any instructions - I don't even know the
wattage I should be setting it on. I'm assuming that the antenna goes into
the back on the side with ANT and the radio goes into the side marked
TRANS - but I'm not sure - does anyone know of any webpages that provide
some sort of instructions on how to use SWR meters?



They're pretty easy. The cables hook up just like you figured.

Start by setting your radio to ch 18 AM (not SSB). Switch the matcher
off (you won't even need it), set the power switch for 10W, the top
switch to FWD CAL and the SWR/CAL switch to CAL. Key up and adjust the
slider so the meter reads full scale. Then unkey, switch the SWR/CAL
to SWR, key up again and read the meter. Adjust your antenna to get
the lowest SWR -- the lower the better. Then check SWR at both ends of
the band. An SWR of 2:1 or lower across the band is fine. If you can't
get it below 3:1 on any channel then there's something wrong with your
system, like a bad ground or coax cable.

If you want to play with the matcher, make your initial adjustments
while listening to the noise in receive. Start with TUNE all the way
left and sweep LOAD until the noise peaks. Check SWR. Then turn TUNE a
little bit to the right, sweep through LOAD again for the noise peak,
and check SWR again. If the SWR is better then keep going through the
process until it starts getting worse. Eventually you will find a spot
for both knobs that work to give you the best SWR. But remember that
when the matcher is tuned it's tuned very sharply to that freq -- you
will need to retune the matcher every time you move more than a couple
channels away.




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