Com Standing Wave Ratio?

Standing wave ratio is a measure of how efficiently power from the
radio is being coupled into the antenna. A high standing wave ratio
is a result of impedence mismatch between any or all of the radio,
the coax and/or the antenna. Any power that is reflected back (not
coupled into the antenna) will travel back up the coax to the radio,
and, since it is out of phase with the forward power, will produce
a standing wave on the line, even on the outside of the coax.

Needless to say this is unsatisfactory and these standing waves can
radiate into other nearby equipment. Wet coax and bad connections
are the usual cause especially in a setup that was previously working.
One culprit is the coax balun... and/or the antenna connections
themselves. If your coax and connections are old you are better off
just replacing them all.

Thanks both Tauno and ktbr.

Second question. After we returned home, I swapped the KX155's returning
them to the original slots. #1 KX155 (the wet one) didn't give us any
pitching problem with the auto pilot, however, thinking of coax, conection,
or antenna problems, we had a local tower operator complain about very
staticy transmisions. Reception was fine, Nav functions were fine.

#2 transmitted much better however only #1 is coupled so we couldn't check
the #2 radio/tray/coax/antenna against the autopilot.

Next step to swap coax antenna leads?

Thanks again,
Jim

As I stated, if the coax is old (I'm talking like 10.. 15 or more)
years... just replace it. I don;t think I'd waste a lot of time trying
to troubleshoot old coax. Don't forget about the balun to the NAV
antenna, it can get lossy when old and degrade NAV reception.

A high VSWR can ultimately damage the transmitter as well, since that
reflected power if coming back into the RF power stage where it will
increase the operating temperature and ultimately cause failure.

Jim B wrote:
Thanks both Tauno and ktbr.

Second question. After we returned home, I swapped the KX155's returning
them to the original slots. #1 KX155 (the wet one) didn't give us any
pitching problem with the auto pilot, however, thinking of coax, conection,
or antenna problems, we had a local tower operator complain about very
staticy transmisions. Reception was fine, Nav functions were fine.

#2 transmitted much better however only #1 is coupled so we couldn't check
the #2 radio/tray/coax/antenna against the autopilot.

Next step to swap coax antenna leads?

Thanks again,
Jim

Replacing the coax will have to wait until annual time when we can pull the
interior and the headliner. We're planning on changing the headliner
anyway, so the ceiling will be open at that time. Meanwhile we'll keep a
record of what occurs, swap antennas, and try to follow the problem.
Thanks
Jim

Also check that the radio is going ALL the way in. The lip on the rack
should tocuch the faceplate. Sometimes the faceplate is hitting the
mounting rails and not going ALL the in and the atenna connector is
make a poor connection.



On Feb 26, 10:52�am, "Jim B" wrote:
Replacing the coax will have to wait until annual time when we can pull the
interior and the headliner. *We're planning on changing the headliner
anyway, so the ceiling will be open at that time. *Meanwhile we'll keep a
record of what occurs, swap antennas, and try to follow the problem.
Thanks
Jim

Jim B wrote:
Thanks both Tauno and ktbr.

Second question. After we returned home, I swapped the KX155's returning
them to the original slots. #1 KX155 (the wet one) didn't give us any
pitching problem with the auto pilot, however, thinking of coax, conection,
or antenna problems, we had a local tower operator complain about very
staticy transmisions. Reception was fine, Nav functions were fine.

#2 transmitted much better however only #1 is coupled so we couldn't check
the #2 radio/tray/coax/antenna against the autopilot.

Next step to swap coax antenna leads?

Thanks again,
Jim

You should take the wet (and now hopefully dry again) unit
to a shop for a checkout. Swimming can create weird effects
in electronics.

I once repaired a handheld COM, which had been diving, and
all the glass-tube diodes were broken, as electrolytic corrosion
ate the wire at the more positive end, and water got into
the glass encapsulation.

--

Tauno Voipio (PA28RT-201T, OH-PYM)
tauno voipio (at) iki fi