[ICOM] AT500 problem on 18 and 24 Mhz

[Gary Fiber]

Bert,

The AT-500 can have a couple of preset positions. Many times when you 
do the preset the capacitors will be almost fully open. So you might 
remove the top and have a look. The caps should be a bit more meshed.
I used to tell people to connect a known dummy load and do the 
presets into that to get to a known starting place. Then reconnect 
the antennas and do over the presets. I also recommended they use a 
SWR meter not the LED's within the unit. It worked for many operators.
Remember the AT-500 will show you a faulty antenna pretty quickly. I 
once had an antenna that would be fine and then go into trouble after 
a few minutes of transmitting.
Up on inspection one snowy evening on the tower top I found the coax 
braid to be corroded to a very black color. Replacing the coax solved 
the problem.

Hope some of this helps

Gary K8IZ

At 07:13 AM 1/7/2006, you wrote:
>I have problems with my AT500 on 18 and 24 Mhz bands.
>
>This is the setup: IC-765, IC-2KL and AT500. 3 antennas are connected to the
>AT500. Ant1 - yagi for 14/21/28 Mhz,
>Ant2 - Carolina Windom for WARC bands+7+3.5 Mhz, Ant3 - Inverted L for 1.8
>Mhz.
>
>When switching the trx to 18 and 24 Mhz bands, AT500 in AUTO positon, the
>signal/noise drops drastically and only very strong stations can be heard.
>It seems like the AT500 is not tuning properly.
>
>If I manually switch the AT500 to another band, trx is still on 18 or 24
>Mhz, using the Windom, e.g. 3.5 Mhz the signals are back to normal or much
>higher than when in the AT500 is in the AUTO position.
>
>I have gone through the preset procedure and checked all connections and
>everything seems to be OK. Still, the AT500 does not tune properly on 18 and
>24 Mhz, which are the only two bands where you have two bands in the same
>band switch position, i.e. 18/21 and 24/28. Any suggestions would be much
>appreciated.
>
>73 Bert, VE3OBU
>
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Gary Fiber K8IZ
GROL PG-19-6691
Washington State Resident