Bob, it starting to sound like it really is an antenna problem, being
unable to receive beyond few miles. You've said that people can hear
you OK, but an antenna working at 25% efficiency will still put out
about 2 watts from your A200 (theoretically good to several hundred
miles). Modern panel-mount receivers or base stations with
audio-leveling circuitry reading you loud and clear means nothing.
But 75% loss of received signal is going to give all the symptoms
you've been reporting.
I've not seen an internal adj. on any comm that that requires
in-flight tweaking. The improved reception could be due to differing
daily atmospherics, or merely reconnecting a poor coax connector.
Any field strength meter you can borrow can compare your xmit output
to someone's else's of similar pwr and at same distance from the
antenna. Does anybody's base station have a built-in signal strength
meter? Many do.
Re grounding, just about anything's possible with avionics, but DC
grounding and RF ground are two different things entirely. There's no
shorts or opens in the antenna coax I hope....
Regards,
Fred F., A063
"Bob.Harrison" wrote:
>
> Hi! To all those who tendered advice re my ICOM AC 200 Transcom.
> Well today came and went. We went to Wolverhampton to see the "oracle"
> there,
> having disconnected one end of the Mag switches shielding grounds for which
> there was no improvement.
> He ....... could only bench test the damn thing, in spite of saying bring
> the
> 'plane. He told me what I already knew.... that the set was set up as the
> maintenance manual recommends( which I already knew!)
> Under pressure he decided to put his screw driver in the squelch adjust hole
> tried a slight adjustment (NOT having noted where it bloody was before he
> started!) and we re-installed it in the a/c. We were getting Wolverhampton
> Radio (who have an Icom Base!) fives at 10 miles and very faintly at 15
> miles. So we though we had improved the thing.
> Got back to Wickenby regularly calling them but only got reception in the
> circuit!
> Just tell me ,Chaps, why isn't it possible to make a slave harness and plug
> it into the a/c with co-ax extension piece to the a/c antenae to enable the
> set to be put on the engineers knee whilst in flight to ajust the damn thing
> as the transmissions
> are recieved or NOT as the case may be?
> Perhaps a mechanical engineers' solution for some reason doesn't apply to
> radios?!
> He also has suggested that all equipment or any structural ground tails
> should be taken direct to the battery.?
> Regards
> Bob Harrison
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