[ICOM] AT500 problem on 18 and 24 Mhz

[Frank A. Ellis]

The problem with the AT-100/500 is that you only get
one preset frequency position for 18/21 MHz and 24/28
MHz. For instance, if you set the presets to
frequencies in the 21 MHz and 28 MHz bands, then when
you change bands, the tuner will go to those presets
every time by default, even if you are actually on 18
or 24 MHz.

However, once you transmit (on 18 or 24 MHz, in this
example), the reflectometer will detect the mismatch,
and the tuner will dynamically tune to the actual
frequency being used.

It's inconvenient, but normal.

73 Frank W3UHF

--- Gary Fiber <gfiber at comcast.net> wrote:

> 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
> >
> >----
> >Your Moderator: Dick Flanagan K7VC,
> icom-owner at mailman.qth.net
> >Icom Users Net: Sundays, 1700Z, 14.316 MHz
> >Icom FAQ: http://www.qsl.net/icom/
> 
> Gary Fiber K8IZ
> GROL PG-19-6691
> Washington State Resident
> 
> 
> ----
> Your Moderator: Dick Flanagan K7VC,
> icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
> 



		
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