[ICOM] TX Problem IC970A 2.4 GHZ module

[Gary]

I have this problem with my 1.2Ghz module. I'm still troubleshooting but it's looking like a bad PA module. The effort is a major pain without a schematic. I've asked for a
schematic copy from every forum I could find but nobody replied. Not even Icom America or Scott Malcolm had literature on the 970 option modules. Doug is the first in my
experience to even admit to having one of the 2.4Ghz modules, I hope he has literature to go with it. Good luck Doug.
Gary

"NICK.WALLACE" wrote:

> Hi All,
>
> I am posting this on behalf of Doug VK4OE. We were wondering if anybody else had encountered the same problem which is as follows. I will pass any info received onto him.
>
> Thanks in anticipation.
>
> Nick   ZL1IU
>
> >From Doug.....
>
> Just to save you some typing, I'll describe again what I am
> experiencing, which only relates to the 2.4 GHz module in transmit
> mode....the other features of this excellent radio are currently working
> well.
>
> The problem is one of "fading" transmitter power as something obviously
> is heating up in the 2.4 GHz transmit path.  The scenario is that the
> radio has been switched off for a time long enough for it to cool to
> room temperature internally, then it is powered up and switched to 2.4
> GHz transmit mode (continuous, e.g. FM).  The RF output control is set
> to maximum.
>
> It transmits the full 1 Watt for 2 to 3 minutes (or 5 minutes if ambient
> temperature is cooler) then, over a period of about a minute, the
> transmitter power gradually falls away to around 50 mW.  Whilst this is
> happening the ALC gradually climbs to a high level.
>
> Momentarily switching to RX or switching the whole radio off briefly
> then on again do not lead to a return to 1 W output.  Only powering off
> and letting the whole radio cool for an hour or so leads to a return to
> 1 W output, and being ready for the whole fault sequence to occur again.
>
> It is conjectured that there is something wrong with one or more
> component in the RF path between the TX amplifier and the antenna
> connector, something which is thermally active.  Has anyone else had a
> similar problem and found the solution?
>
> Thank you
>
> ----
> 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/