[wxsig] Signal being detected with no signal

[Mark Patton]

Over the past few months my T238+ has been up and running pretty well.  
One thing that I've noticed is that for periods of time from 45 minutes 
to 2 hours, the T238+ will not transmit.  This is intermittent and will 
happen sometimes several times per day, sometimes not for several days.

The other day when it was not transmitting, the yellow LED (showing a 
received signal) was stuck on - even though there was no input signal.  
I have the radio on a switch controlled by the T238+ and the radio was 
not powered at the time.  To test it further, I unplugged the radio from 
the T238+ but the LED stayed on.  I touched the input plugs with my 
fingers (thinking that it may induce noise) but the LED still stayed 
on.  Under "normal" circumstances the LED will remain off between 
transmissions with the radio off.  The T238+ won't transmit if it thinks 
the channel is busy (ie yelllow LED is on).

Unfortunately, the T238+ is remotely mounted in a box outside my house 
so it is difficult to get to and to monitor the LED's or to probe around 
when an issue like this comes up.

The only thing I can think of is that the filter section between the 
audio in and the modem chip may be going into oscillation or is locking 
on to some noise from somewhere. The cables between the T238+ and the 
radio are short and are shielded.

Has anyone else seen anything like this?  Does anyone have any ideas of 
things I can try to eliminate the problem?

Mark