Gradual Loss of RX Signal

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  • Problem
  • Updated 3 months ago
Flex 6300  SN: 1015-4175-6300-2622  SmartSDR V2.0.19

My rx signal slowly disappears and the only way I have found to get it back to normal is to trip the tx.  It is almost as if it is a sticking relay.  It is also intermittent and variable in loss.  It can happen quite often, or go for some time without causing a problem.  It does it on all antennas. The panadaptor also varies and will disappear below the -140 line when it is very bad.      

I have done a factory reset, uninstalled SmartSDR etc and reinstalled.

Any ideas? 

73 Andy F5VAI  (G3HCU)     
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Andy F5VAI

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Posted 7 months ago

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NM1W

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Is this on all bands, or just low bands? eg, 160/80?
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Andy F5VAI

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On all bands, I am on 20m at the present time and it is bad 
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Andy F5VAI

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I think I have found a problem with the ATU.  With the ATU in circuit the SWR is very high and yet my real SWR is about 1:5.  I guess the best idea is to remove the ATU and see whether that cures the problem.   
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Scott N8UMW

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No issues with SWR on mine and it still does. It still could be a relay on the ATU though.
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Scott N8UMW

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I have the same issue. The only difference being that it only happens when I have the attenuate/preamp switched on. It drops down to -145 to -150 and when I hit TX, it comes back up to -130 to-135. Within a few minutes, it drops again.
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Scott N8UMW

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I noticed it doesn't appear to happen on 6 meters. It does happen on 10 to 160 to varying degrees, and on both antenna inputs, with or without the ATU enabled. Never happens with attenuation / preamp turned off.
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Scott N8UMW

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I tried this on three different antennas, all connected directly to the radio, and got the same results. This rules out any connections or issues with the amp, tuner, meter, and coax jumpers.
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WH6HI - Pat

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Call and open trouble ticket. I believe that the TR switch is solid state and could be failing.

Pat
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Ross - K9COX

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I had the same issue with my 6300...was told that I was nuts. It is gone now.
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Scott N8UMW

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Did you switch to a different model?
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Andy F5VAI

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I have found the problem and it is not the Flex!  My rig etc is remoted in my garage, so today I stripped everything down and isolated items one by one.  It turns out the fault was most bizarre!  It was a right-angle PL259 adaptor!  In all my 52 years of AR I have never come across this problem.  I have now removed all right-hand PL259 adaptors as you can imagine. 

Why it should show up as a gradual loss is in the RX path, and only when using the ATU seems to be very strange.  Anyway I am pleased to know it is not the Flex and it is a salutary lesson!     
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Scott N8UMW

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Interesting. I did have that exact same problem with a 90 recently on another rig setup, but none on the Flex.
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Bill -VA3WTB

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Andy, good work. I knew this was not a problem with your radio, but I had no answers.
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Craig Williams

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I bought a lot of new, Communist China, Rt angle PL259's and 1/2 of them were bad or intermit. A friend of mine had an old mil spec one from 20 years ago and it had turned bad. Very strange considering no moving parts on the center core.
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Greg, N6GD

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Andy, has your TR problem come back?  I ask because I am having the same problem with my 6500.  Received signals will disappear after a transmission (usually in DIGU mode) and will only be restored by switching to transmit a short burst of CW in a different slice.
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Paul

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This may or may not help, but I have had a similar problem. It turned out to be a 'rectifying break' in one conductor of the twin feeder to my full wave 160m wire loop. It seemed fine on tx (ssb) but rx would gradually fade and somtimes many phantom am signals would appear. Prior to tracing the cause I could temporarily cure it by transmitting a brief carrier. I only traced it after a careful visual inspection - it had clearly been arcing slightly on tx as the insulation was slightly melted. I wonder if elbow connectors have a tendency to do this at the point of the 90 degree bend. Good luck with tracing the cause.