Gradual Loss of RX Signal

Andy F5VAI

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)     

NM1W

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

Andy F5VAI

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

Andy F5VAI

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.   

Scott N8UMW

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.

Scott N8UMW

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

Scott N8UMW

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.

Scott N8UMW

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.

Patrick

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

Ross - K9COX

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

Scott N8UMW

Did you switch to a different model?

Andy F5VAI

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!     

Scott N8UMW

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

Bill -VA3WTB

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

Greg, N6GD

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.

Craig Williams

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.

Essgkay

I had this same problem with a new Flex 6400, and when I read Andy's post above, I checked out both of my right angle connectors in the coax path. Sure enough, one of them had a cracked dielectric and a singe mark, possibly from a lightning strike I had in 2017 which damaged a previous radio. I removed both of the right angle connectors from the coax path and that solved the problem. The 6400 is working perfectly now. I also had a problem of intermittent transmit. It would stop transmitting for a brief second on FT8 and immediately resume again. This problem has also seemed to have been solved. I've also been a ham like Andy for 52 years and have never seen these issues before. Thanks, Andy! Good detective work!