PTT intermitently not dropping for amp

W9ILY

I  am suddenly having an issue when using USB with an amp and my 6500. I have two amps, the Expert 1.3k-FA and the Acom 2000A and this occurs on both amps so I believe it is being caused by my Flex 6500. Here's what is happening. After making a USB transmission using my footwitch, OCCASIONALLY the amp stays in the transmit mode. I can see this by the transmit lamp staying on on either amp and I need to press the footswitch once or several times to have the TX lamp go off and RX return to normal. When the failure happens, the SmartSDR screen returns to the normal receive mode, but there are no signals on the panadapter, only a noise floor and the red transmit lamp on the 6500 is no longer on. I have checked connections and done a factory reset. I thought the reset had fixed the problem but it returned very shortly, after about 10 QSOs in the WPX contest. This has not been observed on either CW or RTTY or FT8 and I'm at a loss as to what to do now.

KD0RC

It could be RF getting in.  Try a ferrite on the foot pedal switch line as close to where it plugs in as possible. A .01 or .1 uf cap across the line might help as well.

Len, KD0RC

Paul - K6HR

Yes, sounds like RF getting into PTT footswitch. What happens with footswitch disconnected? I had this same problem once with a PTT switch and the ferrites eliminated it. You must also rule out the footswitch.

W9ILY

OK will try ferrites. I had not considered that as the 6500 is returning to normal RX mode.

KD0RC

If it is only the amp, there is also the possibility that you are hot-keying the amp causing the relay contacts to weld a little.  Are all the delays set correctly to prevent hot-switching?  If the amp does not have a keying relay, this is of course, not the issue...
Len

Bill -VA3WTB

Does it still do it without the amp?

JohnSweeney

John - please see my direct email to you.  If keying 2 amps from a single Flex output, please make sure you are using isolation diodes

W9ILY

No all works fine with no amp turned on. I just added the ferrites and am testing now., It appears to be working OK now but we'll see.

W9ILY

Well the ferries seemed to have fixed the issue. Will do some more testing tomorrow including removing the footswitch entirely.

KD0RC

Good to hear.  Where did you put them? Are they on the foot pedal cable near the Flex?

Lucas - W6AER

I am also curious about this as I have experienced the EXACT same issue with my Flex 6600M except I am using the Flex Amplifier and I already have ferrites in place where ever I could think of. Also only seeing this issue on SSB and seems to be no related to power. Very odd and made it very frustrating during the CQ contest as while trying to hear the exchange after transmit, the signal would drop on the RX and have to key down again and release for it to come back. Like the PTT is sticky. Does this with Heil hand key as well as the foot pedal and both have ferrites. Anyone else seeing this?

W9ILY

Placing ferrites on the foot-switch did not cure my problem. They seemed to help but then the failures began after 15 or so QSOs. I placed them first near the Flex and then moved them to near the FS and there was no difference. The cable between the FS and Flex is shielded but now the shield is not connected on the Flex end.I actually replaced the FS with my old one and no difference. When simply operating by mousing on the MOX button everything was perfect even with the FS plugged in. This is precisely the same issue that Lucas W6AER describes. Any more ideas?

W9ILY

Lucas,
These are my exact issues, too. See my comments below.
John W9ILY

W9ILY

I might add that I operate very few SSB contests using high power. Last year I operated the WAE on 9/14 for 30 Qs, Calif QSO party for 22 Qs and CQWW for 267 Qs on 15 meters. The question is what has happened since 11/23/2019 when CQWW was operating. I noticed this issue only during the two SSB contests using the amp in 2020.

W9ILY

Just made several QSOs using VOX and it was perfect.

Terry K7NY

I have a 6500 running 2.6.1 everyday with foot switch works fine. Using with a Ameritron AL-82 1000 - 1500.
Terry

DL4RCE

Same here as well!

Terry K7NY

what software are u guys using?

KD0RC

It seems like the ferrites are making some difference, but not a complete cure.  Is that a fair assessment?  If so, try more ferrites and/or a .01 uf cap across the PTT cable.  I have had similar issues in the past, and it can be the smallest thing that cures it (or triggers it...).

Len

W9ILY

Yes, that seems to be the case, Len. BTW I am running SmartSDR v2.6.1. I'll give your suggestions a try and post the results when I have them.
Tnx.
John W9ILY

W9ILY

I tried 4 ferrite snap-ons and the .01 across the PTT line and no difference. I have been plugging the PTT line into the adapter that is used for the Heil boomset that includes both the mic, headset and PTT accessed through the front panel mic connector. I have now moved the PTT line to the RCA connector on the rear panel and will see how that effects the issue. Will advise after the next SSB contest. By the way this happens on two different amps so it is not the case of hot switching.,

W9ILY

Plugging the PTT into the rear RCA jack made no difference. I believe the issue may be caused by the mic picking up RF so I added two snap ons to the mic line where it enters the front panel connector. Initial tests have shown that this may be the corrective action and this weekend's contest will be a good test. Will post the results.
John W9ILY

KD0RC

Excellent!  I hope that is the final cure.

Len

W9ILY

Unfortunately this was NOT the cure. I had at least 3 failures yesterday during the Hamvention QSO party among the 22 QSOs that I logged.Next I will try a different value CAP on the footswitch line.

KD0RC

If you unplug the footswitch and key the rig with the MOX button in SmartSDR, does the problem go away? Would be nice to know if the footswitch is truly the culprit. Len

Paul - K6HR

Have you tried a different footswitch?

W9ILY

I’ve been using SmartSDR 2.6.1 and upgraded to 2.6.2 today. No testing with the new S/W

W9ILY

Will try it by keying with the MOX and leaving the F/S connected and then with it disconnected and will post the results. Will have to wait until a contest weekend as I need quite a few QSO s to make it happen.

W9ILY

Yes two different ones with no difference John W9ILY

K1ESE

Make sure you or some profile isn't accidentally turning on the VOX at the same time you are using the footswitch.  I speak from experience.

W9ILY

OK I'll look for that but when the PTT hangs the amp the TX lamp is green on the 6500 and everything looks normal. The SmartSDR screen returns to the normal setting. On whichever amp is in use the TX lamp remains on and the antenna does not switch to the RX position (no incoming signals received). Quite a mystery. As I mentioned this happens only occasionally.