I have a Flex 6300 and have been running SSDR 1.6.21 successfully for many months, and am able to drive my amp to full power. I decided to upgrade to SSDR 1.8.3., which went successfully, but now when I use the amp, I get a short burst of full power and then it drops back to almost zero. In TUNE mode it will drive to almost full power, but as soon as I stop tuning and try to operate, it drops back to a very small power. If I don't use the amp, the 6300 seems to put out power normally, but only 75 watts max. The input SWR on the amp is low, but I used the autotuner to make sure.
I subsequently dropped back to SSDR 1.6.21 and everything returned to normal, with full power out of the amp getting about 85 watts max from the 6300. I notice that there was a "fix" which relates to cutting back power on adverse SWR, and I'm wondering if this is causing my problem. I'd like to be able to upgrade.
Anyone else seeing this?
Paul - AA6Z
Based on your diagnose and that nothing else has changed, you may want to open a support case. it does sound like a software issue.
Are you testing in unmodulated FM mode just to make sure you are putting out a constant carrier?
Other than that, I can't think of anything that might make a difference. Possibly a profile issue?
Others have reported similar issues driving amplifiers. Best enter a help ticket.
I noticed in the SSDR V1.8.3 Change Log there has been a change to the firmware:
#3644 Firmware: Added automatic power foldback for high SWR situations (starting at 25 W reverse power)
Are you sure your SWR is low between the Flex and your Amp? Do you have an external tuner inline after the amp?
I have a bunch of fer-rite beads (8 on each jumper) on EVERY Coax jumper between the Radio, Amp, Antenna tuner, coax switch's and every peace of cable so probably between the radio and each Antenna there are 18 to 24 fer-rite Beads to stop any skin effect or RF Common Mode Current from coming back down the Coax starting with the Antenna feed point.
I so far have not noticed any RF Power cutbacks here running full legal power at least on 40 and 80 meters, I haven't tried the other bands yet so MY MILEAGE may very.
Just wondering if this could be the root cause of some people's problems, I do know that my OLD FT847 had this problem and when I first started looking into it years ago the abundant amount of IRON on the COAX jumpers have stayed in my shack design.
How does it act into a dummy load running the AMP if you have a Dummy load large enough to dissipate the power which every HAM who owns a Amp should have?
A good Read and a great resource is below.
Just my thoughts
Thanks for all the comments. I don't think I have excessive SWR out of the Flex as I'm using the internal antenna tuner and my amp has a tuned imput. The SWR is low enough. Why did they need to make this change?
Yes, perhaps some common-mode RF is getting back into the Flex. I have regressed back to SSDR 1.6, but may try some Ferrites over the holiday, to see if it helps. I don't suppose we will hear any response from Flex until after the holiday. Cheers.
Why would you run the Flex auto tuner into your amplifier, if you amplifier has a tuned input?
Over the years I can't count the number of bad patch cables and badly soldered PL-259's that I've run into... first thing I always change is the patch cables.
For the fellow with the ML-2500, they did offer an external tuned input which you absolutely need to match to a solid state rig and keep you IMD from going through the roof. I'm also going to be the internal 100 ohm swamping resistor has be cut out of the input circuit... that's not really a good idea either. You can't match the input with an autotuner in the radio as the match changes as the RF cycle is amplifying.
Common mode currents are something we can't measure, but we know when we have a problem when we have a problem. :)
If the radio measures any reverse power, then it will fold back to protect the finals. This also means any RF on the patch cords that work their way back into the radio can be interpreted as bad SWR. People with random wire tuners see this all the time.
You might want to try inserting an SWR meter between the radio and the amp. Try some Mix 31 or Mix 43 chokes.
There are many excellent articles on the net about RF Common Mode Currents that help explain this much better than I can.
What's the SWR between the AMP and Radio measured with a EXTERNAL SWR Bridge between the Radio and AMP with the AMP enabled and internal Tuner is OFF?
If the SWR is high going into the input to the AMP it will change abruptly going from AMP Bypass to Enabled OR PTT activated to Receive mode.
So maybe it's simply just your input network or lack of on the AMP.
OK, I pulled out the 6300 and totally simplified the installation with a short coax jumper into the amp and put several 31-mix ferrites on all leads in/out of the Flex including the 14 volt power. The SWR is below 1.5:1 on the antenna and into the amp. I see no other signs of RF in the shack. All of this has had no effect on the Fold Back of power. I am able to run about 500 watts from the amp with just a slight fold-back, but if I go to 600 watts, it folds back to almost zero. I have no access to a high-power dummy load at this time, which would be a further good test.
I feel something is wrong with either the 6300 or the implementation of the software fix. If I bypass the amp there is no fold back to full power on the 6300. If I revert back to SSDR 1.6 of course I get no fold back. Once the fold back hardware warms up, it seems to occur at much lower power. If I wait for it to cool down, then I can run 500 watts.
Thanks to all for trying to help solve this mystery. While some seem to have no problem, I now see other posts indicating the same problem. Why could we go more than a year without this fix with no problems, and now suddenly need it? I am reverting back to SSDR 1.6 and I'll wait for a response from FRS.
You are seeing @500W no foldback but @600W fold back to zero
My best guess is that you still have RF in the shack but the ferrites are reducing the RF in the shack when you are below 500W so the RF in the shack does not reach a threshold where it may cause fold back.
Solution: More Ferrites in more places (Power leads and anything else that can pick up RF from common mode currents) and a better grounding system to reduce current loops... Suggest you read my "How to build a Quiet Station" paper posted in this community...
@Steven - since the code works well for virtually all modern Solid State Amps - you are likely totally wrong about your guess that there is an error in the code relating to the foldback circuit.
My Expert 2k-FA Amp is capable of running 2,300+W key down. During beta tests there was NO FOLDBACK whatsoever running this amp so clearly the software is working as it should. But then I have spent a lot of time and effort to make sure there are minimal common mode currents on my leads...
Also it would appear that you do not understand the benefits of introducing the foldback feature. Flex PA are very robust. However there may be extra-ordinary circumstances (such as an antenna failure) where having an extra layer of protection on expensive final transistors would be quite beneficial to most people. I do agree that a simple solution might be to make it optional for those who don't mind blowing finals and have older tube amps with lots of RF in the shack... I suspect however, if your finals blew, then you might one of the first to curse Flex for not having a foldback feature and/or making it optional. Personally I would rather fix the RF in the shack issue and save my finals...
I'm happy that the Flex folks added this feature.
Thanks again for all the replies and comments on this problem. I am not suggesting that the fold back protection should be eliminated or disabled, only that it is excessively sensitive to common-mode RF which is present in every ham shack to some degree. Fold back should not occur due to a small amount of common mode RF. I'm not suggesting that I have no common-mode RF coming into the shack, but I have no overt indication of RF in the shack other than the Flex which goes belly-up. All of my three HF antennas have baluns and the fold back occurs with every antenna on every band. I have used several other transistorized transceivers (which all have SWR protection) without this problem. I have installed multiple 31-mix clip-on ferrites on every line in or out of the Flex, and it still folds back at 600 watts output with low SWR.
I am waiting for FRS to respond on this and will continue to try to find the source of whatever is causing the fold back.
I strongly recommend that you read and implement suggestions in my paper
"How to Build a Quiet Station" Baluns and Ferrites along won't fix ground loops. The other radios do not have networks and computers as part of their configuration so they are less likely to have ground loops that will pick up RF in the shack.
Like everyone else, I was in denial regarding RF and common mode currents. My SGC500 Amp on my remote base kept tripping off due to high currents, 40M was a mess, etc. I thought having a good balun was good enough. However, that doesn't prevent the feedline from other antennas (the ones you aren't using) from picking up RF from the active antenna and feeding it back to the radio.
See what I mean?
I highly recommend reviewing it. For me, I ordered a case of Mix 43 and Mix 31 cores. It was one of the best purchases I have made for my station.
Since then, zero issues. My SGC500 stopped having over current errors. My KPA500 also works perfectly and all this on my remote base.
Every antenna has cores below the balun. The feedlines to the radios have cores at the antenna switches and just before the radio.
You need chokes at the antenna, after the amp, between the amp and the radio, etc.
I am a choke convert. Mike va3mw
I seem to notice a positive change to AGC-T action so I'd rather not go back to the previous release.
You can never have too many ferrites.....
Heck.. I have one of the quietest stations possible .. then the cleaning people moved some wires and BANG suddenly more RF in the shack... More ferrites fixed it...
I would strongly recommend upgrading to 1.8.3 because the items it fixed are more global in nature that the few reports we have received regarding the SWR issue. If you upgrade and have the SWR issue, I strongly recommend that you open a HelpDesk support ticket so we can characterize your issue. And you can always easily and conveniently revert back to 1.7.30.
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