SSDR V 1.8.3 Update Problem

Paul Burton

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

Mike va3mw

Paul

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?

Mike va3mw

Paul Burton

Thanks Michael.  No, I'm just using CW mode.  Everything is the same between the two versions.  My amp is a TenTec Centurion which requires about 100 Watts drive for full power.  It works perfectly with SSDR 1.6.21, but not quite full power since the 6300 is a bit wimpy.

Bill W2PKY

Hello Paul- Others have reported similar issues driving amplifiers. Best enter a help ticket.

Paul Burton

OK Bill, thanks,  I didn't see other posts on this.  A support ticket was submitted.

Cal N3CAL

Paul,

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?   

Cal/N3CAL

WX7Y

I wonder if the Flex is getting a HI SWR false reading with High RF in the Shack or RF Common mode currents on the COAX shielding when the AMP is enabled? 
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.

http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf


Just my thoughts

73's 
Bret
WX7Y

K7FU

Having the same issue driving my Denton MLA2500. Downgraded the software to a version without the swr fold back option. Works ok for now.

K7FU

Having the same issue driving my Denton MLA2500. Downgraded the software to a version without the swr fold back option. Works ok for now.

Paul Burton

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.

Paul

Rob Blackie

i think there should be an option to turn off the SWR foldback addition. it is clearly a problem for some

WX7Y

Common Mode RF has nothing to do with having a high SWR.

Paul Burton

Yes, but it may be getting into the detector within the Flex and setting it off.  Stray RF can do lots of weird stuff.  It's all just speculation without further testing.

Gerd Henjes

Why not first establish the actual problem. The former version of the Flex software doesn't have SWR foldback limiting, the new version does. Is the new version seeing something the older version wasn't even looking for, I'd first suspect that is the case?

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.

Gerd, W2ISB

Mike va3mw

Gerd makes some good points.   

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.

Mike va3mw

Lawrence Gray

I have a 6500 driving a Yaesu FL-7000 solid state amp.  I have not experienced any amp drive or power fold back issues since upgrading.  I use a manual tuner following the amp--no issues so far.

Larry, KC1DAD

AA0KM

Bypass the Flex internal tuner and see if it works out.

"The input SWR on the amp is low, but I used the autotuner to make sure."
"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."

Cal N3CAL

What's on the other end of your amp?   What antenna do you have hooked to your amp? Could  be your antenna is presenting a high SWR?    If you happen to have a dummy load you could hook that to you amp output and see if you still have the issue with a 50ohm dummy load... 

I use an external  Auto Tuner on the output of my amp which matches any of my antennas.  I keep my Flex 6500 internal tuner off.  Since upgrading to V1.8 I have seen NO issues and have not seen any fold back.  . 

Cal/N3CAL

Mike NN9DD

Same configuration here works great. Someone made the comment earlier to check your coax jumpers. I have had more then one of those over the years

Mike

Mike va3mw

I use a KPA500 without issue on my 6300.  I suspect if you are getting SWR foldback, then something else is contributing to it and you should solve that problem rather than try to mask it.

Mike va3mw

Paul Burton

I only ran the tuner as an experiment to see if it would help.  The fault occurred with or without the autotuner on.  The SWR was low in either case.

Paul Burton

I hadn't suspected common mode RF, as I don't have much other indication of it.  The Flex must be really sensitive to it.  I have three different antennas, all with baluns.  This happens on all antennas and bands. 

Yes, when I get some time I'll apply some ferrites and replace the coax jumpers.  I just didn't expect to set off an SWR detector which I have low SWR.  I have seen some other slight indications of RF in the shack, so that's likely the problem. 

WX7Y

Also one thing I just thought of, with the AMP in standby or in Receive mode your AREN'T going through the amp's input network so when the AMP is in operate mode the SWR will change because your radio is no longer connected direct to the External tuner or antenna but rather to the AMP's input network.

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.
Bret
WX7Y

Paul Burton

Bret, the SWR indicated by the Flex is below 1.5:1 when using the amp without the internal Flex autotuner.  With the autotuner on, I can bring it down much lower, but the fault occurs with or without the autotuner.  The SWR on the output of the AMP is  below 1.5:1 on 17 meters, and I have the problem there  as well as with other antennas/bands.  I have no antenna tuner outboard of the Amp. 

WX7Y

OK Paul, Well I would really get the toroid's to trap the RF Currents  http://palomar-engineers.com/ferrite-products/ferrite-beads for the proper MIX for your frequency of operation,  and here is there KIT's  with Heat Shrink for outdoor or indoor installation. 
Anyway hope you get it figured out.
73's
Bret
WX7Y

Paul Burton

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.

Paul AA6Z

[Deleted User]

Does it fold back going straight from radio to antenna with no amp. I believe it is a bug in the foldback code in this new feature we had to have.

Paul Burton

No, only with the Amp.

KY6LA_Howard

@Paul

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...

Terry K7NY

1.8.3 works fine with my 6500 and ALS-1300, I will try it with my SB221 later this weekend.
Terry

Lawrence Gray

I agree with you Howard.  My solid state amp has built-in foldback at an SWR of 3 or higher.  It has saved me a couple of times when I misconfigured something.   If the Flex is folding back, there is an issue in the station that needs to be resolved.  Disabling the foldback could easily lead to an expensive repair.   A better idea is to track down the reason for the foldback and eliminate the issue.

I'm happy that the Flex folks added this feature.

Larry, KC1DAD