Linear amp tripping to standby at FT8 using Flex Radio 6400M

  • 1
  • Problem
  • Updated 2 months ago
  • (Edited)
My linear amp is tripping to standby when running FT8. I have Flex 6400M, SSDR 2.4.9 and the antenna system has low SWR (1.24). DAX TX slider is in the green area and Flex radio driving power about 10W with amplifier output about 300W.
The amplifier is happily running 1000W output in CW and SSB modes with Flex 6400M driving power around 20W.

The tripping of the amplifier starts in the middle of a QSO after about 10 seconds TX. Once tripping starts each consecutive TX period is tripping the amp at even lower settings on DAX TX and Flex radio driving power. This behaviour is similar on different bands and different antennas. In the end tripping occurs with below 3W output from the 6400M.

I am thinking that the Flex 6400M maybe is prone to get distorted if there is any RFI around and that will effect the amplifier. In order to minimize that I have disconnected the CAT cable, headphone cables and CW paddle cable from the 6400M. I have also wound ferrit toroids (FT-240-31) on the data cable, power cable and coax output cable. I have also completely removed and reinstalled SSDR 2.4.9 with the DAX drivers a number of times. Still tripping the amplifier, no change!

In order to isolate this tripping by the amplifier I have also got tripping using a dummy load. Finally I have switched out the Flex Radio 6400M and run FT8 with my bacup radio and then I have absolutely no tripping of the amplifier. I can run 1000W output in FT8 digital mode and the amplifier is happily pushing on.

I can operate FT8 without amplifier at full 100W power from 6400M without problems.

As the amplifier is OK using the backup radio I do not think the problem is in the amplifier. I am now running out of ideas!

Any ideas are welcome!

Erik SM0JCA

PS: I have intentionally left out the name on the amplifier and backup radio in order to avoid flaming!
DS


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Erik Mellgren

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  • frustrated!

Posted 2 months ago

  • 1
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AB4RW

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Why would you use an amp on FT 8? Too each there own, just curious
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AB4RW

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Well, I have done FT 8 for couple weeks, not my bag, from everything I have read and heard it was a weak signal mode, pardon me from butting in, just wondering why anyone would run that much power, but none of my business! Hope you get the problem solved
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Bob Craig, K8RC

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"Weak Signal" does NOT equal "Low Power"!

EME is weak signal but you need to run all the power you can muster.

Lack of sunspots is weak signal. If the path needs a few db more to decode you need the amp.
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Jimmy Collis

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Well ive been on ft8 since the beginning and I have 17,800 contacts logged and ive never used over 65 watts no need for amp that I know of ..a lot has to do with a good antenna system more than an amp 
(Edited)
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Burt Fisher

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Erik SM0JCA wants to use an amplifier on FT8, why are you on his case for his operating style? You want an award for your power level?
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Jimmy Collis

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im not on his case I don't care if anyone wants to use an amp go for it im just saying if you have a good antenna system you don't need an amp on ft8 100 watts will be all you need but ill take the award thanks Burt 
(Edited)
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Mark - WS7M

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Eric,  what is the amp?  If any one flames you on your amp you have my permission to just ignore them!  :-)

I had an ALS600 solid state amp for a while that was VERY FLAKY with power.  Any long TX at full power even into 1:1 dummy load would trip the amp with a fault.

Since you isolated to a dummy load and it works then I have to suspect RF getting into your system somewhere.

You can try starting the Flex into the amp at 1w output, then 2, 3, etc on up to your 10W where it fails.  I suspect you will find some point where it works and then beyond that it doesn't.

You can try wrapping all cables going into the radio with cores.  More is generally better but get good ones.

It is amazing what these cores can do.  I had a buzzy RF on my spoken audio.  I took a core and did one wrap.  Not much change listening on a WebSDR.  2 wraps.  Better.  Finally 5 wraps in and the RF was mostly gone.  I added a few more for safety then went online and spoke to my usual group who all reported clean audio.
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AB4RW

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Mike W9OJ

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Which cable were you wrapping through the core?
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bahillen

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Does the Flex and amp work normally on cw and ssb? Does it work ok in the tune from SSDR? I have had issues in power jumping up to 100 watts from Flex when keyed from WSJT-X and kicking amp off.

Very frustrating but had to change how I change bands or hitting the TX button. Probably not your issue. If you can take wsjt-x out of the issue it would help.

Are you using SliceMaster?

What amp are you using and how is it connected?

73
Bill W9JJB
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Larry Loen WO7R

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I have consistently found that FT8 is a high duty cycle mode.

How much power are you running?  Whether using an amp (useful on 80m at least) or running barefoot, I have never been able to convince myself that amateur gear safely and reliably runs FT8 or JT65 at more than about 35 per cent of max rated output.  So, Flex 6xxx barefoot is about 35 watts.  A 1K amp would be about 350. 

Maybe you can run more power, but I have found things like power fluctuations when I try it.  My Expert 2K backs off to its "mid" position within about 10 seconds when I forget and try MAX.

It's just a heavy-duty cycle mode.  Note that most manuals for most amateur gear suggest reducing to 50 per cent of the max even for conventional RTTY.

The fact that it works on some combinations and not others is _not_ proof of much.  The longer the session, the more what I suggested is true.
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WX7Y

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have you tried to set the RCA TX your using timing to maybe 20 or 30ms on the Flex setup / TX screen?
73
Bret
WX7Y

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Chris Tate - N6WM, Elmer

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Try working with TX delay..  maybe RF is hitting the amp before key up...
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Erik Mellgren

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Hi all,Thanks very much for your comment, much appreciated.
A hort answers summary:
- Yes, TX delay 30-100 ms tested, no improvement
- Will never run more than 350 W (< 50% power cycle). Tripping at 250W and down. Now tripping at 3W from Flex Radio 6400M
- Ferrit torids (FT240-31) already on cables
- CW, SSB and SSDR tuning no problem to 1000W.
- Reduced DAX TX level to peak at -10dB, still tripping at FT8. TX signal looks clean on the scope.
- Using FT8 Tune button in these tests
- Using Slice Master for WSJT-X in FT8 mode

I give up! Now running FT8 barefoot.
My backup rig Icom IC-7600 have no problems with the amp in FT8 mode.

I will now go to HRD and investigate PSK31 for the 6400M as well.

See you down the log.

Erik SM0JCA



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Bill -VA3WTB

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Just wondering,,have you been using the ALC?
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Erik Mellgren

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No ALC, the Acom amp does not have one.
Erik SM0JCA
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Bill -VA3WTB

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It is very unusual for this to happen using these radios.
I would suggest starting a Help Ticket so Flex support can work through this with you.
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Erik Mellgren

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A new observation regarding this story: Just for quriosity (?) I changed mode in the WSJT-X program from FT8 to JT65 and did not change any settings except increasing driving power to 10W and the DAX TX peaking just below the red line.
What happened? Everything is working OK with good modulation pattern on the scope and the amp giving 500W output and NO TRIPPING. Went back to FT8 and the old story stared again with tripping the amp at low driving power. Again over to JT65 and everything is normal with high output. I just changed modes and some driving power, the Flex 6400M with SSDR plus Slice Master and WSJT-X and the Acom 1200S amp was running all the time.

Does the wave form in FT8 differ much from JT65 and cause overtones (?) or are there possibly different RFI frequencies. A nice research subject for a curious radio designer or software developer, myself I am now tired since it is one o ́clock in the morning here.

73 de Erik SM0JCA
(Edited)
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Pat - WH6HI

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Maybe you should delete current wsjt-x program including config fills. Then down load a fresh copy of newest version then config and try again.
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Erik Mellgren

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Hello Pat!

PROBELM SOLVED!

You are my savior! You nailed it! After deleting WSJT-X and downloading, installing and testing on several bands everything is now OK. Software driven systems can sometimes drive you crazy and then it turns out that the solution is really obvious and simple, thank you very mych Pat.
Nothing wrong with Flex radio 6400M and Acom 1200S amp, they are playing just fine together now.
I learned a lot in the meantime.

Erik SM0JCA
(Edited)
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Erik SM0JCA

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I was a bit premature when stated that the problem was solved. I had to clean up the drivers on the computer and after a suggestion from Tim Ellison to change the length of the coax cable between the Flex radio and amplifier. That will change the complex impedance of the cable for the amplifier.
The coax cable was finally added with 2 m RG58 turned into a round bundle with 6 turns and connected. Now I can run FT8 at full power 1000W and the amplifier runs much cooler as well. Tim was right!
73 de Erik SM0JCA

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rjguidrysr

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I can, if needed, run my SPE 2k-FA at 1-1.3k on FT-8 with 6600 running only about 15-25 watts and does not trip.

FT-8 is like a solid RTTY signal for 12 seconds or so.  I normally only run it at 300 watts or so for all but the hardest to work.

Russ K5OA

Tim puts out another fire!
(Edited)