Flex 6500 abruptly shuts down after Tx

  • 1
  • Problem
  • Updated 1 year ago
In the middle of a transmission or right after a transmission my Flex 6500 totally stops.  The red MOX button remains red but the radio is not on.  I have to restart the radio connection which is successful but the dropout has occurred four times today.  I am running my Flex 6500 with a Palstar HF Auto antenna tuner and an ACOM 1000 amplifier.  I thought that I might be using too much power so I backed down the power level to 50%, yielding around 800 watts of output power.  The problem still occurred and I am at a loss for what is causing this issue.  I know that I should open a service issue ticket with Flex but wanted to see if this is commonly occurring and if a resolution has been found.  I searched the forum but did not find an answer. Please advise.     - Richard Everett K5RBI
Photo of Richard Everett

Richard Everett

  • 7 Posts
  • 0 Reply Likes

Posted 1 year ago

  • 1
Photo of Neal - K3NC

Neal - K3NC, Elmer

  • 574 Posts
  • 198 Reply Likes

Sounds like RFI to me, I would test whether it happens without the amp. Does it do it on every band? I always try connecting just a dummy load to the radio, turn the tune power to 10 watts and then press tune. If it doesn't cut off, move the tune power to 50 watts then press tune. slowly increase the power until you are at 100 watts. Do this for each band. If it doesnt turn off, its not the radio.

Photo of Gayle Lawson

Gayle Lawson

  • 130 Posts
  • 47 Reply Likes

Does the shut down happen when connected to a dummy load?  Running the radio at 100 watts? etc.    That will tell you . if you have a RFI problem or not.

Gayle K0FLY
Photo of AH0U


  • 380 Posts
  • 59 Reply Likes
Sounds like RFI..... try it barefoot ...
Photo of Richard Everett

Richard Everett

  • 7 Posts
  • 0 Reply Likes
Thanks for the advice and suggestions everyone.  It looks like it is indeed an RFI issue.  I backed down on the power significantly and no crashes whatsoever.  I will creep up the power from here when DXing and find that "point of no return".   Thanks again for your help!
Photo of Larry - W8LLL

Larry - W8LLL

  • 541 Posts
  • 116 Reply Likes
I keep a bucket full of MIX 31 Snap on chokes of different I.D. sizes on hand, I am not using that many but I have not had an RFI issues yet that could not be solved using them. For me the usual suspects are USB cables, network cables, speaker cables. I would guess that RFI is getting into your network cable by your symptoms,  that is a good place to start.


MIX 31 Snap-on

1/4 id ferrites   623-0431167281

1/2 id ferrites   623-0431164181

3/4 id ferrites   623-0431173551
Photo of Al / NN4ZZ

Al / NN4ZZ

  • 1881 Posts
  • 697 Reply Likes
Hi Richard,
I also had RF issues on my 6700.   I documented the fix on my web page.


You might also be interested in this link for RF on your network cables.


Al / NN4ZZ  
al (at) nn4zz (dot) com
6700 & SSDR-W  V 2.4.9