DM780 Transmit Problem

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  • Updated 5 years ago
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I would appreciate guidance on the following problem: Using Flex 3000, PowerSDR v2.6.4, DM780 6.1.4

When transmitting PSK or RTTY, I often get the transmit text scrolling rapidly by the screen and a static filled transmission on the air. My next transmission is usually normal.

This pattern (normal transmission alternating with rapid abnormal transmission) appears to alternate, but is not always reproducible.

DM780 settings are: PTT via COM port, with Set DTR and Set RTS both checked.

Power SDR settings are CAT Control by COM port, and PTT Control with Enable PTT checked.

HRD support is unable to help "ask the Flex Guys".

Thanks in advance. 73, Phil, N1DN
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Phil, N1DN

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Posted 5 years ago

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George Molnar, KF2T, Elmer

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Almost sounds like RF. Does it happen at all power levels and bands?
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Phil, N1DN

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Thanks George. Great point (wish I had though of). Happening at low power levels down to 5 watts...haven't correlated with various bands as I mostly operate 30-80 meters. RF could explain the unpredictable / erratic nature of the problem. I'll add suppression beads to my equipment and update on the results. Phil
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Ken W9IE

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Phil,
Are you using a WIRELESS Keyboard
If so try a WIRED ONE

Ken W9IE
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Ed baker

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On PSK31 right now.
If you are having this problem it is RF for sure.

Use Mix 31 Ferites

The 6500 works great on digi modes using the DAX . Follows the radio via cat .
DM780 works extremely well with DD utility . As you do not need to run HRD radio control.
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Phil, N1DN

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Thanks Ken and Ed.  I've changed over to a cabled keyboard/mouse, and added some RF chokes picked up at the local Radio Shack (not Mix 31).  The problem persists.   Proper Mix 31 Ferites ordered from DX Engineering, and I'll report back with results.  
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Andrew O'Brien

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Just for the sake of experimenting, does the same thing happen if you use other digital mode software?  Try Fldigi and see it the same problems exist. If it was really RF, you should be able to stop the problems with super low power and all the chokes you have tried. 

Also, are you sure you don't have some extra funky stuff in your settings that might by some bizarre chance be causing this?  You seem to have a lot more settings established than I do.  I just loaded DM780 with my Flex 3000.  I don't have PTT selected on PowerSDR, I leave that check-box blank.  I just have PowerSDR set  as "enable CAT" .  I also don't have any PTT set in DM780, I just have HRD set for a comm port off of DDutil. CAT commands do all the PTTing.  TX works fine.  Bo messing with DTR or RTS.  It should not really be the cause of your problems but I thought I would mention it.  See this video i just made of my set-up.  https://www.youtube.com/watch?v=Ld-Advk5-vw
Andy K3UK

(Edited)
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Phil, N1DN

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Thanks to all for your help and guidance! I wanted to provide a brief update. I think I've addressed any potential RF with Mix 31 Ferrites and eliminating cordless devices. The problem (rapid transmission of digital modes every other message) persisted. To Andy's point, FLDigi and WinWarbler work very well. This is likely due to my DM780 settings. Andy THANK YOU for the video....I'm going to emulate your configuration with DM780 and will let you know the results.