Hi @all,

I have a problem with the headphone jack on the front of my "SunSDR2 DX". When I transmit I have extreme RF interference in the headphones. This happens already at lowest power levels. Ferrites in all variations and quantities bring only slight improvement.

Right next to the "SunSDR2 DX" is a "Yaesu FTdx 3000" and a "Yaesu FT 991A". With both Yaesu transceivers absolutely 0% of disturbances is to be heard. I don't even need to put a folding ferrite on the cable.

All transceivers are grounded by a 3m long ground rod in the garden.

I hope someone can help me. With the "MIC1 jack socket" there were also instructions to remove the interference.

My serial number is: EED06511900145 (if needed)

Thanks in advance!

Mathias, DD5MD

I have the same issue when I use the headphones jack on the front panel.
Looks like RF is getting it to the Audio amps on board.
Im planning to test this better but this requires loads of time.
I will simply disassemble the radio and separate RF amplifier board from the mainboard when the audio circuit is located.
I hope that extra shielding will fix the issue.

Hi,

I have received instructions from Roman on how to fix the problem.

Enclosed is the PDF.

Greetings

Mathias

Thank you very much.

Using headphones around RF I have always placed a .001 disk cap across the tip- shield and ring to shield, this seems to bleed RF here pretty well

I soldered in the two ceramic capacitors today. The interferences at the headphone jack are completely eliminated.

The location marked in the instructions is on the back of the board. To be able to remove the lower PCB the back of the case has to be unscrewed.

The 4 screws and the two fasteners of the D-SUB15 socket. None of the other screws on the board itself need to be unscrewed. The board can then be pulled out to the back.

Good luck!

Thank you for the update!

Hi,
I did open the TRX with the instructions of the document you provided. However, I can't locate the place where the C's need to be applied. Any hint?

Regards, Gerben

The location marked in the instructions is on the back of the board. To be able to remove the lower PCB the back of the case has to be unscrewed.

Thanks for the guidance. Have done the modification and now it is OK.

Today I made the mod with two capacitors. The problem has been eliminated and works very well !
Thank you very much
IZ2FLX Mauro

I have opened the case to do this modification and the first thing I noticed was the red and green wires are reversed compared to the photo in the pdf Roman provided. My question is, should I reverse the red and green in my radio to match the photo provided by Roman or leave them as they are in my radio. I attached a picture of my radio.
Thanks,
Dennis, WA0YPC

In the process of removing the 3 wires, the green one fell apart. It looks like it was never attached correctly and is definitely too small to try and reconnect. Any help in finding a new green wire with connectors attached would be appreciated.
Thanks,
Dennis, WA0YPC

Now that I have the radio apart, my circuit board doesn't have the pads to solder the capacitors to. See attached photo. Now I have a non functioning radio until I find a new green jumper wire.

Hi guys,

I want to look at this document if it is still available, please. If someone could post I would be very grateful.
I also have a persistent RFI issue with my SunSDR2DX from the headphone jack.

73
Andrew
VK6IA

DD5MD wrote: