Headpnone out anomaly... and solution

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  • Updated 5 years ago
Today I tried the headphones on my 6500 for the first time.
Running two pans with one slice in each ear on headphones (20 M & 10 M), I decided to transmit on 20 SSB and monitor with my headphones. (100 watts and a dipole)

I encountered the following problems that others may have as well:

1) upon beginning of transmission, the headphone volume control went from 3/4 volume to totally 0 on the slider. This was repeated several times.
2) The next time I tried with monitor activated and the 10 meter slice & pan closed.
This time, the volume stayed constant, but the monitor button flickered on and off at random (later I discovered it coincided with my voice peaks.) and the monitor sound was intermittent.
3) at no time was any of the sound distorted - it just switched on and off at "random."

The solution: I wrapped my headphone cable about 8 times on a ferrite core. Problem solved. I had never had this particular effect of mild RF in the shack before and thought others might find it helpful if their headphones start acting weird.
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Ken - NM9P, Elmer

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Posted 5 years ago

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Dave - WB5NHL

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I've been using a Heil PSE 6 headset and foot switch regularly with no problem. Ken, have you had any "RF in the shack" issues with any other gear?
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Ken - NM9P, Elmer

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I have been using the Flex-1500 for a while, so at 5 watts RF issues are small. I recently (Sunday) changed to a different form of antenna. It solved RF problems on one band and moved them to another one. But with the Balanced feed, none of it has gotten into the transmitter! It has gotten into my Lepai audio amp and Dayton Audio speakers on 10 & 15 meters though.

Still, I'm chasing my tail for a while...
Radio is fun....!
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Paul RN3A

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Ken, interesting stuff. I have tried my 6700 with Acom 2000 PA (appx. 1,5 kW to Ant connector) and HF antenna 30 meters right above me. Never noticed anything of the kind. I had a major issue with RF in the shack in the past, so I had to invest a lot of time and effort to get it fixed. Primarily by getting RF ground right.
It sure looks like Flex 6000 are very sensitive to RFI, so special attention to RF grounding needs to paid.
As part of the solution, I use ferrite clamps on all cables switched to the radio, including Ethernet, power, headset, microphone and all others. This alone eliminates 75% of RFI. Another 20% is about your grounding wires (should be connected as a "star" to the main wire which goes outside to the main ground. And the remaining 5% are sometimes a complete mystery. In my case I had to re-run one of the rotator cables.
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Dave - WB5NHL

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Ken, an easy solution that might help addresses the length of your shack ground. My shack is in the "bonus" room (a southern term for room/bed room over the garage). Being on the equivalent of the second floor my shack RF ground is a significant fraction of a wavelength particularly at higher bands. This caused me to have some RF hot grounds on the equipment!!!

The solution for me was easy..... artificial ground, the cheap way. I use some old multi-wire cable. Stripped the outer covering and cut one wire to be ~1/4 wavelength at each ham band. I attached the common ends to point where the station ground exits the shack and laid the wires in the unused attic storage floor.

No more RF in the shack. The 1/4 wavelength wires make the ground point look like ~0 ohms from an RF perspective.