apache-labs.com

Here's my story about severe RFI problems and the cure with my 7000DLE (1 week old) black.

On 40 meters and above I had the following RFI problems (All CW related)

1. Thumping in speakers when keying
2. Distorted sidetone
3. Reports from others of bad CW note (Sounded like a buzzer)

I am using a pair of RS Optimus 8 ohm speakers directly plugged into the rear 1/4" jacks.
These jacks require a Stereo type plug and the ground lead is not used. This is due to the balanced output.
RFI was much worse when using the amplifier over 400 watts.
Grounding and bonding was improved using wide braid.
When looking at my signal on another receiver I could hear my signal break into horrible sounding, wide, hash as i gradually increased power.

Unplugging the speakers and listening to my sidetone via the front panel headphone jacks eliminated the problem.

I concluded that RF was getting into the radio via the speaker leads. See schematic..No bypass capacitors inside!!

Installed 240 - 31 mix toroid rings, 15 turns on each speaker lead. Installed 3 more for antenna coax. Another on PSU cable.
No change

I replaced the shielded single wire cables to the speakers with shielded 1 pair cables. I grounded the shield to the Stereo plug's ground.
No change.

Installed a .22 uf capacitor from each of the hot speaker leads to ground inside the Stereo plug.
No change

On a hunch I measured the continuity between the 1/4" Speaker jack's nut and chassis ground lug.
Measured infinite !!! I had a floating ground.

Removed the nut from each jack, scrapped off the paint under the washer and replaced the nut.

Problem cured.. Fixed.... No thumps, clean CW note and pure sidetone! Happy user now.

Steve N4LQ

Very interesting, Steve. In the end, what did the speaker wiring wind up looking like, the shielded pair with the cap's and toroids?

Steve,

I have problems on 40 as well while running legal limit....
my question:
did you keep the shielded leads AND the 0.22 caps or did you remove them?

thanks

Volker
DL4ZBG

I ended up keeping the caps and shielded 1 pair cable. These were necessary however they couldn't work until I cleaned off the paint under the washer. There is a possibility that shielded cable isn't needed but I didn't go back and try it. The toroid aren't necessary when using shielded speaker cable.
The proper cure would be to install a capacitor to ground from all 4 speaker leads inside the radio's enclosure plus make sure the jacks are grounded.
Eventually I will get around to this.