Chasing RFI

Erik SM0JCA

Chasing RFI on my station 6400M + amplifier
I have been mitigating RFI with toroids on all station cables and measured common mode currents with a RFI meter and now most of it is down to less then 20 mA when running the amplifier at CW 1kW. However on the ground lead I have still about 300 mA RF current. The antenna is a Cushcraft R8 multiband vertical and SWR and with the tuner activated the amplifier is seeing 1:1.3. I am interested in any feedback regarding ground lead RF current level in this setup as I have no idea what is reasonable.
Erik Sm0jca

Roger_W6VZV

I cured all of my RFI problems by going to a lan cable rather than wireless.

Neal Pollack, N6YFM

Jim Gilliam

K0FLY

Neil:

Great questions, especially number 2 and 3.  The common mode choke on the Vertical is very important. You might also ask what power level the  interference starts to occur and if any one cable  toroid  reduced the problem more than others.  It might be helpful to know if the shack in on the first floor of a house or the 10th floor of a condo.

What is being interfered with, TX audio (Mic), RX audio (powered speakers), Computer etc. .  My worst problem was on 40,  RF was getting into t he computer HDMI cables, the threshold was about 130 watts.     

Other:

1) Station grounding-- Are the grounds for the Flex and Amp separate wires going to the earth point or are the two units tied together and grounded with a common wire.  Flex has a recommended grounding configuration on its site.  

2) Common mode choke on the coax between the 6400 and the AMP?  This can also help.

It's all magic

Gayle K0FLY

Erik SM0JCA

WA2SQQ

Neal Pollack, N6YFM

Eric, you mention that the antenna is only 15 to 20 feet from your radio operating point, and you were running a kilowatt. This puts you and the radios in the extreme near field. This will also explain the high rfi common mode currents, since that much RF that close will be coupling into all metal objects at a kilowatt.

Is there no option to put more distance between the antenna and the equipment, if you are going to run high power?

I know that the RF safety calculator thinks you are just about maybe safe if you switched up to the 15 meter band, but personally, I would want a little more safety margin at a kilowatt. It would be good for the RFI and also good for you. Finally, is there a specific RFI problem occurring, or are you simply trying to reduce the 80mA on the ground cable?

Cheers

Neal

Erik SM0JCA

Erik SM0JCA

Erik SM0JCA

Gene Duprey

Erik SM0JCA

Bobby

Try an mfj-915 isolator inline ... that should do it.

Gene Duprey

Ground wire does not have to be solid, but most use solid. Stranded of appropriate size will work.

FISHULA X

K9SO

Reggie

When you twisted the line isolator, did the coax on both ends of the line isolator twist together?

Reggie 

FISHULA X

  Reggie, Yes they did. And I still use this method today.

Ray Sylvester

try a simple Collins style choke on both feed lines at the shack end of both feed lines 8 turns of rg8u 10 inch in diameter .  

Ray Sylvester

w8ji web site on station grounding for lightning protection is a must read.    

Neal Pollack, N6YFM

Neal Pollack, N6YFM

Neal Pollack, N6YFM

Excellent choice!

Neal Pollack, N6YFM

K9SO

Gene Duprey

Yes we are talking about ref no dc, however braid is still poor as it weathers and becomes a noise generator. Copper wire, stranded or otherwise and copper strap is far superior. Yes braid is popular, unfortunately promoted back in the early days.

Stan VA7NF

Erik SM0JCA

WA2SQQ

I was looking for information on the meter that you're using or plans to build one online. Anything you can share would be appreciated. Not sure what to search for regarding plans to build one

Erik SM0JCA