[RFI] Recent Posting on RFI with intercom.

[Tom Rauch]

> First, forget the high pass filter -- it won't help at all
with RF that isn't
> detected  by the input stage of the FM radio. And, as Tom
Rauch noted, the
> high pass filter is only configured for differential mode
RF. You've got
> common mode RF.


Jim had some good suggestions, and let me add one more
thing.

When I had to RF proof systems in or near high power BC
stations, without fail high pass filters did NOTHING. What I
did do successfully is use a pair of back to back baluns
with a Drake 300-ohm filter in between, but the cures Jim
suggested work just as well. (The old Drake filter was
almost like disconnecting the antenna lead for common mode,
most other filters did nothing.)

What won't work for sure is using a regular 75 ohm
high-pass.

I had a large box full of filters (literally hundreds of
them) I pulled out of apartments and homes near BC stations.
The RFI was cured simply by grounding the shield of the
cable to the power line safety ground feeding the consumer
device, and the filters weren't needed.

73 Tom