[RFI] HIGH POWER and RFI...
jim at audiosystemsgroup.com
Mon Mar 5 11:43:51 EST 2007
On Mon, 5 Mar 2007 14:41:13 +0100, Claudio Astorri wrote:
>He wanted kindly to inform me that on his computer's speakers and on the
>phone he could listen to me (not so loudly.) all weekend long.
It is VERY important that you make you neighbor understand that THIS is
the cause of his problem, not your station. He would have the same
problem if he lived near any other transmitter, like a broadcast station.
Both of these product types are very cheaply made, and are well known to
have poor rejection of RF. They usually suffer from all of the following
1) They are unshielded (in plastic boxes), so the internal wiring acts as
an antenna to receive your signal.
2) They lack RF filtering on their signal wiring, so that signal wiring
acts as a receiving antenna.
3) They have "pin 1 problems," which also causes their wiring to act as
4) Every semiconductor junction in the box can function as an RF
RF gets into equipment by a COMBINATION of these mechanisms. Some may be
stronger than others. You may fix one and still have some RFI from one of
A US company called K-Com sells a very effective filter for telephones.
You can find them on the internet. They come with US-style connectors
(like Ethernet connectors, but 4 contacts).
You can fix problem #3 with BIG ferrite chokes. See my tutorial for
The only fix for problem #1 is the bucket treatment. Fill a bucket with
water. Put the speakers in two times. Take them out once.
Jim Brown K9YC
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