[RFI] Re: Overload (was: Ferrite Loops)

[Tim Groat]

>"Ward Silver" <hwardsil at centurytel.net>:

>If they are receiving interference on just one or two channels, it's a 
>harmonic.  With a LPF, your troubles should be over.

Often true, but not necessarily...

Moderate overload of the receiver's mixer can cause high order products 
that appear to be harmonics, but aren't. For example, 2Frf +/- Flo (3rd 
order), 3Frf +/- Flo (4th order), etc. Severe overload will cause blocking 
on all channels. Lesser overload causes spurious mixer products at 
harmonically related receiver frequencies. Some sets are more prone to 
doing this than others.

You may also have harmonic generation from "rusty bolt" connections, 
broadband TV preamps, and other non-linear devices. A low-pass filter can't 
reduce harmonics generated past its output. Unfortunately, these external 
harmonic generators can be hard to track down and eliminate (especially 
when the problem source belongs to a neighbor).

73,
--Tim (KR0U)