[RFI] RFI Signature

[Frank W3LPL]

Hi Dave, 

Most inband RFI is broadband buzz caused by consumer devices 
overloaded by the extremely strong signal from the nearby ham 
transmitter. No amount of bandpass filtering will help at all. 

The most common inband RFI source is fundamental overload of 
wall wart switching power supplies, but there are many other 
possible RFI sources. They're very easy to isolate using standard 
RFI hunting methods, but God help you if the offending device is 
in a neighbor's home... 

73 
Frank 
W3LPL 




From: "David Eckhardt" <davearea51a at gmail.com> 
To: "K9YC" <jim at audiosystemsgroup.com> 
Cc: "Rfi List" <rfi at contesting.com> 
Sent: Tuesday, November 25, 2025 4:19:27 PM 
Subject: Re: [RFI] RFI Signature 

To state the obvious: Even the absolute best bandpass filter will not 
eliminate in-band RFI. 

Dave - WØLEV 

On Wed, Nov 26, 2025 at 12:16 AM Jim Brown <jim at audiosystemsgroup.com> 
wrote: 



On 11/25/2025 11:46 AM, Jeff (W4DD) wrote: 
> I think the antenna is a StepIR vertical. It seems to have a narrow BW. 

I wouldn't expect it to be narrow on receive. 

I'm not familiar with Flex rigs. Elecraft has very good RX bandpass 
filters on each band (or pairs of higher bands, and I would expect Flex 
to do the same. 

Do you hear the noise on on other bands? 

73, Jim K9YC 





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-- 

*Dave - WØLEV* 
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