[RFI] Frustrating White Noise

Frank N. Haas KB4T kb4t at arrl.net
Fri Feb 19 12:34:29 PST 2010

"Gentle Readers???  Here???? 

Over what portion of the spectrum does the noise appear to be copyable?  At
what frequencies does its signal strength seem to peak? 
Take a portable receiver with a signal strength indicator tuned to the same
frequency at which you hear the signal the strongest and go for a walk or
drive around your area.  Do you notice an increase or decrease in signal

Very broadband noise like you describe could be coming from any number of
possible sources the most common of which are poorly designed and built
switching power supplies. Battery Chargers are common culprits. But it's
important to ASSUME NOTHING!!!

Take the walk or drive and see if there is an area where the signal seems to
be strongest. Once you find that spot, determine the highest frequency at
which you can still detect the noise. If it can be heard at VHF frequencies
you might be able to pinpoint it using a smallish directional antenna. If
not, a Loop Antenna should direct you to the source. 

Good luck. 


Frank N. Haas KB4T
Professional Interference Investigator

-------- Original Message ---------

Date: Fri, 19 Feb 2010 08:48:39 -0800
From: Joe <wa6rkn at gmail.com>
Subject: [RFI] Frustrating White Noise
To: "RFI" <RFI at Contesting.com>
Message-ID: <000f01cab183$64639380$cd01a8c0 at main>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";

Bear with me gentle readers, this is a tale of woe!  <<GRIN>>

About a month ago, my noise floor on 40 and 75m , ie:  white noise, rose to
9 and 10 over.  In the AM, the noise floor is where it normally is...1 - 3 s
units.  Then, around 9 or 10, give or take, the noise floor gradually climbs
back up over 9.  Temperature does not appear to be the culprit.  

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