[RFI] National RF HFDF Vector Gun Update

Paul Christensen w9ac at arrl.net
Sun Jul 10 14:31:35 PDT 2011

Great news, Frank.  Thanks for investigating this product for us.

Paul, W9AC

----- Original Message ----- 
From: "Frank N. Haas KB4T" <utility.rfi.pro at gmail.com>
To: "Paul Christensen" <w9ac at arrl.net>
Cc: <rfi at contesting.com>
Sent: Sunday, July 10, 2011 5:14 PM
Subject: Re: National RF HFDF Vector Gun Update

> Paul:
> National RF now offers loops that go as low as 3.8 MHz. They may not
> have updated their web site.
> Back in Feb 2011 when I first spoke with NRF, I inquired about a loop
> option down to 3 MHz. I was told that one had been created that went
> down to 3.8 MHz  but it  not been fully tested. I got one and it works
> well for me.
> 73 de Frank KB4T
> On 7/10/11, Paul Christensen <w9ac at arrl.net> wrote:
>>> With the Vector Gun, I have been able to pinpoint 2 noisy switching
>>> power supplies that produce RFI primarily in the 10 MHz range...
>> Frank, nice report and much appreciated...
>> One limitation of the National  that it is only specified to work down to 
>> 10
>> MHz.  I had seen this unit before but stopped short of a purchase due to
>> this limitation.  I have had many instances of SMPS noise where it is 
>> only
>> prevalent between 160m and 80m and no trace of noise whatsoever at higher 
>> HF
>> frequencies.  In fact, nearly all the HF SMPS noise sources I've 
>> encountered
>> in my neighborhood have all produced noise under 6 MHz.
>> Any idea to the frequency limitation?  I suspect it is the size of the
>> antenna loop needed at the lower HF frequencies.  Also, how sharp is 
>> tuning?
>> Broadly sharp is fine -- but not too sharp that one cannot make out the
>> peaks and valleys on a pandapter when using an SDR receiver connected to 
>> the
>> RDF antenna.
>> Paul, W9AC
> -- 
> Frank N. Haas KB4T
> Utility Interference Investigator
> Florida 

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