[RFI] National RF HFDF Vector Gun Update

Frank N. Haas KB4T utility.rfi.pro at gmail.com
Sun Jul 10 14:14:47 PDT 2011


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

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