When I need to DF something in the HF spectrum I have had much success
using the National RF Model HFDF Vector Gun kit.
It is a loop antenna system with a wideband tunable amplifier. DFing with a
loop antenna requires multiple bearings to be taken and plotted to see
where they cross. Your source will be very close to the point where the
lines cross.
Search this reflector's archive for lots of discussion about the HFDF and
loop DFing.
Good luck!
Frank N Haas KB4T
Utility Interference Investigator
Florida
On Sun, Dec 23, 2018, 21:06 bill K7WXW <K7WXW@qrpdx.org wrote:
> First, thanks for the help and suggestions. A number of people thought
> my laptop might be generating artifacts, so I ran a couple of tests.
>
> On the assumption that the laptop was generating the RFI:
>
> 1. Separating the laptop and SDR by a long USB cable that had two 31
> clamp on ferrites.
> 2. Running the captures using a different computer.
>
> Distance made no discernible difference in signal strength. I changed
> the distance between the laptop from sitting on the SDR to six feet
> away. Change in computer also made no discernable difference. I am not
> completely convinced that the SA software isn't creating artifacts but
> there does appear to be some signal there that it is seeing.
>
> I put a Siglent spectrum analyzer on the feedline. I just got this box
> and I haven't used an SA for forty years, so I have a bit of a learning
> curve but I know the basics. There still appear to be groups of
> frequency spikes separated by 10KHz. They are a good deal easier to see
> and measure on the SA. There is also pairs, separated by 69.33Khz,
> which are actually much stronger. The noise spans roughly 2 to 5 Mhz,
> and is strongest from 2.8 to 4.2 Mhz. Net the spikes, the noise floor
> is roughly -100dBm, as I would expect in my part of the world.
>
> Based on the data I've already collected, I am guessing this source is
> outside my home. Next step is to figure out how to track it down. I can
> use the SDR/laptop setup, even though I can't fully trust it.
>
> 73 Bill K7WXW
>
>
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