[RFI] Poor man's portable spectrum analyzer

[Dave Cole (NK7Z)]

Hi,

I have been using an SDRPlay RSP-1, and one of those portable seven inch 
"official" Raspberry Pi touch screens, and the "official" case, as my 
goto portable SDR/loop.

I set up my portable SDR using a Raspberry Pi, mounted in the touch 
screen "official" case, and using an external battery.  I use one of 
those portable rechargeable batteries that are designed to recharge an 
iPhone.  I Velcro it to the touch screen case.

You could use a laptop in place of the Pi/screen combination, then 
download the Spectrum Analyzer software beta off of the SDRPlay site and 
run that if you want absolute numbers.

Works like a charm and gives me a totally portable SDR.  I also use an 
application called "Theodolite" on my iPhone.  Theodolite will do on-map 
live triangulations from two bearings.  I just site down the center of 
the loop after I null the offending signal, then, using the iPhone I hit 
the "A" button in Theodolite.  Next I move to a new location, do it 
again from that second location, then this time hit the the "B" button. 
Theodolite then draws a map with two bearing lines that hopefully cross 
someplace.  If they do cross, I then go to that location and do it all 
again.  After two or three of these, I use the three element Yagi on VHF.


See:

https://www.nk7z.net/sdr-rfi-survey-p1/

for part 1 on how I characterize my RFI environment.  Part 2 is linked 
from there as well, and goes further, and covers interpretation of what 
you see as well.

It really helps me to have an overview of my RFI environment before I 
start hunting.  It lets me ID the offending signal by what it looks like 
on the waterfall.  Then when I am portable with the loop, I look for 
that signals signature again, once I find it, I just turn the loop until 
I get a dip on that signal.  That lets me sort which signal I am 
tracking from all the others...

The entire setup costs around 100 bucks...


73s and thanks,
Dave
NK7Z
https://www.nk7z.net

On 07/13/2018 07:16 AM, N2TK, Tony wrote:
> Looking for something portable that would show the spectrum 160-2M with some
> kind of small loop directional antenna. The purpose is to walk the
> neighborhood looking for noise sources. I had used my car AM radio to track
> down a bad wideband noise source that turned out to be a leaking transformer
> about a mile away. It was quickly replaced.
> 
> I have a dusk to dawn noise source that is on 1817, 1825, and 1828 only. I
> have been using my Tecsun PL-880. So far I got the general direction and
> have to go farther out at night to try to find it.
> 
> Because of these type of noise sources  I was wondering if there is
> something available other than the $1K high end portable spectrum analyzers
> that I could use to walk the neighborhood looking for noise sources that
> affect the Ham bands?
> Tnx for any feedback
> N2TK, Tony
> 
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