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Re: [RFI] Poor man's portable spectrum analyzer

To: rfi@contesting.com
Subject: Re: [RFI] Poor man's portable spectrum analyzer
From: "Dave Cole (NK7Z)" <dave@nk7z.net>
Date: Fri, 13 Jul 2018 07:59:04 -0700
List-post: <mailto:rfi@contesting.com>
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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