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Author Topic: Tiny Spectrum Analyzer for Noise Direction Finding  (Read 287 times)

KK4GMU

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Tiny Spectrum Analyzer for Noise Direction Finding
« on: January 22, 2023, 02:44:18 PM »

I have continuous (not pulsing) broadband noise (rushing water) across the 2 meter band that ranges between S2 and S9 on my IC-7100. 80% of the time it is above S4; 30% of the time it is above S8 and varies throughout the day in no discernable pattern. I have confirmed that the noise is coming from OUTSIDE my QTH.

Would the Tiny SAs such as this:
https://www.amazon.com/Portable-tinySA-Spectrum-Analyzer-Touchscreen/dp/B08H1S2SYR/ref=sr_1_6?keywords=spectrum+analyzer+handheld&qid=1674426525&sr=8-6&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840
be useful for a search of the noise source?

If so, what type of antenna is most useful:  A small receive loop, or a small handheld yagi or something else?

Or would I be better off hooking up the appropriate direction finding antenna to my Kenwood 2 meter HT?
Or other noise finding method?
« Last Edit: January 22, 2023, 02:51:45 PM by KK4GMU »
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IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

W9IQ

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Re: Tiny Spectrum Analyzer for Noise Direction Finding
« Reply #1 on: January 22, 2023, 02:48:49 PM »

You will probably find that the stock telescoping antenna is sufficient. You can reduce its length and shield it with your body to give it sufficient directivity on 2 meters. I have even taken the antenna off all together for very close in snooping.

I do carry a programmable attenuator in my kit as well.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

K6AER

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Re: Tiny Spectrum Analyzer for Noise Direction Finding
« Reply #2 on: January 22, 2023, 03:53:47 PM »

You will only need one 30 dB pad. The analyzer has 80dB of dynamic range. The signal signature is great on a VNA for interference work.

I use one with a ferrite antenna stick for HF and a 3 element beam for VHF.

Lastly a ultra-sonic dish will also come in handy.
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KK4GMU

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Re: Tiny Spectrum Analyzer for Noise Direction Finding
« Reply #3 on: January 22, 2023, 03:57:24 PM »

What would be more accurate and easier to use for noise direction finding on 2 meters, an RA or VNA?

I already own a tiny VNA.
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IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

KK4GMU

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Re: Tiny Spectrum Analyzer for Noise Direction Finding
« Reply #4 on: January 23, 2023, 04:20:42 AM »

...or would I be just as well off using my 2 meter Kenwood HT with the "proper" direction finding antenna?  Then what is the recommended broad band noise hunting antenna for 2 meters?
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VK3OD

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Re: Tiny Spectrum Analyzer for Noise Direction Finding
« Reply #5 on: January 27, 2023, 09:25:53 PM »

Just use what is known to work. A2 metre radio in AM mode with a directional antenna. I have built a small moxon, tape measure yagi and a simple dipole. A 10,20, 30 db attenuator can be helpful.

Not all interference extends above 200 mhz, however if you can hear the same interference around 300 to 340mhz on AM you are pretty close to the source. 440mhz has similar characteristics in terms of finding close by interference. From experience the interference has to be pretty bad to extend above 200mhz. It mostly powerline arcs that extend this far.

I would starting cruising around your blocks in the neighbourhood with the whip antenna and attenuator. its amazing how you can almost nail the source of the interference just using nulls and attenuation if you are persistent.

Good luck.

...or would I be just as well off using my 2 meter Kenwood HT with the "proper" direction finding antenna?  Then what is the recommended broad band noise hunting antenna for 2 meters?
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WA3SKN

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Re: Tiny Spectrum Analyzer for Noise Direction Finding
« Reply #6 on: January 31, 2023, 03:35:47 PM »

Does the HT have a signal level indicator (S meter)?
How hard is it to make the ic7100 portable?
It is usually easier to use AM than FM to locate a noise source.  Since you are already detecting it you should only need a receiver and a directional antenna... and maybe an attenuator.
The best antenna for this that I have found is two dipoles spaced 1/4 wave apart with a 1/4 wave out-of-phase wire feed and end fed.The dipoles do not have to be a full 1/2 wavelength... they can be shorter.  The wire between them can be ladder line or open wire with a twist.  You get a cardiod pattern with a single null.  And the null points in the direction of the signal.
Since it is outside, go to the four corners of the house or yard and try to get directional readings for the null.  They should meet at the location of the noise source.  The more different locations in the area, the more line crossings to verify the location of the source.
The antenna is an easy build since it is receive only... just don't transmit into it!  Leave the mic unplugged.

-Mike.
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W9IQ

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Re: Tiny Spectrum Analyzer for Noise Direction Finding
« Reply #7 on: January 31, 2023, 04:08:49 PM »

What would be more accurate and easier to use for noise direction finding on 2 meters, an RA or VNA?

I already own a tiny VNA.

I think you mean a nanoVNA vs a tinySA. The tinySA is the way to go.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.
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