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Frustrating mid VHF interference

zefie

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Premium Subscriber
Joined
Apr 5, 2013
Messages
45
Location
Columbia County, NY
I have been experiencing interference that looks like wide-band data bursts from 120MHz - 150MHz+ which is destroying my NOAA APT captures.

Here is a YouTube video of it happening:


What its not:
- My phone or router (tested LTE/2.4ghz/5ghz/Bluetooth)
- My PC directly (only happens on outdoor antenna, tried different ports)
- Likely anything in my house (don't run much, tested appliances and other electronics, and could not find any correlation between anything and the interference)

What I've tried:
- MW High-pass
- FM Filter
- Ferrite on each end of every cable used
- Air Choke coil (this has the most effect, without the coil, the energy bursts are stronger, but shortening or lengthening the coil does not appear to help)

Geo Info:
- Using an AirSpy R2, although interference can also be observed on RTL dongle attached to same antenna
- A supermarket is within 1000 feet
- An iHeartRadio tower broadcasting 1230 KHz and 93.5 MHz at 1 kW is within 1 mile
- An iHeartRadio tower broadcasting 98.5 MHz at 1 kW is within 5 miles
- LTE signal is strong with this antenna.
- Antenna is Custom Turnstile made of Coathangers
- Is intermittent, but damn coincidental with satellite passes (happens other times too)
- This is what it does to APT captures

Any ideas would be appreciated, thanks in advance.
 

iMONITOR

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Sep 20, 2006
Messages
6,643
Location
MACOMB, MI.
The Par VHFSYM152HT is scanner intermod filter that has a notch band of 152 to 153 MHz and a useful passband of 0 to 1 GHz. The notch band covers the offensive pagers in this range. The notch depth is up to >38 dB. Typically, PAR symmetrical filters have a 3dB bandwidth of ± 1.5% or roughly 2.25 MHz for VHF HI filters. Designed for receive-only, scanner use. BNC female input and BNC male output. Size: 4 x 2 x 0.75 inches. Made in the U.S.A.
PAR VHFSYM152HT Scanner Intermod Filter
1552840151130.png
 

Ubbe

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Joined
Sep 8, 2006
Messages
3,146
Location
Stockholm, Sweden
Looks like normal SDR receiver overload? Try to find where the signal are strongest in your whole frequency range. It looks as if it gets stronger the higher the frequency are. Maybe you'll find the peak where a signal goes up to the top and then you will know what frequency to use for a notch filter.

/Ubbe
 

zefie

Member
Premium Subscriber
Joined
Apr 5, 2013
Messages
45
Location
Columbia County, NY
The Par VHFSYM152HT is scanner intermod filter that has a notch band of 152 to 153 MHz and a useful passband of 0 to 1 GHz. The notch band covers the offensive pagers in this range. The notch depth is up to >38 dB. Typically, PAR symmetrical filters have a 3dB bandwidth of ± 1.5% or roughly 2.25 MHz for VHF HI filters. Designed for receive-only, scanner use. BNC female input and BNC male output. Size: 4 x 2 x 0.75 inches. Made in the U.S.A.
PAR VHFSYM152HT Scanner Intermod Filter
I will keep this in mind, but I don't think its pager related. We do have a few pager systems here, but none are that strong or wide enough to cause such interference, unless their transmitter is damaged.

Looks like normal SDR receiver overload? Try to find where the signal are strongest in your whole frequency range. It looks as if it gets stronger the higher the frequency are. Maybe you'll find the peak where a signal goes up to the top and then you will know what frequency to use for a notch filter.

/Ubbe
I have not been able to find another signal that looks and behaves like this interference. It looks almost like 2.4ghz Wifi/BT but that is outside of my tuner's range, plus I did speed tests and stuff on my connected equipment to force high Wifi usage and it did not correlate to the noise. Unless its someone else's wifi.

---

Something of interest I did find though, is that the cable TV system may be leaking RF. My antenna run is nowhere near the cable lines (outside or inside. About 25ft is the closest the two shielded RC6 ever get), but yet I can get faint audio from their TV channels. (Ch 6 fadeoff is from FM trap)

SDRSharp_2019-03-17_21-13-32.png

I know this is from CATV because where else would the "QVC" channel be coming from, plus it matches up with CATV Ch 5, which is QVC.


Problem is this is probably just one of many RF leakages in this area because I don't think the interference in the original post is caused by the CATV RF leak, because the QVC audio is consistent, the noise as you can see, is not.
1552873111727.png
 
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