800 MHz sweeper?

mancow · Jul 14, 2018

Recently I've noticed what looks similar to the HF propagation sweepers but in the 800 MHz range. It starts at 831.600 and sweeps to 861.450 in 150 kHz steps every 17 seconds.

Any ideas what this could be from?

W8RMH · Jul 14, 2018

Maybe Spread-spectrum telecommunications.

mancow · Jul 15, 2018

Yea I wonder if it's a 900 MHz image or maybe something local in the house or nearby or there is some sort of diagnostic system at the local P25 system tower that is sweeping the antenna for resonance. At least that's what I can theorize.

RFI-EMI-GUY · Jul 15, 2018

Certainly does not sound like anything FCC compliant. When you track it down, let us know.

You might check to see if their is a fundamental at 1/3 or 1/9 etc ., of the frequency. It could be a harmonic from some other service.

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RFI-EMI-GUY · Jul 15, 2018

Do you have another scanner running neaby?

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Ubbe · Jul 15, 2018

It couldn't be any of your own receivers searching that range and you pick up its local oscillator?

/Ubbe

mancow · Jul 15, 2018

RFI-EMI-GUY said:
Do you have another scanner running neaby?

Sent from my SM-T350 using Tapatalk

I do. Now it is gone. I wonder if propagation was bringing it in. I will try to set up the same scanners and watch for it again tonight to see if it can be duplicated.

zz0468 · Jul 15, 2018

If you see it again, try changing the RF bandwidth of the SDR and see if it goes away with either a wider or narrower RF span. Frequently, when I see anomalies, changing the span I'm watching makes them go away. I'm not sure what the mechanism is, but it might be some sort of aliasing occurring in the A/D sampling.

majoco · Jul 15, 2018

What receiver are you using? If it's something with a wide open front end, ie. no filters, it could be a sweeper in a completely different frequency band.

RFI-EMI-GUY · Jul 15, 2018

Maybe one of your neighbors bought one of these to mess with you:

RFSG002 -- 45 - 2700 MHz RF Signal Generator On Sale! - HCF Engineering

http://www.hcfengineering.com/RFSG002_PS_REVD.pdf?attredirects=0&d=1

I bought one a few years back for a project and it has a pretty cool frequency sweeper. I just swept the FRS/GMRS band the other day and honestly, this could be used as a jammer with a proper amplifier connected. I bought it as a portable generator to test repeater desense in the field so I wouldn't need to lug my 8920B onto planes. The only complaint is that the 1000 Hz tone isn't quite 1000 Hz so my Motorola portable SINAD meter said "meh?" when connected.

mancow · Jul 15, 2018

majoco said:
What receiver are you using? If it's something with a wide open front end, ie. no filters, it could be a sweeper in a completely different frequency band.

Airspy 2 on a DPD Productions LOG periodic at about 25 ft.

mancow · Jul 15, 2018

Ah geez, it's the PRO-197 searching lowband from 35-50 MHz. I disregarded it because the 197 didn't have an antenna attached at the time.

Don't I feel stupid.

800 MHz sweeper?

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