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136

North American Shortwave Pirate / Re: Radio Boo Boo 6935 USB 2248 UTC 27 Jan 2018

« on: January 27, 2019, 2340 UTC »

2339 UTC : Metallica "Orion" S1-2 but good audio
2342 UTC: Barry Mann "Who put the Bomp in the ..."
2344 UTC: Commander Coty "Hot Rod Lincoln"
2347 UTC: Roger Miller "King of the Road"
2349 UTC: CW McCall "Convoy"

137

North American Shortwave Pirate / Cold Country Canada 6969 LSB 0035 UTC 24 Jan 2018

« on: January 24, 2019, 0037 UTC »

0035: Sweet home Alabma -137dBm, fades to QRN

138

For Sale / Wanted / Barter / Wtop broadcast studio auction

« on: January 23, 2019, 1314 UTC »

Just throwing this out there in case folks are looking for studio stuff...

M21967 WTOP Glass Enclosed Nerve Center Broadcasting - Washington, DC

WTOP Broadcast Studios Relocating - WTOP Is Moving To All New Digital
Studios And Make A Complete Liquidation Of Its Existing Studio, Editing,
Broadcast And Technical Assets. This Is A JV With Our Partners At OLS

https://rasmus-auctions.appspot.com/auctions/OwR6dTP05JkunB47BeSD?fbclid=IwAR2LynPhOTrnp9vbCBNUhYqQa45JUFrpowGiF0NfxctdVD_R-Yn42QjjQHA

139

SDR - Software Defined Radio / Re: RTLSDR based scanner for P25

« on: January 21, 2019, 0235 UTC »

Check out the SDR forum on radioreference.com...I was going through the same teething pains. Try tuning to whatever freq your rtlsdr sees as the control channel (and without a -d or -q offset) and see if you start pulling in talkgroups (audio or not). What I did from there was a lot of trial and error with the control freq in trunk.tsv....I’d try fine tuning in the op25 program and then ~~punch that corrected freq into trunk.tsv as the control freq.~~

For the constellation plot (‘2’) apparently you’re trying to minimize the spread of the data points within each of the 4 sections. I THINK what you want in the datascope (‘4’) is 6 very distinct and clear openings in the data stream....this isn’t perfect but gives you some idea of what I’m talking about...
https://goo.gl/images/q453W6

In short...tuning is a lot of trial and error!!!!

UPDATE: apparently you should put the actual control freq. from the RR database into the trunk.tsv file, and then correct any RTLSDR tuning errors within OP25 or with the -q and -d options. Not exactly sure why....

Also, here's a screencap from gnuplot on a successful tuning effort...

140

SDR - Software Defined Radio / Re: RTLSDR based scanner for P25

« on: January 20, 2019, 0256 UTC »

OK update on my 'audio issues'. Turns out they didn't have anything to do w/ the audio routines in the OP25 software...I just wasn't hitting the control frequency. I'm still trying to fine tune things, and understand why tuning the center of the control freq. doesn't apparently work (don't think there's a DC spike....). The control freq. for a system near me is 774.043750 MHz, but my RTLSDR shows it as 774.044563 (more or less). However, i don't get good decoding if I tune into the latter...in fact, i have to bump it up to 774.044900 MHz or so to get good decoding and actual audio out.

So, it's just a lot of semi-informed trial and error at the moment. At least now I know the setup works, and what a properly tuned QPSK signal should look like on the gnuplot datascope...

141

SDR - Software Defined Radio / Re: RTLSDR based scanner for P25

« on: January 19, 2019, 1516 UTC »

I'm not a hardware (or software!) guy so probably not the most informed opinion....but i wonder if dedicated hardware still has the edge for scanning purposes. I think the fast scanners do about 100 channels/s (of course, you have to identify the channels first!), but with the wide bandwidth of the SDRs it would make sense that they could identify and track transmissions a lot faster _as long as the transmissions are in that reception bandwidth_! I think it would be an interesting exercise to build something on top of a framework like rtl_power that grabs a power spectrum over a chunk of bandwidth and then shifts to the next chunk, etc. while looking for repeated transmissions on a frequency over a user-defined time frame. Unfortunately by the time i have those skills everything will be digital and encrypted, probably $:-\$

Anyone care to comment on the bottleneck is for SDR based scanners....data transfer over the network, demodulation,

There's also the issue of with things going digital, it's not so much the # of different frequencies you can scan but whether or not you can parse the data coming in.

142

SDR - Software Defined Radio / Re: RTLSDR based scanner for P25

« on: January 15, 2019, 2136 UTC »

ARGH. It's decoding the traffic (or at least recognizing broadcasts from the various talkgroups) but I can't get it to push the decoded audio to my headphones. The headphones and software audio device works (at least for speaker-check!), but I don't know if it's a decode problem or a communications problem between rx.py and the audio system

143

SDR - Software Defined Radio / RTLSDR based scanner for P25

« on: January 15, 2019, 0239 UTC »

Ran across this tutorial, and it worked very well for getting a somewhat operational (still working on audio issues!) scanner going based on a rtl-sdr stick and a Raspberry Pi...

https://www.hagensieker.com/wordpress/2018/07/17/op25-for-dummies/

144

HF Mystery Signals / Re: UNID 9000 kHz 1914 UTC 11 Jan 2019

« on: January 12, 2019, 2021 UTC »

Thanks!! No point chasing TDoA if it's just analyzing noise.

One update....there's some drift in the carrier this afternoon. Looks like it's a few Hz below 9000kHz now, but drifting back up.....

145

HF Mystery Signals / Re: UNID 9000 kHz 1914 UTC 11 Jan 2019

« on: January 12, 2019, 1823 UTC »

Has it moved again? Would be nice to catch some indication on the spectrum that there was a switch.....

Any TDoA experts care to weigh in? Are we just chasing timing errors or is this carrier really being broadcast at multiple sites?

146

HF Mystery Signals / UNID 9000 kHz 1914 UTC 11 Jan 2019

« on: January 11, 2019, 2017 UTC »

Maybe our 8000kHz carrier moved to a new frequency? -87dBm here, started around 1914 UTC 11 Jan. The spectrogram looks very similar. TDoA is all over the place, but seems to converge in the midatlantic area somewhere.

147

HF Mystery Signals / Re: UNID 8000kHz persistent signal

« on: January 11, 2019, 1723 UTC »

Back on for ~4 min 1719-1723 UTC 11 Jan and intermittently for a few minutes after: TDoA suggests not on the east coast this time:

148

HF Mystery Signals / UNID 8000 kHz 1434 UTC 10 Jan 2019 signal

« on: January 11, 2019, 0202 UTC »

Strong carrier (-85 dBm at my location currently); about 3Hz wide; might be LSB?. Has been on since at least 1434 UTC 10 Jan. TDoA during the day (~2000 UTC) suggests possibly two transmitters...one east coast, one midwest.