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Messages - IQ_imbalance

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There's a company that benchmarks and assembles desktops based on intended software use....


0323 UTC:  news story about longline fishing negotiations
0329 UTC:  music
S2-3; SIO 333.  Pretty amazed that it's coming in this well! 

Equipment / Re: Question about radiation.
« on: June 30, 2019, 2326 UTC »
Ditto what Chris said.  Alpha emitters are harmless until you ingest or inhale them.  It's probably radium, but could be promethium, strontium, or (less likely) tritium....(https://www.orau.org/ptp/collection/radioluminescent/radioluminescentinfo.htm).  Promethium, strontium, and tritium are beta emitters which aren't quite as bad when ingested as alpha emitters, but you still want to limit your exposure as much as possible.

I think it would be a very interesting question which isotope the USSR preferred for their instrumentation. 

There are spectrum analyzers that can measure the radioactivity coming off a sample and return a list of the radionuclides present.  If you know any first responder types you might ask them if they have access to one....

Perhaps you could seal the paint back onto the radio with some nail polish or something similar?

Two signal enter.  One signal leave.

HF Mystery Signals / UNID pips ~ 14220kHz 1337 UTC 7 June 2019
« on: June 08, 2019, 1806 UTC »
These came up at multiple frequencies (although I don't recall if they were concurrent) on the morning of 7 June.  Interesting thing is the train on a frequency would cycle up in magnitude and back down again....maybe a directional antenna sweeping around? 

2008 UTC AC/DC Hells Bells...right at QRN. SIO 222, brief bump up to SIO 333
2011 UTC AC/DC Shoot to Thrill
2016 UTC AC/DC ???
2019 UTC off?

1643 UTC:  Irish music.  S1-S2, SIO 344.
1645 UTC: ID as Irish Rose Radio
1651 UTC:  off the air due to banshees
1657 UTC: back on the air?
1703 UTC:  S2-S3 w/more Irish music.

started off as carrier only, now instrumental music  SIO 333.
1630 UTC:  back to just a carrier with the occasional hint of music.
1634 UTC: switched to the loop and got slightly better reception.  some peaks at S2.
1708 UTC: off

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"

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

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


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....Iíd try fine tuning in the op25 program and then punch that corrected freq into trunk.tsv as the control freq.

For the constellation plot (Ď2í) apparently youíre trying to minimize the spread of the data points within each of the 4 sections.  I THINK what you want in the datascope (Ď4í) is 6 very distinct and clear openings in the data stream....this isnít perfect but gives you some idea of what Iím talking about...

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...

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...

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.

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