P25 -APCO (APCO P25 Phase I, Motorola, EDACS, LTR

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Re: P25 -APCO (APCO P25 Phase I, Motorola, EDACS, LTR

Postby jimh » Mon Dec 07, 2015 8:20 pm

> so is there anywhere in UK that is unencrypted
The Salisbury Plain SPTA P25 system has always been in the clear. I've heard some Fairford P25 in the clear (but a lot is encrypted too) and at least some Croughton comms also in the clear.
I've only ever heard HMRC using P25 in encrypted mode.
Can't comment on the others listed in this thread.

>Did the USA also change to digital cellphone
The world moved from 1G to 2G, then onto 3G etc. The North American analogue AMPS network was switched off in 2008.

>spend thousands to listen to tetra but it is possible
Technically speaking, building a TETRA decoder is quite cheap with the right software and an SDR dongle. It's the encryption that's the difficult bit, which would cost a small fortune to break. But of course your point about Radio User printing duff information on a monthly basis is well made: simply not worth paying the money for IMHO.
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Re: P25 -APCO (APCO P25 Phase I, Motorola, EDACS, LTR

Postby G4RMT » Tue Dec 08, 2015 12:24 pm

The decision to always denote a USAF base as an RAF one is an historic one, and does actually make sense. If they were the same status as an embassy, for example, then they would be outside UK Government control - the USAF are effectively tenants, they don't own the site and have any diplomatic status. So in effect, the RAF 'hosts' the USAF as guests. The actual document explaining how it works is now available https://www.gov.uk/government/uploads/s ... 51_doc.pdf
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Re: P25 -APCO (APCO P25 Phase I, Motorola, EDACS, LTR

Postby Minus1 » Tue Dec 08, 2015 4:42 pm

I'm not aware of any US P25 transmissions that are encrypted except Menwith Hill.

Everything else I've heard, including fire dept, police, maintenance is unencrypted.

I've heard unencrypted stuff from Molesworth, both in the area and via occasional dx. Fire Dept TGID is 46118.
Alconbury, I believe, use the same mast (at Molesworth). I found no base transmissions at Alconbury. Explains why it's so powerful too.
I reserve the right to ignore people who have made no attempt to the read the manual, and expect others to do it for them.
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Re: P25 -APCO (APCO P25 Phase I, Motorola, EDACS, LTR

Postby Fires999 » Wed Dec 09, 2015 2:19 am

Morning Minus 1,
Ok to PM you ? Got some info re Alconbury and Molesworth.
Thanks
Fires999 :smiles:
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Re: P25 -APCO (APCO P25 Phase I, Motorola, EDACS, LTR

Postby Minus1 » Fri Jan 08, 2016 10:36 am

jimh wrote:OK many thanks for that document.

But isn't that just saying that there a number of airwave freqs made available in the 420mhz range for base, 410mhz for terminals. It then shows where use of those channels would interfere with existing users of that spectrum....largely USAF bases.

None of the freqs listed earlier match the airwave freqs in the document.

Where they're close they nearly match the airwave portable freqs, which are very difficult to detect with a scanner anyway.

And where they do match listings in the back of the document, the bandwidth of the transmissions are under the 25khz needed by airwave TETRA.

I actually see that document as further proof that these aren't airwave comms on these two frequencies ? Does that make sense?


The 410-412 and 420-422 band is only used for Airwave in London as far as I know.
And not all channels in the band are used.
USAF use of the band is far enough away to not be an issue, given the relatively short range of an Airwave transmitter.
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