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Re: [Discuss-gnuradio] The PLL for the burst signal


From: Ron Economos
Subject: Re: [Discuss-gnuradio] The PLL for the burst signal
Date: Sun, 23 Apr 2017 14:51:40 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0

Current NTIA spectrum documents are here:

https://www.ntia.doc.gov/page/federal-government-spectrum-use-reports-225mhz-6ghz

Ron

On 04/23/2017 02:29 PM, Vitt Benv wrote:
Hello!
About frequencies pay attention that there are more than a single (406.025 MHz) frequency.
In my direct experience there's also 406.028 / 406.039 MHZ in use. So also tuning has to be on the right frequency.

Take a look also at https://www.ntia.doc.gov/files/ntia/publications/compendium/0406.00-0406.10_01MAR14.pdf , but I suppose that also this document isn't up-to-date...

2017-04-23 17:07 GMT+02:00 Marcus Müller <address@hidden>:
Had to google that; for the others: http://www.epirb.com/

Emergency Position Indicating Radio Beacon ; 406 MHz, bursty, wikipedia
says:

> The digital distress message generated by the beacon varies according
to the above factors and is encoded in 30 hexadecimal characters. The
unique 15-character digital identity (the 15-hex ID) is hard-coded in
the firmware of the beacon. The 406.025 MHz carrier signal is modulated
plus or minus 1.1 radians with the data encoded using Manchester
encoding, which ensures a net zero phase shift aiding Doppler location

So, a PSK that can only take values of +1.1 and -1.1, relative to the
"idle" carrier. Bit rate is 400b/s, so that makes it a 800 S/s PSK
symbol rate (manchester-encoding happening in between).

Cheers,
Marcus

[1]
http://www.cospas-sarsat.int/images/stories/SystemDocs/Current/cs_t.001_oct_2013.pdf

On 04/23/2017 04:48 PM, Vicfield Medici wrote:
> Hi,
>
> When trying to decode the signal, I always use the PLL Carrier Tracking to
> solve the error
> about phase shifting, and it’s always doing a good job.
>
> But I start trying to decode the EPIRB signal, I just got a sample with only
> one burst,
>  and PLL seems not work anymore even I tuned the parameter in many ways.
>
> Does the PLL Carrier Tracking can’t handle the discontinuous signal somehow?
> Or it’s my misunderstanding?
>
> I really want to know how to take that, thanks for any help.
>
> Regards,
>
> Vicfield
>


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