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Re: [Discuss-gnuradio] Cross band relais / bridge - DMR?

From: Stefan Gofferje
Subject: Re: [Discuss-gnuradio] Cross band relais / bridge - DMR?
Date: Thu, 28 Apr 2011 23:19:45 +0300
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On 04/28/2011 10:03 PM, Nick Foster wrote:
>> Without any details at all on what systems you're trying to communicate
>> with, the answer is "very probably, but you'll have to do it all
>> yourself". In other words, the hardware when used with Gnuradio will
>> generate and receive pretty much any signal less than [25MHz for N210,
>> 8MHz for USRP1, ~4MHz for E100] wide. But you're going to have to
>> implement the whole transceiver system yourself, and that's not a
>> plug-and-play proposition by any stretch of the imagination.

Basically, we are just talking about good old analog FM narrowband radio
com. MAYBE - as I said as a creamtip - ETSI DMR 2 Analog. But if nobody
has written a trx yet, I guess, I have to forget about that. My
developer skills are way out of that league. There might be a chance
that I could get our boss to put out a bounty for that but I have to
prove that the USRPs are what we need before that.

>> This is readily accomplished with existing Gnuradio blocks when combined
>> with Python code for the main application. You may or may not be able to
>> get such a system working entirely within GRC. There are multiple
>> existing squelch blocks based on tone decoding and/or receive power
>> level. I've been meaning to put in an "FM quieting" squelch like COTS
>> handheld FM radios use, but haven't gotten around to it. Power squelch
>> works fine for most uses.

Marcus has already given me some pointers about the squelch / PTT thing.
One thing however is not totally clear to me.
A conventional radio has some "startup time" for the PLL to "swing in"
when you start transmitting. How is that with SDRs or the USRP in
specific? Does feeding data to the TX immediately result into a clear
and stable signal or is there also some "swing in" time to consider?

Specifically, does one have to consider some prerun time of transmitting
some "filler" before transmitting the actual payload?

- -S

- -- 
 (o_   Stefan Gofferje            | SCLT, MCP, CCSA
 //\   Reg'd Linux User #247167   | VCP #2263
 V_/_  Heckler & Koch - the original point and click interface
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