[amsat-bb] Re: D-STAR repeater problems in Copenhagen
oz1my at privat.dk
Mon Dec 8 08:33:46 PST 2008
Hi Graham, Trevor and David and the rest of the "listeners" on the amsat-bb
Thanks for the answers.
I may return to this subject later - but I found a very interesting
It looks like a very solid piece of work to me.
----- Original Message -----
From: "Trevor" <m5aka at yahoo.co.uk>
To: <amsat-bb at amsat.org>
Sent: Monday, December 08, 2008 12:52 AM
Subject: [amsat-bb] Re: D-STAR repeater problems in Copenhagen
> D-STAR repeaters should theoretically be less of a problem on 145.7875 MHz
than 2.5 kHz deviation FM repeaters as they have a slightly narrower
> The use of 145.7875 assumes that people are using 2.5 kHz deviation FM
radios fitted with filters with an 8 kHz bandwidth at -6db and max 16 kHz BW
at -60 db, however, in practice most Amateur rigs don't meet that spec.
Realistically anyone within 15 km of an FM or D-STAR repeater on 145.7885 is
going to find the ISS downlink gets clobbered.
> The IARU bandplan allocates 145.800-146.000 MHz to the Amateur Satellite
service, doppler causes the 5 kHz deviation ISS signal to be below 145.8
thus there is a conflict with the IARU Region 1 2.5 kHz deviation FM
repeater output channel on 145.7875.
> Lets hope that eventually the ICOM and Kenwood NXDN™ 6.25 kHz channel
spacing Digital Voice standard is adopted for 2 metre repeaters as a
replacement for FM with an upper channel limit of 145.7875 MHz.
> 73 Trevor M5AKA
> --- On Sun, 7/12/08, G0MRF at aol.com <G0MRF at aol.com> wrote:
> > From: G0MRF at aol.com <G0MRF at aol.com>
> > Subject: [amsat-bb] Re: D-STAR repeater problems in Copenhagen
> > To: oz1my at privat.dk, amsat-bb at amsat.org
> > Date: Sunday, 7 December, 2008, 11:28 PM
> > Hello Ib.
> > Interesting allocation for D-Star.
> > -60dB at 145.800 may sound suitable, but in practice what
> > matters is how
> > many dB down it is at 145.800 minus one half of the
> > bandwidth of your IF filter.
> > Ball park.........
> > So -4kHz of doppler and -7.5kHz for a narrow FM filter
> > gives your receivers
> > bandpass down to 145.7885 MHz just 10k above the D-Star
> > Which means the two are probably going to overlap.
> > 73
> > David
> > In a message dated 07/12/2008 20:34:56 GMT Standard Time,
> > oz1my at privat.dk
> > writes:
> > The theoretic spectrum should be more than 60 dB down
> > on 145.800 MHz,but that does not seem to be the case.
> > Including doppler the downlink from ISS is 145.796 MHz,
> > when
> > it is going away from us to the East, which is the
> > direction
> > of the repeater :-(
> > Personally I am just 6 km away from the repeater with
> > no obstructions on the pass from it.
> > _______________________________________________
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