[Uram-rejections] What repeaters can you access?

Wed Mar 16 17:40:35 GMT 2016

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> From webstump at chiark.greenend.org.uk Wed Mar 16 17:15:51 2016
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> From: "Jimbo ..." <james.stewart497 at ntlworld.com>
> Newsgroups: uk.radio.amateur.moderated
> Subject: Re: What repeaters can you access?
> Date: Wed, 16 Mar 2016 17:15:14 -0000
> Organization: A noiseless patient Spider
> Message-ID: <ncc451$ldp$1 at dont-email.me>
> References: <nc6aor$o8l$1 at gioia.aioe.org> <memo.20160315091500.2260H at postmaster.cix.co.uk> <nc9cve$1cta$1 at gioia.aioe.org> <nc9r8f$vgk$1 at dont-email.me> <nca6oo$n97$1 at gioia.aioe.org> <ncb56s$re1$1 at dont-email.me> <ncbkuk$juu$1 at gioia.aioe.org> <ncbq7d$9ur$1 at dont-email.me> <ncbub6$s49$1 at jstuckle.eternal-september.org> <ncc0jo$62a$1 at dont-email.me>
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> 
> "Brian Reay" <no.sp at m.com> wrote in message 
> news:ncc0jo$62a$1 at dont-email.me...
> > On 16/03/16 15:36, Jerry Stuckle wrote:
> >> On 3/16/2016 10:25 AM, Brian Reay wrote:
> >>> On 16/03/16 12:52, Jeff wrote:
> >>>>
> >>>>>> You are right, nowadays stability is not an issue, even the amateur
> >>>>>> repeaters use GPS synchronized oscillators.
> >>>>>>
> >>>>>> At VHF doppler (one TX behind you, one TX in front of you), is 
> >>>>>> limited
> >>>>>> to 200 Hz (900 km/h), but at UHF it can be around 600 Hz for 900 
> >>>>>> km/h.
> >>>>>> For aircraft flying above Mach 1 the situation is different (worse).
> >>>>>
> >>>>> Can amateurs transmit from aircraft in P land? Our licence doesn't 
> >>>>> allow
> >>>>> it?
> >>>>>
> >>>>> If you can't, we only need to consider the 200Hz figure, as air band
> >>>>> is VHF
> >>>>> (other than mil. air band).
> >>>>>
> >>>>
> >>>> If you are not considering /AM then the figure is a lot less than 
> >>>> 200Hz,
> >>>> I can't think of a car that goes at 900 km/h!!!!!
> >>>>
> >>>> Jeff
> >>>
> >>> Indeed Jeff, which is why I asked about /AM in P land. Plus, of course,
> >>> even light aircraft (the type most PPLs fly) aren't that rapid. I forget
> >>> the recommended cruising speed of the Robin DR400 but I think is was
> >>> about 65kts.Even allowing for a tail wind, getting to 900km/h would be
> >>> 'adventurous' ;-) but I'm sure Wimpie wasn't suggesting that could
> >>> happen. However, mil. jets do use the VHF aviation band so Wimpie's
> >>> point is valid.
> >>>
> >>> Perhaps it would be better to come at from the other direction (no pun
> >>> intended), and ask what difference/error in frequency due to Doppler
> >>> shift is the the performance degraded to a point defined as being out of
> >>> spec. Then, use that to calculate the speed (or speeds, they will vary
> >>> slighlty across the band) the vehicle can be travelling.
> >>>
> >>> I suspect the tolerable error is small as trouble has been taken to lock
> >>> the units frequency together but there may be another reason for that
> >>> and I confess I'm not with the details of the system.
> >>>
> >>
> >> Most single engine light planes (not light sport category) cruise in the
> >> 100-140 kt range, with a few above or below that.  Turboprops may get up
> >> to 200 kts.  Most can't afford multi-engine planes as a hobby (not that
> >> single engines are cheap).
> >
> > Oh, quicker than I thought. Perhaps I was thinking of the optimal climb 
> > speed, it is some decades since I let my qualification lapse. I have 
> > thought of renewing it but I can't see my having the time to make it 
> > worthwhile. Plus my stroke may be an issue.
> >
> >
> >>
> >> And at those speeds, Doppler shift would be less than error margins
> >> unless you had some expensive, lab grade equipment.
> >>
> >> GPS detects location by the difference between time signals received
> >> from the satellites, and velocity by the differences between locations.
> >>   AFAIK, it doesn't use Doppler shift at all.
> >
> > Trigulation. But we weren't discussing Doppler on the GPS signal, Wimpie 
> > was referring to Doppler shift on the voice channel- hence the difference 
> > at UHF.
> >
> >
> >
> >
> we should be discussing what repeater to use ...I suggest the thread ends 
> now ...... 
> 
> 
> 
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