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Re: 400.1 MHz again ...



In listening at 400.1 today I kept hearing a strong, unmodulated signal that
varied + or - about 3KHz ... It didn't seem to have any doppler ... or is the
bird in a high orbit and I just didn't listen long enough ...

John
K0UWT

Glenn Little wrote:

> AS an ex Submarine navigation ET of 22 years, I have listed to more than a
> few Transit passes.  The Transit satellite, when operating properly, was a
> carrier only.  At the even minute that was a "Barker word" that was
> transmitted.  This was the orbital elements/almanac for all satellites in
> the constalation.  The computer used the Barker Word to determine time, you
> had to know time within one minute to track a pass.  The computer used the
> doppler shift of the carrier to compute latitude and longitute offsets.
> The computer would first generate a set of expected doppler curves for
> where the nav system thought it was.  The doppler curves obtained from the
> navsat were overlayed in the computer.  The difference in the curves
> represented the LAC and LOC.  The Navsat used two channels one at just
> below 150.00 MHz (149.995 I think) and one just below 400 MHz (399.995 I
> think).  The two channels improved the fix accuracy to eliminate
> difraction, refraction and containment due to the difference in propagation
> properties of the two frequencies.
>
> I do not remember the type of modulation for the Barker word.  It sounds
> like a short duration data burst tone through the headset.
>
> Just for information.  And BTW the Coast Guard says the Transit system has
> been turned off.  I found this out after I bought a Magnavox Navsat
> receiver at a local pawn shop.  This was a commercial receiver and used the
> 400 MHz channel only.
>
> 73
>
> Glenn
> WB4UIV
>
> At 09:36 PM 1/6/00 +0100, you wrote:
> >As far as i remember, the Transit carrier were psk modulated and carried
> >the orbital elements of the sat as well as the almanach. F  was 150 and
> >400.00 Mhz. After check it seems that telemetry from orbcomm is on
> >400.1.
> >Ghis,
> >
> >Satedu Team.
> >
> >Richard Allen wrote:
> > >
> > > my original message:
> > >
> > > > Can anyone tell me what satellites are transmitting
> > > > what appear to be unmodulated carriers on 400.1 MHz
> > > > +- > 7 kHz of Doppler?  There appear to be many LEO
> > > > birds transmitting.
> > >
> > > Thanks to the 25 or so folks that replied so far.
> > >
> > > They are definitely not TRANSIT since the carriers are never
> > > modulated.  Evidently Iridium and Teledesic are out.  One
> > > reply said ORBCOMM with what appeared to be certainty and
> > > another two blamed the Russian navsats.
> > >
> > > Richard  W5SXD ...
> > >
> > > ----
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> >
> >--
> >______________________________
> >Ghislain RUY
> >F1HDD/ON1RG
> >---
> >SATEDU TEAM
> >______________________________
> >
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> >
> >
> ---------------------------------------------------------------------------
> Glenn Little                         glittle@awod.com   QCWA  LM 28417
> Amateur Callsign:  WB4UIV            wb4uiv@amsat.org   AMSAT LM 2178
> QTH:  Goose Creek, SC USA (EM92xx)                      ARRL  TAPR
> ---------------------------------------------------------------------------
> ----
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