[MilCom] UHF Space shuttle frequencies?

Wed Jul 13 09:44:16 EDT 2005

Sorry Bill, but that is old stuff below from an old NASA press kit on their
website that has not been updated in years. The new 410 MHz system is in
place and was designed to kill off the use of the four UHF milair freqs
aboard the shuttle (DoD wants them out of their band). We will all know soon
enough (between 3-4 pm EDT this afternoon).

 73

 Larry Van Horn, N5FPW
 Assistant Editor/Milcom Columnist
 Monitoring Times Magazine

> ----- Original Message -----
> From: "Bill "Superspy" Boltinghouse" <elint_sigint_comint at cox.net>
> To: <MilAirCommsChat at yahoogroups.com>; <flacom at yahoogroups.com>; "MilCom"
> <milcom at mailman.qth.net>; "Scansavannah" <scansavannah at yahoogroups.com>;
> <MilGovMonitoring at yahoogroups.com>; <ScanNorthAmerica at yahoogroups.com>;
> "ScanJax" <ScanJax at yahoogroups.com>; <CSFRC at yahoogroups.com>; "Stavro
> Giovani" <mykonos21 at adelphia.net>
> Sent: Wednesday, July 13, 2005 9:04 AM
> Subject: Re: [MilCom] UHF Space shuttle frequencies?
>
>
> > The UHF system is used as a backup for the S-band PM and Ku-band voice
> > communications primarily during extravehicular activity. For
> communications
> > with the STDN ground stations, the UHF system operates in a simplex
mode,
> > which means that the orbiter flight crew can only transmit or receive,
but
> > cannot do both simultaneously. The UHF transceiver takes the voice
signal
> > from the audio central control unit and transmits it through the
external
> > UHF antenna on the bottom of the orbiter forward fuselage. The incoming
> UHF
> > signal goes through the external antenna to the UHF transceiver, which
> sends
> > it to the ACCU for distribution in the orbiter.
> >
> > UHF transmission is controlled through the UHF mode control knob and the
> > three two-position toggle switches on overhead panel O6 labeled xmit
freq,
> > splx pwr ampl and squelch . The xmit freq switch selects one of the two
> UHF
> > frequencies, 296.8 MHz primary or 259.7 MHz secondary, for external
> > transmission. The splx pwr ampl switch selects the UHF antenna on the
> > external skin of the orbiter's lower forward fuselage or the airlock
> > antenna. The UHF antenna on the lower forward fuselage is covered with
> > reusable thermal protection system. The airlock antenna is used by the
EVA
> > astronauts, in extravehicular mobility units, to check out their
> > transceivers before exiting the airlock; it is also used for air-to-air
> > communications during EVA.
> >
> > The squelch switch permits on or off selection of UHF squelch. A
> > five-position rotary knob on the UHF control panel activates power to
the
> > UHF transceiver and selects any of the following modes of UHF
> transmission.
> > When the knob is positioned to EVA , EVA transmissions are made on one
> > frequency selected by the xmit freq switch, and the message is received
on
> > the other frequency. The off position removes all electrical power. When
> the
> > UHF mode rotary contral knob is positioned to simplex, transmission and
> > reception are both on the frequency selected by the xmit freq switch.
> > Positioned to splx + g rcv, transmission and reception are the same as
in
> > simplex except that reception of the UHF guard (emergency) frequency
> (243.0
> > MHz) also is possible. In the g t/r position, transmission and reception
> are
> > both on the UHF guard (emergency) frequency.
> >
> > Access to transmission and reception of UHF signals is controlled by
> > two-position toggle switches located on the bottom of the audio center
> panel
> > on panel A1R at the aft station. The switches are labeled t/r for
> > transmission/reception, off for blocking UHF signals to or from the UHF
> > transceiver, a/g for the air-to-ground channel and a/a for air-to-air
> > channel. All three of the UHF frequencies (296.8 MHz, 259.7 MHz and
243.0
> > MHz) are preset in the UHF transmitter and cannot be altered by the
flight
> > crew.
> >
> > The UHF system is used for EVA operations. The EVA astronaut's UHF
> > communication are through the orbiter UHF airlock antenna. The two
> existing
> > UHF frequencies of 296.8 MHz and 259.7 MHz are used; an extra UHF of
279.0
> > MHz is added to the EMU backpack. The 279.0-MHz frequency can transmit
or
> > receive only among the two EVA astronauts and the orbiter, not the
ground
> > stations.
> >
> > One EVA astronaut operates in mode A, transmitting data and voice to the
> > orbiter on 259.7 MHz, transmitting voice to the other EVA astronaut on
> 259.7
> > MHz, receiving voice from the orbiter on 296.8 MHz and receiving voice
> from
> > the other EVA astronaut on 279.0 MHz. The other EVA astronaut operates
in
> > mode B, transmitting data and voice to the orbiter on 279.0 MHz,
> > transmitting voice to the other EVA astronaut on 279.0 MHz, receiving
> voice
> > from the orbiter on 296.8 MHz and receiving voice from the other EVA
> > astronaut on 259.7 MHz. The orbiter then communicates through a switch
in
> > the orbiter via the UHF EVA relay mode by retransmission over
> air-to-ground
> > through its S-band system to the STDN ground station, its S-band system
to
> > the TDRS or its Ku-band system to the TDRS. As a backup procedure only
> when
> > the shuttle is over a UHF ground station, the EVA astronauts, orbiter
and
> > ground can switch to the 259.7-MHz UHF, simplex. During EVA, the EVA
crew
> > members' biomedical data also are transmitted to the airlock antenna and
> > separated from voice signals in the orbiter instrumentation system for
> > transmission to the ground.
> >
> > The UHF system may be used after entry during the approach and landing
> phase
> > of the mission. Air-to-ground voice communications take place among the
> > space shuttle, the landing site control tower and chase planes (if
used).
> >
> >
> >
>
http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/comm/orbcomm/u
> hf.html
> >
> > Found by searching NASA web site
> >
> > ----- Original Message -----
> > From: "Stavro Giovani" <mykonos21 at adelphia.net>
> > To: <MilAirCommsChat at yahoogroups.com>; <flacom at yahoogroups.com>;
"MilCom"
> > <milcom at mailman.qth.net>; "Scansavannah" <scansavannah at yahoogroups.com>;
> > <MilGovMonitoring at yahoogroups.com>; <ScanNorthAmerica at yahoogroups.com>;
> > "ScanJax" <ScanJax at yahoogroups.com>; <CSFRC at yahoogroups.com>
> > Sent: Wednesday, July 13, 2005 7:49 AM
> > Subject: [MilCom] UHF Space shuttle frequencies?
> >
> >
> > > These are listed. But are they any good and if so what can we expect
to
> > > hear on them if anything?
> > >
> > > UHF Frequencies
> > >   259.700 Air-to-Ground voice downlink (AM) (Primary)
> > >   279.000 EVA voice orbiter only, no ground link (AM)
> > >   296.800 Air-to-Ground voice downlink (AM) (Secondary)
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > http://groups.yahoo.com/group/ScanNorthAmerica/
> > > Scanners ham radio and more.
> > > ______________________________________________________________
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> > >
> > >
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> >
> >
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