Satgen95  Mir Operating           21st Jan 91   by GM4IHJ

You have probably seen the numerous pleas asking " What frequency does Mir
listen on ". The good news is of course that U2MIR has been very active up
until 0100 ut some night , calling Europe on 145.55 .The bad news is that
very few Gs have had a reply from him. Why is this?

Firstly Mir cannot listen on his downlink or it would cause Chaos. The
reason for this is what is called FM CAPTURE. Unlike other modulation
modes , when a station receives two FM signals, if one is a couple of dBs
stronger than another , the strong station will be heard clearly and the
weaker station will not be heard at all. If a crowd of stations all call
at once they generate a pile of noise at the space bourne receiver and no
one gets heard clearly unless his individual signal IS STRONGER THAN THE
SUM OF THE REST. So FM Capture makes simple space operating an Alligators
Paradise. ( Alligator = all mouth ,no brains, too much power ).

Pity the poor G. Last week Mir's 1900 to 2100 orbits  passed well to
south east of UK. A station in Southern France using 10 watts puts a 6 dB
better signal into Mir than does a G with the same power and antennas.Many
of the continentals are using a lot more than 10 watts. A poor old GM has
very little hope ,he is about 12 dBs down on the Southern Frenchman or the
Italian simply because he is much further from Mir Eg 2000 plus Kms versus
500 or so. So any G contacting Mir this week did very well indeed.

Next week should see a change if UK stations concentrate on the orbits
which come high over UK. Then London and the south east are in the best
position and even GMs are as well placed as Frenchman. Please note this is
not a chauvanistic racist diatribe ,it is a simple fact of orbital
mechanics. 

What can we do for the future. We could suggest Mir listens over a wide
range and picks a few from each group. Eg purely as a suggestion.
GM,SM,OZ, LA  call downlink -25Khz  :G , GW,PA,ON call -20: F , DL , SP
call -15 : EA, EI, CT ,GI  , GJ , HG call -10: HB, I, OE, OK and any
others call -5, when Mir is over Western Europe. Mir picks and choses
where he listens, at random. What do you think ? These are just
suggestions

RM-1,the suggestion last week that Satgen got it wrong, turned out to be a
misreading of a rather tortuous piece of Russian. As reported in Satgen
RM-1 has independent transponders for mode B analog and Rudak. So Mode B
RM-1 is still likely . Launch Plesetsk 27 Jan ????? Doobra Ootra !!!

SALYUT 7  I hear that one viewer has had a good visual of Salyut and
he reports another object about 4.5 minutes behind Salyut on a similar
track. This seems to be somewhere vaguely near the latest NASA/NORAD keps
which separate Salyut and 1686. But the Soviets are still saying that they
(Cosmos 1686 Space Tug and , the old Salyut 7 station) have not separated
So what the second object 4.5 mins behind is ,is unclear. Soviet spokesman
Dzanibekov ( a very famous cosmonaut) still says Salyut 7 and Cosmos 1686
will re enter and burn up together Feb 10 + or - 10 days. 73 de John
GM4IHJ @ GB7SAN