Satgen 11   UFO's QRMing Oscar 13

One of these birds ( thought to be American Experimental Sat Polar Bear)
,continues to transmit on 435.9744 + or - doppler, from an orbit of 105
minutes period, inclined at 89.56 degrees.

The other satellites which were using this frequency ( period 101 min,
inclination about 80 degrees ), were only transmitting on one orbit per
day last week, and have not transmitted at all this week when in range of
UK.

MIR has not been heard on 166.122 MHz for 2 days. It is known that Mir 
has a battery problem , so perhaps they are only commanding the telemetry
ON, at rare intervals, in order to preserve what limited power supply
remains. This is not a good sign.

Polarisation Skew Angle, an explanation.  This is a problem encountered by
users of geosats which transmit linear ( horizontal or vertical)
polarised signals.

Skew arises in the first case because the vertical at the geosat is not 
parallel to the vertical at your station. Most of this is compensated for
when the geosat controllers set their aerials to send X and Y polarisation
tilted with respect to the geosat in order to arrive at the earth near V
or H. But this only gives complete cancellation of skew to stations
located on the same meridian of longitude as the geosat. So Astra 19.4
east does not produce true V and H in UK .The skew angle for IHJ 56N is
about 16 degs clockwise.By contrast Intel VA at 27.5 west produces a large
anticlockwise skew at IHJ. 

Only expensive TVRO receivers have facility to memorise and auto correct
skew. So when IHJ goes from Astra to Intel VA, it is necessary to manually
adjust skew on the hand control at the back of the TVRO Rx.

Fortunately most new sats ( Eg BSB , TDF-1 ) will use circular
polarisation, which does not suffer skew problems and is easily achieved
by inserting a small Teflon insert in the waveguide. This insert can be 
left in place when you watch linear polarised signals. 

73 de GM4IHJ  14th June 89