Friday, February 5, 2010

How To Work Satellites By VU2GUR :

On a single channel frequency of the Birds, one has to give a counter effect to the Doppler Effect at the birds Receiver.

For Eg.,

Bird AO51
uplink :145.920MHzFM
Downlink : 435.300 MHZ

As the Bird approaching

Signal is good

For Rx at 435.310 to 435.305

Tx at 145.915

This holds good for all Birds according to the respective frequency.

But in Linear Transponder (eg., VO52 Hamsat only) one should not use FM on Dx-Birds which is using Linear Transponder.

For FM use only 435.250 up – Listen on 145.905, 145.900 & 145.895

If you want to hear your own signal.

Then Transmit on 435.245 as the Bird Coming to you

435.250 Bird is nearer

435.255 Bird going away

If you are interested in CW & SSB on VO52 please refrain from the frequencies of 435.245, 435.250 and 435.255 so that FM operators can enjoy at the middle Band.

For CW & SSB can be operated on 435.220 to 435.240 & 435.260 to 435.280

To the questions which antenna to be used for Satellite QSO

To start with: It is better to have 2 Handies or base one for VHF and another for UHF so that you can tune the frequency on Down Link for the Doppler effect and another set for uplink for Tuning for the counter effect on uplink to the Bird.

A dual Bander may be cumbersome to switch over with button pressings. Mostly dual Bander has single port for Antenna to use Dual Band antenna.

With Rubber Duck dual Band Antenna is ok for short duration of a pass when the going is good on high angle of elevation to a QTH for a short duration in the pass.

Even a ‘J’ or slim jim can be used as a dual Band Antenna because UHF is the 3rd Harmonic of VHF eg., 145 * 3 =435MHz

However a well tuned antenna to a frequency will give the best performance in Reception and Transmission. One can check it for self and understand it on Reception.

  1. Since the Birds passed from North to South (~) in the daytime of the day and from South to North (~) in the evening/night of the day.
  2. Birds angle of Elevation to a QTH will vary from Low angle of elevation to overhead pass.
  3. It is better to have a ‘J’ or slimjim of omni directionall for Low/medium angle pass of Bird (one who does not have the rotator facilities). The Vertical Antenna cannot sense the signal from the Bird passing on High angle or over head.
  4. If you are an experimenter keep the ‘J’ or slimjim horizontally between start azimuth to end azimuth. Keep their ends East & West. You can find the quality of Reception & Transmission to Birds.
  5. Considering the climate (weather) and other obstacles etc, it is better to keep a omni directional Antenna one for VHF (2 mtr) another for UHF (70 cm) and two more antennas kept horizontally ends pointing East & West (eg., Dipole) for High Angle Elevation Pass. Change the antennas accordingly for the purpose.
  6. Once the interest increases one can go for all beams with Azimuth/elevation angle rotators etc for Long Distance QSO (ie Dx)
  7. No need to push more than 10 Watts. If pumped with High power then you are going to smugging Low power stations.
  8. Even if you put 100 Watts the Birds gives out only milliwatts, 1 or 2 watts only. So your equipments should be good enough and able to receive weak signals.
  9. Might is Right Hi Hi Hi
  10. Many other Factors are there still…….

Courtesy : OM Guru, VU2GUR

4 comments:

  1. Very Good. Also they are a lot of tutorials on AMSAT -
    http://www.amsat.org/amsat-new/echo/EchoHT.php

    And a very good video one-
    http://www.youtube.com/watch?v=1HfvmU_utI8

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