UHF-Satcom.com - Molniya HEO - UHF monitoring Updated: (19/09/2006 21:43:23 +0100)
The Russian Molniya series of UHF / C-band spacecraft have for some reason not been studied in detail as far as the radio transmitters go. xBr and pjm spent a few happy hours trying to identify the signals from Molniya after Internet searches simply revealed that they use a "0.8GHz / 1.0GHz" transponder. It has been determined that the downlink transponder runs from 991 MHz to 1001 MHz and transmits RHCP. Please also see the C-Band page which includes some details about the Molniya C-Band downlinks.
Satellite and space aficionado Sven Grahn has a page about his experiments with Molniya reception, here.
If you are experimenting with Molniya reception, PLEASE come to the #hearsat IRC channel to coordinate your experiments with other enthusiasts!!
The picture below shows the basic design for a 1GHz LHCP helical that is suitable to feed a dish antenna for RHCP Molniya reception. You'll need to make a supporting arm to hold the actual helix, as having it dangling in free space isn't pretty. (see picture below). The ground plane for the helical can be a tin lid of about 30cm diameter.
|
|
|
Since many of the Molniya 1- and 3- series have been monitored, the table below shows the operational status of each of the recent satellites:
Satellite Name Status Frequency band Molniya 3-53 OK C-band Molniya 3-51 No signals - Molniya 3-50 TBA - Molniya 1-89 No signals - Molniya 1-90 OK UHF (possible local scatter from 1-92) Molniya 1-91 OK UHF (Strong DSSS 990.6MHz Molniya 1-92 TBA - Molniya 1-93 OK UHF (1000.45 and 992.45)
The current list of frequencies found to be active is as follows:
Molniya 1-91, 1-90, 1-89 Freq MHz Modulation Comment 991.083 DSSS 490KHz wide 992.443 Mux / Multi carrier tt&c? 994.306 PSK (New 19/09/2006 Molniya 1-91 possibly) 996.013 framed PSK 996.037 2PSK 996.133 PSK 996.193 PSK 996.313 PSK 996.373 2PSK 996.413 PSK 996.533 PSK 996.593 PSK 996.653 2PSK 996.785 PSK 997.033 2PSK 999.775 Framed PSK (New 19/09/2006 Molniya 1-91 possibly) 1000.444 Mux / Multi carrier tt&c?
(above) Molniya PSK downlinks.
Molniya 1-92 992.454 Mux / Multi carrier tt&c? 1000.450 Mux / Multi carrier tt&c?
The FFT's below show plots of the strong 'telemetry' that was observed from each satellite.
(above) 992.454MHz
(above) 1000.450 MHz - this set of carriers also includes two sweeping tone sets. (click the picture to hear how it sounds)
(above) DSSS signal from Molniya 1-90 centred on 991.083 MHz
(above) A typical cut-over from Molniya 1-91 and Molniya 1-90 - centred on 996.412MHz. Interesting is that the signals increase about 10dB for 1minute before the cut over occurs. This is presumable to allow the PLL's that are locked to these PSK streams to re-capture the signals ready for the swap to new lower frequency streams.
