During the last few days while I was trying UHF Packet on the international space station .I noticed several time a sudden dip in the signal strength and loss in connection with packet system. ISS elevation was reasonable and the signal strength on the VHF packet system was strong!
I’m thinking of 3 cases:
1- The patch antennas position!
(The patch antennas are fixed on the Meteorite Debris Panels (MDP) protecting the hull of Columbus. On the port cone of the module, where it attaches to the ISS)
http://www.ariss-eu.org/columbus.htm
2- Radio and power used!
3- Doppler Effect!
As long as the signal dip was sharp and suddenly
And the transceiver was drive by Doppler shift correction software
I think the position of patch antennas plays the major role for the sudden signal strength weakness.
More Information needed to confirm this notice.
One thought on “Columbus patch antennas position!!”
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The 70cm packet downlink does not use the patch antennas on Columbus (these are for future use on 23 and 13cms).
Instead it uses one of the two flexible monpole type antennas that were installed on the outside of Columbus during a spacewalk ?sometime early in 2011?. These are intended to be dual band a they will function both on VHF and UHF. One is presently used for reception of AIS signals around 170MHz. They are very similar to the antennas originally installed on the Russian module so rpesumably their performance should be similar. I have never seen a foto of Columbus taken after their installation so do not know their precise location/orientation but I assume they are nominally earth pointing. Possibly they have a big null off the very tip of the antenna – especially on UHF?
cheers
Graham G3VZV