[amsat-bb] Re: A0 40 replacement - mode K cubesat?

Ross Whenmouth ross at topwire.co.nz
Thu Sep 5 00:09:02 PDT 2013


How feasible is it to fly a mode K (15m uplink, 10m downlink) linear 
transponder on a cubesat?

I expect that retty much any ham with an HF transceiver would be able to 
work this bird, and I expect that due to the lower frequency, the 
footprint might be a bit larger than that of VHF/UHF bird in the same 
orbit and doppler shift would only be about 7% of that experienced on 70cm.

The biggest problem that I see though is squeezing a somewhat efficient 
10m antenna into a cubesat and deploying it by remote control once on 
orbit. (I think that the cubesat antenna should be optimised for TX 
performance, as cubesat TX EIRP capability is severely limited compared 
to the average HF transceiver).

Would two 2.5m lengths of steel tape (the same stuff that tape measures 
are made out of) - mounted on opposing sides of the cubesat, be able to 
unroll in microgravity to form a generally straight 1/2 wave dipole with 
a low risk of tangling, snagging or kinking, etc?

Alternately, what about using some sort of thin plastic tubing 
(something like dialysis tubing, but suited to the space environment?) 
with a wire inside it, and rolled up. Then, once on orbit, the tubing is 
inflated with self-expanding polyurethane foam, which will extend the 
tube (and the wire inside it). The foam will then harden, so future loss 
of gas pressure in the plastic tube (micrometeorites?) will not cause 
failure of the antenna?

73 ZL2WRW Ross Whenmouth

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