[amsat-bb] Re: LF Satellite ideas?

Bob Bruninga bruninga at usna.edu
Sat Dec 11 15:37:24 PST 2010

My initial 1100m long satllite antenna idea (with no knowledge of propogation possibility through the ionosphere) is:

a) connect a product detector (SSB) receiver to the 1/2 wave 137 kHz satellite antenna and downlink the audio that it hears on the UHF FM downlink.  Then anyone can hear the 137 KHz experimenters if the satellite does. USA Hams cannot transmit on the 137 KHz band. But no licensing of the LF uplink is needed since we are only "listening to an ionosphere experiment"...

b) Connect a small CW transmitter on 137 KHz to the 1100m antenna and see if the LOFERS can hear it?  But there is no ITU/IARU amateur satellite authorization there.  But again, on-off keying of some electrons on a long ionosphereic tether would be a physics experiement, not comms.

If such a link is possible, then people can transmit up on 145.825 MHz with normal PACKET, and the satellite will convert the packet message to CW on the 137 Khz downlink.

The #1 question is whether 137 KHz will pass anything through the ionosphere?  Maybe only straight up?  I hoipe some real space-physics people can contribut knowledge here.

>     Is 137 KHz possible from space?
>     Our next Cubesat will have a 1100 meter long
>     antenna (think tether satellite).  It will
>     ultimatelly be an electrodynamic tether but the
>     first one will have NO ACTIVE ELECTRONICS
>     connected to the tether.
>     So I have asked them to make it 1100m long instead
>     of a generic 1km tether to try to make it resonant
>     in an amateur band.  THe path loss at 137 KHz is
>     60 dB LESS than it is at 2 meters, so it shouldn't
>     take much to communicate with an 1100m long
>     antenna.
>     I'm sorry I didnt think of this sooner, but I need
>     a real SCIENCE justification for this.  Maybe LF
>     that low will never punch through the ionosphere,
>     or maybe it will be completely absorbed.  Can give
>     good science on this idea?
>     Bob, WB4APR

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