[amsat-bb] Re: 10m band kibitzing

John B. Stephensen kd6ozh at comcast.net
Sun Sep 10 19:58:15 PDT 2006

There are three disadvantages compared to the 70 cm band. The commercial
amateur satellite transceivers are desgned for U/V. The 10 m band can have
extremely high losses at low elevations and Eagle is designed for an
equatorial orbit. The antenna has to be deployed so it is another possible
failure mode.



----- Original Message ----- 
From: "Robert Bruninga" <bruninga at usna.edu>
To: <Amsat-bb at amsat.org>
Sent: Sunday, September 10, 2006 16:17 UTC
Subject: [amsat-bb] 10m band kibitzing

> > In the San Diego meeting, there was discussion about using
> > the V, U, L, S, C and X bands. The spacecaft is too small
> > for a decent HF antenna...
> I hate to suggest this low tech approach, but we do have plenty
> of uplink bandwidth in the 10 meter band if we could find a way
> to use it.  I know that most of the future thinking AMSAT
> engineers abhor this idea.... But it is still something to think
> about.
> While an HF -gain- antenna cannot fit on a HEO satellite, a
> simple 10m dipole could be deployed...  The main advantage is
> the users can use high power on the  uplink.
> Lets assume users with a 500W transmitter and the link equation:
> PR = PT + GT + GR -LI - LS
> PT - power transmitted on the ground is say 500W = 57 dBm
> GT - Gain of transmitter Ant is say 6 dB?  (3 element beam)
> GR - Gain of satellite receive antenna is 0 dB?
> LI - is say 3 dB to cover all losses in the system
> LS - is (4Pi*R/wavelength) squared = -154 dB
> PR - is then 57+6+0-3-154 = -94 dBm
> That is a pretty strong signal, but it is the Signal to Noise
> ratio that counts.  And the problem is the GALACTIC AND other
> NOISE...  It's just as high up there as it is here, and  That
> can be as high as 20 dB ??? Over the noise floor of the
> satellite receiver? (someone more knowledgible here please fill
> this in.).  If it is 20 dB of galactic noise, then the receiver
> noise floor might be more like -105dbM and now we just barely
> have a 10 dB margin over noise.
> I just don't know whether it is worth doing.  We had hopped that
> the HF uplink on PCSAT2 would have given us good info.  But the
> transponder failed and so we still have no experience with 10m
> uplinks.  It would be nice to do some more expermeintating with
> the 10m uplink receiver on AO-51 some time...
> But one thing is certain, NO ONE is targeting the 10m band for
> consumer electroncis devices other than all the ILLEGAL CB
> operations.  I just don't know how bad that is.  In the solar
> max, it will probably be a ZOO!!!  But maybe they will stay down
> at 27 MHz and leave 10m alone.  Especially if we go after the
> 10m interlopers with a vengence...
> Maybe just like HAM radio, the "HF-ers" are finding it easier to
> just play on the internet than mess with all that "RF" stuff...
> Just babbling and thinking out loud.
> Bob, WB4APR
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