[amsat-bb] Re: 10m band kibitzing

[John B. Stephensen]

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.

73,

John
KD6OZH

----- 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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