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RE: AO-40 Satellite RF Architecture Question



"Nick" wrote

> If AO-40's design is not classified or proprietary, maybe we
> could build
> linear transponder
> clones to supplement the antiquated FM repeaters in the V/UHF bands.
> Constructive flames accepted...

Peter, DB2OS was able to find a copy of a note I posted over a year ago
giving a simplified description of HELAPS. Thanks to Peter for sending it
because I couldn't find my copy!

In that note, I commented that the InterModulation Distortion products from
a HELAPS amplifier are not that great (~-30 dB). This IMD makes little
difference on a spacecraft where all uplink signals are nearly equal, but if
you tried to use it in a terrestrial environment, you would rapidly become
the most unpopular station on the band! You've all heard strong signals on
20M that have so much crap that they wipe out half the band. That's what
you'd get if you tried to use HELAPS.

If you are just suggesting a linear transponder on the ground, then your
idea is great. Since DC power is not a limit and you can get rid of heat
with a good heatsink, then you would make such a device run Class A (or
maybe AB) amplifiers.

I note that Yaesu touts the fact that the FT1000 Mk5 has Class A amplifiers
to eliminate transmitted noise. And the Mk5 comes with an incredible "Gucci
Design" heat sink!

A small request, Nick. Maybe you can sign your messages with a call so we
know who you are -- I think its KU2A!

73 de Tom, W3IWI


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