[amsat-bb] idle comments

[Don KB2YSI]

Not only is the equipment to get on linear satellites more expensive, they
also require more skill to operate OR even more equipment for automatic
control (if your equipment can be controlled).  That is why the FM
satellites are so busy, inexpensive hardware + lower skill requirements =
more people will try it.

The SDR market will surely help on the receiving side, but it is the
transmission side that causes the big hurdle.

Hopefully with the coming warmer weather I'll be able to get more
experience with my linear setup. It is not all that great standing out in
below freezing temperatures with wind and attempting to learn how to
operate two radios and hold an arrow at the same time.

73, Don KB2YSI


On Mar 16, 2018 14:02, "Zach Metzinger" <zmetzing at pobox.com> wrote:

On 03/15/18 21:07, Mac A. Cody wrote:
>> At the sacrifice of some bandwidth, the following advantages can be
>> had with
>> using DSB modulation:
>> 1) DSB modulation is relatively easy to achieve.  The band-limited audio
>> is fed into a double-balanced mixer, bandpass filtered for harmonics, and
>> fed into a PA for transmission.  The resulting hardware is comparatively
>> inexpensive to construct and to tune.
>> 2) Sideband inversion caused by some linear birds is no longer an issue.
>> Having both sidebands present in DSB modulation means that the correct
>> sideband will always be available for reception.
>> 3) Interoperability with SSB stations would be maintained, as DSB
>> modulation
>> is a superset of SSB modulation.

Why not use the new LimeSDR Mini and do a SDR-based design for satellite
work? It already has separate TX and RX paths, ready for duplex operation.

One simply, for various values of simple, needs to design a
receiver/transmitter design to go into the Altera FPGA, bolt on a
suitable CODEC (might I suggest the MAX9860?), and then add some
filtering and a PA.

[Mic/Spkr] <---> [MAX9960] <---> [FPGA] <---> [Limechip] <--> PA/Filter

I'd bolt on a LCD, rotary encoder, and a few buttons for user I/O. No PC
needed for control. Add antenna and you're done.

You'd have a complete all-mode (SSB, AM, FM, etc.) solution for perhaps
$200.

(This is a back-burner project for me -- I won't be offended if anyone
gets there first. hihi)

--- Zach
N0ZGO




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