[amsat-bb] idle comments

[Mac A. Cody]

Hi Zack,

I honestly wish I had a LimeSDR Mini.  I learned about it just about
a month ago.  Don't have the funds at the moment to divert to getting
one.  I'd almost be willing to sell my SDRPlay RSP2 in order to get
one.  In the meantime, I'm trying to cobble something together to be
able to work the linear birds.

I understand that SSB and CW have been the 'mandated' modes used to
work the linear birds for a long time.  SSB use appears to be the
predominant mode of operation. I'm still not hearing, though, any real
arguments against the use of DSB as a means to drastically lowering the
barfor transmit to the linear satellites.DSB could be implemented with
relatively simple analog hardware that would avoid the complexity of
DSP development and I/Q modulation balancing.

Mac / AE5PH

On 03/16/2018 01:01 PM, Zach Metzinger 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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