[amsat-bb] FM vs Linear Transponders

[Paul Stoetzer]

That's me, not Drew!

It was the FUNcube Dongle Pro+. Unfortunately, the FUNCube Dongle, despite
decent filtering, still struggles in environments like Dayton. In normal
conditions, it performs very well for this purpose. N8

Some form of integrated, small, full duplex VHF/UHF transceiver is
definitely the holy grail of linear satellite operations. I'd love a KX2 or
KX3 sized VHF/UHF full-duplex all-mode transceiver. Sadly, the maximum
sales figures for something like that are probably measured in the
hundreds, which makes it tough to justify commercially.

73,

Paul, N8HM



On Fri, May 8, 2020 at 1:57 PM Zach Metzinger via AMSAT-BB <
amsat-bb at amsat.org> wrote:

> On 05/08/20 11:42, Stephen DeVience via AMSAT-BB wrote:
> > The ground station complexity for using the linear satellites is a real
> > issue, especially for anyone trying to rove or use a handheld antenna.
> I've
> > always found the suggestion to use two FT-817s strapped to your neck very
> > awkward (and pricey).
>
> On the downlink (RX), one can use a very cheap SDR dongle such as:
>
> Here's a demo from Drew (KO4MA) at Hamvention 2018:
>
> https://www.youtube.com/watch?v=hBZvWCKxjcM
>
> He's using a FUNcube dongle (not sure if Pro+ or not, but ~$155 for the
> Pro+), but the same could be done with an RTL-SDR dongle ($35):
>
> https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/
>
> Gqrx, the software "receiver" already runs on a cheap Raspberry Pi 3:
>
> https://gqrx.dk/download/gqrx-sdr-for-the-raspberry-pi
>
> Your choice of transmitter includes an existing multi-band radio, or one
> of many SDRs with transmit capability (assuming that one appropriately
> filters the output before amplification).
>
> > I'm starting to think of what would be needed for a handheld-size linear
> > satellite transceiver. It would have to do SSB on UHF and VHF, and the
> > Doppler correction could probably be handled by a phone app which would
> > also provide visual tracking.
>
> Well, if it were an _open_ digital voice format (down with AMBE!) with
> error-correcting codes, one might create such a transceiver quite
> easily, using highly-integrated modem ICs already on the market.
>
> Someone might already be thinking about this.
>
> --- Zach
> N0ZGO
>
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