[amsat-bb] 70cm LNA

[Zach Metzinger]

On 08/11/20 21:47, Zach Metzinger via AMSAT-BB wrote:
> Success! The SAW filter eliminated the offending cell-tower sources.
> The noise floor barely moves when the preamp is switched in, while
> the desired beacon signal increases significantly.
The 3-D printed passive Lindenblad + homebrew LNA, driving 75' of 
look-alike-LMR400 is working well for receiving RS-44 now. The LMR400 is 
optional, as there is plenty of gain from the MAX2640 LNA, but was used 
to keep losses down when transmitting on this antenna.

I can reliably copy the RS-44 beacon about 8 degrees above the horizon, 
and SSB is quite readable at about 20 degrees.

A horizon-to-horizon pass recording is located here:

http://www.n0zgo.net/oscar/rs44_12082020_1802.mp3

(The good stuff starts at about 7 minutes into the recording. I chase 
the beacon at the end in CW mode, and it disappears at 5 degrees elevation.)

A FT-847 was used for reception, but a cheap SDR dongle would probably 
work just as well for a lost-cost entry into 70cm downlink capability 
(as required for the GOLF satellites).

Now to wire it up for automatic Doppler correction and we're in business.

73,

--- Zach
N0ZGO