[amsat-bb] SatPC32 Antenna Swapping with SDR

Erich Eichmann erich.eichmann at t-online.de
Sat Jun 1 10:34:42 UTC 2019

Hi Tim,
I have described the feature on my website www.dk1tb.de, Engl. page 
'Downloads', sect. 5g  (Buffer Interfaces).
You don't need a PC with a phyical COM port. The voltage at the DTR pin 
of  my USB-to-Serial converter (which generates the Radio 2 COM port) 
changes between +6 (high) and -6 V (low), when the user switches 
between  v/u and u/v satellites. The corresponding option in menu 
'Options' must be checked, of course.

If the DTR pin is low, the buffer interface locks and the relay remains 
open. If the pin is 'high', the interface is routed and the relay 
closes. I do not have a transfer relay, but have successfully tested the 
function with a 12 volt coax relay.

73s, Erich, DK1TB

Am 31.05.2019 um 22:30 schrieb Tim Rife via AMSAT-BB:
> In reading the SatPC32 manual, section 3.C.bb, I see that SatPC32 provides
> an automated way to switch the antenna feeds by outputting a high or low on
> the DTR pin of the radio 2 com port through a transistor to switch a coaxial
> transfer switch.   Is there any other way to do this if you are not using a
> traditional serial port but USB ports or virtual ports?
> My setup has a Yaesu radio for TX and an SDRplay for receive.  When
> switching from V/u to U/v, it is necessary to swap the antennas and I would
> like to do this automatically with a coaxial transfer switch.  As above,
> SatPC32 can do this in automated fashion.  However, I am not using a DB9 com
> port for either radio (USB or internal ports only) and am trying to figure
> out how to get access to this DTR signal to use it for the automated
> switching.  Has anyone used an SDR for the downlink and set up automatic
> antenna swapping and if so, how was it accomplished?
> Thanks,
> Tim
> KK9T
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