[amsat-bb] Completion: Re: SatPC32 Antenna Swapping with SDR

Scott scott23192 at gmail.com
Sat Jun 1 18:43:57 UTC 2019

Yes, I can also confirm that you get functional DTR & RTS from a 
USB-to-Serial cable.  I use one for connecting to my PTT relay as 
illustrated here:


-Scott,  K4KDR


-----Original Message----- 
From: Tim Rife via AMSAT-BB
Sent: Saturday, June 01, 2019 1:22 PM
To: amsat-bb at amsat.org
Subject: Re: [amsat-bb] Completion: Re: SatPC32 Antenna Swapping with SDR

Hi Erich,

Thank you for this.  Yes, that was going to be the general plan.  I am 
looking through my junk box to see what parts I have and if I have the 
needed hardware.  I was not aware that a USB to Serial converter derived the 
extra pins (per your earlier post) like DTR and RTS from the USB inputs of 
Vcc, GND, D+ and D- and made them functional.  I assumed it only provided 
TXD and RXD at RS-232 levels.  So, if it makes those pins available and 
functional, that should do it.  I just need to construct and test which 
might take a couple of days for me to accomplish.  Thanks again.




Hi Tim, a problem with that configuration:  you need access to the pins 
Ground and DTR (pins 5 and 4) of the serial port to steer the buffer 
interface.  To steer your Yaesu radio via the Radio 2 COM port you will use 
a USB-to-Serial converter + a Yaesu CAT cable, e.g. the CT-62. This cable 
comes with a DB-9 connector on one side  that connects to the converter and 
a mini DIN plug on the other side, that connects to the radio.  So, you 
don't have direct access to the lines Ground and DTR. What you could do: 
Solder a short cable with a female DB-9 connector on one side and a male one 
on the other side. Connect the female side to the USB-to-Serial converter 
and the male side to the DB-9 connetotr of the CT-62.  With that cable you 
can then easily lead out 2 extra wires to the Ground and DTR pins to control 
the interface.

73s, Erich, DK1TB

Am 01.06.2019 um 14:48 schrieb Tim Rife via AMSAT-BB:

Thanks for the reply Erich.  I will give that configuration a try.



Hi Tim,
I have described the feature on my website www.dk1tb.de 
<http://www.dk1tb.de>   <http://www.dk1tb.de> <http://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 

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