[amsat-bb] Re: beginner question re: uplink power

[Edward Cole]

At 12:22 PM 10/19/2008, corner5 wrote:
>Thanks for replys (Re: beginner question re: uplink power)
>===snip===
>A: This is a very interesting approach.  If I understand your idea 
>here, you suggest to use the relay that is
>on the RF switch board and toggle this relay with a PPT signal from 
>the TS2000 (and not make use of the RF sense at all. Yes?
>I do not know about the details of using the PPT signal in this way. 
>I guess I need to hope that the PPT signal
>is compatible with the relay (voltage).  And then if I need to 
>abandon the RF switch all together, are there suggestions
>as to what is a good (not too expensive) remote relay design?
>

Most radios have an aux. TX key line.  This will either key the line 
to ground (like PTT does), or will provide (usually +12) voltage in 
transmit to drive a relay.
Most likely the relays in the Ramsey unit are 12volt relays.

In case #1, you lift the ground lead of the relay and attach that to 
your control line from the radio.
In case #2, you lift the +12v lead to the relay (from the RF sense 
ckt) and attach that to your control line.
You probably only need one wire as the preamp dc power wiring will 
provide the other wire which ever case# applies.  If the preamp is 
powered over the RF coax line, the radio may not supply sufficient 
current to drive the unit (check this out in the radio manual and 
Ramsey specs).

I would also disconnect the relay from the RF sense ckt in any case 
so that it does not cause any false keying issues.

Simple!  Enjoy!

73 - Ed