[600MRG] U3S with T/R relay

[Edward R Cole]

Steve,

I  spent about an hour going thru the U3S instruction page and not 
finding enough info on it to give you specific ideas.  I had no prior 
knowledge about this "kit".  Definitely a computer/qrp wonky project 
so have you talked with the designer or operators group?

What RF output does the basic unit run?  If at mw level then one 
could use a pin diode to hold output off while the standard "+5v Key" 
would control a sequencer.  The sequencer would control TR relay and 
key ext amplifier before the sequencer final stage would bias the pin 
diode ckt to pass RF.

This is only workable if U3S operates in 1-50mw range.  If it outputs 
a few watts or more, then one needs to understand the internal ckt of 
the U3S to intercept the Tx control line.  That will require pcb 
mods.  That is a question for the U3S designer.

If you want any help understanding sequencers or pin diode TR ckts I 
may be able to help.  I built a 2m 40mw pin diode RF switch into 2m 
80w amps I built.

GL & 73, Ed - KL7UW

At 02:12 AM 11/1/2016, Steve Flood wrote:
>I plan to use an Ultimate 3S for WSPR operation.  I will be using it to
>drive an external Class D amplifier (using the square-wave output from the
>U3S synth chip with its own PA disabled).
>
>
>
>I am having trouble figuring out how to activate the output T/R antenna
>relay prior to RF transmission.  Likewise I need to key the driver stage of
>the external amp.  This all needs to be automated for unattended WSPR TX/RX
>sessions.
>
>
>
>I was hoping to use the +5v "KEY" output from the U3S to activate the relay
>and driver, but Hans tells me that it is essentially simultaneous to the RF
>output.  I am trying to avoid hot-switching the T/R antenna relay or causing
>a load fault shutdown.
>
>
>
>Any ideas?   How have others used the U3S with a T/R antenna relay?
>
>
>
>Thanks,
>
>Steve KK7UV/WH2XNV
>
>
>
>
>
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73, Ed - KL7UW
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