I can think of at least a couple solutions. One is to create a high
external ALC voltage that decays 50 milliseconds after PTT arrives. It
might be possible in some software to delay the tones, but I suspect the
rig blaster can be creating PTT from the presence of the tone. It might
need a different option to separate the sources of tone and PTT.
The box cure is to look up W1GHZ.com and his sequencer. This is a
standard problem at VHF and microwaves with transverters and such.
Typically a sequencer (and there have been several schematics published
in QEX and proceedings of VHF conferences and Microwave Update
Conferences over the past two decades), is started by the external PTT
which then switches the antenna relay, then after a selected wait, keys
the PA, then the transverter, then after all the relays have seated it
applies PTT to the exciter. Does it in reverse to go back to receive so
no relays get keyed hot, no exciter power hits a delicate tranverter or
antenna mounted preamp.
Last I knew, WA3IAC sold kits for the W1GHZ sequencer kit. Direct or on
epay. I bought one last year that I've not yet used, but I will probably
need more in time.
Links:
http://www.w1ghz.org/small_proj/sequencer_V2.pdf
http://www.qsl.net/wa3iac/kits/
Or one can install auxiliary contacts (such as a microswitch) on the PA
relays and wire them in series with the PTT signal from the rig blaster
so the PA relays have to seat before connecting PTT to the exciter.
Since the PA was built without provisions for those controlling
contacts, the timed sequencer is what works.
73, Jerry, K0CQ
On 3/22/2010 6:36 PM, Gary Hoffman wrote:
Hi All,
I'm having a new (to me) problem with one of my rig/amp combinations.
I've begun using my Corsair II with my SB-200 amp in some digital modes -
mostly RTTY of course.
These rigs were not meant for digital service nor computer control of
course.
What I have is a rigblaster, and I use a serial port from the computer to
both send the digitaal data and the PTT signal to
the Corsair through the Mic Jack - in the well known manner.
The Corsair switches the amp into transmit through its key line.
Unfortunately the rigblaster sends data and PTT to the corsair together, at
the same instant.
Thus when the amp relay is being switched - the corsair is already
outputting RF. Hot switching the amp in that fashion
allows 1 kw of power to see momentarily an open circuit, as the amp relay
has not yet reliably closed the contacts to the antenna.
This does a LOT of damage !!!
I'm sure others have run into this.
What are people doing ? Some other external control box I don't know about
? Somehow delaying the production of tones in the
rig control software ( I'm using N1MM) ?
I'd appreciate any useful ideas.
73 de Gary, AA2IZ
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