[Ham-Mac] Digital Interface for PSK with PTT - more info.

[Dick Kriss]

John,

Your design sounds like something many of us would be interested in reading
about in QST.  You may want to consider publishing a construction article
with pictures and diagrams.

73, Dick AA5VU

ps: I have no idea how the SignaLink SL-1+ works.  It detects a signal from
the Mac or PC and its Auto-PTT closes the PTT line to the rig.


On 6/20/06 1:55 AM, "John Townend" <jltownend at btinternet.com> wrote:

> Hi,
> 
> Comments so far raise two points.  I have not been happy using the VOX
> control - muting or disconnecting the mike was a nuisance in my set up.
> 
> I use two Icom IC706Mk11Gs and a Yaesu FT817.  Control from the
> interface is via the ACC  or Data sockets both of which have the PTT
> line on one of the pins. It is just a question of pulling down this
> line to switch to TX.
> K1QW's circuit of the interface takes the PSK/RTTY or whatever signal
> from the Mac (or PC) and feeds it into a band-pass amplifier (one
> section of quad op amp). The amplified signal passes to Comparator,
> Integrator and PTT delay circuitry (one section of the op amp plus 2
> transistors). From there it goes to a schmitt trigger (one section of
> the op amp) the output of which feeds the base of a 2N4401 NPN
> switching transistor across the PTT line.  The fourth section of the op
> amp is used for the meter amplifier
> 
> I am not sure Dick how unique the Auto-PTT feature on the SL-1
> interface is but this home brew interface does the same thing. The VOX
> is not enabled at any time.
> 
> 0800 in the UK ----- sunny morning----- have a good day------73 John
> G3BBD / N3YZR
> 
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