Off the decafe Doug, :-)
I looked at the circuit for methods to mute the ctcss
encoder output using a portion of low pass filter
section U3A.
[paste]
> Use a small (low cost - high preformance) fet like
> the 2N7000 or the same VN10KM (also VN10LP) (same fet,
> just a different part number) with a low on-resistance
> to mute the audio output line to ground at some place
> like the junction of U3A parts R35-C21
You could control the fet with the output status of
the decoder, but using a cos/cor input would allow you
to also control the encoder in carrier squelch repeater
operation. More inovative types could set up a cos and/or
ctcss decode control.
Grounding the input to the U3A filter at the junction of
parts R26-R27 & C20 will also work if you can be sure
the fet or optional transistor takes the output to very
near ground (to prevent ctcss leakage through U3A).
> Ground one of the mentioned locations when cos or
> encoder detected output changes and the encoder output
> should halt.
For the new to using small fet people, you should provide
two resistors, a capacitor and a diode to the fet gate
lead. A series 2.7k min value 1/4 watt resistor to input
to the fet gate, call it "gate solder junction A". At
the gate junction A position, solder a 470K resistor from
the gate junction to ground, which is also where the fet
source lead is soldered.
Parallel both a 1N914/1N4148 diode and a 220pf disc capacitor
with the 470k 1/4 watt resistor, the banded end of the diode
(cathode) pointing up/connecting to the gate junction A.
The resistors isolate and protect the fet, the diode prevents
excess fet gate reverse voltage (mistakes) and the 220pf cap
will help keep stray rf off the gate. The fet drain lead
is soldered to your choice of locations mentioned above in
the ts-32 board. My first choice might be the junction of
U3A parts R35-C21.
Small signal switching transistors also work ok, but you need
to ensure they switch on and off 100%.
cheers,
skipp
> Doug Bade <[EMAIL PROTECTED]> wrote:
> Cancel that remark NO PTT on that board.. I was off on that
> comment... one of the other boards..... grrr.......... I went and
> looked at the schematic.. The factory app note used a clamping diode
> or transistor maybe on the encoder side of the circuit on board of
> the ts32 at the network in front of the op amp. It looks like it
> would yield about the same results as the clamping transistor.. it
> was just on board the ts32 instead...
> I recall it was tied to the output transistor as noted below... that
> part was correct........
> Doug
>
>
> At 01:47 PM 3/21/2006, you wrote:
> >The PTT input of the ts-32 controls encode.... If it is
> >connected to your rx mute gate it would track carrier
> >input.... The factory recommendation Coy referred to as
> >I recall was for gating tx tone off rx tone, which was
> >connecting OUT 1 or 2 ( whichever is the correct
> >polarity) to the ptt input of the board. This allows
> >encode to track decode, and does so very well but ......
> >..if you are in carrier sq mode, would not ever encode
> >...... Connecting ts-32 ptt input to station rx mute or
> >an inverter ( or something on the squelch gate for
> >other vendors besides GE) if needed solves the problem.....
> >Doug
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