Batboard

I have a UHF Dashmount Spectra:

# 1 TX audio, input

Should I use a coupling capacitor here? If so, what size and type?
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# 11 Detected audio from receiver, unsquelched buffered discriminator. MUST use a coupling capacitor, DC on this pin.

What size and type of capacitor should I use?
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# 13 PTT Push to talk, zero true. Ground to transmit, 5 VDC thru a 47 k pullup resistor.

I think I can just hook up the PTT from the controller without the pullup?
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# 8 Ground
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COS - The two speaker leads switch to aprox 6 volts DC on a valid receive signal with the proper PL or DPL. You can use a simple transistor circuit, emitter to ground, 10k base to ground, TWO 47k resistors from the base, one to each speaker lead. The collector is your COS< or more correctly, RUS signal= Receiver Un Squelched. - (Thanks, Will).

I'm guessing that the speaker leads want to see an impedance of what a Spectra usually requires. Does the Spectra look for an 8 ohm load? If so,
can I use an 8 ohm wirewound resistor with the correct power rating in
lieu of a speaker with the above mentioned transistor circuit connected to 6 SPKR Hi and 7 SPKR Lo?
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Victor, KB5AKO
[email protected]

On the TX audio input, AKA mic, use a 2.2 to 5uF cap, the + side to the Spectra as the Spectra has mic bias 9 volts here.

The RX out is the discriminator and it goes thru an opamp, so it needs a coupling cap of 1uF, again + to the radio assuming that the controller has a medium to high impeadance input.

The PTT is alogic input and a ground here keys the Spectra.

Audio output, Speaker leads, can be terminated using a 8 to 25 ohm resistor, and the volume turned down as required. 25 ohm 2 watt resistor works good.

Will,

I appreciate your help in this matter. You are one of the fellas here on the board that is patient enough to deal with people like me that are not electronic techs.

The COS circuit as I understood you to convey; and as I built it results in a double squelch tail. This resulted in the inability to program the ICS Linker IIa repeater controller that is programmed with DTMF strings. The second COS hit was inserting an unwanted zero in my command string. To cure the double COS signal feeding into the base of the transistor; I disconnected one of the speaker leads feeding into the base of the transistor. Now, the controller sees only one COS signal and interprets the correct DTMF string. I hope this helps someone else in the future.


Victor, KB5AKO

Victor,

Very interesting problem, I will set one up in "the lab"and see what happens.

One question, did the Spectra have a speaker, or any load, on it?
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Yes, an 8 ohm 5 watt resistor. I figured I better keep the audio amp looking into a load that keeps it happy.

Victor, KB5AKO

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Will wrote:Victor,

Very interesting problem, I will set one up in "the lab"and see what happens.

One question, did the Spectra have a speaker, or any load, on it?
.