Ramsey Electronics FZ-146 Specifications download pdf (Page 123)

FX-146 • 123

assures that the otherwise-silent PTT circuitry is indeed functioning and

obviously has nothing to do with the RF output of the transmitter.

The PTT circuit may also be activated at pin 3 of the Packet I/O jack. A

direct short to ground is not necessary. The author noted very positive PTT

action with resistance as high as 100K from pin 3 to ground. This is a highly

reliable and efficient PTT system provided that careful attention is given to

correct selection and installation of all parts: resistor values, PNP transistors,

zener diode orientation, U4 installation, correct wiring of microphone jack.

Stage M: ASSEMBLY PROCEDURE:

Install the following parts:

 M1: C86, .001 uf (marked 102 or .001 or 1nf).

 M2: C83, .001 uf.

 M3: C88: .001 uf.

 M4: C77, .001 uf.

 M5: C23, .001 uf.

 M6: R57, 2.2K (red-red-red).

 M7: R59, 100K (brown-black-yellow).

 M8: R58, 270 ohms (red-violet-brown).

 M9a: R50, 10K (brown-black-orange).

 M9b: R49, 10K (brown-black-orange).

 M10: R51, 47K (yellow-violet-orange).

 M11: R56: 47K (yellow-violet-orange).

 M12: R61: 2.2K (red-red-red).

 M13: R37: 100K (brown-black-yellow).

 M14: C93: 4.7 or 10 uf. (Watch polarity!)

 M15: C89: .001 uf.

 M16: C24: .001 uf.

 M17. Install U4, a 14 pin DIP IC, type LM324, which contains all 4 op

amp sections of this circuit. Orient the notched end as shown on the

board. If you elect to provide a DIP socket, use the same care as if

soldering the IC itself.

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Ramsey Electronics FZ-146 Specifications Page 123