Interfacing Hand-Held Radios
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This section is for those who need more information than that given in the “In
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stallation” chapter.
Many transceivers, especially most hand-held models, obtain Push-To-Talk key
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ing by completing a circuit between the mic input and PTT ground. A direct PTT
input to the mic input line of units with this type electret condenser microphone
is not usable without some type of isolation.
If you plan to operate a hand-held transceiver with the KAM’98, you will have to
add a capacitor and resistor to your radio cable.
While you will need to check the exact requirements of your hand-held radio, the
following guidelines may be useful:
• A .1 uF capacitor (non-polarized) usually is required in the transmit
audio line from the TNC to any handheld transceiver (HT) radio. Even if
a capacitor is not required for connection to a particular radio, it can still
be installed, and the transmit audio (packets) will pass through to the
radio.
• ICOM HT radios key the PTT by providing a low impedance path from
the mic input to ground. To accomplish this, simply install a resistor
(approximately 3.9K seems to be a good value) in series with the PTT
wire from the KAM’98, and connect this to the mic input along with the
AFSK line.
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The ICOM 2A style wiring is most common, and can be used with some
Alinco, Azden, and Standard HTs.
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YAESU radios are similar but use a mono plug and a different value
resistor.
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The wiring for Yaesu HTs can also be used with Radio Shack HTs.
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Most KENWOOD HT radios key the PTT line by connecting the sleeve
of the mic connector to the sleeve of the earpiece connector. This means
that you will not need a resistor in the PTT wire from the KAM’98,
simply connect the PTT wire to the sleeve of the mic connector. Another
point to watch – most of the KENWOOD HTs (2600 and later) use a
Appendix A: Advanced Installation Connecting to your Radios
User’s Guide 332 KAM’98 v 8.3
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