TINY-2/MICRO-2 Technical Ref., 2. Ed 1989
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Audio Input Level
The TINY-2/MICRO-2 is designed to operate with from 10 to 700 mV audio input. If you obtain au-
dio from the headphone or external speaker jack on the radio, place a shorting block on the pins
of JPR (factory default) and adjust the audio level to approximately 20 mV with the aid of a high
impedance Voltmeter or oscilloscope. If no such measuring equipment is available, set the volume
control at a position below that normally used.
If direct connection is made to the radio's discriminator (demodulator) or any other high impe-
dance audio source, remove the shorting block from JP R.
NOTE: The audio level should be set as to as low a value as possible if an unsquelched radio is
used. The TINY-2/MICRO-2 modem will show false DCD indications on noise if the audio level is
set too high.
Transmit Level Setting
Connect the TINY-2/MICRO-2 and radio as shown in the radio interfacing chapter. Turn on the
packet controller and computer and start the computer communications program. Connect the ra-
dio to a dummy load and listen to the transmission with another nearby radio. The output level is
set by adjusting trimpot R12 which is accessible through the rear panel opening marked "TTL Com-
puter."
1. Enter the command CAL<CR> and the letter 'K' to cause the TINY-2/MICRO-2 to key the radio
with a steady tone. The high or low tone is selected by pressing the space bar. NOTE: The
watchdog timer will cause the PTT circuit to reset approximately one minute after the 'K' key is
depressed. If you need a longer adjustment time, type 'Q'<CR> to return to the command
prompt and restart the procedure.
2. With the TINY-2/MICRO-2 keying the transmitter and the higher frequency tone selected, ad-
just the transmit audio level trimpot (R12) while observing a service monitor or deviation meter
tuned to the transmitting frequency. Set the deviation for 3 to 3.5 kHz on the higher pitched
tone and check that the lower tone is at least 2.5 kHz deviation.
3. If the proper equipment is not available as described above, make the deviation adjustment by
turning the adjustment screw on the trimpot until no increase in output level is heard at the
monitoring receiver. Then rotate the adjustment screw of the trimpot in the opposite direction
until the audio signal on the monitoring receiver is slightly, but noticeably, reduced from the
maximum level.
NOTE: It is better to have too low than too high a drive level. A high drive level causes over-
deviation, unnecessary interference, and makes your signal less copyable. Listeners may also
notice some low-level packet tones when using the radio for voice work.
4. The transmitter deviation is now set to approximately the correct level. Type the command 'Q'
to unkey the transmitter.
