User's Manual

RF
Technology T350/T500
Page 9
4 CHANNEL AND TONE FREQUENCY PROGRAMMING
Function Signal Pins Specification
DC power +12 Vdc
0 Vdc
1, 14
13, 25
+11.4 to 16 Vdc
Ground
Channel Select 1
2
4
8
10
20
40
80
21
9
22
10
23
11
24
12
BCD Coded
0 = Open Circuit
or 0 Vdc
1 = +5 to +16 Vdc
RS232 Data In
Out
15
2
Test and Programming use
9600, 8 data 2 stop bits
600W Line
High
Low
20
6
Transformer Isolated
Balanced 0dBm Output
150W / Hybrid
7
19
Direct PTT input 3
Ground to key PTT
T/R Relay driver output 16 Open collector,250mA/30V
Sub-Audible Tone Input [+] 5
>10kW, AC coupled
[-] 18 (1-250Hz)
High-Z Audio Input [+] 4
>10kW, AC coupled
[-] 17 (10Hz-3kHz)
External ALC input 8 <0.5V/1mA to obtain
>30dB attenuation, O/C
for maximum power
Table 3: Pin connections and explanations for the main 25-pin, D connector.
5 Circuit Description
The following descriptions should be read as an aid to understanding the block and
schematic diagrams given in the appendix of this manual.
5.1 VCO Section
The Voltage Controlled Oscillator uses a junction FET
which oscillates at the required
transmitter output frequency.
A varactor diode is used by the PLL circuit to keep the
oscillator on the desired frequency. Transistor Q20 is used as an active filter to reduce
the noise on the oscillator supply voltage. The VCO is keyed ON by the
microcontroller through Q10. It is keyed ON when any of the PTT inputs are active and
OFF at all other times.