One cheap and easy way to go is with a simple circuit board and a pair of TNCs.
With a simple voltage divider consisting of a trim pot, you can calibrate the DC value coming from a power meter or sampler to the A/D channels on the board. With some careful calibration you could have 100 on the readout relate to 100% power out. That way you don’t have the crying of “why only (??) watts out on the repeater?” from the whiners. With 4 A/D channels, you can also do the S-Meter and DC Power Supply as well. 138 as a numeric value could relate to 13.8 volts. Easy to observe without any conversion. I’ve used one of these before and had great luck. >From HYPERLINK "http://www.gctelecomar.com/"www.gctelecomar.com MEasure & CONtrol This board gives to any TNC the ability to command three turn on/off ports, read four A/D input ports and three digital input port. The board is connected to the RS232 TNC connector at 1200 BPS 8n1 baud rate. Also you can connect to your PC or Palm serial port directly and command with any terminal software, as HyperTerminal or ProComm. One of the most obvious uses for MECON board would be in remote repeater installation. Useful information such as building temperature, amplifier temperature, backup battery voltage and AC power status can easily sent upon a connect request. You can also use MECON to turn on transmitters, lights, amplifiers, antennas and just about anything else that can be activated by a relay. MECON board also looks at the status of binary inputs. MECON is a powerful and economical tool for anyone considering remote control applications via Packet Radio. Ideal for equipment in remote location. Give a useful task to your TNC with this board Once you connect via other TNC or TNC sound card emulator you can turn on/off any device or measure four variables between 0 to 5 volts. The board has few simple command words to manage it, as: =T gives the value of the four A/D channels and the status of the three digital ports. The TNC will respond with the a sentence, 000 000 000 000 111, where the four numbers of three digits are the values of the A/D channels between 0 to 255 and the last number of three digits indicate the status of each digital input channel where a 1 indicate is on and a 0 is off. =S# turn on the specific port indicate by the # symbol, (1,2 or 3). =C# turn off the specific port indicate by the # symbol, (1,2 or 3). Every time that MECON executes a command its sends an answer confirmation with the ! symbol. To make work the board you needs a 7 to 30 volts source. Price MECON, telemetry and control board with full documentation U$ 22.50. 73, Rod Lane N1FNE Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.17.1/1182 - Release Date: 12/12/2007 11:29 AM
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