[Today’s run: nothing yet]
I have this NiCOM NT250 FM broadcast transmitter which we are going to use for our LPFM station (WMFH-LP). The thing has 9-pin serial port on the back and NiCOM kindly sent me the software which talks to the transmitter. The software is a simple windows executable. It will let me change the frequency, turn the output power off/on, and it shows me the forward and reflected power output.
That’s all good stuff, particularly the ability to turn the RF off.
I asked NiCOM for a spec about the serial commands and never heard back from them.
So, today I finally had some success reverse-engineering the connection. I downloaded a program called Free Serial Analyzer. It can show me the serial port activity between the NiCOM control program and the transmitter. Using that I figured out this much:
Serial settings: 4800 8 N 1 (no flow control)
sent: ctl-D (0x04) received: 140 (in ASCII followed by a ‘.’) // forward power
sent: ctl-E (0x05) received: 3 (in ASCII followed by a ‘.’) // reflected power
sent: ctl-F (0x06) received: 4.0 (etc) // firmware version #
sent: ctl-G (0x07) received 159 // unknown
sent: ctl-H (0x08) received 9 // ???
sent ctl-I (0x09) received 0995 // frequency setting
sent ctl-J (0x0A) received 9 // ???
sent ctl-K (0x0B) received 9 // RF power turn on
sent ctl-C (0x0C) received 0 // RF power turn off
The windows program has some method of changing the frequency. And it also shows the current temperature. Obviously I am missing some of the command set. I now know how to read forward and reflected power, and how to turn the power on and off. That’s really all I need.