Posted on October 29, 2011
Ever since becoming active in Part 15 I have been adding frequencies to the game. Right now I lay claim to 3 AM frequencies, 3 FMs, 1 long wave and 1 shortwave. Not all of those frequencies are developed yet, namely the carrier current and long wave, but they will be soon. There may also be a 900 mHz STL (studio transmitter link). Of course, all of the transmitters are spread far apart from each other to avoid mutual interference. Turning them all on or off takes about 5 or 10 minutes running between them. That’s why I am now designing a remote control system so they can all be controlled from one location.
Getting a focus on how to proceed with the remote controlling circuitry has been a study project for a long time, but the other day I found a circuit in a book which I absolutely love and this will be the starting point. Keep watching this blog because I am going to scan the schematic and invite comments plus I have some questions.
I have the fondest memories of the clunky rack mounted remote control rig that controlled the 70 kW FM where I worked. It contained a literal telephone dial on it’s front panel and by dialing “2” and “raising” the filaments the transmitter, 10-miles away, would warm up. A meter displayed the filament voltage so I could verify it was turned on. 10-minutes later by dialing “3” I would “raise” the carrier, and the needles on the frequency monitor all stood up and the speaker monitor went silent with a city-wide carrier.
The smaller version I am building will show by LED which transmitters are on. I won’t need to lease a phone line because all the wiring will be a private little home-owned “phone system.”
I will be opening a project page at kdxradio.com for the remote control system, and the information will belong to the Part 15 community.