OS Digitron DP-3, 3-Channel Radio Control System

OS Digital 3-Channel by World Engines advertisement in American Aircraft Modeler from a 1968 edition.

Here is the OS Digitron DP-3 Radio Control System User's Manual.

My first R/C system (OS Digitron 3-Channel) with my first R/C vehicle (Cox .049-powered air boat made from foam and covered in Solarfilm).

This is a rare find. After having a Saved Search on eBay for years, looking for an O.S. Digitron DP-3, 3-Channel Radio Control System with original packaging and documentation, one finally came up for sale. It was listed with inexact wording in the title, so maybe that's why I found it before others. It had only been listed for a few minutes, and I bought it instantly. This has got to be one of the primo examples left in the world. All the original packaging and documentation is here, even including a set of O.S. Digital decals. Why the enthusiasm, you might ask? This was my very first R/C system that I bought from a neighbor for $100, back in 1973, when I was a mere 14 or 15 years old. To my best recollection, it came with everything here. The fitted leather transmitter case was very nice, and it kept the metal chassis in excellent condition. My radio was on 27.195 MHz (green flag), and at the time, an FCC license was required to operate it.

Above and to the left is a photo of my DP−3, that was first installed in a homemade air boat (Cox .049 used for power). A single servo controlled the rudder. I had to swim out for it more than once when the engine cut out unexpectedly.

I believe the first airplane the R/C system was installed in was a Sterling Cirrus sailplane. It was really way too heavy, but I managed to get a couple flights in after my father wore himself out running to launch it on a towline for me.

Next, I installed the O.S. Digitron 3−Channel radio in my Andrews S−Ray model airplane. It had a steerable nose gear and throttled engine, which allowed me to run it up and down the road in front of my house for fun - yes, at 14 years old that counts as fun. My neighbors begged to differ, however, since the transmitter, at 27.195 MHz spewed some pretty significant harmonics (television interference, TVI) at the VHF television channels. The 2nd, 3rd, 6th, and 7th harmonics fell squarely into the band. When I switched the transmitter on during the summer afternoons when soap operas and game shows were being viewed, housewives within three or four houses of mine would stick their heads out the door and yell at me to turn it off. VHF channel 5 seemed to be the most vulnerable to my interference (76-82 MHz, so 3x27.195=81.858 MHz falls inband). They weren't too thrilled with the engine noise, either.

The pictures below is my OS Digital 3-Channel that I bought off of an eBay auction. It looks exactly like the system I had. It did not come with the sewn leather case that went on the transmitter, so I am still looking for one if you know where it can be gotten. The case came in handy once when I left the transmitter sitting on top of my car after loading the airplane and field equipment into the car, then puling out of the driveway and seeing the transmitter bounce off the road. Yikes. The only damage was a hole in the side of the leather case where one corner of the metal case punched through.

I would like to one day install the electronics from my Futaba Skysport T4YF transmitter (72.750 MHz FM) into it for use with my 85% Aquila sailplane.

Here is are photos of an OS 6 channel radio that went up for bid on eBay in July of 2008. I've been waiting for one of the 3 channel models.