H5487

My first rig was a circa-1968 Digi-Trio 4-ch digital proportional built from RCM plans. I didn't build it but bought it second hand from an older club member in 1970. He did a good job putting it together and his quality of workmanship rivaled many of the commercially-produced rigs of the time. ('cept maybe a Kraft. We all oozed for a Kraft!)

Well, I installed the receiver, servos, and giant battery pack in my Falcon 56 and proceeded to teach myself the fine art of gluing airplane parts back together. (There was no Buddy Box training system back then. []) I remember that the receiver was actually pretty small for a hand-built unit but the servos were awfully big by today’s standards and slow too! But it was my first R/C rig and I didn't know how archaic it already was by the time I bought it. I loved it!

I had to shelve my R/C hobby when I entered the USAF in the early '70s (fragile model airplanes don't pack and travel easily) and I eventually sold my Digi-Trio to a fellow Air Force buddy. It seemed like an ideal opportunity to move up to a newer rig but I've come to regret letting my beloved Digi-Trio go. Oh well, who would've thought that it would become part of my teenage memories?

Anyway, I was wondering how many other old R/C greybeards like me cut their teeth on a Digi-Trio? Since they were homebuilt and complicated, they weren’t staples at every flying field, but I remember reading somewhere that the multi-issue Digi-Trio series was one of RCM's most popular construction articles.

How about it? Any other Digi-Trio memories out there?

Harvey

BobHH

My Feedback: (18)

You mean one of these? My Dad use to build and service the Digitrio. I actually have a complete unit in stock!!

Bob Harris

H5487

Hi Bob,

Yep. Other than mine having a blue case, yours looks like mine did. Does yours still work and do you have the plastic-cased servos (single linear output) or the metal-cased Bonner type?

Harvey

iflyj3

My Feedback: (7)

Yes, I built one in 1965, starting with the first RCM issue that covered it. A buddy also built one which I ended up with when he quit the hobby in 1970. I expanded mine to 5 and 6 channels. I have one on 6 meters and one on 27 MHz. I have the Controlaire servos that were the reed servo with the Digitrio electronics. I also have one Orbit PS2 with the Digitrio amplifier.

I flew a lot of flights with the Digitrio and cleaned a lot of feed back pots. Compared to today's $12 servos, the Digitrio servos were slow, slow, slow. However, even as slow as it was, it sure beat the analog system I was using.

I still have both systems in a box.

BobHH

My Feedback: (18)

Yep, mine has the older Controlaire reed type servos. One must clean the wiper board with a pencil eraser though!! Mine is 4 channel and the last time I fired her up she worked.

Bob Harris

etownflyer

My Feedback: (4)

Another Digitrio builder flyer here. Couldn't afford commercial proportional and had a reed set. I had a background in electronics so I built one. And helped two other pilots trouble shoot and tune theirs. Build the transmitter case from a Bud box and made the stick assemblies from brass. Had access to a photo shop so I made negatives, coated copper clad with photo senstive material and exposed and etched the boards. We did buy the servo kits, starting with the Controlaire and moving on to the the Orbit PS-2 mechanics.

We flew hundreds of flight with these things. Usually more reliable than many commercial sets. Except Kraft and Proline. A couple of years later I was finally able to get a Kraft Gold Medal. Another great radio.

Lots of fond memories of Digitrios. Still have one and part of another in the shop.

etownflyer

My Feedback: (4)

I just noticed that you are in Houston. I have a brother-in-law there that I visit from time to time. Would love to get together and share Digitrio stories sometime.

Marshall Sanderson

H5487

When did Heathkit introduce their GD-47? Could it have been a result of the popularity of the Digi-Trio or was the Heathkit already on the drawing board when the Digi-Trio articles were published?

Harvey

JMP_blackfoot

I had been flying single channel escapement, then pulse and four-channel filter sets for two years with my buddy Robert Cossé, all with home-made radios, when I met an American girl in Paris. We fell in love (still are to this day). At the time we were 22 and I was studying to become a mechanical engineer.
For one year I worked small jobs to earn the money to go see her in the US. I spent the summer of 1966 in Ohio, during which stay and amongst many discoveries, I found the Digitrio in RCM. With such spare money I had, I bought two receiver kits (RF part only), eight linear Controlaire servo kits and four Bonner sticks. Back in France, I had a student job in a Philips subsidiary research lab, with the resources and spare time to build a four channel decoder and a transmitter PCB. I was encouraged by the lab manager who thought the exercise a valuable teaching help. He thought I was building a single set, but I had to think of my buddy, so whenever a circuit was finished and tested, I took it home, somehow it had a problem and I had to bring it back and fix it. I was actually bringing the second one for adjustment, which I was building in the evenings. I still don't know whether or not he was aware of what I was doing. We made our own receiver and transmitter boxes out of aluminium sheet and soon had two functional four-channel digital systems.
They worked quite well, had a ground range of 800 m. (1/2 mile) and were reliable. I do not remember that the servos were slow, but then We had nothing to compare them to and the planes flew well with them. My friend flew an Enya 60 powered Taurus with his. First time out for a contest in Rouen where some big names came from France and England, we witnessed how the users of the then expensive fashionable through-hand Simprop digital system users had all sorts of problems while the Digitrio performed flawlessly. It was an eye-opener for me, the beginning of many home-built digital radios and of a career in the field of electronics. I later sold my own Digitrio set to another friend, but now wish I had kept it. All great memories!!!

maxpower1954

I have one of those in my flying vintage transmitter collection. It was introduced in either late 1967/early 1968, so I doubt if the Digitrio had much influence on it's being brought to market. It used the first Kraft digital system design, IIRC, while the GD-19 used the Gold Medal Series. Russ Farris

pd1

My dad built two DigiTrio's in 1964 or 1965.
Mine worked great compared to the reed set ups I used til then.
It did have a nasty habit of only failing when in my best planes.

I was offered a Citizenship unit in 67 at a deal I couldn't refuse.
Loved the Citizenship but moved to the new Heathkit in the spam can soon after.
Stayed with that until the newer Heathkit came out with the plug in frequency modules.

Paul

rc doc

My first proportional radio was a Digi-Trio [quad] that I put together from kits that I purchased through The RCM magazine. I had a single stick unit that I purchased from some one in California. I was working for a gold mine at the time and our electrical engineer [also an RC nut] helped with the tuning. It worked a lot better than I was a flyer. I kept it until 1972 and gave it to another pilot. I also built a Royal unit. I still have it in my shop. It worked very well but one of my receivers had problems with vibration and spread my Lanier Comet all over Wyoming.
The Digi-Trio was an excellent radio if assembled correctly and started me on using single stick transmitters.
John Smith [RC DOC

spaceworm

I have a Heathkit GD-47 transmitter, receiver, battery box and several servos, AND the construction manual. Anyone interested? I have to downsize my "stuff".

H5487

Me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me me!

What are ya asking?

Harvey

skypupmut

I built a digitrio in 67 moded it to 4 channel. I sold it to a boat modeler ( durn )
after building a kit Cannon 5 radio. I still have the cannon and it works still
boy those servos were slow.
should have kept the digitrio, still have the build instructions somewhere

HIr/cer

My Feedback: (74)

A Cannon 5 radio kit?! Built one myself and used it with a Cox Dune Buggy. Remember the neutrals slowly shifting during use. Still have it fortunately altho a bunch of stuff was stolen from me recently. Will have to post what was taken. BTW, I recall being interested in the Heathkit GD-47 but was disappointed at the size of the receiver after seeing a set that had been completed by a flying buddy. Another buddy had built a Digitrio and had used it for about a year without any problems (before the intro of the GD-47).

cmanios

My Feedback: (1)

My Two Cents

My first proportional system was the digitrio which I built from RCM plans and World Engine supplied receiver and servo kits. The satisfaction of building my own airplane and my own radio systems was beyond belief!

The electronic concepts and ideas presented in RCM magazine for the the Digitrio by Ed Thompson (Design Engineer) can still be seen and is utilized today. If any of you recall, Ed Thompson stated that it is up to we modelers to tell the manufacturers what it is that we want in radio systems and to demand it from them! Do you think we do that today? Do you think they would respond to our request? If so try asking them for a Single Stick Radio System!

I also loved Grid Leaks and RCM magazines because they provide across the board projects and ideas that todays magazines just do not have. Will there ever be another one where we modelers can share ideas and get the enjoyment that I have experienced?

Conclusion is I am glad to see there is others out there that experienced the Digitrio and I now know that I am not the oldest still enjoying modeling and all those other related fields!

northiceman

Hello!!! Just (finally) caught this thread on the DidiTrio - what a radio system !! I could not afford one way back then - had to make do with a single channel Citizenship!!

And YES - where are the single sticks - this hobby has come to be CONTROLLED by this cheap plastic junk that pollutes and breaks easily.

I STILL fly on my single stick Krafts that I bought way back in the 60's - LOVE single stick !!!!

jrfromdallas

When the digitrio article came out, I was working at Collins Radio Company and we had our own RC Club and we jumped on that article with great enthusiasm. We redesigned it for 5 channels and built a bunch of them. We were happy to say goodbye to our Reed systems. I flew the digitrio for many years and finally built a couple of Heathkets which worked very well. I have been flying RC since 1948 and as most people know, the only single-channel radios did not work very well.John Reed

H5487

Hello John. Thanks for making your first post on RCU about the early years of radio control. I'm probably not the only one in the vintage section who would love to hear more of your memories from the early days of R/C!

And welcome to RCU!

Harvey

H5487

I don't believe that the manufacturers drive the industry. I still believe that the customers do, if only by default sometimes. Let me explain...
Manufacturers produce products with features that will sell. If a particular feature doesn't bring in the expected buyers, the feature will be dropped. That's the cornerstone of manufacturing. I'm pretty sure that the R/C manufacturers would produce single-stick systems again if their sales were certain. However, let's be realistic...The modern R/C pilot is so used to dual sticks that he or she would unlikely give a single-stick system a second look when shopping for a new rig. And the dozen or so of us who prefer single-stick R/C wouldn't buy enough of them to make it worthwhile for the manufacturers. Therefore, all of the major manufacturers will undoubtedly continue producing dual-stick systems and the buyers will reward those manufacturers by buying them, thereby telling the manufacturers (by default) that there's no reason to deviate from dual sticks.

So, here's the silver lining on this cloud: If you want a single-stick system, you're gonna have to build it yourself. I like that concept because it brings back the good 'ol days of individuality and handcraftmanship; two traits that have been in awfully short supply in our hobby for far too long now!

Harvey

bcchi

Hi RC Doc,
You would't happen to be the Dr Smith that lived in Riverton Wy. I am still flying.This getting old sucks.I never built a Digi Trio,but built a bunch of Royals.Send me a PM.
Bill Carpenter. BCCHI

sidgates

My Feedback: (2)

I think I also know Dr. Smith. I know I know Bill Carpenter. I was involved in the design of the Royal Classic, the follow on design by Ed Thompson.

I was getting ready to build a Digi Trio when I found out Ed Thompson was stationed at Lowery in Denver so I looked him up and we ended up doing the Royal Classic design together. I started R/C in 1952 with a Babcock tone receiver and borrowed a transmitter, couldn't afford one at the time. I was going into the USAF in 1954 so I was going to loose the use of the borrowed TX so I took it to the local Radio Parts store and said I wanted one of each part in it. Built up my copy and it didn't work so I ordered a Heath VTVM, built it one evening and the next evening found out I had a shorted tube socket in the home built TX. Got a new socket and it worked.

Over the years I built a WAG Dual, Kraft Single Channel Tone System, Marcy 6CH system, Kraft Triple simul reed system, copied a Sampey 404. Test flew and consulted with Bob Boyce and Chris Pederson on their 4ch analog propro sytem. Convinced Bob and Chris digital propro was the better way and next they designed a true digital system in 1967 but I think we had a servo motor failure on every test flight. I think the receiver had 112 transistors, no suitable IC's at that time. In 1970 Bob and Chris came up with a new receiver with FET fron end and IC decoder which I produced commercialy until 1983.

Bob Boyce and I still fly together at Chatfield in Denver area.

Sid Gates

bcchi

Hi Sid,
Never built a Digi Trio but built a lot of your Royal kits.Flew Royal for years. Do not believe I ever lost a plane with Royal radio. Just sent my Royal Classic White case,to Bart Phillips along with my Heathkit. Both worked fine.You should remember Bart.
Have closed downC&H due to Old age health problems and China.I am still able to get out and fly but have had some very serious health problem,Hospital caused.Have not heard from Dr Smith in years.
Wedd Higgins was killed in a car wreck.Bad things happen to good people.
Bill Carpenter BCCHI

sidgates

My Feedback: (2)

Bill - Very good to hear from you. I know what you mean about getting old. I realized a couple of days ago I am probably the oldest guy actively flying at Cherry Creek or Jefco.
My direct email is: [email protected]

My current model projects and a list of my model videos on YouTube are on my web site: http://www.sidgates.us