Old RC transmitters

This page is intended for people who are interested in old proportional transmitters. I hope it is an inspiration source on how to bring them to life again, either completely original or with modern components. I got into this very recently, thanks to the time freed up by stopping the production of the jet model kits. I guess this nostalgic trip is due to the fact that those transmitters costed a fortune half a century ago and my spending hours as a kid drooling over catalogs, wishing I had the money to buy the equipment...

 

line up of old transmitters

So I own a series of  transmitters which had been lying around in my attic for years until a short while ago, I decided I would clean and update them. First thing was to remove the batteries. All had leaked. I really should have removed them a lot sooner... Luckily, only one transmitter got badly damaged by the acids creeping between the aluminium casing and its brown vinyl cladding. It was a Heathkit donated by my uncle Jacques, the man who got me into aeromodelling and inspired me to become a Belgian Air Force pilot. Thanks Jacques! The damage is not visible on the photograph below. I restored the transmitter cosmetically only and substituted newly printed labels.

Heathkit transmitter from uncle Jacques

Actually, I still have all my original transmitters. The first one was a MagGregor Digimac IV (upgraded to 6 ch), bought in a shop in Bruges back in 1973 or 1974. I paid 400 euro at that time, which would equate to around 2000 euro today... It was put to a lot of use and abuse, so it is pretty much in poor condition, but I intend to put  the transmitter in working order again. Probably not to fly as the gimbals are really worn.

MacGregor Digimav IV on 27 MHz

This was followed by two Tower Hobbies transmitters which were actually built by Kraft but were priced much cheaper (200 US Dollars). One of these has been upgraded, see further on.

Tower Hobbies on 72 MHz

Two Multiplex Royal transmitters with servo reversing, dual rates and mixer functions came next. These features were necessary to allow me to fly the F-15C twin ducted fan model which would eventually grant me my first F4C Scale World Championship title. I intend to make at least one operational again with a 2.4 GHz upgrade.

Multiplex Royal on 40 MHz

My first computer radio was a Futaba FP-T9VAP, followed by a Futaba 9ZAP, both on 35 MHz and my current Futaba T12FG, my first 2.4 GHz radio.

my Futaba computer radios

I acquired some other vintage transmitters in the course of the years bringing my total number to around 40. I plan to put most of them in working order again. Some will be upgraded with a 2.4 GHz RF module, a modern encoder and LiPo batteries, some others will remain fully original. Still others will get a restyling if I don't like the looks of the original... Some photographs below.

 

Kraft 76, Microprop 68 and Multiplex 4

Multiplex Combi, Kraft 74 and Robbe Mars

ProLine Competition singe stick, Robbe Supra and Space 5

 
 
Upgrading old radios to modern standards
 

I had first read about this possibility on the Dutch modelbouwforum.nl and it captured my attention. I was keen to do something similar, but when I first read about it, I estimated it was beyond my capabilities as I'm really an electronics analphabetic. I believed it was far easier to buy a modern radio and disguise it in a retro case. So that's what I did with a Futaba T6L Sport radio, explained in detail here.

Meanwhile, in my eagerness to do a true conversion, I had been reading more about the subject on the singlechannel.co.uk and mode-zero.uk websites, and got into contact with Phil Green. He gave me some good advice and at a certain point, I felt confident that a true 2.4 GHz conversion was within my reach, using a  preprogrammed encoder from Phil and using an off the shelf  Futaba  TM-7 RF module. As I have my own CNC router, it was easy for me to create supports for the encoder and the module and to create drilling templates to make the necessary holes for the switches and buttons. I chose a Tower Hobbies transmitter for this proof of concept exercise because I have three of these, see here.

During the conversion of the Tower Hobbies, I continued to gather information and I was delighted when at one point, I was able to upload a sketch to a DIY More Strong board on my own. I think that's where I got addicted... It is simply very rewarding to be able to make an old transmitter fully functional again with a lot more features than were available on the original. I then read about Mike Kitchen and his efforts on new encoders and his adaptation of Phil's sketch to better suit F3A retro style models, so I proceeded to convert a Kraft series 78 transmitter. I also read about how to make the power level indicator compatible for LiPo batteries with zener diodes and resistors, so that was incorporated as well. I can charge the LiPo through the original DIN 6 pin receptacle at the bottom, directly connected to the balancer cable. At the time of writing, I still need to do the flight tests however, but on the ground, everything seems to work as advertised.

I also converted a Belgian made Space 5 transmitter but this time keeping everything on the outside original. This was a simple conversion, no added switches, just a buzzer.

A friend of mine recently donated me a carton with 4 old transmitters. I cleaned and restored these and gave two of them also a cosmetic make over: a Graupner MC-16 and a Robbe Supra. I think they look much better now, but that's individual taste. The Multiplex 4 and the Multiplex Royal 5+2 were given a good cleaning. Thanks for the donation Marc!

By far the easiest conversion was the Kraft Bicentennial 76 transmitter. I simply bought a Kraft 2.4 GHz DIY TX module from Cal Orr so I can switch conveniently between modules, keeping the transmitter 100% original.

More transmitters will definitely follow. On the list of projects: a single channel transmitter with Phil's purpose made single channel encoder, and a conversion of another Tower Hobbies or Kraft transmitter with one of Mike's new encoders with hidden display and many features like model memories, programmable mixers etc.

 
 
Futaba T6L in retro case
 

This was the first transmitter I modified. I bought a simple and brand new Futaba T6L sport transmitter (from the excellent Aerobertics shop in Bruges) with the idea of installing the hardware in an existing vintage case. When I discovered that the antenna was integrated on the PCB, I switched to a self made wooden case as I don't have the knowledge to substitute an external antenna. It was a fun project, designing a nice wooden case with the typical seventies look. I added a period correct logo which looks very nice. It's from Tenco, a Belgian RC trading company that sadly ended its activities in the early eighties.

The antenna outside is a dummy wooden thing, just for looks. I painted the case with Motip Hammerite Blue to give that industrial metal look. The transmitter is operational and has been flight tested.

 

inside

finished

 

wooden case

finished

 
 
Tower Hobbies
 

I own three of these transmitters. They were relatively cheap back in the late seventies, being simple 72 MHz AM transmitters. They were good quality, being manufactured by Kraft. I decided to modify this one first as a sort of proof of concept. I learned a lot from the singlechannel.co.uk and mode-zero.uk websites and used the 7 ch encoder software (sketch) published on those sites, courtesy Phil Green. This software allows the radio to be used as a single channel radio with just one push button, while retaining the full proportional 6 channel capability with a switched 7th channel as a bonus. It features  dual rates, exponential, servo reversing, range checking mode and a very convenient timer. This transmitter was the first to be modified and that's why it has all the whistles and bells as provided by Phil's software. It has a receptacle for a modified Futaba TM-7 module, so it can work with a selection of Futaba Fasst receivers. A 2S LiPo provides the power.

The transmitter is operational but has not been flight tested yet.

 

inside

outside

front view

 
 
Kraft series seventy eight
 

I purchased this transmitter some 10 years ago. It has received the same treatment as the Tower Hobbies above, but the original software (sketch) by Phil Green is modified by Mike Kitchen and more adapted to retro F3A style models and that's exactly how I intend to use this transmitter. More info on this software can be found on the mode-zero.uk website.

The transmitter is operational and has been flight tested.

 

inside

outside

front view

 
 
Space 5
 

This is a transmitter that was donated to me. I don't know anything about the manufacturer except that it was Belgian made as the label on the back indicates. At least, that was what I thought until I got my hand on a Japanese made Digiace transmitter, and except for some cosmetic diffrences, it is basically identical.

I kept this conversion simple. I didn't add any switches or buttons, just a buzzer. It uses the  same Futaba TM-7 receptacle as the Tower and Kraft conversions above. Nothing on the outside except the antenna will reveal the transmitter has been upgraded.

 

inside

outside

 
 
Graupner MC-16
 

This is a work in progress. I just removed the badly leaking batteries and all the old electronics and gave the transmitter a good cleaning and cosmetic make over as I didn't like the very busy looks of the original. It will probably be made operational again in the future.

 

before...

...after

 
 
Robbe Supra
 

Same treatment as above although the transmitter was not nearly in as bad a shape as the MC-16. I simply did not like the looks of the original. Very nice gimbals, so definitely a user in the future!

 

before...

...after

 
 
Multiplex 4
 

I removed the batteries from this simple 4 channel transmitter and gave it a thorough cleaning. The joystick covers were given a fresh coat of paint.Some day, it will receive a 2.4 GHz upgrade.

 

before...

...after

 
 
Multiplex Royal 40 FM 5+2
 

Same treatment as above but added new 3D printed joystick covers as the original chromed ones were too badly damaged. Thank you Wim for the 3D printed parts!

 

before...

...after with original joystick covers

and with new 3D printed joystick covers

 
 
Kraft Bicentennial series seventy six
 

Another donation from my uncle Jacques. This was actually my very first "effort" in converting a transmitter to 2.4 GHz. The transmitter was given a good cleaning, new NiCd batteries were installed, and it was soon operational again, albeit on 72 MHz. I then bought a Kraft 2.4 GHz DIY TX module from Cal Orr so I can switch conveniently between modules, keeping the transmitter 100% original. His website can be found here.

The transmitter is operational but has not been flight tested yet.

 

with original 72 MHz module

with 2.4 GHz module from Cal Orr

front view

 
Multiplex Royal 27 FM 5+2
 

Very nice example of another older Multiplex Royal 5+2 transmitter, this time on 27 MHz. I converted the transmitter to 2.4 GHz, leaving the outside fully original except the substitution of a 2.4 GHz aerial. A push button is installed almost flush inside the opening of where the crystal was originally accessible.

 

before the conversion

 

after the conversion

 

The battery indicator is adapted to show the LiPo voltage in expanded scale. futhermore, the exact voltage can be read through the DIN socket. Finally, PPM can be read out through the same DIN socket, which can be helpful to memorize trim settings on multiple aircraft.

 

LiPo voltage readout

 

PPM readout

 

almost invisible push button in oval slot of crystal

 

 
Multiplex Europaserie 4+2 orange
 

I modified this transmitter for Stef De Wit, a passionate and nostalgic modeller and a big fan of my work. It is pretty much the same conversion as the white Multiplex Royal above. A complete description of the work and the dedicated instructions (in Dutch) can be downloaded here.

 

outside view

 

inside view

 

 
Multiplex Royal orange
 

I'm a fan of the Multiplex Royal series introduced in 1980. I've flown a lot with two of these as can be seen earlier on this page. I recently bought a couple more. One was in very bad shape and needed major body work which made it impossible to preserve the brushed aluminium look. Painting remained the only option. Another one I bought was almost in pristine condition, so I decided to not only paint the very bad example but also one of my brushed aluminium ones which didn't look so well. I chose a light gray for the latter while the former would receive a look very much akin to the Orange Multiplex 4 series of the early seventies. I found the matching RAL colour number and made some new decals to finish off this unique orange Royal. The transmitter is now added to the list of to do 2.4 GHz conversions...

 

 

 
Multiplex Royal gray
 

This is the other one which was painted in light gray. I'm not sure but I think early Royals of this series were in off white or very light gray. Anyway, I like the styling with this gray and the transmitter looks like new again.

 
 
Multiplex collection
 
Here are a couple of photographs of similarly looking transmitters of my Multiplex collection.
 
 
 
Digi-Fleet XP/FM
 
Nice example of  a 5 channel Digi-Fleet  XP/FM transmitter
 
 
 
Graupner Varioprop C 8
 
Nice example of  a Grundig Graupner Varioprop C 8
 
 
 
Webra transmitters
 
Webra was well known for its engines, but they also manufactured a line of radios.
 

Webra 5 FMSI

Webra Space 8/16

 
 
Simprop transmitters
 

Simprop had a very good reputation and was the choice of champions back in the seventies. The internals of the gimbals are quite different to what you see in most transmitters and definitely contributed to that good reputation.

 

Simprop Alpha Contest

Simprop SAM FM

 
 
Robbe transmitters
 

These are two other Robbe transmitters next to the ones shown above. The Luna has a typical end of seventies styling. The more recent Promars has a peculiar styling, not embraced by everybody...

 

Robbe Luna

Robbe Promars FMSS

 
 
More Kraft transmitters...
 

Kraft 70

Kraft 79

 
 
...and Multiplex transmitters
 

Multiplex Combi 80

Multiplex Royal MC

 

Multiplex Professional on 434 MHz

Multiplex Europa Sprint

 
 
Digiace
 

Japanese made Digiace transmitter. Very similar to the Belgian Space 5 shown above and almost  certainly from the same manufacturer.

 

Digiace

 
 
Digicont
 

It is said that the Meinberger Digicont was the very first PCM transmitter in the world. Here is a nice example

 

Digicont PCM

 
 
 
I will probably add some more transmitters in the next few months...Keep on the outlook!
 

 

Philip Avonds Scale Jets

Doornhofstraat 6
B-8670 Koksijde
Belgium
Phone: +32-58-514451
e-mail: info@avonds.com