TOPIC:

A little background before I get into the technicalities, I do like to tell a good story;
I'm addicted to tools & tech when it comes to RC, I tend to develop an obsession with brands or specific technologies. This means over the years I have amassed far too many transmitters and other components spread across different bands & radio systems including 27MHz AM & FM, 35MHz FM (even though I don't fly.....yet) 40MHz FM & multiple 2.4GHz band systems.

Apart from my collection of vintage Acoms (for purely sentimental reasons) I am mostly attracted (addicted?) to Hitec radio gear.

The basics of this project began with my purchase of a Hilift Hilux 58397 back in 2009, fancy plans for modifications & extra functions & the need for a multi-channel radio with which to operate it. A Hitec Focus 6 35MHz radio was bought cheap from Ebay & despite not being modular, the internal RF board was pluggable & I exchanged internals with a 40MHz unit suitable for surface use. I also added a 7th channel, although I only intended to use 6 for the Hilux. House moves & other real life interruptions meant that the Hilux still remains unfinished to this day (but I am getting there, honest). Deviations into racing expanded my 40MHz gear & also led to forays into 2.4GHz.

Modernisation of my gear and attempts at rationalisation.
Earlier this year I bought a Hitec Optic 6 (grey version with a Hitec / Futaba module bay) along with a Hitec 2.4GHz AFHSS module and 40MHz module,  & the little gears in my brain started ticking as they are prone to do. The modular transmitter concept is of course, to allow you to use a single radio for multiple frequency bands / RF systems, mostly used for aircraft, but there's no reason it can't be applied to surface models. The basic principle uses just 4 connections; Power, ground PPM signal & RF out, every manufacturer's module bay system differs of course & 2.4GHz tends to have an inbuilt antenna rather than an RF output on a module pin. The major designs are Futaba / Hitec, JR (KO?) and Sanwa. Sanwa is mechanically compatible with a Futaba bay but the pinout differs.

So I posed this question to myself;
Q. Can I use just one TX to operate all my toys ?
A. Yes* (although the practicalities of it suggest more than one is necessary)
The discovery and purchase of a 27MHz AM Sanwa module intended for the Kyosho Mini-Z tipped the balance meaning I could use any of my major radio receiver systems from a single radio.

So, to business;
Part 1. For the 3 speed(s) , I need 6 channels using gates on the stick for gears & throttle plus one stick axis for steering leaving 3 functions for other things (winch, lights etc), this is the easy one.

The simple answer to part 2 is to use a wheel radio but I can't be doing with one of those weird things

For normal vehicles I need steering on Ch1, X axis on the rh stick, throttle, y axis on Ch2 lh stick - two stick aircraft radios aren't wired this way of course. Actually they are, see below. Mechanically it can be restricted with circular shift gates just like the 3 speed or possibly by locking x or y axes on left & right sticks as appropriate. Extra channels are a bonus for lights etc but not a strict requirement
Electrically there will need to be some swapping around internally, but thankfully the Optic 6 is mostly plugged, although I may need to extend wiring or swap switches around to get things where I want them.

Part 3. Modify the Sanwa module to fit in a Futaba/Hitec bay. I have an old 29MHz Futaba module that is of no use to me other than the case, so I can swap in the Sanwa & make the necessary wiring adjustments, plus cut a hole for crystal swapping. The final piece of the puzzle for this is the purchase of a  PN Racing KO Module Adapter for 3PK, M8 and M11 which really only provides the necessary wiring information to plumb the Sanwa in the Hitec pinout. Thus far I have been unable to determine the exact Sanwa wiring & a Sanwa modular TX is something I don't have (despite owning probably 30 or more TX's of various makes :O ).

The ultimate aim is to end up with two modular TX's suitable for 3 speeds, cars & boats on any band, but easily reverted to aircraft if I turn to the dark side & learn to fly. I can complete my collection of boxed vintage Acoms while actually reducing the sheer amount of gear I have.

I'll add some more pictures later this evening which will hopefully tie my ramblings together a little better.
For now, here is the Sanwa module & PN Racing adaptor;

 

So here are the various modules for this project;

L~R
Hitec 40MHz FM, I have crystals for 20 of the 34 channels in the band.
Hitec Spectra DSSS 2.4GHz, intended for surface use with the Aggressor type wheel handsets, no telemetry
Hitec Spectra AFHSS with telelmetry, intended for air use, came with one of the two Optic6 radios

 


2nd pic FrSky V8 reciver plus V8 & D8 modules (the D8 is in a JR module case but could be swapped into a Futaba case if necessary.
D8 has telemetry, V8 does not, but I don't actually have any D8 receivers, the module came with a batch of V8s from Ebay. If I find myself needing telemetry for flight use, I'll probably go with the Hitec anyway.

 

3rd pic
OrangeRX DSM2 that should be Spektrum compatible (as yet untested) and the Futaba 29MHz module that will become a case donor.

 

Then we have the better of the two Optic6, came boxed with the 40MHz module but lacking a receiver. I have a dozen or more Hitec 40MHz RXs. This will retain it's channel assignment & dual axis sticks. If I can fit a 2nd ratchet to the left stick X axis that would be my ideal scenario & have no spring return on that stick at all, making it ideal for 3 speed throttle & gear selection.

 

Then the ratty Optic that came with the AFHSS module, this is the one I will modify internally to reassign the stick channels, switches etc & fit slotted gates to restrict it to just throttle & steering. It will retain all 6 channels but effectively be a "2ch" radio.

 

Had a flash of inspiration at 3am, the x axis gimbal is mounted in it's entirety on the Y axis, so swapping them over should be simple mechanics. Opening up the case this afternoon showed my idea was correct. In fact the left stick X pot has nice long wires, the right stick being the limiting factor, but since it get's rotated 180° when mounting that neatly solves the issue of wire length, making the swap simple enough. Undoing the 4 small screws holding the trunnion bearings liberated the potentiometers & sticks from each side;

 

Then it's a simple matter of turning them round & refitting;

   

A little fiddling with wire routing & mounting points & we're done.
There are still a couple of other potential hiccups but neither is a show stopper;
The axis direction has probably reversed for each of those, that can be solved either by swapping the outside wires on the pot or done in software in the radio. The latter being a non-invasive & easily reversible fix.
The trims are now in the wrong place, left stick being the right trim & vice-versa. If the wires are long enough and the connections are not commoned with the other axis of each stick then the relevant connections can be de-pinned & swapped left / right (connectors are hidden under the main processor board). Worst case them have to remain as they are & I just have to remember they are "on the other stick".

I haven't tested this yet, it is as you see it above, awaiting reassembly currently.

My favorite transmitter is Futaba Attack R 27mHz.

Wonder if that is possible to convert to 2.4 without too much mods??



My current 2.4 radios are Spektrum SLT TTX300, old LRP A2-STX and newest Radiolink RC6GS which I love. Good range, 6 channels and more adjustments that I ever need..

caprinut wrote:

My favorite transmitter is Futaba Attack R 27mHz.

Wonder if that is possible to convert to 2.4 without too much mods??



My current 2.4 radios are Spektrum SLT TTX300, old LRP A2-STX and newest Radiolink RC6GS which I love. Good range, 6 channels and more adjustments that I ever need..

 

It depends how you define "too much mods".
If you are prepared to use Frsky, they made DIY modules to convert almost any regular TX to their 2.4 system, I have a Hitec Flash Pro-Car with such a module. With a bit more effort, you could probably hack something like an OrangeRX module into it and have Spektrum DMS2 / DSMX compatibility ? Pulling the 27MHz crystal is enough to disable the onboard RF, then it's just a matter of finding power, ground & PPM signal. If you have a spare case back it may even have enough room to bond a Futaba module bay in ?

Short answer, yes it can absolutely be done, it just depends how far you want to go to achieve it ?

If you can find or take a picture of the circuit board we can probably identify the points to tap in from a photo ?

Meanwhile, the gimbal swapping exercise above, while an interesting diversion, has ultimately proven unnecessary. While testing with a 6ch receiver to determine actual channel assignments, I had reverted the TX to mode 1 in programming (throttle right stick for non flyers), and noticed the channel assignment were not as I had intended. Swapping the module back to the better of the two TX's & resetting that to Mode1 showed that all the mechanical shenanigans inside were wasted because in Mode1, steering, from a 2ch car perspective, is on the right stick X axis, and throttle is left stick Y axis, just like a regular 2ch radio.......DOH!!!
  

So the only "mods I actually need to make for 2ch use are restrictor plates to lock out the unused axes, and even these won't be needed if I can find a non destructive way to lock the axes internally somehow, but I still think carbon effect ABS discs will look good on it & are completely reversible.