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Old Aug 24, 2012, 05:43 PM
Rabbit5487
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Houston
Joined Jul 2008
51 Posts
Question
Reincarnating an old Digi-Trio with new innards?

Hey guys,

My first radio back in 1969 was a 4-channel Digi-Trio built from RCM plans. It was cutting edge technology back then but probably not as much now as it once was. Anyway, I'd like to reincarnate it with modern innards but retain the original external appearance so it will fit right alongside my soon-to-be-built Proctor Antic kit. (It was a Christmas present from my folks back in 1970. I haven't built it yet because I don't like to rush into things. )

Before I go any farther, let me state right up front that I'm fully aware of the FCC's admonition against unauthorized persons diddling with transmitters. My intent is not to modify a transmitter but to simply repackage one from its modern plastic case into an older aluminum one. Also, as for my capabilities, I'm a retired USAF radar maintenance technician so I know my way around a soldering iron. However, my 1972 USAF electronics training is getting a bit rusty these days so I'm probably not even up to par with a modern 14 year old electronics hobbyist!

Anyway, my plan is to use the board from a modern (current production) Futaba 72MHz 4YF. I chose the 4YF because it's a very basic transmitter (I'd like to avoid the complication and clutter of a bunch of exotic features that I don't need), it appears to be an easy retrofit into the Digi-Trio case, and (most importantly) I already have one. Of course, someone is going to respond that if I'm going to go to all the trouble, I might as well go all the way to 2.4GHz. I thought of that but the little stubby antenna would really look out of place on my Digi-Trio box; it needs a long antenna to look right!

So, am I nuts or what? Your comments are solicited. (About the transmitter upgrade. My wife already tells me that I'm nuts!)

Harvey

PS
I intend to use a modern (unaltered) 72MHz flight pack in the Antic.
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Old Aug 24, 2012, 06:39 PM
Balsa addiction since age 3
ScottSails's Avatar
Upstate NY
Joined May 2005
1,241 Posts
I like what you are doing - but you would likely have less grief potentially by using a 2.4 GHZ modular RF system (modular in that RF is self contained - you could just provide power, ground and PPM signal - done) with the old radio - that is pretty simple these days...
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Old Aug 24, 2012, 08:00 PM
Rabbit5487
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Houston
Joined Jul 2008
51 Posts
Quote:
Originally Posted by ScottSails View Post
I like what you are doing - but you would likely have less grief potentially by using a 2.4 GHZ modular RF system (modular in that RF is self contained - you could just provide power, ground and PPM signal - done) with the old radio - that is pretty simple these days...
Scott,

Thanks for your response. However, is the "2.4GHz modular RF system" that you spoke of a SIMPLE system or is it loaded with a ton of features that I don't want (i.e. a readout screen, digital trims, mixing, swashplate, expo, epa, telementary, multiple model memory, USB output for a PC, a clock, automatic earwax remover, etc)?

I already had this conversation with someone else who refused to believe that I don't want any fancy features that I don't need, don't want to pay for, and don't want to get in the way. (I'm the guy whose VCR perpetually flashed 12:00!) All I want is a simple modern transmitter board that I can wire to my existing Digi-Trio joysticks and trim pots and the Futaba 4YF seems to meet those requirements.

If your modular 2.4 RF system is, indeed, a simple system, I'm all ears. (But I'm still not sure about the little 2.4 antenna.)

Harvey
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Old Aug 24, 2012, 09:52 PM
59 years of RC flying
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Canada, ON, Ottawa
Joined Feb 2006
16,265 Posts
If you want a practical transmitter for real flying, give up the nostalgia for a long antenna and go with an FrSky V8HT for under $40 including receiver. For source, go to Aloft Hobbies.

Once you've gone 2.4, you will not want to go back. Getting rid of long antennas on the transmitter and receiver is one benefit. But the biggest ones are freedom from the risk of frequency conflicts and resistance to electrical noise and any type of interference. And of course no crystals.

A 2.4 RF module is as simple as it gets. It has nothing to do with the features of the encoder section of the radio. It should be easy to connect to the encoder.
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Old Aug 25, 2012, 07:34 AM
Balsa addiction since age 3
ScottSails's Avatar
Upstate NY
Joined May 2005
1,241 Posts
Quote:
Originally Posted by Rabbit5487 View Post
Scott,

Thanks for your response. However, is the "2.4GHz modular RF system" that you spoke of a SIMPLE system or is it loaded with a ton of features that I don't want (i.e. a readout screen, digital trims, mixing, swashplate, expo, epa, telementary, multiple model memory, USB output for a PC, a clock, automatic earwax remover, etc)?

I already had this conversation with someone else who refused to believe that I don't want any fancy features that I don't need, don't want to pay for, and don't want to get in the way. (I'm the guy whose VCR perpetually flashed 12:00!) All I want is a simple modern transmitter board that I can wire to my existing Digi-Trio joysticks and trim pots and the Futaba 4YF seems to meet those requirements.

If your modular 2.4 RF system is, indeed, a simple system, I'm all ears. (But I'm still not sure about the little 2.4 antenna.)

Harvey
I am making a distinction between the processor/memory/LCD based solution of a computer radio that provides the programming functions of the current type radios and the RF section - for some radios they are quite separate and distinct (old ones were tightly coupled but still required a PPM stream - that is how buddy box cables worked for the most part)...

Here is the 2.4 GHZ RF section that I am referring to:
(It requires, power, ground, and the PPM output from your Pulse Position module encoder of your choice).

http://www.alofthobbies.com/diy-telemetry-module.html

Make more sense now?

You will still need some module, the 4YF for example, that reads the stick inputs and converts to PPM stream. You would just disable the RF portion of the 4YF (remove crystal possibly and antenna) and tap into the PPM stream that is on the trainer output connector and feed that to the PPM input of your selected RF module.

Earwax remover still optional
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Old Aug 25, 2012, 09:02 AM
Rabbit5487
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Houston
Joined Jul 2008
51 Posts
Thanks Daedalus & Scott, your explanations are making things clearer for me.

If I go with the FRSky DIY RF module (without telemetry), will I need to retain the complete Futaba 4YF board (with the RF output disabled, of course) for the joystick encoding functions or is a simple encoder-only module available somewhere?

I'm still not sure of the little weenie 2.4 antenna on the transmitter though. However, I'm not interested in keeping a dummy 72MHz antenna "just for looks" either. Do I have any options other than the standard "hinged" 2.4 antenna?

Harvey
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Old Aug 25, 2012, 09:18 AM
Balsa addiction since age 3
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Upstate NY
Joined May 2005
1,241 Posts
Quote:
Originally Posted by Rabbit5487 View Post
Thanks Daedalus & Scott, your explanations are making things clearer for me.

If I go with the FRSky DIY RF module (without telemetry), will I need to retain the complete Futaba 4YF board (with the RF output disabled, of course) for the joystick encoding functions or is a simple encoder-only module available somewhere?

I'm still not sure of the little weenie 2.4 antenna on the transmitter though. However, I'm not interested in keeping a dummy 72MHz antenna "just for looks" either. Do I have any options other than the standard "hinged" 2.4 antenna?

Harvey
Sorry, antenna is a change and I will warn you it does effect the balance of the radio (the 72Mhz antenna moved the CG higher). Yes, the 2.4 antenna looks wimpy and not authentic... If the case wasn't metal, you could consider mounting the 2.4 antenna inside and then have the 72 for looks (or keeping it as a pointer to your aircraft).

I would still recommend the telemetry RF module - gives you option of telemetry or no telemetry - compatible with both with a switch setting.
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Old Aug 25, 2012, 09:23 AM
Rabbit5487
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Houston
Joined Jul 2008
51 Posts
What encoder options do I have?

Harvey
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Old Aug 25, 2012, 12:50 PM
Balsa addiction since age 3
ScottSails's Avatar
Upstate NY
Joined May 2005
1,241 Posts
Quote:
Originally Posted by Rabbit5487 View Post
What encoder options do I have?

Harvey
Why not use what is there now?
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Old Aug 25, 2012, 09:05 PM
Registered User
Quincy IL
Joined Jul 2006
504 Posts
I used a FrSky DTH-U module to update this Royal Omega 7 channel. This transmitter was a pre sales kit I built to check the instructions. Many hours on this unit on 72 MHz.

All I did was remove the old RF deck which plugged in, added a 3 pin header to the circuit board, Plugged the three wires from the DTH-U and powered up.

A very advanced high end TX designed and produced by Royal Electronics, Denver, CO. circa 1982, servo reversing, two mixes,
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Old Aug 25, 2012, 10:58 PM
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USA, TX, Grapevine
Joined Dec 2008
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Replacing the RF deck or module is usually fairly straightforward. It does appear on the surface that replacing the electronics shouldn't be a big deal. But I haven't come up with a good solution for replacing the trim pots with the push button digital trims on the TX's yet. I think once that is solved the rest of the conversion is straightforward.
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Old Aug 26, 2012, 05:14 AM
Oxford Panic
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United Kingdom, Oxford
Joined Feb 2003
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Quote:
Originally Posted by earlwb View Post
... But I haven't come up with a good solution for replacing the trim pots with the push button digital trims on the TX's yet. I think once that is solved the rest of the conversion is straightforward.
Earl,

If the original trims are on pots rather than mechanical offset in the gimbal, it may be feasible to replace them digital potentiometers, the type with non-volatile memory then all you need is find some way of indexing them up and down. This will probably require a microcontroller as most of them have a serial interface.

A.
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Old Aug 26, 2012, 11:12 PM
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USA, MA, Weymouth
Joined Mar 2004
1,095 Posts
You COULD brew up an all-NEW Tx with a MicroStar 2000...

Dear Rabbit5487:

The PIPE Here...a VERY proud owner of a computer-chipped knobby (single-stick) radio I built in 2003...



...using the earlier Mk.III version of GORDON ANDERSON's fantastic MicroStar 2000 computer encoder unit as its main "innards"...



...and here ARE its "innards" in the above photo for your viewing pleasure.

I'm currently using it from time to time to keep my "stick'n'knob" skills well enough tuned with my Aerofly Pro Deluxe RC flightsim on my PC, until I can GET BACK TO WORK (unemployed since September 2008). I've also got more than enough "Tx innards" to implant into a second Ace MicroPro 8000 knobby radio's case, complete with a matching MicroStar 2000 Mk.III encoder to use in a twin to the one in the above photos, with both intended to be on the 50 MHz Ham band - I've been a General class Ham, callsign KA1ABG, and with my Ham license since 1978, and thanks to a renewal back in June of this year, it's good until 2022 !

The latest Mk.V version of the "MS2K" encoder has much MORE capability than the older Mk.III version (hint here, it CAN take DIGITAL trims!!!), and is a SMALLER sized board than the Mk.III. Also, the Hammond Manufacturing firm in Canada puts out a very rugged, ALL METAL style of case to use for any imaginable radio control transmitter case as their p/n 1455T1601 case, available at Digi-Key and Mouser for just a bit under $30 apiece. I've also attached a copy of the Adobe PDF file from Hammond for that case, with the drawing of the case to clue you in on its physical size.

And even better, there's an entire online COMMUNITY at Yahoo's MicroPro/MICROSTAR User Group, there to help you with bringing one together...their original purpose was to support the vintage Ace RC MicroPro 8000 computer Tx, which they ARE still doing, and they've also been supporting the MicroStar as well for quite a while...sometimes, even yours truly has something to post up on their forum at Yahoo about the MicroStar.

The "MS2K" (users' abbreviation for the MicroStar encoder) has been used with a range of 2.4 GHz Tx modules already - my pick, when I can build another pair of knobby MS2Ks that way after a return to work, would be Futaba's FASST TM-8 module - and Gordon's even brewed up a 50 MHz SYNTHESIZED RF deck to fly the MS2K on the Ham bands with (I've got a pair of those myself for my first pair) if you think a Technician class Ham ticket just might be in your future.

DEFINITELY check out Gordon's site, and our gang at Yahoo...I'm already there, along with Gordon himself, if you're at all interested in a MicroStar 2000-encodered RC radio that you can whip up with your own two hands, plus a goodly amount of help for whatever you need help with in crafting one for yourself...hint-hint, even TONY STILLMAN, who's built custom RC Tx-es for a number of flyers for a good while now, visits there from time to time as well !!!

Give it a checkout...you MIGHT like what you see there!

Yours Sincerely,

The PIPE....!!
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Last edited by The PIPE; Aug 26, 2012 at 11:24 PM.
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Old Aug 27, 2012, 06:10 AM
Rabbit5487
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Houston
Joined Jul 2008
51 Posts
Thanks Pipe but the MicroStar is much more complicated than I want. At my age, I prefer "garage door opener" simplicity.

Harvey
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