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Sep 27, 2019, 12:26 AM
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Mini-HowTo

BUDGET 2.4GHz transmitter for plane/glider/heli...


Paid all of $23 TOTAL for an old Futaba Skysport 6A on that popular online auction site that is headquartered in San Jose, California USA. But WHY would I buy such a basic “plain-Jane” old school 72MHz FM radio? To convert it into an ultra-simple, beginner-friendly, inexpensive FrSky 2.4GHz NON-TELEMETRY transmitter for basic airplanes, utilizing the 2.4GHz FrSky DIY module kit sold at various hobby dealers. I bought several of them from Aloft Hobbies at just $24 each, which I believe to be the best price on the web.

At the time of writing this modification tutorial, the FrSky DIY module kit was only $24 at ALOFT HOBBIES, however it was grossly overpriced on that ever so popular online auction site…what else is new? That very same online auction site DOES SELL some TINY generic 4 channel NON-TELEMETRY micro receivers which utilize FrSky D8 protocol for just $10.99 each. Just do a search for “receiver FrSky D8”. I bought my 20 micro receivers on Banggood for $7.99 each (actually even less, because I bought them in two different quantity lots). HOWEVER, the 2 orders of micro receivers I bought on Banggood included header pins which must be soldered into the tiny receiver board by the buyer. While that is fine for me, it might not be fine for everyone. If you have no way of soldering them, I would advise you to just buy the ones on that popular online auction site. Actually I just checked again on Bangood. The price has been increased to $9.99 each and they now come with all the header pins factory soldered into the micro receiver board. So the latest version receivers are ready to plug your servos and flight battery into. Just watch your polarity markings and match them up with the color coded wires on your servo plugs.

The plain truth is, most basic airplane setups utilizing 2 to 6 control channels don’t USUALLY need a fancy schmantzy whiz-bang do-it-all newfangled computer transmitter…OR any telemetry functions. Neither do most 4 channel fixed-pitch helicopters for that matter. So if you wish to convert a simple old radio for 2.4GHz FrSky with NO TELEMETRY…..this is 2.4GHz NON-TELEMETRY FrSky on a tight budget 101!

I wrote this assuming you have little or no soldering experience or electronics knowledge. You may learn to solder by watching some online videos and taking my advice in this tutorial. Then just practice on old junk /salvage circuit boards.

Find some soft foam or towel(s) to set the transmitter upon, FACE DOWN. Remove the Skysport 6A battery, but make sure you have at least one Tx battery and one Rx battery fully charged. You will need them sooner than later for testing and binding. I am assuming you have at least ONE FrSky receiver? I certainly hope so. I have about 30 of them. Exactly 20 of them are simple, generic 4 channel non-telemetry TINY micro receivers (D8 version FrSky prototcol) that were about $8 each on Banggood and they work just fine with very good range. In fact, their usable FLIGHT range is much farther than I can effectively see!

LOOK at the 2 upper switch panels on the FRONT (not top) of the Futaba Skysport 6A transmitter. There are just 2 dual rate switches; one for Aileron and one for elevator…right? But wait a minute now…BEHIND the two thin aluminum DUAL RATE switch panels, the inner plastic chassis has factory molded cutouts for TWO MORE inboard switches. How convenient indeed. That means less holes you will need to drill to install the 2.4GHz DIY module mode switch, binding button and LED.

Before going on, I want to define 2 different sets of parts containers right here and now. When I say “PARTS JAR”…that means you WILL NEED THESE PARTS AGAIN for reassembly of the Skysport 6A transmitter! When I say “SPARE PARTS BIN”….that means you may use them in a future project, fabrication, retrofit or repair… but they will no longer be a part for this transmitter….Capisce? NEXT!!

Unscrew the telescoping 72MHz antenna and throw it in a spare parts bin. Remove the 4 rear plastic case screws (PARTS JAR) and pull off the rear plastic cover (too BIG for the parts jar, but SAVE it). Remove the 72MHz Tx crystal (spare parts bin). Remove the 2 Phillips screws that anchor the motherboard in place (PARTS JAR). One is next to J1 and J2. The other is almost at top center, next to the 2 adjustable trim pots (trimmer potentiometers)….which are nothing more than miniature variable resistors…just like the volume, bass, treble or balance controls on a vintage analog stereo receiver/amplifier. Newfangled digital stereo gear often uses digital encoders instead. IF the knob keeps turning without ever reaching a STOP point, it is a digital encoder…NOT a variable resistor. If it is spring-loaded in either direction with a very short stop, it is a digital encoder OR spring loaded digital toggle switch....but NOT a variable resistor....totally different animals.

Remove the slotted nuts on the dual rate toggle switches (PARTS JAR). I highly recommend you use a switch nut spanner or socket for removing the slotted toggle switch nuts. Otherwise you run the risk of scratching your transmitter case pretty badly. As an alternative tool, you may be able to use snap ring pliers with very small angled tips...OR very tiny precision needle nosed pliers...but BE CAREFUL! NO NEED to disconnect the switches or pull any wires. Just pull the switches out of their holes and leave them in the vicinity. Pull the antenna plug out of the Z5 jack at lower left of the motherboard (just below IC3). Grab a Phillips screwdriver and remove the other end of the antenna cable from the plastic molded body, under the motherboard. Antenna cable and associated hardware goes in the spare parts bin…bye-bye 72MHz!

The next step depends upon YOUR PREFERENCE and your degree of PATIENCE. Patience is definitely NOT one of my strong points. You can try to pilot and then drill centered holes THROUGH the 2 thin aluminum switch panels and preserve them as they are (if you are VERY careful)…OR you can try heating them with a heat gun and attempt to SLOWLY remove them without actually bending or creasing them (very tedious and time consuming)….OR you can be like me and simply realize that the switch positions will be pretty darned obvious, even without preserving the thin aluminum switch panels with printed dual rate labels. After all, isn’t it pretty much standard to have all toggle switches in the NORMAL or START position when they are in the UP position? That is exactly how both dual rate switches work on the Skysport 6A, so any switches we install should preferably be in the NORMAL mode when in the UP position.

Personally, I just heated the thin aluminum dual rate switch panels with the mighty heat blower on my SMD/SMT solder rework station, peeled them off rather harshly and just tossed them right into the trash can in a highly deformed and bent-up state. Then I cleaned off the residual adhesive left behind from the thin aluminum switch panels. You may need to wet a Q-tip with some GOO-GONE or GOOF-OFF to get the plastic switch panel areas really clean (that is what I did). If so, you should then clean the plastic again, with alcohol after all adhesive residue has been removed. If you hate the idea of having plain black plastic switch panels, you can just use acrylic paint markers to paint the black plastic switch panels or even cover them with adhesive bare metal foil if desired. I couldn’t possibly care any less about dressing up the switch panels…this ain’t no fancy-schmantzy highly expensive whiz-bang radio…so…NEXT!

Let’s talk about good soldering/desoldering habits for a moment. I was MIL-SPEC certified in both through-hole and SMD/SMT soldering for a very long time, but started basic through-hole and point-to-point soldering around age 11 or 12. I am now 50 years old. Rest assured, I know how to solder very well. The very first word to be said about ANY type of working with solder is….CLEAN. You should be working with a clean solder tip, clean ROSIN CORE 60/40 SOLDER and a clean substrate, surface, connector or terminal. Clean terminals with a small wire brush. Clean your soldering iron tip after EVERY TIME your tip touches a solder joint. Use a water DAMPENED (not sopped) sponge….or even better yet, a small canister of rosin type “tip tinner/cleaner”. LEAD FREE solder SUCKS and I NEVER BUY IT. Takes more heat/time to flow and can be a real pain to remove from small component leads, pads and tiny through-holes. Use a toothbrush and 90% alcohol to clean EVERY area where you will be soldering or desoldering….then let it dry completely. Old flux, oils, dirt, dust, solvent residue, oxides and contaminants will erode and RUIN the coating/finish on your solder tip pretty fast. A good quality solder tip should survive a LOT of soldering. If not, you’re doing something very wrong. Solder flows much better when all is clean. BEST WAY TO DESOLDER stubborn old crickory solder joints is to actually ADD plenty of fresh new rosin core solder to the old solder joint first. So essentially, you will first be soldering any joint that you plan to desolder. May seem silly, but the joints will heat and flow MUCH faster. Also makes it MUCH EASIER to suck up all the old solder with a solder bulb/sucker, so you won’t need to use up expensive desoldering wick. I always keep desoldering wick on hand…but I only use it as a desperate last resort. If you actually LIKE using lead-free type solder, then I am very happy for you, because you obviously have a lot more patience than I do!!

We don’t want the old 72MHz transmit section to be draining any battery current. Also happens to be in this particular case, that removing all the major 72MHz transmit components will provide a great place to mount the new 2.4GHz FrSky DIY module. The tiny piezo alarm buzzer on the 2.4GHz FrSky DIY module will also end up being very close to the rear transmit crystal window, where it is even more audible. How convenient indeed. So we are going to REMOVE ALL TEN of the major 72MHz transmit components from the motherboard (actually main chassis board is the old school term, but the newfangled term is probably motherboard). Get your solder iron and soldering tools/supplies ready for some action. Finding a helper would be best if you have little or no experience with desoldering and removing electronic parts and components.

First components to remove are Z5, J41, Q3, XTAL. Start with the crystal socket marked XTAL. Try to salvage this part if you plan to tinker with other old radios in the future (SPARE PARTS BIN). ADD fresh rosin core 60/40 solder to the 2 solder joints on the solder side of the motherboard by simply heating the joints and flowing in more NEW solder. Then try to heat both solder joints simultaneously and pull out the crystal socket with small pliers. Do all 3 things simultaneously OR you will need to completely desolder the 2 joints with a desoldering bulb or spring loaded solder sucker….or solder wick as a last resort. It is actually MUCH FASTER to just heat both joints simultaneously and PULL the part out with pliers. Get a helper to hold the motherboard steady for you…OR have your helper use the pliers to pull the part while you steady the motherboard with one hand and use the solder iron in your other hand, to heat the 2 solder joints simultaneously. After the crystal socket has been removed, be sure to reheat the solder joints and use a desoldering bulb to suck up all the residual solder you possibly can.

*** Always best to clean off excess solder after removing a part***

Now remove, but try to salvage the RF OUTPUT TRANSISTOR Q3 if you plan to tinker with radios in the future. RF output transistors always have at least 3 leads/legs and are HANDY to have around. Major radio heads and ham radio operators just LOVE having them on hand in a parts bin drawer, both new and used. A used RF output transistor is just as good as a new one…as long as it ain’t fried! Ham operators who like to scratch build QRP transceivers will find parts like this especially useful.

Now desolder and remove X5 and J41. No need to be careful with them. Just heat the solder joints and pull them out with needle nose pliers. I threw these 2 parts in the trash can in a very bent-up and abused condition, because I got very rough with them and I enjoyed it.

Next we need to remove ALL SIX tuning coils (variable inductors) L1, L2, L3, L4, L5, L7….otherwise known as “tin cans”. In RF circuits, these do the jobs of fine tuning things like current flow (inductance), frequency alignment, receiver sensitivity, transmit RF power output…and they can even affect bandwidth. They often work in conjunction with various capacitors (fixed and variable types) to form inductive-capacitive tuning, filtering and even impedance matching circuits, known as LC networks. *NEVER USE a metal tool for tuning/tweaking these tuning coils! You will permanently alter and thus damage the magnetic properties of the coil. You also might BREAK the fragile powdered iron slug core. These are tuned with PLASTIC FINE TUNING TOOLS ONLY! Powdered iron slugs can be broken even with a plastic tuning tool..IF the slug is turned too far. Variable resistors or “TRIM POTS” may be tuned carefully with a small metal screwdriver, but NOT TUNING COILS! Some radio techs just stick with static-free PLASTIC fine tuning tools as much as possible for ALL tunable trimmer coils, trimmer capacitors and trimmer potentiomers….because you can never really go wrong in doing so.

Look at the photos and you will see that there are 7 holes through the motherboard for each tunable coil (L1, L2, L3, L4, L5, L7). The 5 ROUND holes are for primary and secondary leads or windings (yup, just like a power or audio transformer). The 2 opposing SLOTTED holes are just for the mounting tabs on the thin rectangular metal shielding cans. These shielding cans are usually soldered to the main ground buss to help protect the magnetic field and to prevent stray harmonic signals. Trying to desolder and remove these coils intact is a tedious waste of time and a very moot point in this case. But go ahead and do it IF you have lots of time to kill. What did I do? Just grabbed each coil with a small pair of pliers and rocked them back and forth until they broke off the motherboard. IF they are stubborn, just remove the pliers and grab them again at the other axis, 90 degrees from your first grab. They will break off. Use a small slotted screwdriver and/or needle nosed pliers to get all the little pieces off the motherboard.

Now call your helper to come aid you for a few minutes. The area of removed coils needs to be clean and smooth. So you need to desolder each remaining coil lead and pull them all out of the motherboard with small precision pliers or needle nose pliers. Heat the solder joints on the bottom “solder side” of the board and pull the leads out of the top or “component side” of the board. You are now done removing parts from the radio. It’s all about ADDING parts now and that is the fun part which creates great newfangled capabilities within your old transmitter. Also a good idea to hold the radio over your workbench and shake out any broken little pieces that may have fallen inside the plastic transmitter case.

Physical layout and mounting of parts: Just look at my crappy photos and I think they will actually suffice in showing where I mounted everything. If I recall correctly, I had to trim the tiny circuit boards on the back of the dual rate switches with a Dremel cutoff wheel. Just be sure to LOOK at the circuit traces and don’t cut any that you NEED. If you do, then you will need to solder in some jumper wires, which is just extra work. Then I had to relocate and solder the 3 conductor connector pins DIRECTLY to the rear contacts on the toggle switch assemblies going STRAIGHT BACK into the transmitter. This afforded me ample room to mount my FrSKy controls just inboard from the dual rate switches on both sides.

Looking at the FRONT control panel of the transmitter, you can see how I mounted the binding button and status LED board just inboard from the elevator dual rate switch at top left. If you look at the inboard switch/pot cutout from INSIDE the plastic transmitter case, you will see a smaller hole at 12:00 for a toggle switch or control pot ALIGNMENT TAB. You will need to drill this smaller alignment tab hole all the way through FROM THE BACK (inside the transmitter case) for the binding/status LED. Best bet is to use digital calipers to identify the best drill size…but do as you will.

AFTER getting the status LED to fit in that smaller upper hole, you may need to use a larger drill bit or tapered Dremel grinding stone to remove enough black plastic so that the binding button body (tact switch) rests well down within the larger switch cutout hole. TAKE YOUR TIME and don’t drill or grind too far! AFTER ALL DRILLING & TEST FITTING, I mixed up some 5 minute epoxy and DABBED it on the inside ridge of the larger switch hole. Then after installing the tiny binding button/LED board, I also DABBED some more epoxy at the top and corner of the tiny circuit board, near the top of the transmitter case. PLEASE NOTE that I did test fit everything BEFORE mixing any epoxy…just to make sure the rear internal RIDGE of the larger round switch cutout would be touching the tiny circuit board AROUND the body of the binding button (tact switch), but NOT TOUCHING the body of the binding button (tact switch). Make sure the epoxy is anchoring the tiny circuit board in 2 places….all along the TOP of the tiny circuit board…AND all around the binding button, from plastic cutout ridge to the tiny circuit board. Make sure you PUSH DOWN moderately on that tiny circuit board and HOLD it there with a popsicle stick until the epoxy hardens. This will ensure that your epoxy is holding/anchoring that tiny circuit board in TWO places.

As far as the 3 position FrSky toggle switch (1-way/2-way/FW mode switch), I simply mounted it inboard from the aileron dual rate switch at top right. I like ALL my toggle switches to be in starting default normal position when in the UP position….just like the dual rate switches. So I mounted my 3 position toggle switch so that the UP position is the FrSky NON-TELEMETRY (1-way) position. Middle position is the FrSky Telemetry enabled 2-way position. When the switch is all the way DOWN (or rocked all the way toward myself when holding the transmitter), it is in the Firmware Update position, marked “FW” on the 3 position toggle switch. I very seriously doubt I will ever need to move this switch from the UP (non telemetry 1-way) position at all, but I felt it best to just install it anyway.

As an alternate plan, IF YOU ALREADY KNOW you will never need to use the telemetry enabled (2-way) or firmware update (FW) positions, you really don’t even need to mount or even use the 3 position toggle switch at all. Just solder the correct 2 wires together, cover them with heat shrink tubing, and tuck them away somewhere out of the way. I just now checked the remaining 3 of my 4 bagged FrSky DIY module kits, and in every case, it would be the green and black wires that you want to solder together. You don’t need the yellow wire at all.

Always remember when looking at any TOGGLE switch, the circuit contacts are closing at the OPPOSITE END from the direction you are throwing the rocker. Slide switches are just the opposite. The direction you throw the switch is also the side where the contacts get closed to complete a circuit.

ALTERNATE PLAN B: For non-telemetry usage, you really don’t need the 3 position toggle switch OR THE SWITCH HARNESS AT ALL. Just follow the black and green wires back to the small LED circuit board. Find the 2 solder joints that the black and green wires connect to and solder them together on the LED side of the tiny circuit board with LED and binding button. Now you may simply unplug the switch harness and toss the 3-way toggle switch with harness into your spare parts bin for another project or repair. Please be sure to complete that solder joint as quickly as possible and keep your tip away from the LED. Let the solder joint cool, then scrub the tiny LED board with a toothbrush and 90% alcohol.

Module mounting: If you think you might need to update firmware in the future, then I would seriously recommend that you mount your RF module just slightly higher than I did mine. Notice how the lowest header pin on the lower right of my module is almost touching the insulated and isolated cylindrical outer case of electrolytic capacitor C31? Really, I just wanted to get this done and I did not care about firmware updates. I had already tested and confirmed that my modified transmitter worked fine with my tiny $8 to $11 NON-TELEMETRY generic 4ch FrSky micro receivers (see last 2 photos). GOOD ENOUGH for my basic/inexpensive planes of all sizes, both glow and electric. I just mounted my module with a couple square pieces of double sided squishy foam tape. I think they were the 3M brand with the green and white peels on them. Regular double sided servo tape should do just as well. BE SURE to leave that screw hole to the left of the new 2.4GHz FrSky module very accessible! That is one of the 2 screws which mount the motherboard to the rear transmitter case half!

Antenna mounting: in order to mount your gold 2.4GHz SMA female antenna jack inside the original plastic antenna housing/hole, you WILL NEED to hog out some of the material BELOW the tip of the plastic molding and ONLY on the INSIDE. You will need to do that with BOTH PLASTIC SHELL HALVES. Obviously, the front half is even more important, because that is the half where your golden SMA antenna jack will be epoxied. I used a tapered stone grinding bit in my variable speed cordless Dremel, but I left the tapered grinding stone bit sticking waaay out at the end of my Dremel 3-jaw chuck, so I would not mess up the outer or upper portions of the plastic antenna housing. I used my variable cordless Dremel at LOW RPM and took it slowly. Just hog out a little bit of material, then test fit it. It may take 3 or 4 short bursts of hogging out the plastic, but very easy to do. IF you use too much RPM or keep grinding for too long, you will heat the plastic too much and MELT it...and you don’t want that! Short bursts of grinding at low to medium RPM will get the job done.

Once you have the gold SMA antenna jack positioned correctly, MAKE SURE your antenna can screw ALL THE WAY INTO THE CONNECTOR WITHOUT quite HITTING THE PLASTIC TRANSMITTER CASE HOUSING. Do this BEFORE before mixing your 5 minute epoxy. Once I CONFIRMED the correct clearance and positioning was achieved, I clamped my gold 2.4GHz SMA female antenna jack into position with the included gold nut, then DOUBLE CHECKED for a good square positioning....and that the antenna would screw ALL THE WAY into the golden SMA female jack. My first epoxy mix was just enough to tack it in place, while filling all the tiny little gaps near the very top of the gold SMA antenna jack. I then quickly dipped Q-tips in 90% alcohol, squeezed off the excess alcohol, then wiped off any excess epoxy that would hinder proper assembly fit of the plastic case halves. I did this THREE TIMES just to make darn sure I got it all perfectly cleaned off. Once hardened, I did a couple more sequential 5 minute mixes and filled in a lot more area below the golden SMA female antenna jack. Some of my epoxy ran down onto the inside of my analog battery meter, but I knew it was not visible on the outside of the transmitter, so who cares? Less likely my battery meter will ever break loose, right?

SIMPLE final wiring:
Take a good look at my crappy photos of the bare naked motherboard. Try not to get too excited when you see all the naked parts that are showing (like C3PO once said to R2D2). Refer to my photos and look down in the lower right corner, at the 6 pin DIN style TRAINER JACK on the back of the motherboard. You will see a red mark I made with my red sharpie marker. That is the PPM SIGNAL OUT. It is always actively supplying that PPM encoder signal. I know this because I checked it with my handy dandy little pocket digital oscilloscope. It revealed some nice cute little waveforms that differed from any other signals in this radio. BAM! I knew right away, this was the signal I needed for driving my DIY module.

Route your module’s yellow PPM wire around C31, then around IC4, then down to the corner, right next to fixed inductor L14. Run it around to the solder side of the board and solder it to the solder pad that is marked OUT. If by chance your solder pads are NOT MARKED as IN and OUT, just find the solder pad that has DIRECT continuity with the trainer pin that I have marked with my RED Sharpie marker. Your PPM signal path is now completed. Now we just need to connect positive power and ground.

Look below C31, next to the mounted FrSky module. You will see 2 bare wire jumpers. The upper one is a regulated +5VDC supply for the Integrated circuit chips, which is produced by a very small, LOW current rated +5VDC voltage regulator that looks like a tiny half-moon transistor. However, it is NOT enough voltage to activate the FrSky module. But the jumper below it is marked VCC and that is where to connect the RED wire from your Frsky module. It supplies a tad bit less than full battery voltage, which is just fine. I LIFTED my bare VCC jumper lead just a bit in the middle, with my xacto knife. Then I stripped about 6 to 8mm of RED insulation from the RED wire end. Then I TINNED the stripped wire end with clean rosin core solder to make it more SOLID. Then I used flat precision pliers (lead bending pliers) to fold the stripped wire end into a tight (almost closed) “V” shaped bend. Then I crimped that “V” onto the LIFTED jumper and then I soldered it. There are other more basic ways to just solder it directly onto the bare VCC jumper, just MAKE SURE there is a solid connection when you are done.

Look down in the lower left corner, near the 4 trimmer pots marked P7, P8, P9, P6 and you will see some more solid bare wire jumpers. Jumper J6 is the ground, coming directly off the battery pack. Route the BLACK wire from the FrSky module down to jumper J6 and solder it on just like you did the last one. Wiring is DONE.

Reassemble the transmitter slowly and carefully. Tuck all excess wires away, while making sure they will not interfere with mechanical movement of the control gimbals. Be sure not to pinch any wires when reassembling the plastic transmitter case halves.

Testing and binding: IF you even opted to use and mount the 3 position toggle switch that came with your FrSKy DIY module, you need to make sure your 3-way toggle switch is in the 1-way position for non-telemetry receivers (hopefully in the UP position, just like the default position of all other toggle switches). Just follow the binding instructions included with your FrSky DIY module and smile all the way to the bank. You now have a good working radio for flying your basic planes, sailplanes and fixed pitch helicopters using inexpensive yet reliable 4/6/8 channel FrSky 2.4GHz receivers AND 4 channel generic receivers that are FULLY COMPATIBLE with FrSky D8 protocol. It’s a wonderful thing, so have fun with it! KB1BBY/Scott.
Last edited by KB1BBY; Oct 06, 2019 at 06:19 PM.
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Oct 04, 2019, 10:24 AM
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Very retro
Oct 04, 2019, 11:19 AM
Marion
Excellent !!! I love this sort of "tinkering" that produces a very usable result :-)

Marion
Oct 06, 2019, 01:00 PM
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KB1BBY's Avatar
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Very basic functions...


Yes they are very cool. You just need to keep in mind, that you are NOT going to have all the advanced features of the late model whiz-bang 2.4GHz computer radios with MANY control channels. But many beginners and old timers WANT it that way and PREFER to just KEEP IT SIMPLE!

That being said, WE ALL KNOW there are MANY fliers who just want to fly very basic 2, 3 or even 4 channel planes/gliders/sailplanes....or even basic 4 channel FIXED PITCH helicopters.

For those fliers, this is an inexpensive solution that keeps things very simple, with little or no real "programming" to be done....just set a few switches and trim pots for servo direction, dual rates, ATV and basic mixing functions....DONE DEAL!

FYI, I will soon be selling various older transmitters converted to 2.4GHz FrSky and ready to use. Some will be available with matching 4 channel MICRO receivers, which run on the older FrSky D8 protocol. These work VERY WELL for micro planes and park fliers...as well as all basic 2 to 4 channel aircraft of any size, glow or electric. ALTERNATELY, you may want more channels and you may wish to look into some of the very reliable 6 or 8 channel FrSky receivers that sell for about $15 to $30 on the new and used markets.

Some of the CONVERTED OLDER TRANSMITTERS I will soon have available for $40 to $100 each are: Futaba and Hitec single stick 3 channel radios (Hitec NEON SS is capable of adding ATV trim pots and 4th channel switch, slider or knob), Hitec Flash 5, JR/CIRCUS 6 channel with front panel slider control, Futaba Skysport 6A, Futaba 7U series (including Super 7), Aristo Craft Challenger 720, World Engines EXPERT 7, Futaba 8U series....and possibly others from Airtronics, Futaba, Hitec, JR, Kraft or even Tower Hobbies. The Futaba Skysport 6A is one of the best "simple" radios to convert. It is inexpensive to obtain, yet it has a great deal of functionality for such a simple radio. The list of radios I can easily convert goes on and on. I REMOVE all the major 72MHz transmit components to minimize current draw and create a little more space inside the transmitter. Then I just trace down the control encoder "PPM" signal with my digital oscilloscope. PPM encoder signal output is always produced by an Integrated Circuit chip...OR a transistor circuit in the very old radios. Even the older AM radios have an encoder output signal to drive the RF section with. Then I tap into that signal to drive the new 2.4GHz module. If you have an older radio you would like to convert, but you are not into soldering or tinkering with electronics, just send me a PM and ask me about converting it for you.

Thanks for looking and happy landings....KB1BBY/Scott in Knoxville, TN USA
Last edited by KB1BBY; Oct 11, 2019 at 07:11 PM.
Oct 18, 2019, 05:50 AM
Who let the dogs out?
Phil_G's Avatar
Hi KB1BBY, thats an excellent, well presented post and its clear that a lot of effort has gone into producing it. You might be wondering why the lack of response, given the revelation of these conversions, and I can see how that would be disappointing. In the nicest possible way may I suggest you're preaching to the long, long converted - this was over 10 years ago. You say "I wrote this assuming you have little or no soldering experience or electronics knowledge" but this is the hobby electronics section, theres no-one here at that assumed level. Typical practises here include the actual own-design and build of RF modules, including multiple protocols, UHF and LORA, own-design Flight Controllers, variometers and telemetry projects, often way ahead of commercial development, with sophisticated test equipment and homebrew surface mount stations. I'd humbly suggest that you'd probably get more responses in the Radio section, where there may still be some who are new to conversions. Please dont take this as dismissive, its not intended that way - although its late in the day, yours is an excellent post which deserves a wider audience.
Cheers
Phil
Last edited by Phil_G; Oct 19, 2019 at 03:35 PM.
Oct 19, 2019, 01:32 PM
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Bruno van Hoek's Avatar
Hear, hear...
Oct 20, 2019, 05:09 PM
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KB1BBY's Avatar
Thread OP
Quote:
Originally Posted by Phil_G
Hi KB1BBY, thats an excellent, well presented post and its clear that a lot of effort has gone into producing it. You might be wondering why the lack of response, given the revelation of these conversions, and I can see how that would be disappointing. In the nicest possible way may I suggest you're preaching to the long, long converted - this was over 10 years ago. You say "I wrote this assuming you have little or no soldering experience or electronics knowledge" but this is the hobby electronics section, theres no-one here at that assumed level. Typical practises here include the actual own-design and build of RF modules, including multiple protocols, UHF and LORA, own-design Flight Controllers, variometers and telemetry projects, often way ahead of commercial development, with sophisticated test equipment and homebrew surface mount stations. I'd humbly suggest that you'd probably get more responses in the Radio section, where there may still be some who are new to conversions. Please dont take this as dismissive, its not intended that way - although its late in the day, yours is an excellent post which deserves a wider audience.
Cheers
Phil
Thanks for the kind words and useful info Phil. I'm just a busy old guy who is half a century old and it has been a very long time since I have worked in the engineering field or even delved very deeply into the applied sciences at all. So I am definitely NOT even remotely close to fluent with the latest cutting edge technology. Fabricating my own surface mount station would be darn near impossible, as well as comprehending current software and firmware programming languages. I was just trying to help those with minimal electronics experience who might be on a limited budget. After reading your message, I see very little point in reposting this, so I will just leave well enough alone. I am also far less than fluent with utilizing the MANY features of this forum!! If I had more free time to study it and actually utilize it more frequently, I might stand a chance of actually learning how to navigate it and use it 100% properly. At any rate, I certainly did not want to ignore your helpful and informative message. Have a great day and have fun with your high tech fabrications....KB1BBY/Scott


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Help! Budget Transmitter for APM 2.6 Ardupilot - also ESC question for newb build Lobojpm Mini Multirotor Drones 5 Feb 28, 2017 12:58 PM
FAQ The low budget FrSky Transmitter > Taranis Q X7 snappyhh Radios 14 Feb 23, 2017 01:29 AM
Question Best transmitter for newbie on a budget baker0408 Beginner Multirotor Drones 35 Aug 20, 2016 09:14 AM
Discussion No joy with 9x transmitter and SmartieParts SP Basic firmware programmer for Er9x MT3003 Radios 1 Jan 03, 2016 03:04 PM