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Posted - 05/29/2012 :  11:28:58 PM  Show Profile
LOW COST SAILPLANE RADIO Part 2 -- An Open Source Option
A Research Project
By Ed Anderson

Originally published in the Long Island Silent Flyers May Newsletter

Last month I did an article about upgrading 72 MHz sailplane radios to 2.4 GHz. This offers an option for people who are happy with their current sailplane radio to stay with it while moving to 2.4 GHz. It also offers a potentially lower cost entry point for new pilots buying their first sailplane radio. If you missed it, take a look at the April edition of the LISF Newsletter, the April ESL Newsletter or the Radios forum of the Eastern Soaring League Website.

ESL Newsletters

If you are still learning about sailplanes and sailplane radios, this article on the Eastern Soaring League web site might be of interest. It may help you understand what I consider the elements of a sailplane radio.

Selecting a sailplane Radio - What to consider

It has been common for our newer members to purchase an entry level radio, like a Spektrum DX6i for its lower cost only to spend again for a sailplane radio. Sailplane radios, like the JR9503, Hitec Aurora 9, Futaba 8FG Super or the Airtronics SD-10G cost between $400 and $600 and the receivers that go with these systems run $70 to $150 each. There is no question that these are excellent sailplane radios, each with its own strengths. However I wanted to see if there was a lower cost option.

If we can find a workable sailplane radio at entry level prices we could save people a lot of money and help them advance more rapidly into the fun of thermal soaring with more complex planes. I may have found a path to that objective based on a new approach to RC radio systems, open source.

Insert Image:

The FlySky TH9X radio came onto the market several years ago. You can find the same radio under the Turnigy, Eurgle and iMAX brands, but it is exactly the same hardware. The typical price runs from $60 to $100, depending on source and packaging. That usually includes an 8 channel receiver.

Initially it had a poor reputation for quality. The original 72 MHz version of this radio was OK but the early software was buggy. When they moved to 2.4 GHz the first RF system was not very robust. But things have evolved a lot since then. Today this radio is being used by giant scale pilots, glider pilots as well as parkflyer pilots, and the reports are good.

As discussed in the first article of the series, RC computer radios are made up of two components. The part that we think of as the radio is the box with the sticks and dials and the main circuit board which includes a processor that runs the program that displays the menus. Thus we call these computer radios. This same processor runs the software that translates stick and switch input into signals that are sent to the radio frequency section, RF, of the radio to be transmitted to the receiver in the plane. Some systems are one way and some systems are two way to enable telemetry back to the ground.
Since the practice of changing 72 MHz channel modules was eliminated with 2.4 GHz most new 2.4 GHz radios have the RF section built in so you cannot easily change it. Others, like the FlySky TH9X and the Hitec Aurora 9 have a modular RF system that can be easily removed and changed so you can use 72 MHz, 35 MHz, 50 MHz or a variety of 2.4 GHz systems. The photo shows the RF module in a Turnigy 9X which is HobbyKing version of the FlySky TH9X. The label is different but the RF system is the same as the FlySky TH9X.

From this point on I will refer to all the various branded version of this radio as the 9X. The 9X, typically comes with the FlySky RF module and an 8 channel FlySky receiver. Additional receivers are about $10. The radio has 3 dials, 6 switches and one 3 way switch. There are no side sliders and no controls on the rear of the radio. Battery and charger are not included. It comes with a battery holder for alkaline batteries.
The system provides 9 channels in FM PCM mode on 72 MHz or 8 channels in PPM mode which is what is used with the 2.4 GHz modules. This is exactly how my Futaba 9C works. So, this is an 8 channel radio on 2.4 GHz.
The standard set-up provides 8 model memories. The standard software is more than capable for airplanes, helis and basic glider functions. In fact the basic interface looks a lot like my Futaba 9C. You can see a video here that shows the user interface and some of the standard features.

Setting up the FlySky TH9X, Turnigy 9X, Imax9 or the Eurgle 9X

What really makes this radio system interesting, aside from the low price, is that the software is based on an open source model. That means that users can get into the code to add or enhance features and then give back their changes to the community in the spirit of openness and sharing.

Those of us from the computer industry are quite familiar with such things. Linux is one of the open source community's shining stars. It is a freely available operating system alternative to UNIX or Windows. For many companies it has replaced high priced UNIX systems as well as the Windows Server operating system. And major companies are moving their mission critical applications to Linux, a free operating system.

The FlySky TH9X is going through the same type of evolution. It offers the user a far less expensive radio system that is useable right out of the box. However it can be modified in hardware and software so you can load the available updates created by others. You can also change the RF system, as mentioned above.

Many users say they have no need to change the hardware or the software as the standard system suits them just fine. The 9X can certainly do more, with the standard software, than a Spektrum DX6i, and it costs $100 to $130 less than the DX6i.
If you want to rev-up the software, you can buy an add-in board, $45, which lets you load new, free software. There are several alternate software offerings, but ER9X software seems to be the most popular. http://code.google.com/p/er9x/ With ER9X software it becomes a mixing powerhouse and it can also store 12 to 16 models depending on the complexity of your set-up. You can download and upload models to your computer so you can have as many set-ups as you like. Just load the 12-16 you want to use today.

Owners who fly larger, more costly aircraft tend to replace the standard FlySky RF module and receiver with one from FrSky for its greater receiver selection, dual antenna diversity and telemetry system. Will a 9X with the FrSky RF system match a JR 9503, JR 11X, Futaba 8FG, Airtronics SD10G or a Hitec Aurora 9 for sailplanes? Perhaps, and perhaps not, but the people I have spoken to on the forums say it is great for their Jets, 40% giant scale planes, thermal and slope gliders as well as their gas and glow planes. They say it can do almost anything. When I posted the list of mixes and flight conditions I use on my 9C Super, the response was that 9X, with the ER9X software, could recreate this set-up.

Graphic provided by www.alofthobbies.com USA based FrSky Distributor

Based on reports from high end users, the FrSky system is rock solid and will match any of the name brand systems for the reliability of the link, but it does so at a fraction of the cost. Adding a FrSky RF module and 8 channel receiver to the 9X costs about $45. By comparison, an 8 channel Futaba FASST module, with an 8 channel receiver for my Futaba 9C costs $300. FrSky receivers run $12 to $35, or about 1//4 to 1/2 the price of comparable Spektrum, Futaba, Hitec, JR or Airtronics receivers.

The link below goes to a discussion on the Flying Giants forum. It includes several posts by XJET, Bruce Johnson. You may know him from the review videos he does as RCModelReviews. His comments are quite revealing and typical of the reports I have read.
www.flyinggiants.com/forums/showthread.php?t=62466" target="_blank">http://www.flyinggiants.com/forums/showthread.php?t=62466

Here is a discussion about the 9X among some glider pilots
www.rcgroups.com/forums/showthread.php?t=1606788" target="_blank">http://www.rcgroups.com/forums/showthread.php?t=1606788

This user posted his set-up template for DLGs. They can be downloaded.
www.rcgroups.com/forums/showthread.php?t=1428583#post18049473" target="_blank">http://www.rcgroups.com/forums/showthread.php?t=1428583#post18049473

Of course, if you read the forums you will find negative posts too. And while most are from pre-2010 you will find a few people who bought the current model and were not happy. But you can say the same for JR, Futaba, Hitec, Airtronics or Spektrum. The forums are full of those who swear by one of these top brands and those who trash them. However, for the major brands, and the 9X, the positive reports far outweigh the negatives

So, what do you give up when you go to this low cost system? Customer service is poor and warranty repairs may be a challenge. HobbyPartz and HobbyKing probably provide the best support but even these may not be especially good. Don't expect to get on the phone line and have someone hold your hand while you try to set-up crow for your sailplane. For these things you turn to the user community.

XJet said that when he dropped and broke his 9X he just threw it away and got another one. Fixing it would cost as much as a new one. There have been a few reports of the FlySky receivers not binding, but I don't see us really all that interested in the FlySky RF system anyway. It should be great for parkflyers and the receivers are only $8-12. But as a sailplane radio it should be upgraded to the FrSky system and that one gets great reports.

While the overall manufacturing of the radio and main board gets good grades, people suggest you check the solder joints on the wires inside the radio. Occasionally something is not up to good workmanship standards, so you might have to resolder a wire. In the early days this was a big problem, today not so much.

In the open source world the community is the support mechanism and there is plenty of that. There are forums dedicated to this radio, under the various brands, and people are developing software and hardware enhancements.

Clearly this is not the radio of choice for everyone. If you only buy RTFs because ARFs are too much trouble, this is not the sailplane radio for you. If setting up flapperons on a DX6i seems too daunting, this radio may not be for you.

But if you can take the time to read and understand things, will take some personal initiative, then this could be an option that could save you hundreds and perhaps thousands of dollars. So, for some, this may be an excellent option.

I believe the 9X, with the FrSky RF system and one of the upgraded software offerings can be set-up to at least match the features and mixes I use on the 9C Super. Considering the 9C Super cost $430 when new that would make this radio pretty capable sailplane radio at a fraction of the price.

There may be members of the club who are in the market for a sailplane radio and are not pleased about the cost. Perhaps one or more might wish to embark upon a project to work with this radio system. The radio can be purchased for $60 to $100. The standard software and RF system should be fine for small electric planes and probably 2M gliders. Add the smartparts board for $45 and you can load ER9X or one of the other advanced SW systems. The upgrade software if free. Now you have invested $105 to $145.

If you like it then you might want to rev up the RF system to take advantage of the high end features of the FrSky RF system, the module with 8 channel receiver are about $45. With all the upgrades done you are in for about $150 to $190, which is less than the price of a Spektrum DX6i. That should put you into a highly capable sailplane radio with two RF systems and 2 receivers. That would be less than half the price of a Hitec Aurora 9, Futaba 9FG or an Airtronics SD-10G. And it would be about than 1/3 the price of a JR 9503.
The FrSky receivers are about 1/4 to 1/2 the price of the comparable Hitec, Spektrum, Futaba and JR receivers. To illustrate what this means, if you put up 5 gliders using Futaba R617 FASST seven channel receivers or Spektrum AR7110 receivers you will spend $400 or more in receivers. Using FrSky 8 channel receivers you would spend about $150, saving $250 in receivers. That is enough for a second 9X for your summer house, car or as a back-up radio, with enough left over for a few more receivers. It might be worth a look.
I have a lot more information in the form of informational links, videos, and places to buy. There are also support forums for these systems. If you are interested, send me a note and I will forward what I have and share what I have learned. I would be interested in working with you on the project.

Also note that at our April LISF meeting one of our members did a rather extensive presentation on the FrSky telemetry system. There are a variety of modules available for things like battery voltage, altitude, motor temperature, air speed and GPS features.


The goal of this discussion was to identify a lower cost path to a good sailplane radio. The FlySky TH9X may offer such a path. Hopefully one or more members of our club, who are interested and comfortable with this open source approach, will give the 9X a try.
Will the 9X take over the RC world? Probably not, but it offers the possibility of providing a highly featured sailplane radio system for less than 50% of the cost of the big name brands.
Clear Skies and Safe Flying!


9X - FlySky/iMax/Turnigy/Eurgle FOR DUMMIES www.rcgroups.com/forums/showthread.php?t=1616229#post21068397" target="_blank">http://www.rcgroups.com/forums/showthread.php?t=1616229#post21068397
Leader Hobby � Fly Sky TH9X FlySky makes the radio. http://leaderhobby.com/list.asp?type=categories&categories=70
www.hobbypartz.com/79p-th9x-r9b-9channel-radio.html" target="_blank">http://www.hobbypartz.com/79p-th9x-r9b-9channel-radio.html
Turnigy 9X � Hobbyking � USA warehouse � www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=19673" target="_blank">http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=19673
FlySky � wowRC
www.wowrcmodel.com/rc-accessories/radio-system/flysky-fs-th9b-fs-th9x-b-2-4g-9ch-radio-system-tx-rx-rc-transmitter-set-mode-2.html" target="_blank">http://www.wowrcmodel.com/rc-accessories/radio-system/flysky-fs-th9b-fs-th9x-b-2-4g-9ch-radio-system-tx-rx-rc-transmitter-set-mode-2.html
Smartie Parts Programming Board � allows firmware updates and provides backlight for display
www.smartieparts.com/shop/index.php?main_page=product_info&cPath=3&products_id=331" target="_blank">http://www.smartieparts.com/shop/index.php?main_page=product_info&cPath=3&products_id=331
Parkflyer RC � TH9X with ER9X already loaded � $160. Basically they take a $60 radio and charge you $100 to Flash it with updated SW. Also they will install the Smartyparts board for cost +$10. http://parkeflyer.com/index.php?option=com_virtuemart&Itemid=275&gclid=CLbz1vDgzq8CFYRM4AodPQ2WHw

Best regards,
Ed Anderson
Long Island Silent Flyers
ESL Newsletter Editor
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