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Mr.RC-Cam

Spektrum / JR Tx Module Conversion Project

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Generic Antenna Option, photo 20.

The antenna adapter board will also accept a SMA connector so that I can install a generic 2dBi dipole whip. This is nice upgrade and the perfect solution to the reports that the stock DX6 antenna is an easy item to break.

Below is a 2.4GHz 2dBi generic whip installed on the optional SMA connector.

post-6-1158635120_thumb.jpg

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Generic Antenna Option, photo 21.

The RF feedline can be directly soldered to the adapter board or a U.FL button receptacle can be soldered instead. I chose the latter, since this makes cable replacement a snap-on affair.

FWIW, U.FL connector is one name for the little connector you find on the Spektrum RF board. It goes by other names, depending on who made it. This is a industry standard receptacle that is used on cell phones and such. It is very tiny and low loss.

BTW, ready made coax cables, with U.FL's on both ends, are available from specialty antenna suppliers. Cost is about $10 (Google is helpful in finding suppliers). The micro sized coax cable is very lossy, so the shorter the better.

Below is a photo of the U.FL receptacle (soldered in place) with the coax cable plugged into it.

post-6-1158635474_thumb.jpg

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Generic Antenna Option, photo 22.

The SMA connector is also helpful in making RF measurements. My RF power meter reported 50mW from the DX6/Unigen module. But this did not include the coax cable losses (about -2dB for my unnecessarily long 300mm cable). Then I later discovered that the duty cycle of the RF carrier is only 80%. So, my measurement needed to account for that too. The net result is that raw RF power, directly on the output of the Unigen module, is estimated to be ~100mW.

Below is another view of the SMA equipped antenna adapter board.

post-6-1158636086_thumb.jpg

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This project's story needs a conclusion. So here it goes...

I have a GWS Formosa that is a very relaxing R/C "pattern" e-plane. This is the same model that is seen in the Landtastic Project page. However, I stopped flying it because the Plantraco DSP Rx I had in it was horrible. I even redesigned the Rx's DSP chip just to tame the wild glitches during flight (I summarized that task in these threads: Plantraco Rx Problems and Plantraco DSP Hack). The new decoder design successfully eliminated the bazaar & scary glitches, but the Rx's poor FM performance gave it terrible range at my favorite park site.

In the end, I decided to upgrade the Rx; it sat around and became another one of those honey-do's that take a while to get to. However, now I had an excuse to use the Spektrum 2.4Ghz R/C Rx in something. Long story short, I've been flying the Formosa with my new Spektrum enhanced JR Tx and it's a blast once again.

formosa3.jpg

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However, I was a bit reluctant to buy a DX6 system, tear it apart, and create a custom plug in module. Mainly because I figured the moment I spent my entire hobby budget doing that, I would see an Ad from JR for just such a thing at some ridiculously low price.

Well, my crystal ball was almost right. Spektrum is releasing a new 2.4Ghz DSSS R/C system. Unfortunately the DX7 is a complete Tx, rather than a RF module based solution. So, my custom module was definitely worth the trouble.

Some sneak peek DX7 details are found here: http://www.rcgroups.com/forums/showthread.php?t=581804

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Mr. RC-Cam,

Great work on hacking the system. I know folks would prefer to plug your module into their 8103's or 9303's because of all the programming they have allready done on the radios.

Why did you get better resolution with the 8103 as opposed to the DX6 transmitter?

Another question. I have popped something trying to charge trans battery too fast. Probably a diode. Where can I look for the broken part, where in the radio?

Thanks and good job.

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The higher resolution is due to the 1000 step (10-bit) encoder in the 8103.

If you have blown the 3A fuse in your 8103, then it can be found by unplugging the RF module from the back of the Tx.

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Truly a fantastic job, I am in electronics and well understand the labour of love involved in such a project. Very well done.

Question, do you intend to make the PCB's available or may be the artwork?

Again very well done.

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do you intend to make the PCB's available

Thanks for the comments. I don't plan on offering boards or art. I had two spare board sets (set = main bd, Spektrum antenna bd, universal antenna bd) that I offered at $36 each with programmed PIC, which was a good deal given what I paid. But, there was no interest at all so I removed the offer. I think it was a good decision since this is a very difficult project to build and would probably just be too much for most folks to attempt.

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Thanks for the comments. I don't plan on offering boards or art. I had two spare board sets (set = main bd, Spektrum antenna bd, universal antenna bd) that I offered at $36 each with programmed PIC, which was a good deal given what I paid. But, there was no interest at all so I removed the offer. I think it was a good decision since this is a very difficult project to build and would probably just be too much for most folks to attempt.

Any chance you still have these? I'd like one and would probably take both.

Brian

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I still have some boards. However, I don't recommend you attempt the project. It is very difficult (on a scale of 1-10, I give it an 11).

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I'd like to give it a go,I doubt you remember me but I bought some of the power zone boards from you at rcgroups last year,I think I bought 3 for my Stykers :)

If your up to selling me one or two let me know and I'll paypal you,don't worry,if I can't make it work I blame me :)

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Just PM me if you want to tackle it. Keep in mind that I don't have written instructions; I can provide a hard-copy of the schematic and a parts list, that's all. Oh, and the photos I posted tell the rest of the story. You will need SMT rework equipment, and low power microscope, to transfer the Spektrum DX6 parts to the custom JR board.

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well you did scare me a bit with the smt equipment but a buddy was of the opinion he could do it at school,then today I found out why mine wasn't working,so now I don't have to start over ;)

A simple little thing like not having the TX in PPM mode will cause this not to work but then most of you guys who have been doing this for a while now already knew this :unsure:

Thanks for the offer and sorry for wasting your time.

Brian

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I was a bit reluctant to buy a DX6 system, tear it apart, and create a custom plug in module. Mainly because I figured the moment I spent my entire hobby budget doing that, I would see an Ad from JR for just such a thing at some ridiculously low price. I eventually decided to tackle the project.

They finally did it! Nine Channel Tx RF deck and matching Rx for under $300. Less than I spent creating my nice looking custom 6-Ch equiv.

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