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FrSky AND JR at the same time??

PostPosted: Tue May 21, 2013 12:50 am
by glofilter
Recently I replaced my long broken antenna on my JR11X. It was out of warrenty, and I didn't want to pay shipping when I knew I could fix it myself. While fixing the radio, I decided to install an SMA connector so I could put on different antennas. I found that when I opened the radio, though JR says they no longer use "modules", they actually do- it's just buried inside the radio (exactly the same place where it used to be, you just have to dig it out).

I love my 11X. I love the features, the versatility, the ease of programming. But I HATE DSM. For whatever reason, I have really bad luck with it. The only truely long range reciever I have is a 12 channel JR RX that came with the radio- it has 3 satalites and a mass of wire. It's a serious RX, and really isn't useful inside anything but a damn big airplane.

Recently I decided to try the FrSky module in my old Futaba 9CAP radio I had from long ago. It was 72mhz, and I wanted to make it 2.4. I can't say how impressed I am with the FrSky module! It is incredible! The range of my little 2 antenna FrSky RX surpases that of my JR RX, and the JR RX has SEVEN antennas oriented in every which direction! (to cover all angles)

Well, I've been watching all of Bruce's videos and came across the DIY FrSky module. The first thing that popped into my head was, "man, I need to outfit my 11X with this!". But the more I think about it, the more of a pain in the keester that might be. I've got a whole garage full of airplanes on DSM, and at least a half dozen DSM RX's sitting around waiting for their turn in an airframe. Even with the FrSky's reasonable price for RXs, it would still cost me quite a lot of cash to replace my DSM stuff.

But then I had a thought. The JR DSM module is connected to the radio by 5 pins. I know three of the pins are pos, neg, and ppm. Not sure what the others are. Do you think you could install a DPDT switch into the radio that will switch the power betwen the JR moudle and the DIY FrSky module? I'm not sure how the antennas would work. Can you splice the same antenna into two transmitters? Would you need some sort of diode to keep one from buring up the other? Am I nuts? Thanks guys!

Re: FrSky AND JR at the same time??

PostPosted: Tue May 21, 2013 7:54 am
by BillGriffiths100
The other two pins are another earth connection and an unused pin that used to take the RF to the long 72 / 35 or whatever frequency aerial. That connector is too lossy at 2.4 GHz so a direct soldered connection or an SMA connector is used for the RF.
You can't use the same aerial for two different modules you would have to use another separate one, there is no easy way of combining their outputs, they would affect each other. You might have to orientate the unused aerial at 90 degrees from the other to prevent absorption of the signal by the other aerial, a theoretical problem to my mind but Bruce has mentioned it as a possibility in his original conversion video.
It will work but you must be happy with the fact that the TX will be somewhat unconventional!

Re: FrSky AND JR at the same time??

PostPosted: Tue May 21, 2013 12:30 pm
by glofilter
That's what I thought. Antenna science is such a pain. lol

Another question: Will the DIY kit still allow the radio to have 11 channels like the 11X is designed to have? (not that there are 11 channel FrSky receivers, but I'm hoping they'll have at least a 9 channel RXs in the future). I have a couple models that use 9 channels.

Re: FrSky AND JR at the same time??

PostPosted: Wed May 22, 2013 7:23 am
by BillGriffiths100
Will the DIY kit still allow the radio to have 11 channels

That I don't know.
My experience has been that the modules transmit whatever the pulse stream is, so it may be OK, but the result will rely on the receiver/s correctly handling the information.