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T-REX 700 › does the 3gx work with 72mhz radio
11-18-2011 06:40 PM  6 years agoPost 1
ply68

rrNovice

Atlanta, GA

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I have a 700e (v2) 3gx and wanted to use the my JR 10x radio. Does the 3gx work with my 72mhz radio or is it necessare to use a 2.4? Thanks

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11-18-2011 07:35 PM  6 years agoPost 2
jschenck

rrProfessor

La Vista, NE.

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You can use a separate receiver. I haven't tried it but I don't see any reason why you'd have any trouble with running a 72Mhz RX.

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11-18-2011 08:14 PM  6 years agoPost 3
coolice

rrKey Veteran

Northamptonshire, England

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Hey.

Yes, it is perfectly fine to run a seperate receiver with the 3GX, I have done so and although it was a Spektrum receiver, the principle is still the same.
Basically all the 3GX needs to do is intercept the signals coming out of the receiver to the 3 eCCPM servos and tail servo.

The only thing to make sure is that the 3GX gets the main power supply into it's dedicated socket located under the main vertical plug in points and then the supplied battery out lead goes into your receiver.
.

Ian Contessa
Team Robbe SchluterUK
Midland Helicopters

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11-19-2011 03:39 AM  6 years agoPost 4
timmay

rrApprentice

Orange County CA

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Tried FM with RX It will not work.

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11-21-2011 06:25 PM  6 years agoPost 5
ply68

rrNovice

Atlanta, GA

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I tried the 72mhz and can not get it to work with the 3gx as well.

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11-22-2011 10:27 PM  6 years agoPost 6
dkshema

rrMaster

Cedar Rapids, IA

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Timmay and Ply -- odd, since the 3GX doesn't KNOW what kind of external RX would be connected, not working with a 72 MHz receiver doesn't make any sense at all. I don't doubt your results, I don't understand what the problem would be. My only guess would be power supply related.

Would be nice to have a 3GX on hand (cause I have the urge to make at least one of my helis FBL) to test that out.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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12-02-2011 03:32 AM  6 years agoPost 7
dkshema

rrMaster

Cedar Rapids, IA

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YES -- the 3GX WILL work with a 72 MHz system.

I took advantage of Grand RC's Black Friday specials, and bought a couple of 3GX systems at a killer price.

Remembering this thread, I dug out my old JR 8103 and an R790 SPCM receiver. I found a functional NiCad flight pack, and plugged everything together.

AND -- nothing worked as it should, although the servos did move when I moved the 3GX controller, and all the lights lit up, and I could select the different setting modes. This told me the 3GX controller was happy, but something else was going on.

Next, I pulled the three wire plug that goes between the 3GX system BATTERY OUT PORT and the RECEIVER BATTERY IN PORT.

I plugged that cable into an unused channel of the 7-channel RX. My thought was that none of the 3GX cables that plug into the servo ports of the RX have a ground wire, perhaps a ground between the two units was missing (although I had to keep telling myself that the ground pin on the R790 is common to ALL connectors on the RX.

But, with the 3GX battery out port connected to an unused RX servo port, the 3GX system came alive, I could control all servos from the TX and the gyro sensors would correct for my moving the 3GX box around.

Next, I plugged the cable back into where it should go between the 3GX box and the RX battery in port. I then jumpered the servo block ground pins to the battery input port pin. Still, although things lit up and the gyro sensors seemed to work, the system didn't. This confirmed that I wasn't seeing ground problems.

Then, it dawned on me. The third "unused" wire in the cable between the 3GX battery out port and the RX battery in port, ISN'T unused. In my JR receivers, it's the DSC port -- direct servo control. Further, that same pin on the 3GX box is used to put satellite RX's that would be plugged into the 3GX (assuming you're using 2.4 GHz Spektrum/JR satellites) into BINDING MODE.

I used an x-acto knife to lift up the contact retaining tab on the ORANGE, "UNUSED" wire in the 3GX battery out to RX battery IN port, so that the RX ONLY sees two pins connected from the 3GX box -- +Volts, and Ground.

Voila. The 3GX system worked as it should. The appropriate servos followed the appropriate stick movement, and the gyro sensor when moved, made all servos move.

So YES, you CAN connect the 3GX system to a standard 72 MHz receiver. Just use a TWO WIRE HARNESS between the 3GX battery OUT port and the RX battery IN port. Power and ground, disconnect the third "signal" wire in the harness.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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12-02-2011 08:46 AM  6 years agoPost 8
coolice

rrKey Veteran

Northamptonshire, England

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Hi Dave.

Thanks for testing that out buddy, I knew it would work but I think as you've found many are forgetting you need to get power to the external receiver from the 3GX's battery out port.
.

Ian Contessa
Team Robbe SchluterUK
Midland Helicopters

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