Stock TX range: FCC potentiometer values

Jaybee · Mar 5, 2014

I opened up a stock TX today and tested the resistance for the CE / FCC potentiometer. Here are the results:

I’m no electronics expert, but I do know the higher the resistance the less power is allowed through. With that said, shouldn’t turning the pot all the way left (anti-clockwise) give the most power?

1.435 some resistance
0.888 more resistance (longer flight range reported)
0.007 hardly any resistance

Can any electronics people out there set me right / wrong?

AlTiTuDe06 · Mar 5, 2014

Jaybee said:
I opened up a stock TX today and tested the resistance for the CE / FCC potentiometer. Here are the results:

I’m no electronics expert, but I do know the higher the resistance the less power is allowed through. With that said, shouldn’t turning the pot all the way left (anti-clockwise) give the most power?

1.435 some resistance
0.888 more resistance (longer flight range reported)
0.007 hardly any resistance

Can any electronics people out there set me right / wrong?

This is on a NON vision Tx?

Jaybee · Mar 5, 2014

AlTiTuDe06 said:
This is on a NON vision Tx?

Yes. I have two identical controllers, both from Phantom 2's.

AlTiTuDe06 · Mar 5, 2014

Interested in explanation myself....

--subscribed

ianwood · Mar 5, 2014

I'm no expert but the pot is most definitely linear. The readings will not be consistent due to what is downstream from the pot.

Jaybee · Mar 5, 2014

ianwood said:
I'm no expert but the pot is most definitely linear. The readings will not be consistent due to what is downstream from the pot.

Cool, cheers. It would make sense that they are linear.

ioafpv · Mar 30, 2014

Did anyone verify whether this approach working for P2?
I really need to find a way to boost my rc range, which is only around 2500 - 2800m.
I saw many people may reach 3000 to +5000m range.

hook3m · Mar 30, 2014

You all do know that this potentiometer on the Phantom 2 - Non Vision does absolutely NOTHING right?

Zinnware · Mar 31, 2014

hook3m said:
You all do know that this potentiometer on the Phantom 2 - Non Vision does absolutely NOTHING right?

hook3m, I was unaware that this had no effect. Can you share references that explain this having no effect? I am not an EE, but I have seen many references of users stating that adjusting the pot to FCC should provide better range. I just want to make sure I am not passing along misinformation.

hook3m · Mar 31, 2014

Zinnware said:
hook3m, I was unaware that this had no effect. Can you share references that explain this having no effect? I am not an EE, but I have seen many references of users stating that adjusting the pot to FCC should provide better range. I just want to make sure I am not passing along misinformation.

CE and FCC mode is only on the Phantom 2 Vision because it is 5.8ghz and laws governing 5.8ghz are more restrictive in some countries.

Phantom 2 Vision Remote Control Manual 5.8ghz
http://wiki.dji.com/en/index.php/Phanto ... Controller
When you power on the Vision controller you get a single beep for CE mode and double beep for FCC mode.

Phantom 2 (non-Vision) Manual 2.4ghz
http://download.dji-innovations.com/dow ... .04_en.pdf
Page 10. Olny references the Potentiometer but that's it. It does nothing on the 2.4gh Controller. Also, no beeps at all when you power on the 2.4ghz controller.

2trickpony · Mar 31, 2014

Well it does appear strange that I flew 2.8 miles with stock controller, and I have adjusted the pot .
Whether it made any difference I do not know.
Is there any chance it does increase power to the 2.4 radio like it does to the 5.8 P2V ??

hook3m · Mar 31, 2014

2trickpony said:
Well it does appear strange that I flew 2.8 miles with stock controller, and I have adjusted the pot .
Whether it made any difference I do not know.
Is there any chance it does increase power to the 2.4 radio like it does to the 5.8 P2V ??

Anything is possible, but if it did adjust something it's odd that there would be no mention of it in the manual. Aside from DJI officially stating what it does or doesn't do it's just speculation. Both controllers P2 and P2 Vision are virtually identical even down the circuit board. If you take apart the P2 Visions controller the circuit board has 2.4ghz stamped on it even though it's 5.8.

2trickpony · Mar 31, 2014

hook3m said:
2trickpony said:

Well it does appear strange that I flew 2.8 miles with stock controller, and I have adjusted the pot .
Whether it made any difference I do not know.
Is there any chance it does increase power to the 2.4 radio like it does to the 5.8 P2V ??

Click to expand...

Anything is possible, but if it did adjust something it's odd that there would be no mention of it in the manual. Aside from DJI officially stating what it does or doesn't do it's just speculation. Both controllers P2 and P2 Vision are virtually identical even down the circuit board. If you take apart the P2 Visions controller the circuit board has 2.4ghz stamped on it even though it's 5.8.

Someone with a bit of electronic circuits/radio experience might be able to tell us.

xgeek · Mar 31, 2014

Or anyone with an RF tester like the immersion RF meter. RemE has one and both a P2 and P2V. Maybe he would be willing tot test?

hook3m · Mar 31, 2014

xgeek said:
Or anyone with an RF tester like the immersion RF meter. RemE has one and both a P2 and P2V. Maybe he would be willing tot test?

That would be the only way to know 100%. Test the output and turn the potentiometer and see if it increases or decreases. My guess is it's disabled.

ianwood · Mar 31, 2014

You'd have to measure RF power output on a scope. Easier just to see if you can replicate your 2.8 mile run with the pot in the other position. I am 99% sure the pot does nothing. More cost effective for DJI to produce one industrial design for both P2 and P2V.

2trickpony · Mar 31, 2014

ianwood said:
You'd have to measure RF power output on a scope. Easier just to see if you can replicate your 2.8 mile run with the pot in the other position. I am 99% sure the pot does nothing. More cost effective for DJI to produce one industrial design for both P2 and P2V.

Thats what I intend to do Ian. I will run 2 flights with extreme pot settings and let you know asap.

japaneezy · Mar 31, 2014

The pot doesn't have any effect on the non vision models. On a vision controller, the firmware reads the value of the pot and sets the output power of TX to one of two modes. On the 2.4GHz models, the pot is still on the board, but is not mapped to anything in the TX firmware. If anyone here is interested in getting longer ranges, I strongly encourage you to get your amateur radio license. This will open up a whole (legal) world of possibilities if you're in the US (UK does not need, sorry). It's also a fun hobby that goes hand in hand with RC. If you're dedicated, you can do it in a few days.

http://www.arrl.org/getting-licensed (US)
http://rsgb.org/main/get-started-in-amateur-radio (UK)

Big Ben · Apr 1, 2014

You might not really need fancy equipment to learn a bit more about this pot. Since the output on the 5.8 GHz model Tx (which is also used with the FC40) is 25 vs. 125 mW depending on the setting of the pot it's not unlikely this would result in a difference in drain on the batteries. If you measure this drain the mA difference between the two settings on a 5.8 GHz model would be the value to compare the 2.4 GHz model against when you do the same with one of those. If there is a difference in drain on the 5.8 model but not on the 2.4 one the conclusion would be fairly obvious.

J.James · Apr 30, 2014

I had to do some pokeing around inside my TX yesterday and today to try and figure out why my FC40 would only get a pitiful 300 meters flight range with the pot turned all the way to the right and I checked the resistance to see if the pot was working right.

Turns out it was except if I went all way to the right my resistance at the very end of the travel actually went up a tiny bit and I could only get 300 meters going by goggle maps. turned it back a tiny tiny bit and my resistance went down and was in the ranges others reported testing between all the way left and all the way right. But was only able to get another 20 meters range out of it and she lost signal.

Turns out the trip pot only ajusts the output power in the range of what the controller is set up in weather its CE or FCC. So its more like a fine tuner and does not change the mode from ce to fcc and only changes it from beeping once to beeping twice. and no detectable increase on the draw on the battery's either. But my meter only goes to the nearest 100th of a volt.

To really get it to change modes I had to hook the usb cable up to the transmitter and change the setting from CE to FCC mode in the rc assistant software and power off the TX and back on again. NOW I should be in FCC mode and the pot is just to fine tune the power out put in FCC or CE mode. After un plugging the usb and even if I turn the pot to the left and power on the TX it just beeps once but if I plug the usb in again it still shows its in fcc mode. So I turned it back the the rt and as soon as the crappy rain clears up I'm going to take a test flight and confirm I can get at least some thing close to the 500m range its supposed to have in FCC mode and the pot to the right. and if I have time I also want to test how far it will go with a windsurfer antenna reflector I made yesterday that got me out from the 300m mark to exactly 425m while in the CE mode. If it works as well to boost the range now in fcc mode I'm hoping to get 600-700 with it on. and if that works Im going to try making one out of some thin alm sheet I have. and putting a nice polish on to make it nice an reflective.