35mhz; 40mhz; or 72mhz best for electric model

[David Ovenden]

A question for the electronics experts out there. I am thinking of equipping a small electric model for use in France. Over there 35mhz, 40mhz and 72mhz frequencies are legal. I have tx modules& receivers for all 3 bands. Which band (in a technical sense) would theoretically be the least troubled by potential RF/electrical interference from the motor/esc?

Anyone have any 1st hand experience of using 72mhz with electric models?

Edited By David Ovenden on 11/08/2018 16:51:21

[brokenenglish]

If you're particularly concerned about being totally legal, check the FFAM regulations.

In the bands you mention, specific frequencies are allowed, but usually not the entire band as used elsewhere.
In any case, I don't think many people fly electric on other than 2.4 GHz.

You can check the frequencies here:
https://vdp-blanc-nez.com/wp-content/uploads/2016/01/29_frequences_allouees.pdf

[David Ovenden]

I know what specific frequencies are legal in France. I am wondering which of 35; 40 or 72mhz will work be most robust in an electric model.

[Geoff S]

I'd be surprised if there was any difference. I know pcm is available on 35 Mhz but I have no idea about the other 2 as they are both illegal for aircraft in the UK so choose pcm. Or go for a receiver with digital signal processing (dsp) or a Multiplex IPD (also dsp) type receiver both of which will work with any transmitter - at least any 35Mhz, I assume also on 40 or 72 Mhz.

I just wonder what your objection to 2.4ghz which is rock solid on all my electric models.

Geoff

[Keith Berriman]

Just a suggestion do you have the facility to add in a separate battery for the Rx and servos and disconnect the red wire from the ESC plug into receiver ?? to try and eliminate any spurious signals from the motor side

[David Ovenden]

Geoff, reason for contemplating using old tech gear is because I have a "spare" radio that might/could be left in France with the model for when I'm there. If it is not viable to use the old FM set I will need to use my 2.4 radio and take it with me.

[Geoff S]

In that case use your 35Mhz transmitter with a DSP type receiver - Schultz, or Multiplex come to mind. I think you'll find a few on eBay at quite low prices now everyone is dumping them and they perform very well in my experience.

Geoff

[Don Fry]

I think 35 meg is best. It's an aircraft frequency in France, look up allowed channels. The others are shared frequencies and there are a lot of bait boats and things in France .

[Allan Bennett]

Before 2.4GHz became popular I was flying all my electric models on 35MHz. I solved the interference problem by using opto ESCs and separate NiMh receiver batteries, as well as positioning all radio connections as far away as possible from the ESC, battery, and their connections.

Beware that many overseas manufacturers and vendors call their ESCs 'opto' to signify that they have no built-in BEC, which is an abuse of the term. A true opto ESC (I use Jeti) has no direct wire connection between its signal input from the receiver and the circuit that controls the motor speed, using instead an opto-coupler to get the signal across.

[Peter Miller]

Never had any trouble with 35 Mhz and electric.

I believe that 72 is or used to be a stanadrd frequency in the USA and they must have flown electric onthat one

[Frank Skilbeck]

The only time I had any glitching on a 35mhz brushless electric model was on an EDF where the aerial ran alongside the motor, but the Rx on this was for small models and didn't have a full length aerial.

I flew quite a few other brushless models on 35mhz (Multiplex Cockpit Sx and MPX IPD receivers) with no issues at all and they all powered the receiver and servos from the ESC BEC. The only reason i don't use 35mhz on any electric models these days is because I like to use telemetry to monitor the flight pack (still using 35mhz in some IC models).