radio range question for all
 

The question is with BL systems what is it that affects the range? the esc or is it the motors? I'm running 2.4 spectrum with the mmm 2200 and all is fine,just wondering though what causes interference? When I first got the system I still had the trx am radio and got about 30ft then glitched like crazy.. I'm looking to put a mmm in a rustler and wondering if I will need another 2.4 receiver. The main question in all this rambling is what causes the interference.

phil

Before you can ask that question, one should ask what the differences between the various types are.

AM:
AM stands for Amplitude Modulation. The control (throttle, steering, etc) signals are superimposed onto a carrier wave (radio frequency) such that the amplitude of the radio signal varies in proportion to those control signals. This works fine, except it is vary susceptible to noise. Noise (RF interference, power line induction, etc) affects the tops and bottoms of the radio waves. Unfortunately, this is where the signal is carried so it gets washed out. The receiver then receives a mix of crap and valid signal and doesn't know what to do (or "guesses" wrong) and you get erratic behavior.

FM:
FM stands for Frequency Modulation. In this type, the carrier wave frequency shifts in proportion to the control signals. During transmission, noise still affects the tops and bottoms of the carrier wave, but the receiver chops these off (and therefore the noise is gone as well) and focuses on the shift in frequency, not the amplitude. Therefore, noise rejection is a lot better. However, if the noise is bad enough, or close enough in frequency, you can still "confuse" the receiver and get erratic behavior similar to AM.

2.4:
This is a whole different animal. Not only is it more than 30X times higher in frequency (helping to avoid the common noise sources), but the control signals are converted to data packets and then modulated into the high carrier frequency. At the receiver end, it performs data integrity checks (like error correction) to make sure the packets are valid. There is a bit more to it, but as you can see, 2.4 is a lot more tolerant to noise.

If you are using a BEC you may try an rx pack and see if things improve. I have no range problems unless I go beyond about 400 feet, with a DX3.0 and rx pack.

so BL esc or motors don't effect 2.4? still wondering which one causes glitching though on am or fm radios is it the wires,esc or the motors you should keep the receiver from?
phil

I'm not having any probs with the Spectrum I was talking about the trx AM radio.
phil

Aha misread that.

I had good range with my old TQ, as lame as it was it did 300 feet anyway...

i still use the stock tq tx that came with my rustler vxl. i used to get 300+ft. now, i get about 70ft. i think it has to do with half the rx wire getting severed and about a 3rd of the tx antenna getting broken off.:rofl:

i'm happy with 70ft though for now. it isn't seeing much use due to my savage bl conversion being my top priority right now. (and the dented vxl motor:oops:)

What to avoid: some bec's, if it is a "switching" bec it will emit alot of noise. power wires, motor wires, and yes, even the motor itself. all of these can create interference. You can get away with sloppy wiring with 2.4, but with am component placement can make or break your r/c

I aways try to mount the Rx in a poition that is away from the ESC and motor and preferbly in the front of the truck

I run FM in my setups for now....After 200' it gets glitchy.

with a 2.4ghz system your range will be as far as you can see

Seems like esc and bec placement has a big impact on range and glitching. I have successfully ran bl with AM, FM and 2.4. The old traxxas tq get good range, always have for me. I have had issues with am and boats, so I use fm for them. Otherwise I have not really had any range issues... Sometimes 2.4 seems to have issues but I play under alot of power lines...

Any radio signal can get washed out with enough noise. And frequency harmonics play a role too, so even if the noise if way under the radio freq, the harmonics may be such that it falls right in that range after all.

From testing various BECs, it seems you get what you pay for. The best performers for low/no noise are Koolflight, DimensionEngineering, and Western Robotics. Even so, I try to incorporate some type of shield, which is usually just a piece of aluminum between the receiver and UBEC. That way, more noise is reflected away from the sensitive circuits.

If you must run low-level signal wires near high current wires, it's best to have them meet at 90* angles. The way electromagnetic flux works, it is more difficult to induce noise into the other wire. This is the principle behind braiding the motor wires.

It depends on where the noise is coming from too. If it's the antenna, only moving it further away from the high current wires, or using a different radio will work. If it's the throttle line, there are still two possibilities:

1) noise entering the 6v power wire. This could be from a noisy BEC or induced from nearby high current wires. Adding a capacitor to the 6v power line can help, as can wrapping the servo wire around a ferrite ring a turn or two.

2) noise entering the signal wire of the throttle cable. This affects the signal the ESC and servo sees, so may cause erratic behaviour. A cap won't help here, but a ferrite ring should work.

overhead city power lines can cause issues as well

the world is polluted with electrical noise. thats why we're switching to digital television. my first wheelchair was very intolerant to noise and sometimes drove itself. that wasn't fun:gasp: