As some of you will know I had my radio go to failsafe mode a couple of times last week. A low power range check appeared to be ok so I took the gear to Mike Ridley of Model Radio Workshop and he found that the receiver aerial had a break in the coax shielding where it exits the case. I had seen the insulation on the aerial had split but didn’t realise the coax shielding was damaged so I had simply put a piece of heatshrink tubing over the split. The damage reduced the range, hence the failsafe, but the low power range check had not shown the problem. Mike fitted a new aerial and it’s now all good again.
Mike is the official service agent for Multiplex and many other makes and his services are very good value, he is thoroughly recommended. He is based in Sholing, Southampton so it’s a quick and easy trip for most PAM members.
While I was there Mike gave me a sheet he has compiled that covers some of the common problems he comes across and which contains some useful tips. He’s given me permission to use it:
2.4G Radio use and installation help sheet
With regards to problems with 2.4G radio, as 2.4G radiation is quite directional, aerial position at the transmitter and receiver is quite important.
In the case of the models with carbon or metal in the way or close by the aerials this will have an effect on the aerials and will reduce the overall range.
Even the wires to the servos will also affect the range, so having any of these items close to the aerials will narrow down the active part of the aerial receiving the signals from the transmitter.
With all carbon models the only thing you can do is to get the aerials outside of the model, it has been found that having the aerials some distance behind the wings is the best. Having the aerials in front of the leading edge of wings will tend to give lock out and failsafe operation as the fatter part of wings will hide the aerials with the model in given positions.
I suggest that once a model has its radio fully installed that you take the model to the edge of its range by using the power down setting on the transmitter and then at the edge of range position the model in different angles and attitudes and see if you can lose the radio link. If this is the case then look at the aerials positions within the model to see if they are being compromised in any way.
When using UBec power supplies avoid mounting the UBec close to the receiver as this can cause direct interference. I suggest when you first install a UBec carry out a short range check with and without the UBec if you find a significant change in the range then have the UBec checked out or replaced. This problem can also apply to some speed controllers that are now also using UBec BEC circuit.
One of the other problem with today’s modern radios is the batteries, as we’ve been forced to use NiMH battery this makes the possibility of battery voltage collapse much more likely, as NiMH have a much higher internal impedance sudden high loading of the battery can make the voltage collapse causing the receiver micro-processors to reset. If you have a lot of servos in your model you should consider using Eneloop batteries as they have a much lower internal impedance and can cope with high loads.
Transmitter aerial position
I recommend that the aerial be put into the vertical position as the signal that is radiated from the aerial is polarized in vertical plane and is more likely to reach the receiver than in the horizontal plan. This also avoids the tip of the aerial pointing directly at the model which is where the radiation is at its weakest.
Third party add-ons
If you are using third party add-ons with your 2.4G radio be aware that some units may radiate interference that can get into your receiver, items like height limiters etc. Mounting such items on top of your receiver can lead to lock outs and failsafe operation, try to avoid mounting electronic items close to the receiver as even a CE marked thing may still upset the receiver.
2.4G with boats
Because boats are at ground level and in water the strength of the 2.4G signal is very weak across the water, so the aerial/aerials should always be mounted in the vertical where possible in a tube, fitting the aerials under the decking can lead to loss of control when the model banks especially as the aerial get closer to the water level.
Once again metal or carbon parts in the model will deflect the 2.4G radiation so avoid mounting the aerials close to these types of materials.
Using the power down button on your transmitter to test the range does not tell the whole story. If we say that the power down output is 10 milliwatts if there is a problem with the R.F. module/board inside your transmitter then you could have just 10 milliwatts when in full power mode.
This effect has caught many people out, one of my customers after crashing a model then carried out a power down short range check on a second model and everything seemed fine, and ended up crashing another model.
I suggest if you get any signs of loss of control with a model, carry out a full range check or at least a test that is greater than the distance where you lost control of the model.
Common faults with 2.4G R.F. in transmitters are fractured aerial wire, damaged aerial, loose aerial, aerial connector not fully home, faulty R.F.I.C. in the R.F. module, all of the above are quite common in most makes.