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MacGregor Industries have kindly given me permission to reproduce some good articles that appear in their Modeller's Guide 2000, and these will appear from time to time in ModelFlight. Here's the first, on Radio Range Testing - something which is always mentioned as a 'must' in all the beginners' books but which I have never before seen spelled out in detail. I hope you will find it interesting and helpful.
The second item is a bit specialised and is a helpful guide to setting up the TeleBee Heading Hold gyro, sent to me by Frank Drecchio, a model flight enthusiast from Maryland, USA.
Finally, there's a brief item of news for helicopter fans.

radio range testing

telebee gyro set-up

news item


radio range testing

Range checks are quick and easy to perform, and could well show up potential problems with even the best of r/c installations.

BEFORE using any remote-control radio system, it is always a good idea to perform a check to verify the operating range of the system.

It is not necessary to verify the range with the transmitter aerial fully extended as a check with the transmitter aerial in the retracted position will give representative results. As a rough approximation, the range on the ground with the aerial up will be ten times that obtained with the aerial down although, of course, if the retracted aerial is particularly long or short, this will affect the figure.

One transmitter only
Since transmissions from other transmitters in the vicinity can affect the result, the test should take place with only the test transmitter operating. Ideally, a clear open field should be used as a test area, but a test along a path or road will be satisfactory provided that an allowance is made for the localised, signal-distorting effects of parked cars and other large metal objects.

Two people are needed for the test. One should take the transmitter with the aerial retracted and operate it as if flying the model, moving a control stick to operate a servo in the model. The other should walk away from the side of the person holding the transmitter, with the model held at right angles to the direction of walking so that the transmitter and receiver aerials are approximately parallel.

The radio signals are emitted from the side of the transmitter aerial. Only a very small signal is sent out from the top, along the aerial's axis. Similarly, the receiver picks up the strongest signal when its full length is exposed to the transmitter. If the receiver aerial is held in a straight line and pointed at the transmitter, only the diameter of the receiver wire is available to pick up the signal and the result will be a very short range. For these reasons, it is recommended that the transmitter aerial is not pointed at the model and the receiver aerial is arranged in two dimensions so that whichever way the model turns, there is always a good length of exposed aerial to pick up the signal. Taking the end of the receiver aerial to the top of the tail fin is strongly recommended.

Ground absorption
The ground absorbs radio signals and makes them weaker. As a model moves away from the ground, the available transmitted signal gets much stronger and because of this, the air range might be two or three times the ground range.


Seventy paces
With the model at waist height, a range of at least 70 paces should be obtained and can be verified by observing the servo or control surface on the model. The servo should smoothly follow the transmitter commands without chattering or hesitation. If the model is held lower, the range obtained will be less and if the model is held higher, the range will be more. Pointing the receiver aerial at the transmitter will dramatically reduce the range.

Gyro set-up



Anyone who is contemplating the purchase of a TeleBee or Arcamax PI gyro or has purchased one and cannot understand the instructions (especially the Telebee) may want to read this.

This is how I set up my Telebee; same for Arcamax PI.

Inhibit all mixing to the tail rotor, rev-mix, offset, etc, centre the trim on the Tx and zero the electronic trim if any. Do not adjust the gain on the gyro, leave it at the default setting. Set your rudder ATV to 100% on both sides.

The cube part of the TeleBee is the sensor unit and has all the electronics in it. The connector box has no electronics in it. You should remove the four Phillips screws in the bottom of the sensor case and take off the case bottom. Stick a piece of very thin foam tape (thin wing saddle tape is good) inside the case bottom and then reassemble the case. This keeps the electronics inside the case from moving around. Now mount the cube on a flat level surface on the helicopter. Use CSM foam tape or Zeal mounting gel. The tape that comes with the TeleBee is no good. Ignore the two arrows on the case. The Phillips screws face the ground. Mount the connector box with the same type tape or gel.

You will notice that the two cables supplied have male plugs on both ends. You will have to supply your own cable to plug into the servo output if you need an extension. Plug the gyro into your rudder channel using one of the supplied cables and plug the rudder servo into the gyro. Plug the other cable (aux) into a spare channel that has a two position switch. The jack on the sensor unit (the cube) is not used - it's for factory set-up only; do not plug anything into it.

Set the AUX channel ATV to 50% to start. set both sides; one is for Normal mode, the other will be for Heading Hold mode.

Now you need to set up the helicopter for a stable hover mechanically. Determine that the gyro is operating in the correct direction. Turn on the Tx first then the Rx. Wait about a minute without moving anything. Now you have to find out if you are in normal or HH mode. If the servo slowly drifts one way or the other, you are probably in HH mode. You can verify by moving the rudder stick. If you move the stick to the right, the servo will not go back to centre unless you move the stick to the left and it will drift if you centre it. In normal mode, the rudder will follow the stick movements. Set the switch to standard mode for now. Now give a right rudder command from the Tx and note which way the servo arm moves (pushes or pulls). Now pick up the helicopter by its head and jerk the nose to the left. The servo should give a right rudder response. If it doesn't, simply flip the reverse switch on the gyro sensor and test again.

Turn one of your tail rotor blades 90 degrees in its holder and with the throttle/collective all the way down, mechanically adjust the blade so it is more or less parallel to the tail boom. This is your rough starting point for a test hover.

You now need to hover the helicopter into the wind in NORMAL mode. Adjust the linkage until the gyro holds the helicopter straight. Do not use the electronic sub-trim for this or the rudder trim on the Tx face. It must be a pure mechanical adjustment. If it "hunts" back and forth, beep down the gain a tiny bit at a time (AUX switch again, not the gain on the sensor) until it stops and then just a tiny bit more. When the helicopter will hover without turning you can now set the HH mode.

Shut it down and switch the two-position switch the other way. You will see the rudder servo drift one way or the other. Now you can use the rudder sub-trim feature on your Tx to stop the drift. Do not use the trim on the Tx face. You simply flip back and forth from normal mode to heading hold mode and keep beeping the sub-trim until the drift stops. It will drift after about 15 seconds or so no matter how carefully you adjust the sub-trim, but that is not important.

Your TeleBee is now set up. You cannot use any mixing while in HH mode at any time. You can, however, use your rev-mix and offset if you to use the gyro in normal mode only. To get the maximum benefit of HH you will need a fast servo - 011 seconds or less transit time.


You can meet Frank Drecchio on the personal profile page!

I see in the model press that MacGregor Industries now have exclusive UK distribution of JR Propo radio control products, having taken over the distribution from
  J Perkins. This means that Macgregor's now distribute the complete range of JR radios and helicopters - something they have apparently wanted for some time.