When I'm testing my servos to see if they are functioning correctly mounted on the plane, I usually have my transmitter antenna retracted. Is it true that this can damage the "crystal" (I don't even know what that is)? I thought I read up on it somewhere when I was researching r/c sims and using your own transmitter to control the sim by parallel port connection.

Should I extend my antenna?
Thanks

You only need to extend your antenna when flying. If your just checking the servo direction/travel, you don't need to worry about it. In fact, when you range check on the ground, you leave your antenna down. Hope this helps.

Read the manual, Futaba says to extend one section of antenna for ground range checking. Leaving the antenna all the way down can cause extensive damage on synthesised modules.
Good Luck
Paul

I doubt that the crystal can be damaged by using the radio with a retracted antenna, but the transistors in the power amplifier may be damaged by overheating. When transmitting with a retracted antenna the RF-power which should be emitted by the antenna is instead converted to heat.
The power output of our radio sets is of the order of 1 W. The heat produced by such a small power is easily dissipated by even a fairly small heatsink. IMHO it's plain bad design if radio sets can't handle a power on, retracted antenna situation.

As far as I know there is no reason why a synthesised module should be more sensitive to heat damage than a plain old crystal module.

/Red B.

Radios differ as to the proper ground range test...

Some are to be extended one joint, others not... My Futaba 9C is NOT to extended at all...

However it DOES state not to run the transmitter for any lengthy period of time without the antenna extended.

So for setting up a plane I often extend out the two bottom (largest) sections... That keeps it short enough to make it manageable indoors, but gives the transmitter "enough" antenna so as not to heat it up.


Range testing should be done as stated in the specific manual. For radios requiring the antenna be completely down, the 5-10 minute process isn't enough to harm the radio.

Take care...

It is not the crystal that gets damaged, it is the output power amplifier. Your transmitter is designed to radiate the power as RF. When the antenna is down, the SWR (standing wave ratio) goes way up and the power that would normally be dissipated as RF is now radiated as heat in the output stage. You probably notice the back of your transmitter getting quite warm if you run for very long with the antenna down. You should always run with antenna FULLY extended except for the short time required for a range check. Note that damage by excessive heat can be cumulative; i.e. won't fail all at once, just dies a slow death. The mean time between failures will approximately double for each 10 degrees C that the output stage rises.