of using correct Crystals.
This is just to explain a little about
crystals, and perhaps show why using the correct type of crystal is vital.
The circuit involved in producing
the 35MHz transmission is known as an oscillator. This circuit produces an alternating current at a particular frequency.
The circuit is made to oscillate by alternately charging a component, which stores energy, and then discharging the energy
via a resistor. The energy storage can be either in a capacitor, an inductor, or both. The resonant frequency depends on the
value of the capacitor or inductor and the resistance. The problem with this type of circuit is its stability. The frequency
will alter with variations in temperature and voltage for example. Hence the use of a crystal, which acts rather like an electronic
tuning fork. A crystal consists of a delicate piece of piezo material cut to a particular size and shape. This material has
the characteristic that when a charge is applied it changes shape. With the charge removed it reverts to its original shape,
which then causes it to produce a similar charge. When a crystal is put in an oscillator circuit it acts as a regulator,
maintaining a very precise frequency. Circuits vary in configuration, and crystals vary to suit the type of oscillator
circuit they are intended for. Without getting too technical it is sufficient to say that the correct
crystal must be used, hence use of another manufacturer’s crystal is a definite NO. In some cases
the circuit will work but the frequency may be shifted, and / or, be unstable and may even radiate onto an adjacent channel.
Another warning may not go amiss.
One characteristic quoted by crystal manufacturers is ageing. Their frequency is known to drift with age, not a lot, but this
does accumulate over time. Hence it is always advisable to carry out an occasional check using our equipment, not just assume
because everything was alright 6 months ago, it still is now.
So if you are using the wrong crystal
/ crystals, change them NOW before it is too late, you have been warned!.
ONE FINAL POINT,
TO MAKE IT ABSOLUTELY CLEAR ON COMPATABILITY, FUTABA crystals and receivers are not
compatible with JR, and vice versa, ie: if you have a FUTABA Transmitter you can't use a JR receiver with a FUTABA crystal,
or even a JR crystal, they may appear to work, but they are simply not compatible with each other. If
you have any doubts do not use, get more information from a reputable source. Again, you have been warned!.
FLY SAFE !!!.
and info added by Dave.