Double tune is extra filtering of the crystal frequency. In the old days a double tuned reciever was longer range. I don't think that a synth receiver can be double tuned the same since it is the double tuning of the crystal frequency and they don't have a crystal....

One or two of the receivers shown are Dual Conversion so is there a difference and which should I buy.. ? Thanks

You have to buy the crystal for the receiver. If the receiver is a dual conversion receiver then you need to get a dual conversion crystal.

Ken

A transmitter crystal transmits on the frequency of that crystal but a receiver does not receive on the frequency of the crystal. Let say you are listing to 100mz on your FM radio the I.F. (intermediate frequency) of that radio is 10.7mz so to receive 100mz the local oscillator crystal needā€™s to be 89.3mz
100 - 89.3 = I.F. 10.7mz band pass filter. This is a signal conversion this is done twice on a duel conversion receiver (using two I.F. band pass filters the second I.F. does not need a crystal because at lower frequencies a inductive capacitance oscillator is stable. The reason why some crystals are not compatible is because receivers use different I.F frequencyā€™s.

OK, then I do not need to concern my self with dual conversion receivers... even if all of my transmitters are Dual Conversion... but it would be better if both the tx and the rx were DC?

dual conversion receivers:
The reason for using dual conversion is that it narrows the needed band with. When you have a single tuned crystal receiver it uses one I.F. frequency lets say itā€™s 10.7mz that means it will only allow the 10.7mz frequency through the crystal lattice filter but it is not perfect there is a (+) and (-) tolerance. Each time you pass the frequency through a I.F the tolerance is smaller allowing more useable frequencyā€™s for a given band with it also cuts down on outside inference.

I am trying to get info that I can share with a group of flyers that I meet each day at the flying field... can I tell them that it does not matter if we mix single or dual conversion equipment when flying? Is DC really important or necessary?

We are having an on going debate on frequencies, DC/SC and mixing of crystals between Futaba and HiTec.... Thanks..

I am trying to get info that I can share with a group of flyers that I meet each day at the flying field... can I tell them that it does not matter if we mix single or dual conversion equipment when flying? Is DC really important or necessary?

We are having an on going debate on frequencies, DC/SC and mixing of crystals between Futaba and HiTec.... Thanks..



sorry double post by mistake... sorry and thanks for your answers...

We are having an on going debate on frequencies, DC/SC and mixing of crystals between Futaba and HiTec.... Thanks..ā€¯

First there is no such thing as a DC Transmitter They call it a DC transmitter only because it is sold with a DC receiver. Second there is no such thing as a DC crystal, a crystal oscillates on one frequency only (some times on a harmonic) they call them DC crystals because they are used in a DC receivers. Transmitter crystals are interchangeable as long as the frequency are the same. DC receivers have different I.F. frequencies the interchangeability of the first mixing crystal must match that receivers I.F. If a second crystal is used it never needs to be changed to change the operation frequency, since the first I.F and the second I.F. are known frequencies that never change. The second crystal (if used) is I.F.(1) - I.F. (2) Equals freq. of second crystal and this is a constant.
To answer your question you will need to know the I.F. frequency of the futaba and HiTec receivers are the same. I would not recommend it because it may appear to work but it just may using a harmonic and this can cause the receiver to act erratically and decrease range