Just wondering what the difference between the transmitter crystal and the receiver crytal are.

Thanks

The fundamental frequency of a crystal is not necessarily the same as the eventual received or transmitted frequency. Inside the receiver or transmitter, the fundamental frequency of the crystal is "mixed" with a frequency generated within the receiver or transmitter to produce the actual received or transmitted frequency. The crystal frequency may also be multiplied or divided within the receiver or transmitter.

Since the receiver and transmitter may use different mixing/multiplying/dividing schemes, they may also need crystals with different fundamental frequencies, even when they are on the same channel.

For similar reasons, dual-conversion receivers need different crystals than do single-conversion receivers.

- Jeff

Transmitter crystals are on the transmitted frequency.

Reciever crystals arent.

Here's the long and exciting version of the explanation, don't read it while operating heavy machinery.

http://www.torreypinesgulls.org/radios.htm

Where do you get this from?
In all radioes I have had the transmitted frequencie is the second harmonic of the TX Xtal...

In the article the author says TX work on 5th harmonic...? Strange.

The author also says you can step up/down 2 channels without retuning TX... This suits neither the strange rules in US, nor the rest of the world.

The authos says the reason for DobbeltSuper/DualConversion is to avoid "noice" from fellow pilots...? The reason why MPX developed DS RC-receivers a lot of years ago was mainly because noice/harmonics from the upper FM-band in Europa caused problems for the 35MHZ RC band. But the author at least do know the problems caused by reduced channel separation for broadcasting...

The author also claim: "Dual Conversion is needed for FM to eliminate in-band interference from other transmitter. " And in an other sentence he claims: "JR has taken note of this and their receivers stick with Single Conversion FM,"

I got myself a good laugh from this article

Sorry it was a simplified explanation on my part.

What I took from the article is dual conversion is to protect against inband interference, and it is, but that JR implemented a different, though effective way to eliminate it.

Thanks guys

This stuff is stil way above my head.
But i guess ultimately you cannot use a transmitter crytal in the receiver and vise versa?!?

Yes thats correct

Infact you cant use single conversion crystals in a dual conversion reciever and you shouldnt even use different manufacturers crystals in a reciever unless they are meant for it.

And please listen to this advice. Your receiver might "seem" to work, but you could have lost a lot of range.
It is even worse in the transmitter; you might be a danger at the field, transmitting on your neighbours frequency in addition.

TX and RX Xtals have different characteristics. In a receiver the Xtal works without changing freq. In the TX the Xtal have to be able to deal with deviation. Deviation is a change in freq, and this is why it is called FM. The frequency is changed to code the signals, or shifthing.