Hi, can anyone tell me if a Futaba 6exa uses single or dual conversion crystals, I have two sets of dual crystals but neither work.

Radios do not use dual conversion crystals. Only receivers use dual conversion crystals.

Edit: Only dual conversion receivers use dual conversion crystals--good point barracuda!

Yea if your trying to put a dual conversion crystal in a transmitter thats pretty much why it wont work. Dual conversion crystals also only work on dual conversion recievers.

I'm unsure of what dual conversions are, I only know I have two sets called dual conversion crystals, in each set one being a tx the other rx. So what you are saying is that I probably have a reciever that does not take dual conversion crystals.

It should say on the rx case what type it is. If not, you can go to the Futaba or Tower sites and figure it out. You will need the model of the rx to look it up. To the best of my knowledge there is only one type of tx crystal although you need to be using Futaba crystals in Futaba radios. In the US it is not even legal to be swapping tx crystals around, as you are apparently doing, for this very reason.

Ya, what started you playing around with crystals, did the Tx. stop working??[8D]

I've done a little quick research on Futaba's site and it also seems that Am and FM/PCM radios use different crystals. Please be very careful. I would recommend sending yours to a repair center and having them changed to the freq you desire and checking over your radios while they have them.

Its nothing that major, I live in the UK where we can chop and change crystals to our hearts content, however we have to fly on odd numbered channels and my kit came with even numbered channels, I've bought two sets of odd channel crystals but they dont work, only my even numbered ones that came with it do.

I switch my Futaba 6EXA & 4VF Xmtr xtls back & forth (ch 36, 38, 40, 41 & 48) betweem Xmtrs without any problems. They are all Futaba Xtls. Like in the UK, it is legal to do so in Canada. I have had no loss of range, or any interference problems with my radios, or caused any problems with other pilot's radios.

Cheers for all replys so far.

My reciever is a r136f futaba, should I be using single or dual conversion in it?

Couldn't find on Futaba list. Is this a real old unit?

F is a single conversion fm reciever. DF would be a Dual conversion FM

Looks like they only sell them in Europe because you can find them on hobby sites over there but its not listed on Futaba's site.

Anyways it's not dual conversion.

Also, seems to me that in the UK, radios are on 35 mHZ, not 72 mHZ. Check to make sure that the crystals are correct for the reciever model. If you somehow got hold of the American based 72 mHZ crystals, the circuitry in a radio designed for 35 mHZ wouldn't work. The frequency determining components would be way off value. I don't happen to have one of my AMI mags with me, but 6EXA as listed in the Tower catalogue only shows the R127DF, so the R136F may be a European or UK only reciever, on a different frequency band. You should be able to find a UK based web site for Futaba for advise, or a UK telephone number.
If the system didn't work out of the box after charging up the batteries as recommended in their instructions, sounds like a return under warranty is suggested.
I think only the American FCC refuses to allow the free changing of transmitter crystals unless you have the proper commercial liscense and the training and equipment to ensure that the resulting output waveform meets specs. Maybe because of the narrow band separation?