Simple question. Can a simple Futaba 4 channel FM xmitter and reciever be changed from 72mhz to 50mhz with just a change of crystals or is there more involved?

The crystal tunes the frequencies, so I would guess it would work. However, it is illegal in the US to change frequencies on your transmitter without having it professionally tuned. You'll have to send it in. And, it will have to be a frequency that is designated for RC use. Why would you want to do this?

Because I can! I'm a ham, and an amatuer radio operator too!

Bruce,
No, the transmitter and the reciver would have to be recalibrated to 50mhz.

Cheers

There you have it....

I've read about staying within your band 72mhz or 50mhz, and also
what 2slow said which is what it reads... That said.... I've seen it
work.... But most likely it's a chance that you'll have to decide on..
keeping in mind the safety part of it... Others around may not do
it that way.... And it would be BAD, unsafe and everything else to
get them involved in that kind of problem....

I think the frequency difference is too great to make the change by just changing the crystal. The tuning coils would have to be adjusted and even then, I doubt it! [8D]

Bruce Bennett - I believe you will find this mod is illegal even for a HAM. I suggest you go to this forum: http://www.rcuniverse.com/forum/forumid_125/tt.htm and pose the question there of the Futaba support people and get expert advice. Be sure to mention you are a HAM operator. I can promise you there is more to it than merely plugging in crystals. It can be done by a Futaba service center but I am not aware of the exact procedures for your radio.

BTW - I am not a HAM but have great respect for them, I just do this for a living with my commercial license.

Another Bruce

Tnx for the info, will try the other forum. Thanks to all for the advice.

Here's what they are going to tell you.

Please also note that 50MHz, commonly known as "HAM BAND" or "6 meters" is legal for both air and ground use. If you have a HAM users license you can safely and legally utilize 50MHz frequency radios for both aircraft and ground models without requiring any changes. Only 72/75 MHZ MODULAR transmitters (ie. 8U, 9C, 9Z, NOT 4VF, 6X, etc) equipment can be converted to 50MHz and vice versa. Receivers and crystal-based (non-modular) transmitters CANNOT be changed.

As an amateur radio operator, you can do whatever you want to the gear as long as it complies with FCC regs when you're done. That means it has to be legal for YOUR license class. You cannot make changes to gear for operation in the 72MHz band but you can make changes if you end up operating in the 50Mhz band (if your license class allows use of that band). Hams often build their own gear so modifying someone else's isn't a legal issue. I was a ham long ago (Advanced class) but was silly enough to let my license lapse while I was in college.

As was stated earlier, this isn't a trivial change. Moving from 72Mhz to 50Mhz is a major frequency shift and will require fairly extensive modifications to the RF circuits (not just a crystal change). Your switching from roughly 4m to a 6m wavelength. Just like with any transmitter or receiver, you're going to have to retune oscillator and amp sections to get them working on the new band. If you are comfortable with this then go for it.

Mark

The above statement, which is quoted from the FAQ on Futaba's website, http://www.futaba-rc.com would say to me that the circuits are not capable of being tuned that far.

How much is the cost of a model and the time to build it compared with purchasing the proper equipment. If its a foamy park flyer or combat plane than you can fix with packing tape, then hey go for it.

If its a scale ship or a helicopter or something you have a lot of time or money in, do yourself a favor and get the right equipment.

Bruce, yes it is possible but it would involve nearly a complete rebuild of the total RF section, about the only original circuitry you could use is the signal conditioning and codeing you will be sending to the modulator. It would most probably cost you more (much more) to make this conversion than it would to buy a commercial unit on 6 meters even if you have the necessary test gear to assure you meet all FCC requirements. However, it you can get ahold of an old Heathkit manual for their AM unit, it would not be an impossible chore and you would have the specs on all the required parts.

dont do it m8