I read on another thread that it is somehow illegal to swap out the crystal in the Tx for another channel. Did I misunderstand this?

One of the reasons I'm asking is that upon arriving here in Japan, the pres. of my local club informed me that the frequencies I had on my Airtronics VG6000 (27) and VG400 (29) were not legal in Japan (they use 72 and 40Mhz but not these particular bands). The solution? A fellow club member gave me a channel 18 set of Tx and Rx dual conversion crystals from Sanwa (the good people who actually make Airtronics radios) and voila, I was off flying. I've salted the other crystals away for my return to the US.

Should I be expecting a visit from Homeland Security upon my return?

In the States, the FCC (Federal Communications Commission) who controls and distributes the whole spectrum of radio frequencies, have said that changing the transmitting frequency by changing the crystal alone, is not allowed.

This is because just changing the crystal doesn't guarantee the frequency doesn't bleed outside the prescribed narrow band without the factory fine tuning the transmitter after the crystal change.

That's how the FCC sees it. In fact in Europe and probably elsewhere, any bleed over isn't actually a problem like it can be in the States. Our frequencies have other users between some of the channel frequencies. Some earth-moving equipment, for example use the frequencies between a couple of our frequencies and it's best not to confuse them at all!!

Changing the frequency using a module (like the Spectra module in the Hitec transmitters) controls the frequencies tighter and is therefore allowed. Also, you can send the transmitter back to the manufacturer for them to fine tune the frequency after a crystal change.

So, whereas it's technically possible to change the channel by changing the crystal, it isn't allowed in the States, as the FCC who control these things have decreed it will interfere with other users of the nominal 72 meg bands. They may or may not be right about the bleed over, but they are the ones to decide so we should comply.

-David C.

David said it well. I doubt that changine the crystal in the Tx in Japan is illegal, just give the channel 18 set back before you fly home.

72 Mhz on channel 18 (11 thru 60) is a legitimate RC aircraft frequency here too, but the fact that you changed it isn't.
Dennis-

It is legal in Canada & the UK -- there are no "bleed over" problems, despite other users on the assigned bands. It seems that the FCC is over-zealous in guarding its turf, or it is a CYA exercise.

Both, probably!



-David C.

[quote]ORIGINAL: David Cutler

[quote]Vehiculul meu pe perna de aer este plin de tipari.

Pardon?



-D

I was hoping for a translation

It's Romanian for 'My hovercraft is full of ells'

(Naturally!)

[&:]

-David C.

Are you citing actual studies or just a lack of any reported problems? I for one like the fact that transmitters need to be sent to a licensed technician for frequency changes. It allows them to ensure that the transmitter is operating within spec after the change. It also ensures that when the crystal is changed, that the frequency number on the transmitter is also changed.