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Basic Radio Question

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Old 07-14-2006, 10:45 PM
  #1  
FlyingFish
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Default Basic Radio Question

I have an AIRTRONICS 4CH. VG400 FM Radio on my airplane. It's operating on Frequencey #33, But I wanna change the Freq. to #26.
So, If I pop out the #33 Crystals and Put in a new set of #26 crystals, Is their any adjusting to be made to my radio by a tech repair guy? or do you just simply swamp crystals and continue as normal ???
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Old 07-15-2006, 08:48 AM
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Default RE: Basic Radio Question

This has been discussed (and argued) a million times; and will be a million more.

In the US, you are not supposed to change a transmitter crystal unless you have the equipment and skills to verify that it is actually transmitting on frequency (within tolerance specified by the FCC)

See page 7 in the manual. If you don’t have the manual, here’s a link to it:
http://www.airtronics.net/VG400%20and%20VG600.pdf

So, it needs to go to a qualified person for the swap. If it doesn’t pass the frequency check after the swap, the tech will adjust it until it does pass. Airtronics recommends having the receiver retuned by a tech but there is no FCC requirement to do that.
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Old 07-15-2006, 03:08 PM
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Default RE: Basic Radio Question

well, aside from the legal issues, will the radio function properly, or will their be irratic glitching if freq. crystals are changed?
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Old 07-15-2006, 03:51 PM
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Default RE: Basic Radio Question

It will probably work fine for you but the output should be verified so you aren't shooting down adjacent channels.
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Old 07-15-2006, 05:50 PM
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Default RE: Basic Radio Question

I fly alone, but I think I'll just buy another Radio on #26 frequency and sell the #33 Frequency radio and be done with it, but thanks for all your help guys!...........
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Old 07-15-2006, 07:17 PM
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David Cutler
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Default RE: Basic Radio Question


ORIGINAL: FlyingFish

I fly alone, but I think I'll just buy another Radio on #26 frequency and sell the #33 Frequency radio and be done with it, but thanks for all your help guys!...........
Please forgive me for asking this, but why do you want to change the channel if you fly alone? If its to match a receiver channel, then you can change the crystal in the receiver to match the transmitter with no problems.

-David C.
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Old 07-16-2006, 01:30 PM
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Default RE: Basic Radio Question

Well, I have 2 airplanes, one airplane is on #26 Freq. and another is on #33. For some reason, although I'm alone, their is some outside source that is interfering with the #33 freq. Airplane, but not the #26 freq. It could be some electronic devices near by that is causing glitches in my #33 freq. airplane. But my #26 Freq. Airplane in that location never has a problem. So, since I can only fly one airplane at a time, I may as well put both airplanes on the same Freq.#26, Because I know That's a clear channel with no outside interference. If I take the crystals from the #26 Freq. airplane and swap it with my #33 Freq. and use the same set of #26 crystals for both airplanes, it may or may not work, because the #33 transmitter is tuned to transmit on #33 not #26. That's why I asked on the forum, but I don't wanna find out that it dosen't work at an altitude of 200 feet or more.............[X(] So I figured if it was a common thing to swap safely I would just replace the crystals instead of the whole radio, But I'm still not sure what would happen in mid flight! So, I figure, better safe than sorry...
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Old 07-16-2006, 02:48 PM
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rainmanoly
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Default RE: Basic Radio Question

All you need is an o-scope. Call your local high school, or community college and see if they will help you.
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Old 07-16-2006, 04:37 PM
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Default RE: Basic Radio Question

In Europe swapping crystals is the way everyone does it and the radios are made for you to do so and need no retuning so the same radio in the US should be the same. It's just a matter of FCC and leagality.

That really pissed me off when I got the Futaba 9CAP. Only way to change crystal was to get a new RF module for $75 - $100. Total ripoff. I guess Futaba made a killing on that.
They got a synth module for 72MHz now but still nothing for 75MHz. Way to go.... [sm=thumbdown.gif]
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Old 07-16-2006, 05:16 PM
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Default RE: Basic Radio Question

Maybe I'll just try a crystal swap and give it a good range check on the ground just to see if your theory works, Im not going to take this plane to the field were others are flying. I'm by myself in the middle of nowhere. the nearest R/C flying field is 15 miles from me.
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Old 07-17-2006, 09:59 AM
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Default RE: Basic Radio Question

Hey, don't hold me responsible but if the radio is made so that the crystal is swappable it will be fine.
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Old 07-17-2006, 10:43 AM
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Default RE: Basic Radio Question

I'm not holding anybody responsible, infact my new #26 Freq. Radio is already on the way. I just wanna give it a range check (With the Prop removed) using #26 Freq. in a #33 Tx just to see if it works! But Im going to use the new #26 Tx & Rx for flying
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Old 07-18-2006, 11:16 PM
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Default RE: Basic Radio Question

I'm sure it works. A channel is only 10kHz wide or so and is set by the crystal. I can't imagine the rest of the analog circuits being that narrow band.

It's just the FCC rule.
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