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changing frequency crystal in radio

Old 12-22-2005, 08:58 PM
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suitcase
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Default changing frequency crystal in radio

Since you can pull the crystal out of a transmitter, is it possible to change your frequency by just buying and changing the transmitter crystal?
Old 12-22-2005, 09:02 PM
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exeter_acres
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Default RE: changing frequency crystal in radio

here we go again[:@]
Old 12-22-2005, 09:07 PM
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JAkridge
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Default RE: changing frequency crystal in radio

From what I here it's a FCC NO-NO, some kind of Law against it ??? Well I have a friend that go's from channel 32 to 37 to 42 to 45 by changeing the crystal in the radio and rec. all the time and he never has any problems.
Old 12-22-2005, 11:02 PM
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Default RE: changing frequency crystal in radio


ORIGINAL: JuzPlaneKrazy

From what I here it's a FCC NO-NO, some kind of Law against it ??? Well I have a friend that go's from channel 32 to 37 to 42 to 45 by changeing the crystal in the radio and rec. all the time and he never has any problems.
Has anyone ever had a crash due to radio problems when he was on a different channel than the transmitter is tuned for? If so, it is "possible" he caused it. A transmitter needs to be retuned after a crystal change to make sure there is no "junk" being transmitted.
Old 12-22-2005, 11:46 PM
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Default RE: changing frequency crystal in radio

ORIGINAL: exeter_acres

here we go again[:@]
Sigh, sad but true. Several months ago I sent a PM to a few of the mods suggesting a sticky so this question could be answered without the inevitable arguements from the .01% of the people who refuse to accept the FCC requirements. Unfortunately, my idea wasn't accepted. []

In answer to suitcase, the FCC has regulations requiring that transmitter crystals only be changed by people who have the know how and equipment to confirm it's operating properly after the crystal change, and if not, to make the necessary adjustments. Regulatory agencies in other countries have similar rules. It's likely you will see some people post here saying they do it all the time and it causes no problems, but as TLH suggested, even if YOUR radio seems to be working ok after a transmitter crystal change, unless you've tested it with the appropriate equipment, you have no idea what kind of interference you might be causing on other frequencies.
Old 12-23-2005, 03:49 AM
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HarryC
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Default RE: changing frequency crystal in radio


ORIGINAL: piper_chuck
Regulatory agencies in other countries have similar rules.
Are there any other countries that have such a rule? In all European countries we can change frequencies as much as we like, there is no rule against it.

H
Old 12-23-2005, 02:05 PM
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Tangofoot
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Default RE: changing frequency crystal in radio

I have heard that the transmitter must be sent in also. The last time I flew there was a fellow there who had bought a transmitter from someone and thought he could just change the crystal. I said I didn't think he should but this was a private strip and you know how that works. Problem I see with that is he will eventually fly at an AMA sanctioned field and it's there he may cause a mishap. I will caution him next time I see him against it. Thanks for the help.
Old 12-23-2005, 04:50 PM
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polstery
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Default RE: changing frequency crystal in radio

STOP THE INSANITY PLEASE!!!!!!!!!
Old 12-23-2005, 08:17 PM
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smokingcrater
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Default RE: changing frequency crystal in radio

*** must *** resist ***

i keep telling myself it was just a troll post, although i'm fairly sure he didn't know and actually wanted the straight answer. this topic has probably had the most heated arguments on the face of the planet!
Old 12-24-2005, 04:16 AM
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JohnW
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Default RE: changing frequency crystal in radio

Ditto with Piper_chuck, etc. Just because you can do something doesn't make it legal or smart. Both my parents (one retired) work(ed) for FCC field offices in enforcement. I've been thru this a zillions times with them before. FCC regulations very clearly prohibit changing the transmitting frequency on a certified TX, which in our case with respect to RC planes is any radio on the 72MHz band. The exception is if the radio uses certified transmission modules (either fixed freq or synth.) With modules, you can change your TX frequency without problem. The 27Mh and HAM bands are exempt because the transmitters don't require certification. And you can do anything you want with your RX.

There is a good reason for the restriction on the 72MHz band. We share the 72Mhz band with other devices, probably most importantly industrial remote control devices and land mobile. I.E., we do not have exclusive use of the band. The restriction is there to help regulate this dual use, among other reasons. Belive me, the FCC could really care less about our silly planes. They would rather sell off our frequencies for some bucks, which would leave us high and dry (unless we all get HAM licenses.) Please don't give the FCC any fuel, be considerate of your fellow pilots, and obey the rules. It's really no big deal if you want to change TX freqs, just get a TX with a synth module. I have one (9ZAP), works great. Thanks.

Cheers
Old 12-24-2005, 08:49 AM
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polstery
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Default RE: changing frequency crystal in radio

resitance is futile, heres one ,WHAT FUEL SHOULD I USE????
Old 12-24-2005, 10:21 AM
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suitcase
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Default RE: changing frequency crystal in radio

To all: In the hobby, there will be different levels of knowledge concerning the more detailed items, such as the question I originally posted. Be assured it was posted, not to just have something to discuss, but to learn whether or not there was actual regulation against changing a transmitter frequency crystal yourself. One of the first things I "heard" when I started out was that one shouldn't do it, and that the radio must be sent back to the company to have the channel changed. It may seem to some that everyone will sort of just know the answers to such questions, even those who frequent these forums. I found out last Sunday that is not the case. The affore mentioned person does come to this site and still is under the impressions that because he can simply pull the crystal out of his transmitter, he can change the frequency himself.

By the way,,,,,,,,,,,,,,,,,,,,what fuel should I use?????????????
Old 12-24-2005, 10:34 AM
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Default RE: changing frequency crystal in radio

synthetic or castor?





Old 12-24-2005, 11:00 AM
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Default RE: changing frequency crystal in radio

ORIGINAL: suitcase

By the way,,,,,,,,,,,,,,,,,,,,what fuel should I use?????????????
Other people's.[sm=spinnyeyes.gif]
Old 12-24-2005, 01:09 PM
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Default RE: changing frequency crystal in radio

couln't you check your tranny with one of those new 50 buck channel checker things from Hobbico, after you change the crystal? Just to play it safe?
Old 12-24-2005, 01:11 PM
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exeter_acres
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Default RE: changing frequency crystal in radio

they are not accurate enough
Old 12-24-2005, 01:20 PM
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smokingcrater
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Default RE: changing frequency crystal in radio

the hobbico thingy tells you if you are on the right frequency, and unless something went REALLY bad during the swap that should be correct. what it doesn't tell you is how much you are transmitting on the spaces between the led's on the frequency checker.

Old 12-24-2005, 02:30 PM
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Default RE: changing frequency crystal in radio

So why the manufacturers make crystal on Tx removable by user?I think if prohibited,Tx crystals should be fixed so only can be changed by services ,not simply users.
Old 12-24-2005, 02:58 PM
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Default RE: changing frequency crystal in radio

ORIGINAL: HarryC


ORIGINAL: piper_chuck
Regulatory agencies in other countries have similar rules.
Are there any other countries that have such a rule? In all European countries we can change frequencies as much as we like, there is no rule against it.

H
When I looked into it a while ago I believe Canada and Australia both had rules similar to those in the US. Since I don't live there, I only did some quick checks.
Old 12-24-2005, 03:06 PM
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Default RE: changing frequency crystal in radio

ORIGINAL: suitcase
The affore mentioned person does come to this site and still is under the impressions that because he can simply pull the crystal out of his transmitter, he can change the frequency himself.
Most cars are able to exceed 100 MPH, but that doesn't mean he can legally do it on the typical US highway. The railings on most bridges are low enough to climb over and jump off, but that doesn't make it a good idea to do so. There's nothing stopping a person from putting their hand on a hot burner, but the consequences are obvious. It's unfortunate that some people never quite grasp that being able to do something doesn't make it right.
Old 12-24-2005, 03:08 PM
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Default RE: changing frequency crystal in radio

ORIGINAL: exeter_acres

synthetic or castor?
Yes!
Old 12-24-2005, 04:15 PM
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suitcase
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Default RE: changing frequency crystal in radio

I can live with that!
ORIGINAL: TLH101

ORIGINAL: suitcase

By the way,,,,,,,,,,,,,,,,,,,,what fuel should I use?????????????
Other people's.[sm=spinnyeyes.gif]
Old 12-24-2005, 08:16 PM
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Default RE: changing frequency crystal in radio

"So why the manufacturers make crystal on Tx removable by user? I think if prohibited, Tx crystals should be fixed so only can be changed by services ,not simply users."

Piper_chuck pretty much answered why the logic behind ease or capability does not equate to legal or smart. Technically, the XTAL is not user accessible as it will be behind a plastic cover. Sure, the cover pops right off, but that doesn't make is a user changeable item.

I've covered this before in other threads, but I'll give a quick explanation again as to why the XTAL is easy to get to, even if we aren't supposed to be messing with it. The FCC regulates the RF spectrum to ensure it's proper use, to guarantee critical communications are interference free, that equipment is radiating only on proper frequencies, etc. However, it makes an attempt to not get in the way of progress and does not want to needlessly hinder manufacturers of radio equipment. To ease the cost of lab certification and to help makers get products to market faster and cheaper, it will allow a single TX to be certified on multiple frequencies, with a xtal change being the freq switching method. This however does not mean a TX is certified across all frequencies, just that with proper tuning, it will meet the certification standards on each freq individually. This can greatly lower the manufacturers cost and gives them more flexibility as they can sell one certified unit (as opposed to having to make 50 different models for all the 72MHz bands), but change the freq as needed at the factory. The downside of all this is the XTAL is often easy for the user to pull and fiddle with.

There have been other cases I know of via my FCC relatives where radios could easily be changed illegally by the user. The FCC finally cracked down and revoked the certification on the radios because the abuse was rampant. The result was higher radio costs as the manufacturer was not allowed the flexibility it used to enjoy. We don't want that to happen to our radios.

As was answered previously, a hobby freq checker is not a valid check for certification. You have no idea on your power output, and unwanted RF.

Again, if on 72MHz and you want to change your freq will nilly, just get a radio that supports modules or has a synth. Very simple solution.

Cheers.
Old 12-24-2005, 10:16 PM
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Default RE: changing frequency crystal in radio

I think I hear the sound of one hand clapping.......... ;^)
Old 12-24-2005, 10:24 PM
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Default RE: changing frequency crystal in radio

No you don't[:-]



that sound is the sound of a tree falling in the forest.... but none of us were there!

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