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Changing tx/rx crystals

Old 03-05-2003, 06:38 PM
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why2cay
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Default Changing tx/rx crystals

I have a 6da Futaba system on channel 28. I am interested in gettin a set of crystals for a different low band channel, but havesen something to te effect that the radio needs to be
retuned. Do I have to send the radio in or can this be done yourself

Thnks for your help

Steve
Old 03-05-2003, 06:41 PM
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Crashem
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Default Changing tx/rx crystals

In the USA changing TX Freq can only be done legally by a certified repair depot. You can change the Rx crystal legally
Old 03-05-2003, 09:35 PM
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staggerwing
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Default Change the Crystal

If you don't have to open the transmitter to change the crystal, then you may go ahead and do it legally. What you cannot do is retune a transmitters final output, or place it on a different frequency that is out of the 72 Mhz band.
Old 03-06-2003, 12:30 AM
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Stick Jammer
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Default Changing tx/rx crystals

Not sure if Tower Hobbies is 100% correct on this but here's a quote right from their website:


*Transmitter Crystals Can Not be changed to another channel except
by a licensed service center. It is against FCC regulations, and
illegal for the user to change a frequency determining component
of a transmitter. If the radio is not retuned, it can be a hazard
spectators, modelers or property, and void AMA insurance coverage
Old 03-06-2003, 05:34 AM
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David Cutler
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Default Re: Change the Crystal

Originally posted by Staggerwing
If you don't have to open the transmitter to change the crystal, then you may go ahead and do it legally. What you cannot do is retune a transmitters final output, or place it on a different frequency that is out of the 72 Mhz band.
I think you'll find this isn't true.

You can't change the TX crystal yourself, wherever it is.

See another thread in this forum. (can't remember it, but Mike from Hitec was involved)

-David C.
Old 03-06-2003, 03:06 PM
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Crashem
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Default Changing tx/rx crystals

StaggerWing,

In the USA there are only two ways that the owner of a TX can legally change his/her freq that I know of. A licencsed Ham operating on the 50Mhz band or owning a 72Mhz band radio that is designed to be changed by the user such as the Hitec Spectra module equiped radios.

I do believe that unless you fall into either of these two catagories that any such modification is against FCC regulations
Old 03-09-2003, 03:47 AM
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cublover
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Default Changing tx/rx crystals

i went from 40 to 15 and no problems....i changed them myself..i guess im waiting for the cuffs...LOL...just seems to be to much bull in the AMA...hmmmmmm..Rod
Old 03-09-2003, 04:58 AM
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JohnBuckner
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Default Changing tx/rx crystals

Originally posted by cublover
guess im waiting for the cuffs...LOL...just seems to be to much bull in the AMA...hmmmmmm..Rod [/B]
To start out with this is not about the AMA it is in fact about FCC regulation (law) and it has nothing to do with your radio working or not. It has everything to do with us impeding on primary users within our band and we are not the primary users! There is a real danger and threat to our use of the entire band if this kind of attitude continues.

If you blatently swapped at our field or any of the events of which I CD then you would be politely but firmly asked to put your aircraft away or leave.

John
Old 03-09-2003, 05:07 AM
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David Cutler
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Default Changing tx/rx crystals

Originally posted by cublover
i went from 40 to 15 and no problems....i changed them myself..i guess im waiting for the cuffs...LOL...just seems to be to much bull in the AMA...hmmmmmm..Rod
cublover eh?

Shame if you couldn't fly your lovely cub anymore, and we all have to give up because we have lost the 72 Meg bands. That attitude could easily get us all in that position.

The law isn't there for no reason at all, as an idle threat. If you change your crystal yourself, you could easily be bleeding over to other channels and sticking your friend's $2000 quarter scale cub or $9000 jet into the ground.

. . . LOL now?

David C.
Old 03-09-2003, 12:43 PM
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cublover
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Default Changing tx/rx crystals

relax guy's...geeze...this was done by a friend,,that doesnt work at futaba, air, or jr.. he is a electronics specialist..and im sure there wont be a prob..
Old 03-10-2003, 06:17 PM
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staggerwing
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Default From The FCC

Radio Maintenance and Repair
You need a commercial radio operator license to repair and maintain the following:


All ship radio and radar stations.

All coast stations.

All hand carried units used to communicate with ships and coast stations on marine frequencies.

All aircraft stations and aeronautical ground stations
including hand-carried portable units) used to communicate with aircraft.

International fixed public radiotelephone and radiotelegraph stations.
You do NOT need a commercial radio operator license to operate, repair, or maintain any of the following types of stations:


Two-way land mobile radio equipment, such as that used by police and fire departments, taxicabs and truckers, businesses and industries, ambulances and rescue squads, local, state, and federal government agencies.

Personal radio equipment used in the Citizens Band, Radio Control, and General Mobile radio services.

Auxiliary broadcast stations, such as remote pickup stations.

Domestic public fixed and mobile radio systems, such as mobile telephone systems, cellular systems, rural radio systems, point-to-point microwave systems, multipoint distribution systems, etc.

Stations that operate in the Cable Television Relay Service.

Satellite stations, both uplink and downlink of all types.

NOTE: Possession of a commercial radio operator license or permit does not authorize an individual to operate amateur radio stations. Only a person holding an amateur radio operator license may operate an amateur radio station.


The FCC does not certify radio repair shops for RC equipment.

From the FCC website.
Old 03-10-2003, 08:15 PM
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Crashem
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Default Changing tx/rx crystals

Staggerwing,

Nice post from the FCC.. I guess eveyone else on this board (including the hitec and Futuba reps) has been wrong.

Bad or incorrect advice is and allways will be the drawback of these types of sites.
Old 03-10-2003, 08:45 PM
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staggerwing
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Default No Editors

Crashem

There are no editors on the internet.

Actually, the FCC does not keep all of the rules and regulations up-to-date with each other. When I got my Commercial FCC ticket, any and all transmitting equipment except for the Hams had to be repaired/adjusted by a Commercial tech. Not so any longer as you can see from the post.
Old 03-11-2003, 09:09 AM
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Steve Lewin
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Default Changing tx/rx crystals

Could you give us the precise URL of that information on the FCC website ?

Unfortunately one of the other drawbacks of the internet is that anyone can post anything they like and claim it came from someone in authority. Not that I'm suggesting that's what you did, simply that I'm much happier when I can read things at source and, for example, see them in their original context.

Steve
Old 03-11-2003, 03:27 PM
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staggerwing
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Default FCC URL

No problem. Go to http://wireless.fcc.gov/commoperators/
Old 03-11-2003, 07:50 PM
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strato911
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Default Changing tx/rx crystals

Staggerwing - changing the crystal to alter the broadcast channel isn't "maintenance or repair". Swapping a crystal to another frequency is in fact an alteration of the tranmission circuit. Maintenance or repair would cover replacing a crystal with another of the same frequency.
Old 03-11-2003, 08:44 PM
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Default Changing tx/rx crystals

Originally posted by cublover
i went from 40 to 15 and no problems....i changed them myself..i guess im waiting for the cuffs...LOL...just seems to be to much bull in the AMA...hmmmmmm..Rod
You might want to rethink that practice:
Sec. 95.218 (R/C Rule 18) What are the penalties for violating these rules?

(a) If the FCC finds that you have willfully or repeatedly violated
the Communications Act or the FCC Rules, you may have to pay as much as $10,000 for each violation, up to a total of $75,000. (See Section 503(b) of the Communications Act.)
(b) If the FCC finds that you have violated any section of the
Communications Act or the FCC Rules, you may be ordered to stop whatever action caused the violation. (See section 312(b) of the Communications Act.)
(c) If a federal court finds that you have willfully and knowingly
violated any FCC Rule, you may be fined up to $500 for each day you committed the violation. (See section 502 of the Communications Act.)
With fees like that, you won't be able to afford flying your cubs anymore. :stupid:

http://ftp.fcc.gov/Bureaus/Engineeri...98/47cfr95.pdf
The RC rules (Part95 - subpart C) starts on page 23 till 31
Old 03-11-2003, 09:46 PM
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Default Changing tx/rx crystals

ok...my head is spinning here :spinnyeye

so, if i have a rx and tx on channel 25 and I crash the plane and damage the crystal in the rx, I can't take a crystal out of a rx on channel 15 and take the crystal out of the tx on 15 and swap it with that one that was on 25 and go flying? same radio, same reciever, just 2 new crystals. what if I buy a new set of crystals on 25...Can i put these in and go flying?
Old 03-11-2003, 10:22 PM
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staggerwing
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Default 75 mhz.

Not saying they are right, but seemingly the RC car and boat folks aren't worried. If you have never been to an RC car event, these guys change crystals between races. Most racers have five or six sets of crystals so that they can avoid conflicts as they move from heat to heat. Guess they'll kill the RC goose before fliers do.

I deal with FCC rules and regulations every day. The FCC does not have the time/man power to keep the rules and regulations up to date. The rules written for RC in Part 95 were written at a time when the FCC required changes to be made by a FCC licensed technician. The rules about technicians have been changed, but Part 95 has not. So the queston is, "what is a Licensed service center?" Who licenses them? My guess is they are "certified" by manufacturers to do warranty work.

For my part, all of this isn't a problem. I fly (legally) on 50 mhz (Extra Class) and have the commercial ticket.
Old 03-11-2003, 10:24 PM
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David Cutler
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Default Changing tx/rx crystals

Originally posted by smchale
ok...my head is spinning here :spinnyeye

so, if i have a rx and tx on channel 25 and I crash the plane and damage the crystal in the rx, I can't take a crystal out of a rx on channel 15 and take the crystal out of the tx on 15 and swap it with that one that was on 25 and go flying? same radio, same reciever, just 2 new crystals. what if I buy a new set of crystals on 25...Can i put these in and go flying?
You are allowed to change the crystal in the receiver to match the transmitter, but not change the transmitter crystal to change the channel.

This is partly because just changing the crystal in the transmitter doesn't necessarily complete the move to a different frequency, as it might take a little tuning in the RF output to get it exactly right. The channels we use are very narrow band, and any compromise in the output frequency might bleed over to an adjacent channel.

If some form of module is used (e.g. the Spectra in the Hitec) then it's quite OK to change the channel, but that's because these modules are not just simply using a different crystal.

Actually the frequency stated is the superhet frequency, which is a more complex process of transmission than just creating the frequency for the receiver crystal to respond to.

But that's a subject for another thread!

David C.
Old 03-11-2003, 11:27 PM
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Default Changing tx/rx crystals

My experience with RC cars has proved to me that it is necessary to stay within 3 channels above or below the original frequency the transmitter was programed for. Anything above or below this frequency split can result in intermittent glitching or total loss of control. Good thing I learned this lesson on the ground and not in the air!! I always stay on the the frequency my airplane transmitters came with.
Old 03-12-2003, 05:24 AM
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Default Re: 75 mhz.

Originally posted by Staggerwing
Not saying they are right, but seemingly the RC car and boat folks aren't worried.
Since I only use RC for flying, I have never concerned myself with the minor details regarding the 75MHz band. Do they also have industrial users interleaved between their channels? They are the main reason for concern when pilots change the transmitter crystal. A spurrious signal can cause all kinds of havoc with industrial equipment, INCLUDING REMOTE EXPLOSIVES.
Old 03-12-2003, 08:50 AM
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Default Changing tx/rx crystals

Originally posted by smchale
ok...my head is spinning here :spinnyeye

so, if i have a rx and tx on channel 25 and I crash the plane and damage the crystal in the rx, I can't take a crystal out of a rx on channel 15 and take the crystal out of the tx on 15 and swap it with that one that was on 25 and go flying?
No you can't but you can put the ch15 crystal in the Rx and fly the plane with the Tx which is already on ch15. It's only transmitters you're not allowed to mess with.

Steve
Old 03-12-2003, 09:26 PM
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Default Changing tx/rx crystals

thanks guys, that clears it up for me!

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