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-   -   JR crystals (https://www.rcuniverse.com/forum/beginners-85/8445187-jr-crystals.html)

richardci 02-06-2009 11:47 AM

JR crystals
 
Have any of you used the "JR Single Conversion 72Mhz FM Crystal Set by Performance Devices" They are sold on ebay. I would like any feedback on their Performance compared to original JR crystals. Is there any problem mixing a tx crystal from one of these sets with a JR original crystal in my rx (or visa versa)? I am using a JR 421XF and a JR SX600 transmitter. My receivers ar JR R600's.
Thanks for any info,
Richardci

mclina 02-06-2009 11:57 AM

RE: JR crystals
 
You shouldn't be replacing TX crystals yourself. It is illegal. (RC Ken frequently cites the exact verbage)

How much cheaper are these crystals than actual JR crystals? Last time I bought a RX crystal, I think it was only $6-8. I don't think I would risk a plane to save a couple dollars on a third party crystal.

Good luck.

mclina 02-06-2009 12:00 PM

RE: JR crystals
 
Here is the ebay listing for a typical set:

http://cgi.ebay.com/JR-Single-Conver...3A1%7C294%3A50

I don't see any mention of getting your TX retuned.....

mclina 02-06-2009 12:05 PM

RE: JR crystals
 
I guess, to be fair, Horizon doesn't mention anything when they sell you the set either:

http://www.horizonhobby.com/Products...ProdID=JRPXF50

It looks like about a $12 savings for a set.

RCKen 02-06-2009 12:12 PM

RE: JR crystals
 
In the United States it is illegal to change the crystals in the transmitter unless you are licensed to do so. This must be done at a licensed shop that can check and retune the output of the transmitter.

If you are interested in the full text of the regulations concerning this matter they can be found at:

[link=http://www.access.gpo.gov/nara/cfr/waisidx_04/47cfr95_04.html]FCC Title 47, Part 95 - Personal Radio Services[/link]

Copied from Futaba's website

How do I change the frequency of my transmitter?
For a unit with crystals: We CANNOT recommend changing crystals to a different frequency. Changing the crystal on your transmitter is illegal unless you have the proper license. The FCC has established guidelines for the modeler's safety and for the safety of spectators. For safety and FCC reasons we must request that both TX and RX be sent to the service center to ensure proper crystal change and retuning to the new frequency. Crystal based radios cannot be converted to another band without parts replacement, and may not be able to be converted at all. Certain radios can be converted, for example, from 72 to 75MHz. Please contact the service center for any other conversions.
The applicable Federal Regulation is as follows:
TITLE 47—TELECOMMUNICATION COMMISSION (CONTINUED)
PART 95—PERSONAL RADIO SERVICES

Subpart E—Technical Regulations
Sec. 95.645 Control accessibility.
(a) No control, switch or other type of adjustment which, when
manipulated, can result in a violation of the rules shall be accessible
from the transmitter operating panel or from exterior of the transmitter
enclosure.
(b) An R/C transmitter which incorporates plug-in frequency
determining modules which are changed by the user must be certificated
with the modules. Each module must contain all of the frequency
determining circuitry including the oscillator. Plug-in crystals are not
considered modules and must not be accessible to the user.

Copied from FCC regulations concerning this issue


[Code of Federal Regulations]
[Title 47, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR95.221]
[Page 539]
TITLE 47TELECOMMUNICATION CHAPTER IFEDERAL COMMUNICATIONS COMMISSION (CONTINUED)
PART 95_PERSONAL RADIO SERVICESTable of Contents
Subpart C_Radio Control (R/C) Radio Service
Sec. 95.221 (R/C Rule 21) How do I have my R/C transmitter serviced?
(a) You may adjust an antenna to your R/C transmitter and you may make radio checks. (A radio check means a one-way transmission for a short time in order to test the transmitter.)
(b) You are responsible for the proper operation of the station at all times and are expected to provide for observations, servicing and maintenance as often as may be necessary to ensure proper operation. Each internal repair and each internal adjustment to an FCC certificated R/C transmitter (see R/C Rule 9) must be made in accord with the Technical Regulations (see subpart E). The internal repairs or internal adjustments should be performed by or under the immediate supervision and responsibility of a person certified as technically qualified to perform transmitter maintenance and repair duties in the private land mobile services and fixed services by an organization or committee representative of users in those services.
(c) Except as provided in paragraph
(d) of this section, each internal repair and each internal adjustment of an R/C transmitter in which signals are transmitted must be made using a nonradiating (``dummy'') antenna. (d) Brief test signals (signals not longer than one minute during any five minute period) using a radiating antenna may be transmitted in order to:
(1) Adjust a transmitter to an antenna;
(2) Detect or measure radiation of energy other than the intended signal; or
(3) Tune a receiver to your R/C transmitter.

(Secs. 4(i) and 303(r), Communications Act of 1934, as amended, 47 U.S.C. 154(i) and 303(r), and sec. 553 of the Administrative Procedures Act, 5 U.S.C. 553) [48 FR 24890, June 3, 1983, as amended at 49 FR 20673, May 16, 1984; 63 FR 36610, July 7, 1998]


[Code of Federal Regulations]
[Title 47, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR95.222]
[Page 539-540]
TITLE 47TELECOMMUNICATION
CHAPTER IFEDERAL COMMUNICATIONS
COMMISSION (CONTINUED)
PART 95_PERSONAL RADIO SERVICESTable of Contents
Subpart C_Radio Control (R/C) Radio Service
Sec. 95.222 (R/C Rule 22) May I make any changes to my R/C station transmitter?

(a) You must not make or have anyone else make an internal modification to your R/C transmitter.
(b) Internal modification does not include:
(1) Repair or servicing of an R/C station transmitter (see R/C Rule 21, Sec. 95.221); or
(2) Changing plug-in modules which were certificated as part of your R/C transmitter.
(c) You must not operate an R/C transmitter which has been modified by anyone in any way, including modification to operate on unauthorized frequencies or with illegal power. (See R/C Rules 9 and 10, Sec. Sec. 95.209 and 95.210.)
[48 FR 24894, June 3, 1983, as amended at 63 FR 36610, July 7, 1998]


[Code of Federal Regulations]
[Title 47, Volume 5]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR95.645]
[Page 561]
TITLE 47TELECOMMUNICATION
CHAPTER IFEDERAL COMMUNICATIONS
COMMISSION (CONTINUED)
PART 95_PERSONAL RADIO SERVICESTable of Contents
Subpart E_Technical Regulations
Sec. 95.645 Control accessibility.
(a) No control, switch or other type of adjustment which, when manipulated, can result in a violation of the rules shall be accessible
from the transmitter operating panel or from exterior of the transmitter enclosure.
(b) An R/C transmitter which incorporates plug-in frequency determining modules which are changed by the user must be certificated
with the modules. Each module must contain all of the frequency determining circuitry including the oscillator. Plug-in crystals are not
considered modules and must not be accessible to the user.
[53 FR 36789, Sept. 22, 1988. Redesignated at 61 FR 28769, June 6, 1996, and further redesignated at 61 FR 46567, Sept. 4, 1996; 63 FR 36610, July 7, 1998]

carrellh 02-06-2009 12:20 PM

RE: JR crystals
 
1 Attachment(s)

ORIGINAL: mclina
I guess, to be fair, Horizon doesn't mention anything when they sell you the set either:
http://www.horizonhobby.com/Products...ProdID=JRPXF50
It looks like about a $12 savings for a set.
JR Manuals do have the "crystal change" warning.

opjose 02-06-2009 12:26 PM

RE: JR crystals
 


ORIGINAL: richardci

Have any of you used the "JR Single Conversion 72Mhz FM Crystal Set by Performance Devices" They are sold on ebay.

Richardci
Several things:

- As already posted you must NOT change the TX crystal. On JR radios 7channel plus radios, you can purchase pre-tuned TX "modules" that permit you to change the channels however.

- DO NOT attempt to change the TX channel by merely swapping out the crystal. Not only is it illegal, but you'll get reduced power output, and also cause sideband signals to be transmitted, that can shoot down other planes at your field.

- The crystals you found on Ebay are sold by various vendors. The OEM company that manufactures them DOES make them specifically for JR sets.
As such they CAN be used SAFELY on the receivers, provided you purchase the right set.

- There are sets of those crystals for the "single conversion" receivers which JR sells, such as the 6UL, and for the full range receivers. You must purchase the correct crystal!

- The crystal for say an R700 receiver is called "dual conversion JR" from that company... however IT IS NOT Dual conversion... and neither is the JR receiver! This is a misnomer, but it does help to identify which crystal goes with which receiver as the single/dual conversion conventions are used by other vendors.

- I've used those JR specific crystals extensively on various JR receivers w/o problems... I've also tested the results with a graphic frequency checker. They provide the same power output and performance as the original JR crystals.

- NORMALLY you cannot use crystals from other vendors this way. This particular vendor is an exception! They engineered their stuff specifically to suit replacing the OEM's crystals.




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