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08-09-2009, 12:04 PM | #1 |
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I am: Geoff B
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Hitec focus 4 question
hello all, i'm setting up a trainer for my dad and am wondering if i can swap TX crystals between 2 focus 4 radios i have. I'd be going from 32 to 53. Not to sure but i thought there was some issues with the specific tuning of the radio or something like that.
thanks geoff
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08-09-2009, 12:20 PM | #2 | |
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Re: Hitec focus 4 question
It's not allowed in U.S. (can't find specific rules for us) but this is from the futaba site (I know, not hitec but it's one source)
Quote:
Although you can probably do it and test-fly on a "junker", it may be enough out of phase to affect another flyer on the next frequency up/down. Other threads I've found suggest it's only the U.S. that forbids user-changes, that other countries allow it. Here's a thread about futaba crystal changing (again, U.S.) http://www.rcuniverse.com/forum/m_89...tm.htm#8963672 And from the Hitec forum on the "other site" http://www.rcuniverse.com/forum/m_8867891/tm.htm Last edited by voyager_663rd; 08-09-2009 at 12:39 PM. |
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08-09-2009, 04:55 PM | #3 |
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Re: Hitec focus 4 question
the spectra module then is an illegal mod. to both Hitec and Futaba. I cna buy the module to cover all the channals.
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08-09-2009, 07:07 PM | #4 | |
RCC Apprentice
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Re: Hitec focus 4 question
Quote:
As additional proof, when you purchase Futaba receivers without crystals, you buy them either low-band or high-band, so obviously there is something different about them out of the box. However, I don't have any info on whether you can make large jumps with the transmitter - I've always brought the receivers in line with the transmitter, not the other way around. Personally I would play it safe and only change either receiver or transmitter crystals within their high or low band. |
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08-09-2009, 07:53 PM | #5 |
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Re: Hitec focus 4 question
To the best of my knowledge the 'HI<>LO' thing only applies to Futabas - most all dual conversion, and the newer single conversion receivers. While it is a pain in the proverbial, I can see the reasoning behind it and stick with it but again to the best of my knowledge it does not apply to most other popular brands.
I have some experience in these things and I would not hesitate to swap x-tals from one HiTec Tx to another HiTec if they are approximately the same age, and certainly if they are the same models. BUT DO A GOOD RANGE CHECK AFTER YOU HAVE DONE THIS and do the change carefully - x-tals are possibly the most delicate parts in our radios and don't usually survive dropping or knocking about - the little quartz disc in there is only a few thou thick! Also I'd use only the proper Hitec Tx crystals. Does that help?? |
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08-09-2009, 08:22 PM | #6 | |
RCC Apprentice
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Re: Hitec focus 4 question
Quote:
Somebody with more RF knowledge than me would have to chime in on that though - I don't know how tight the spacing really is, with respect to the tolerances the transmitters are built to. |
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08-09-2009, 08:49 PM | #7 |
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Re: Hitec focus 4 question
If you can point me to a statement by other manufacturers that they too have a 'HI<>LO' separation, I would appreciate it.
Someone with a modicum of RF knowledge has chimed in - me - a lifetime of work with transmitters of all sizes, frequencies and power, and receivers of most configurations and with radio control systems from 1948/49 or thereabouts to the present, gives me the confidence to make the statements I have. As far as I'm concerned it is only Futaba that I know of, that has this HI-LO thing and that I'm sure it is because they feel that the span of Channel 11 to Channel 60 (virtually one whole megahertz and twice the IF of a single conversion receiver) is a mite too broad to guarantee good selectivity and so tune up their things around the center of the LO band and also the center of the HI band. I'm not going to confound the issue by going into Image Rejection, Band-width and Selectivity or even Adjacent Channel Interference about which you seem concerned, but can only say that it would be down-right irresponsible of me to make the statement I did if I did not know better. I hope that helps?? |
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08-09-2009, 09:29 PM | #8 |
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Re: Hitec focus 4 question
Geoff, I have gone from a CH50 to a CH41 on a Futaba Skysport 4ch with no problems. Just make sure to give it a good range check. I am flying the Ultrastick on CH41 now and the TX was originally CH50. Flew it for an hour today with zero problems.
Curt
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08-09-2009, 09:39 PM | #9 | |
RCC Apprentice
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Re: Hitec focus 4 question
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