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do it yourself tuning?

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Old 08-26-2003, 05:14 PM
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barrywhite
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Default do it yourself tuning?

ive been in this hobby for about 20 years and my first radio was the fantastic futaba M series which was am and never experienced glitches with it,i think it had avery high Rf output judging the complaints of my sister complaining that the tv was going crazy when i turned it on.in all these years everybogdy talks about tuning radios......does anybody know where in the internet can i get understandable guide that teaches how to......i dont live in the US andwhere i live(italy) we do not have strist rf rules and fly on my own so am not worried about adjacent band interference......in fact in italy everbody changes tx an rx xtals and dfoesnt have the slightest clue about having to reallign fr emission after a crystal change...thanks...i would like to tune my iown eqipment just for the satisfaction of it.
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Old 08-26-2003, 09:02 PM
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strato911
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Default Re: do it yourself tuning?

Originally posted by barrywhite
......in fact in italy everbody changes tx an rx xtals and dfoesnt have the slightest clue about having to reallign fr emission after a crystal change...
I can't help you with tuning instructions, but I would like to poin out that in North America, we have PAYING industrial users interleaved between each of our RC channels, while everywhere else they have a frequency band DEDICATED for their RC use. If your Tx is slightly off frequency, you only affect fellow RC'ers. Here in North America, if we are slightly off, we risk causing havoc for the industrial users, including the potential to cause remote cranes dropping their load on someone. That's why the FCC prohibits it.
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Old 08-26-2003, 11:57 PM
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A remote crane will never drop it's load on someone =) OSHA has it's standards too. Something like a crane would have to have failsafe's setup and I'm sure there would be some sort of coded PCM signal not standard RC signals, just the frequencies are the same. Barry, in order to do tuning the main thing you need is access to a decent quality spectrum analyzer, only problem is those things cost many many thousands of dollars. Try looking up local HAM clubs or RF repair shops around to see if they have one that you could use. I can't give you exact information on how to trim them either but I do know that it's simply a matter of tweaking those small metalized blocks with tiny little slot style screw's on the top. They're trimmer caps and trimmer resistors to fine tune the RF stage. Most tx's may have goop covering the top to prevent regular vibration from interfering. Problem is I don't know the proper tuning procedure, that will be more difficult to find. All you do is look at the output on the spectrum analyzer and follow the procedure of turning the knobs in a certain order only a certain amount until you find the spot that gives the least amount of off band noise and peek power.
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Old 08-27-2003, 03:06 PM
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strato911
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Originally posted by Lynx
A remote crane will never drop it's load on someone =) OSHA has it's standards too. Something like a crane would have to have failsafe's setup...
OK, I admit my example was a bit extreme, but it was meant to portray the potential dangers involved if we don't follow proper tuning procedures. Even a PCM signal, with failsafe and redundancy can fail - never is a strong word...
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Old 08-28-2003, 01:52 AM
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When I meant never I meant they had a WAY better failsafe system. Like true CRC32 error correction with parity and other bells and whistles. The chances of a commercial system actually receiving a false packet are probably as close to 0 as a mathematician will admit to. Granted we can still cause an interruption in a few construction worker's day. And that's expensive =>
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Old 08-28-2003, 02:11 PM
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Rodney
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Default do it yourself tuning?

Barrywhite, there are probably some amateur radio operators or clubs in your area. Check in with one of them. In most cases they would be glad to assist you and some one of them may even have the necessary equipment you could use.
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Old 08-29-2003, 07:41 PM
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Thanks for the feedback guys..i know one has to be extremely careful about having the transmitter on tune but theres no reason why if..we perform the procedure carefully..that we shouldnt do it ourselves , after alll thats what a hobby is all about,and maybe the result would be even better because my doubt is that..especially in he case of mass produced cheap 4 channel units would benefit from reglar or careful tuning, after all those coils are subject ,,maybe to temperature related variations,,and maybe they are not tuned carefully in the first place..ie short rande or glitches with brand new cheap eqipment...it would be nice to have procedure bnluenotes from the manufacturars or from some experienced rf engineer in the internet..and ive heard of some addon computer boards that make a personal computer a spectum analyzer but dont know where to buy them..any ideas guys?
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Old 08-29-2003, 09:28 PM
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Can't Barry, it's illegal, FCC won't allow that kind of thing. There's a very good reason, no matter how good the instructions are if some idiot does it the wrong way not matter how hard they think they did it right it will happen a lot. If you're serious about doing it yourself you'll have to find out from the FCC what type of license you need to get in order to legally tune them.
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Old 08-29-2003, 10:29 PM
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What are the legalities in Italy?
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Old 08-30-2003, 05:43 AM
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Not a clue, you'd have to look up the local RF regulator agency.
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Old 08-30-2003, 01:24 PM
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Quote:
"A remote crane will never drop it's load on someone =) OSHA has it's standards too. Something like a crane would have to have failsafe's setup and I'm sure there would be some sort of coded PCM signal not standard RC signals, "

Soory ,not at all true . Me thinks you presume far too much. Actually there are controls still in use that are very rudimentary.
As far as tuning the vague "trimmers and pots" is of little use as well . I doubt the person in question has easy access to a spectum analyzer and just as well . Tuning for "maximum " clean output can and does result in an oscillator that may fail to start or even drop out . The power on most transmitters should be backed off ever so slightly from max power to assure stable ,reliable operation . The bandwidth or deviation level is set by the drive level from the encoder section.
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Old 08-30-2003, 09:15 PM
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barrywhite
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Default do it yourself tuning?

well lynx and avinut i dunno exactly what the rf laws are in italy...apart from the fact that as lomng as we are on the 40 or 35 mhz band we can stick any crystal in our transmitter anyone suggesting that this could cause a problem is regarded as a nut..even shopkeepers l;iberally swap crystals on the customers request!!!! once i needed a tx with a different xtal ..the shopkeeper simply changed it...on my query that this might cause problems the shopkeeper as if i was me like im a hyper precise nut...besides here we have laws like putting seatbelts on but nobody could care less ..its kind of live and let live...in fact sometimes i do have problems convincing other modellers that one should be more scientific in modelling!!!!!!!!!!!!!!ofcourse there are exceptionjs u know marconi did invent rf.....i think
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Old 08-30-2003, 11:19 PM
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Default do it yourself tuning?

Different laws in USA, and the AMA regulations as well.

Don't know if it is legal for you tune your own radio in Italy. Even so, there is a lot to tuning. Besides tuning for max output and proper frequency of both the low side and high side of the modulation carrier (in FM/PPM/PCM systems), you must worry about the proper current drain of the deck. If you tune it wrong, you can cause premature death of the output transistor, possibly in flight.

The spectrum analyzer and current meter (multimeter) are easy to come by if you have money, knowledge and skill are not. I would find someone experienced and qualified to do this task. It is money well spent.
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Old 08-30-2003, 11:40 PM
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strato911
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Default do it yourself tuning?

Originally posted by barrywhite
...as long as we are on the 40 or 35 mhz band we can stick any crystal in our transmitter ...
I've said it before (in other threads), and I'll say it again:

In North America it is illegal to swap transmitter cystals.

It is perfectly legal in most other countries, because they have a DEDICATED frequency band, with no other users interleaved between their frequencies like in the US.
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Old 09-02-2003, 06:01 PM
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barrywhite
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hey lady flyer i know its off topic but ive been looking for a way to down "tune" my taxes too..i think thats not allowed either ....chukle
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