tomegan

My Feedback: (4)

I have done a little research the past two days into this contraversal tx chrystal changing topic. I had purchased a new JR radio that was not shipped to me on the channel I use.Though i have in my appinion little R/C experiance (3 years)I have x-tal swaqpped before and all was well.When a club member heard I was going to change x-tals on my new tx he informed me it is illeagle to do myself and to mail it in.I decided to do what I read here on RCU and make up my own mind.Our field is across the freeway from a hospital undergoing remodeling.Within 15 minutes of having a great day with my eyes in the sky, a "flight of life helicopter"was about to land with a little girl aboard scheduled later that evening for a kidney transplant.I heard this hellacious crashing/banging/slaming noise,I literally felt the ground shake I turned just in time to see the blades bust apart as they hit the roof top.At that same very moment the crane opperator was swinging a very large steel I-beem and was unable to stop the load resulting in smashing into an occupied part of the hospital,(keep in mind I still have a plane in the air)With all the excitement going on I was trying to land as fast as I could.My plane seemed to have a mind of its own, it was very "irradic". At first I thought it might be a gust of wind as it was a little breezy that day.Second thought was the new controller ,mabey I just wasnt used to it? I wish that was the case. Turns out a little girl and a "flight for life" crew of 4 had to die for my neggligence/incompatance/ignorance.Its hard to live with ,beleive me.If for any reason you would like to check the valadititty of my experiance,I'm sorry, but you can't as I just made this crap up as I typed along.Same as many of you are doing when you give us "newbies" your replies.Do some research fellas,and quit being so darn contankerous.It clearly states in every tx manuel changing the chrystal is a vialation of fcc rules. says nothing of a vialation of any laws.In the old days it was dangerous.Today all transmitters are "tuned" to channel 30.Don't believe me ? call the service dept and ask. Thats all it takes. Want to keep all the contankerous ole farts happy? Then send it in.It only takes 30-40 bucks.This information in no way violating any laws or rules

Tom
note: RCU ghestapo has edited this message

P.S please don't try to correct me on any spelling as it won't do any good.I prefere flying over reading an riting

Mad Mad Max

Maybe try a ball of string and two tin cans. Works great!!

wings

Hmm guess the rules that the FCC (Federal Communications Commission) have aren't import.


I guess committing a federal offense isn't breaking a law.


I do like the ball of string and tin cans idea, makes much more sense.

Is that legal Max?

carrellh

Some of what is written on this subject is semantics.

This may not be exactly right, but a tax attorney told me this.

IRS regulations are not laws. Congress passed laws giving IRS authority to create the regulations but the regulations themselves are not laws. So, violating them is not breaking a law. However, the regulations "carry the force of law" and you can be fined or imprisoned for violating them. Whether you committed a 'crime' or not you can still be severely penalized.


The same applies to FCC. Whether or not violating the regs is breaking a law doesn't really matter. The regulations carry the force of law and you can still be severely penalized. Is an FCC agent likely to show up where you're flying and slap on a set of handcuffs over changing a crystal? No.


The real risk is a personal injury, or property damage, lawsuit. If you crash, for any reason at all, and someone sues you over it; and your insurance carriers (homeowners and AMA's) are smart enough to figure out you swapped crystals without getting the transmitter retuned, you will be on your own in court.

That is a worst case scenario that is not likely to happen, but it CAN happen and that's why it is smart to get the transmitter retuned.

tomegan

My Feedback: (4)

100 % agree, I am to undrestand with that all new transmitters there is no chance of danger to anything but the aircraft on that channel,however I also understand it is not only a rule of the fcc but more importantantly the AMA. All members should be abiding by the rules written for our protection (AMA not fcc) however non AMA members (rogue park flyers) should be able to get the information there seeking(with out the answers being edited)for any reason.. no matter how lame.thanks for your input,now i must go and finish cutting the tags off my pillows.
Tom

LSF2298

My Feedback: (4)

Don't think the FCC can enforce its RULES, take a look a this site and look closely at the ones labeled NAL.

http://www.fcc.gov/eb/FieldNotices/

tomegan

My Feedback: (4)

I see nothing about chrystal swapping on this page ,with all the chrystal swapping going on in the world can anybody validate an actual casualty,or fine/imprisonment,or perhaps a boken toenail? HMMmm. If so thats what should be posted.

BarracudaHockey

My Feedback: (11)

It doesn't matter what happens in the rest of the world. What matters is 72 mhz aircraft band in the US. There are commercial users sandwhiched between our channels, they really don't care if you shoot down another model airplane, interfere with the commercial users and they complain, the FCC will come find you and its 10 grand per occurance/day fine.

As someone else said, cause an accident that results in an insurance investigation and the AMA and your home owners insurance will be sending you thank you cards if they find out you swapped crystals without retuning.

tomegan

My Feedback: (4)

O.k then ,the 72 band here in the US.Can you please show of a tragidy from x-tal swapping? Mabey you can't becouse were all abiding by the rules?

Mad Mad Max

tomegan, maybe a P-51 in the trees . . . . .

tomegan

My Feedback: (4)

1- get your memery straight, it was 9 trees.and I believe it was only the big one that did most the damage. 2- that was a transmitter with the factory chrystal installed. hey rick,I'm going to be doing some radio testing today that will answer a lot of questions/ myths.I have been in contact with 2 radio gurus who have 0 interest in r/c flying yet seem to be willing to help just the same. I'll let ya know how it turns out.

049flyer

My Feedback: (18)

Tomegan-

We all have a responsibility to ourselves, each other and the public to operate our equipment in a safe responsible manner. The idea is to go the extra mile to prevent any type of mishap. Changing the transmitter crystal COULD slightly change the exact frequency it transmits on. If the change is small say channel 32 to channel 34 then the degree of error will likely be small, if it the change is much larger then the error may be much greater.

If you fly alone in the country, no big deal. If you fly at a club field then you may be endangering yourself or others by causing interference with a radio that is slightly out of tune.

The point is why take a chance?

brewski

Tempting fate is not a good idea. I have seen one flyer at our field change his tx crystal. It was not good. A kit build 25% cub went in because of it. It seemed okay until in the air and then the glitching began. Be very careful of who and what is around when you do this.

bigedmustafa

My Feedback: (2)

The best explanation I've heard as to why you should send your transmitter in is because it is "fine tuned" or calibrated for its particular frequency channel and that changing the transmitter crystal can diminish the transmitter's effective range by as much as 50% if the transmitter isn't readjusted for the new frequency.

Your best bet for testing, tomegan, would be to range check the system at it's outer range first with the factory transmitter crystal and then again with a different crystal. See how much shorter the usable range is after the change and let that govern your course of action.

You'll either need to do a maximum distance range check with the antenna collapsed, or more accurately get a buddy and a pair of walkie talkies or cell phones and test the system with the antenna fully extended.

I'd actually be curious to find out what you discover. If you have the time and the various sets of crystals, I'd be interested to know if switching just a few channels away causes a smaller drop in performance versus a 20 or 30 channel jump. Let us know what you find.

Mad Mad Max

9 trees? More like a single, albeit slightly taller than normal, rose bush.

tomegan

My Feedback: (4)

bigedmustafa, What i did was took a transmitter ive been using approxamately 1 1/2 years bought by me brand new with a channel 24 pre- installed x-tal and a new tx on on channel 60,down the road from my house, had my daughter drive .26 of a mile up the road with a receiver/battery/power switch and 1 servo (thats as far as she could drive and maintain an un-obstructed line from the transmitters,we first used the old radio on chan 24 no glitches,servo performed nice,no hesitation .I then popped the chan 24 in the new tx, it gave the same performance. .26 of a mile doesnt sound far,but for now thats as far as i can test range.(which is well within my normal flying range)I did receive a response from the hobby store i purchased it from(I had e-mailed them and asked about this x-tal changing contraversy)There reply was if I have a chan 24 tx chrystal to go ahead an use it just make sure I range test first.I'm under the impression the newer radios are "center tuned" now. And yes if you send it in they still fine tune it to your specific channel,Please nobody read this and get the impression anybody is charging us 30 bucks to just change a x-tal.The story above from brewski about the 25% kit cub is the first horror story Ive heard from x-tal swapping,I would like to know how old the tx was,and if the cub was the model linked to the tx with the changed x-tal or was it somebody elses model on different channel.(and ofcourse i hope nobody was hurt)

wcmorrison

My Feedback: (2)

Gee, I thought this was going to about Futaba crystals verses Hitec crystals verses dual conversion against single conversion. Turns out you guys are channel hopping. I thought I might learn some thing about an AT cut verses a BT cut or X verses XY cuts.

BTW I have used Hitec crystals in Futaba receivers and vice versa. Both seem to work just fine.

Any takers?

Cheers,

Chip

sfsjkid

Here is one more data point. Two years ago, with fairly new equipment, on of our flyers got some major glitching, turned out the interference was caused by another flyer that had changed crystals on his transmitter. It did range check ok.

tirador

How about the transmitters using SYNTHESIZED MODULES.
You can change to any channel you want from high to low.
You dont even have to retune the Final TX circuit to the chosen
frequency....what can you say about that?

sfsjkid

There is no problem with switching modules nor sythesized ones, just the swapping of the actual crystal itself in the USA.

fizzwater2

My Feedback: (61)

The "tuning" on a crystal oscillator when swapping crystals is much less about final output power, and more about making sure the oscillator is operating at the proper frequencies. I say frequencies plural because modern "FM" radios actually switch between two very closely spaced frequencies to create the FM - it's really more FSK, or frequency shift keying.

Characteristics of crystals can very slightly from one to the next, and it takes small circuit tuning changes to optimize the operation of the frequency keying. Tuning is intended to make sure that we stay within the FCC allocated channel bandwidths, and also within the narrow receiver bandwidths of the other end of our RF links.

The modules contain all of the tuning circuits for a given oscillator - and are tuned to the crystal they come with. Swapping a module means you're swapping the whole RF part of the transmitter, and it's pre-tuned.

Synthesizers create output frequencies from a master "reference" oscillator - which is tuned at the factory. This one oscillator controls all of the output tolerances of the transmitter, and allows different "channels" by programming in the synthesizer controller itself.

danny03

We had a club member that was having trouble on channel 13 and he got the bright ideal of changing out his transmitter and receiver crystals for a different freq. When he brought the radio out to the field I had him to go get the radio and turn it on. Before he turned it on I got the clubs transceiver and set it to his freq. Once he turn it on I verified that he was transmitting on the correct freq., then I started scanning the other freq's and low and behold I had hits on 3 other freq's. As soon as he would turn off his radio the hits on the other freqs went away. That was enought to get him to send his radio in and have the crystals swapped properly.

tomegan

My Feedback: (4)

I was under the impreesion to cause any interference with another channel was impossible with newer radios,After reading above two scenarios i see it is possible.Those two stories were enough for me to go ahead and send off my tx. Thanks for all the input.

Mad Mad Max

When you send in your tx for the change, ask for a frequency that is seldom used, like ch 60.

mred33

OK, I know about the module swap out and why the cristal is not supposed to be change by the operator and the reason it needs to be retuned, but I still have a question. Futaba makes a 4 channel set that has the cristal right on the front of the face of the transmitter and that makes it very easy to swap out. It even has the finger indents to help you grab it. If you are not supposed to swap them out, why is Futaba making it so easy to do this?????? I have one and while I never changer the cristal, I don't know for sure if this is the cristal that came with it because I bought it used. I works great, however, my 8 channel JR is driving a couple of planes nutts on channel 50 while I am on 24. My 9303 on 24 does not do this, but my 8103 does and it uses the module to change freq. In the old days we could not change the cristal out because it was soldered in on the RF board, but not all sets are that way today. If we are not allowed to do it, why make it so easy??
Ed