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How do I change Tx crystal?

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Old 04-17-2010, 06:26 PM
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Alex7403
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Default How do I change Tx crystal?

Here is the thing I got a transmitter futaba 7CAP PCM on channel 16 and I have several receivers 72 MHz non PCM on channel 47, that transmitter on ch 47 needs a new battery and I kind of reached the end of its capabilities.
Somebody told me that I can fly the non pcm receivers with the pcm Tx in PPM mode.
So I thought maybe to change the crystal on the Tx.

Can it be done?
What do I need to do to replace the Tx crystal from ch 16 to ch 47?
Can I do it myself or I have to send it to futaba?

Thanks
Alex
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Old 04-17-2010, 06:34 PM
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Default RE: How do I change Tx crystal?

The FCC mandates that you send it in.  It'll work fine with your PPM receivers, provided that they're negative shift.  Any FM Futaba will work, in other words.
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Old 04-17-2010, 06:43 PM
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Alex7403
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Default RE: How do I change Tx crystal?

Thanks MikeL,

Now that I'm thinking about it can I change the pcm Rx crystal from ch 16 to ch 47 its low band to high band?

Thanks
Alex
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Old 04-17-2010, 07:07 PM
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Default RE: How do I change Tx crystal?

Not all Futaba receivers are hi/low band, if it's marked thats another matter.

I would get a reciever crystal and do a range check. If it doesn't pass then Futaba or Radio South or whomever can tune it, we have a local guy that charges 10 or 15 bucks to align a reciever, and tuning usually uncovers any problems it may have.
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Old 04-18-2010, 02:51 PM
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Default RE: How do I change Tx crystal?

Theoretically, you can change any channel to another in the same band/radio type. In practice, I don't like to go more than 2-3 channels away from the original. As for the FCC, they're too overloaded now to worry about us changing a 1/4 watt transmitter frequency.
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Old 04-18-2010, 03:12 PM
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Default RE: How do I change Tx crystal?

The futaba 7CAP PCM has a freq module I believe in the TX. You can try to find additional modules probably in the "used" market and you ARE allowed to swap modules as an owner. If you can find a module on ANY freq then a good shop can change the crystal in it. Then all you need to do at the field is swap modules, select the correct model and make sure your modulation is selected correctly. The TX should remember what modulation is needed for each model but ALWAYS double-check for safety.
Oh - and ignore Dr1Driver as while he may be correct (to a point) it is still illegal and inviting interference from an improperly tuned TX.
Remember that jumping off a cliff on a BASE jump is safe too - until you die.[X(]
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Old 04-18-2010, 04:08 PM
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Default RE: How do I change Tx crystal?

Thanks for the replays guys I'm gonna send it to futaba this week to change the crystal on the Tx.
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Old 04-18-2010, 04:10 PM
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Default RE: How do I change Tx crystal?


ORIGINAL: Alex7403 Here is the thing I got a transmitter futaba 7CAP PCM on channel 16 and I have several receivers 72 MHz non PCM on channel 47, that transmitter on ch 47 needs a new battery and I kind of reached the end of its capabilities.
Somebody told me that I can fly the non pcm receivers with the pcm Tx in PPM mode. So I thought maybe to change the crystal on the Tx. Can it be done? What do I need to do to replace the Tx crystal from ch 16 to ch 47? Can I do it myself or I have to send it to futaba? Thanks Alex
Crystal - Swapping Transmitter Crystals (USA)
Crystals - Swapping brands in RC Transmitters and Receivers.

Only a few Futaba receivers are high/low band Futaba - 72Mhz Hi & Lo Band Difference & Markings
and R127DP in particular requires retuning if moved more than say 2 ch either side of original.
Futaba - R127DF - an old Hi/Low Band RX prone to vibration and jitters
Futaba -R127DF..Channel cannot be changed by simply swaping crystal, must be retuned each time.

All other RX are center tuned and and any same brand as RX crystal within same band can be safely used.
[ range test to beperformed as usual before flying each day
electronics do drift out of tune with age and the older the unit, the more care should be taken witrh range tests.]
refer sub section "
Range Test - Check and Range Problem Solving" at


Sub section "Radio Systems, Accessories, Alterations and FAQ" at
Alan's Hobby, Model & RC FAQ Web Links
may well provide answers for other related questions.

Regards
Alan T.


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Old 04-18-2010, 09:25 PM
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Default RE: How do I change Tx crystal?

Oh - and ignore Dr1Driver as while he may be correct (to a point) it is still illegal and inviting interference from an improperly tuned TX.
BS Improperly tuned TXs are a hazard, true, but if the swapper stays within, as I suggested, 2-3 channels of the original frequency, he'll be ok.

What I'd ignore is people who are so anal retentive as to think the FCC will really come after them even if they DO discover the swap.

Are YOU always COMPLETELY legal, sonny? Ever exceed the speed limit? Roll through a stop sign? Jaywalk? Shall I go on? Glass house livers should not throw stones. As for ignoring, you are.
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Old 04-19-2010, 03:25 PM
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Default RE: How do I change Tx crystal?

Its not a good idea to encourage unknowledgeable people to mess with the transmitter crystals. When I was repairing radios I had transmitters come in with receiver crystals in the transmitter.
In the US, other users are spotted on frequencies between our 72MHZ frequencies. The transmitter is made with removable crystals that can be changed in other countries that don't have other other users intertwined with our frequencies.
Granted the FCC don't have the time or manpower to police our bands but I wonder what would happen if someone caused a large crane to come down after an illegal crystal change.
Its best to obey the rules.
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Old 04-19-2010, 03:45 PM
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Default RE: How do I change Tx crystal?

ORIGINAL: Dr1Driver
BS Improperly tuned TXs are a hazard, true, but if the swapper stays within, as I suggested, 2-3 channels of the original frequency, he'll be ok.
Re-read the original post...
The transmitter in question is on channel 16 and he wants to go to 47. That's well beyond 2-3 channels.
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Old 04-19-2010, 04:48 PM
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Default RE: How do I change Tx crystal?

It is safer to change the Rx crystal, if you are doing it yourself. Why risk someone shooting down someone else.
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Old 04-19-2010, 05:01 PM
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Default RE: How do I change Tx crystal?


ORIGINAL: Dr1Driver
BS Improperly tuned TXs are a hazard, true, but if the swapper stays within, as I suggested, 2-3 channels of the original frequency, he'll be ok.
Have you read the thread? The OP is going from 16 to 47.

If somebody wants to do things the right way, and other people encourage them to do things the right way, that's not such a bad thing.

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Old 04-19-2010, 06:50 PM
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Default RE: How do I change Tx crystal?


ORIGINAL: bruce88123

The futaba 7CAP PCM has a freq module I believe in the TX. You can try to find additional modules probably in the ''used'' market and you ARE allowed to swap modules as an owner. If you can find a module on ANY freq then a good shop can change the crystal in it. Then all you need to do at the field is swap modules, select the correct model and make sure your modulation is selected correctly. The TX should remember what modulation is needed for each model but ALWAYS double-check for safety.
Oh - and ignore Dr1Driver as while he may be correct (to a point) it is still illegal and inviting interference from an improperly tuned TX.
Remember that jumping off a cliff on a BASE jump is safe too - until you die.[X(]
Nope, the 7C series is crystal based, not module based.

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Old 04-20-2010, 08:00 AM
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Default RE: How do I change Tx crystal?


ORIGINAL: BarracudaHockey


ORIGINAL: bruce88123

The futaba 7CAP PCM has a freq module I believe in the TX. You can try to find additional modules probably in the ''used'' market and you ARE allowed to swap modules as an owner. If you can find a module on ANY freq then a good shop can change the crystal in it. Then all you need to do at the field is swap modules, select the correct model and make sure your modulation is selected correctly. The TX should remember what modulation is needed for each model but ALWAYS double-check for safety.
Oh - and ignore Dr1Driver as while he may be correct (to a point) it is still illegal and inviting interference from an improperly tuned TX.
Remember that jumping off a cliff on a BASE jump is safe too - until you die.[X(]
Nope, the 7C series is crystal based, not module based.

Oops, you're correct. I was thinking of the 7UAPS. My advice on the module stands for those so equipped as does my advice to ignore Dr1Driver.
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