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Newbe question on TX & RX

Old 05-07-2010, 09:54 PM
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leebart121
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Default Newbe question on TX & RX

I have an old 72 Mhz radio and would like to know if I can switch out the crystals to 75 Mhz and be able to us it for my boat legaly??
Old 05-07-2010, 10:22 PM
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hugho
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Default RE: Newbe question on TX & RX

yes
Old 05-07-2010, 10:54 PM
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leebart121
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Default RE: Newbe question on TX & RX

so it does not mater that the transmiter is a 27 Mhz?? I can plop a 75 Mhz crystal in and it will be fine?
Old 05-07-2010, 11:04 PM
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Ron Olson
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Default RE: Newbe question on TX & RX

No.
The radio system is tuned for certain frequencies only so you can't simply jump around the radio spectrum. It's not even advised to go more than 2 channels in either direction on most radios much less going to another band.
How old is another question. A really old system may not be FCC legal.
Old 05-07-2010, 11:38 PM
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leebart121
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Default RE: Newbe question on TX & RX

Not sure how old it is. it is an arotronics that the police department used for there target range to activate the siliwets that jump out of the doors and windows.
Old 05-07-2010, 11:48 PM
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Ron Olson
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Default RE: Newbe question on TX & RX

Airtronics radio systems go back quite a few years so it may be legal but maybe not. The older Airtronics radio systems were setup bass ackwards from the present ones so any other brand of servo had to have the positive and negative wires swapped around to get them to work. Later on they came out with a "Z" connector that did that for you then finally came up with the RX wired so that it didn't have to be done Now with their servos they'll have a suffix letter Z on them like a 92104Z.
Old 05-08-2010, 07:31 PM
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leebart121
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Default RE: Newbe question on TX & RX

what is a 56 Mhz transmiter for??
Old 05-08-2010, 07:41 PM
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Hydro Junkie
 
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Default RE: Newbe question on TX & RX

Unless it's a HAM frequency, it's not legal here in the States. Frequency bands that are legal here are 27MHz(for anything), 50MHz(for anything with a HAM license), 72MHz(for aircraft only), 75MHz(for boats, cars, robots, etc only) and 2.4GHz(for anything). For toy grade stuff like the RAdio Shack stuff, it comes with(I think) 29MHZ and 49MHz, but that is very limited on range and ability.
Old 05-08-2010, 10:20 PM
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Ron Olson
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Default RE: Newbe question on TX & RX

What model of radio system is it? I've got an old Airtronics radio sytem in the junkpile that uses a module mounted on the top of the transmitter that's held in with 2 clips. The module has to be pulled out to access the crystal. If there isn't an Mhz number there should be a 2-digit number like 82 on a crystal tag. That tag is used to pull the crystal out for changing frequencies.
Other than that, I'm out of answers for now.
Old 09-24-2011, 09:20 PM
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leebart121
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Default RE: Newbe question on TX & RX

the crystals were gone when I got it. I had placed a set of 72 Mhz crystals in the 56 Mhz (police) radio and in the Rx that was with it and they worked. Just do not know why the had a 56 Mhz radio.
Can any 2.4 Ghz radio system be used in a boat. Been seeing alot of 2.4 ghz systems on ebay and most are for a helicopter. Are these able to be used in a boat in legal standing??
Old 09-24-2011, 09:26 PM
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Ron Olson
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Default RE: Newbe question on TX & RX

As long as it's on 2.4 Gig, it's legal. You can use any radio system that you like if it's for air or surface as long as it's on 2.4 .
Running on a police frquency is probably very illegal. I wouldn't want to get caught, that's a Federal offense! [X(]
Old 09-25-2011, 01:49 AM
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Default RE: Newbe question on TX & RX

In the hobby area, radios are tuned to a particular band.  The crystal just fine tunes it to a particular channel within that band.  Radios that started of as non-hobby devices are a different story.
No doubt the law enforcement will prefer to use frequencies that most people don't have access to, quite likely the equipment can use the crystal as the basic tuning device.
In the past, sharp tuning was problematical, so there were few channels on whatever band you wanted.  Transmitters transmitted "near enough", receivers were not too selective. The same bands can now carry many times the number of channels.  The new sets play well together, but an old receiver might well be affected by a new transmitter on an adjacent channel, an old transmitter might well affect new receivers on their adjacent channels.  One that was certified for a totally different use could be a problem for anybody else.

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