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transmitter / receiver

Posted: Tue Jan 06, 2004 7:34 pm
by High4Volts
I need a transmitter and receiver able to switch a relay (120v contacts, 120v coil)on from from a distance of over 300 yards for an alarm beacon. Any Ideas?

Re: transmitter / receiver

Posted: Tue Jan 06, 2004 7:47 pm
by russlk
Check out various garage door openers. Is this line of sight?

Re: transmitter / receiver

Posted: Wed Jan 07, 2004 3:16 am
by cato
I was going to suggest radio controlled plane components...but I don't think they have the Kilometer range you are looking for....and MY garage remote seems to have trouble making it from the far end of the driveway....

Re: transmitter / receiver

Posted: Wed Jan 07, 2004 10:55 am
by wd5gnr
Have a look at a wireless doorbell. Read http://www.wd5gnr.com/rfrem.htm for my experiences hacking one of these for a laptop "clicker." I've also used them to let one Basic Stamp send a signal to another.<p>Hmm... 300 yards? Thought you said 300 ft. Not sure if this would do it or not for that distance. I haven't been in a room large enough to have it not work yet, but I doubt I've been in a room 3x the size of a football field!<p>[ January 07, 2004: Message edited by: wd5gnr ]</p>

Re: transmitter / receiver

Posted: Thu Jan 08, 2004 11:24 pm
by Lin Farquhar
Garage door types will do it if you use a couple of dipoles instead of the coiled monopole and/or dangling wire as supplied. I've had well over 1000 meter range yagi to dipole.

Re: transmitter / receiver

Posted: Fri Jan 09, 2004 8:40 am
by Tommy volts
High4Volts:<p>Would a standard am or fm transmiter and receiver work? There would need to be a decoder/interface at the receiver that would provide a signal to a relay circuit. <p>Don't the CW folks interface hardware to standard receivers?

Re: transmitter / receiver

Posted: Fri Jan 09, 2004 9:27 am
by Rodney
Cato, it is good you did not recommend RC plane components as that is not legal in the USA. The 72 MHZ bands are limited to aircraft use ONLY. You could use the 75MHZ bands as they are designated for surface vehicle use only. If you are a HAM, you could also use a portion to the 50MHZ and 52MHZ spectrum as they are legal to use on either aircraft or surface radio controlled vehicles. Most of the above are limited to 3/4 watt output per FCC rules.

Re: transmitter / receiver

Posted: Fri Jan 09, 2004 9:59 am
by Tommy volts
High4Volts:<p>I didn't notice before my last post, but Lin seems to already have solved the problem.<p>But with regard to my most I thought it worth mentioning the following alternative which is very costly but I use quite a bit when I design municiple pump stations (we use a sub for the electrical/instrumentation/RTU).<p>This is a link to one possible definite solution:<p>Radio Telemetry