An easy question for you Hams

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Rhino
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An easy question for you Hams

Post by Rhino » 04-10-2005 11:43 PM

I have a small problem. I need to build a simple antenna for a baby monitor. I was thinking of something directional that adds about 50 feet of range to the transmitter (the thing worked fine before the addition) I've searched high and low on the net, but the simple stuff I find is for 2.4 ghz and my monitor is 900 mhz. Could I just make a reflector out of some foil or something? How about a soup can?
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Fred_Vobbe
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Post by Fred_Vobbe » 04-11-2005 05:29 PM

A couple options, which are not can and string technology.

There are several products at SuperCircuits which are used for monitoring. Additionally, I know that Jameco Electronics has a camera system that some people use for baby and young adult monitoring. Look for their 6" B/W CCD Camera Kit,
Jameco #: 170616, MFG#:15-K060C1-1

That's video and there are options for audio. If you want something audio only then
Avtech Solutions has something. It's 900 mHz. And
Baby Age has some 49 MHz monitors which are pretty cheap.

To make it yourself can be quite a task. I've built small transmitters and you're looking at 2-3 days of work to make one. If you want to make one, there is a company that sells an FM transmitter and they are called Panaxis. I use their stuff to transmit my sound card out on 101.1 MHz so I can wear a Sony WalkMan radio while cutting the grass on the tractor. You get about 500-1000 feet on one of these. However, the trick is that you need to convert the audio input from LINE to MIC so you can hear properly. That might be a problem.

Finally, a word of caution: As with any RF device, other people can listen in! Encryption is not realistic, unless you want to add some big bucks to the system. As I sit here in my ham shack, I can dial around on my radio and pick up baby monitors, front door intercoms, cordless phones, etc. Just remember what we say in the broadcasting business .... any microphone can be a hot microphone.
Last edited by Fred_Vobbe on 04-11-2005 05:31 PM, edited 1 time in total.
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Rhino
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Post by Rhino » 04-12-2005 05:22 AM

I think you misunderstood my question, I don't want another monitor, I just want to slightly increase the range on the one I have by putting a beeter antenna on it. Thanks for all of the good info though, I appreciate your effort.
"The ruling class has the schools and press under its thumb. This enables it to sway the emotions of the masses." -Albert Einstein

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Fred_Vobbe
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Post by Fred_Vobbe » 04-13-2005 06:22 AM

Sounds silly, but you could use an old Dish Network dish antenna to reflect it. Other that that, I don't know of a way other than getting into the unit and modifying the antenna circuit.
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Rhino
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Post by Rhino » 04-14-2005 05:14 AM

I'm going to try one of these.
"The ruling class has the schools and press under its thumb. This enables it to sway the emotions of the masses." -Albert Einstein

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