Baby Monitor Mod

29 Dec

Most days I’m at home alone with the baby while Callina’s at work.  This is all works out pretty well because I really kinda like the baby for some reason.  Every day at 10 and 2 I put the muchkin down for a nap and go on out to do my farm chores and projects. The days when the baby sleeps for 2-3 hours at a stretch I can actually start to get some stuff done around the farm.

Still, I’m running into a problem that keeps me from being able to do some projects: The baby monitor.

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I take the baby monitor outside with me so I know when the kid wakes up.  The problem is that the monitor, despite having excellent reviews on Amazon pertaining to it’s range, is pretty limiting.  I can get it about 75 feet from the front door before it gives me the “out of range” beep.

That limits me to the garage, the upper part of the woodshed, and maybe inside the barn if I crank the volume on the monitor all the way up.  75 feet outdoors might cut it in the city, where that’s likely to be your property line, but out here on the farm 75 feet isn’t going to cut it.

So, I cracked open the case on the transmitter to see what improvements could be made.

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Right away I noticed that the antenna was rather puny, just as I had suspected. As with most any radio, there are two ways to boost your range, either increase the power, or increase efficiency of the antenna.  Power is usually pretty complex to deal with, not to mention regulated by the FCC.  Antennas are completely fair game, and pretty simple to construct.

These monitors operate at 900mhz, which means that a full-wavelength antenna would be 13.125″ long, or 33.3cm (if that’s your thing).  The antenna on the transmitter is a 1/4 wavelength.  The smaller the antenna, the less gain it has (less gain = less range) up to one full wavelength.

I could probably get a decent improvement in range simply by replacing the 1/4 wave antenna with a longer full-wave one.  If I wanted even more range, I could make a high-gain directional antenna, but an omni-directional signal is pretty important here because I’m using the monitor all around the house.

All it takes is a 13.125″ length of wire with one end stripped. Unsolder the stock 1/4 wave antenna, and solder the 13″ wire in it’s place.

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I had to poke a hole in the rubbery-thing to get the longer antenna wire out, but other than that it all went back together the same way it came apart.

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Wash, rinse, and repeat with the Receiver part of the monitor.

Now I have a solid 100 feet of range in all directions outside the house, with an even greater range (about 200 feet) where I have a direct line of sight to the baby’s room.  Basically, I can work on or in any building on the farm without being out of range.

Hopefully, with this little modification done, I can start getting more stuff done around the farm.

At least as long as the baby stays asleep…

 

Oh, and one more thing: since this obviously pertains to something that’ll be around a baby, be careful.  Keep it out of your tykes reach so they won’t wrap the wire around their neck or anything.  Proceed with caution, at your own risk, bla bla bla.

One Response to “Baby Monitor Mod”

  1. Johan Rodskog May 5, 2017 at 11:34 pm #

    Thanks, this is something I want to try. Do I need to match the length of the antenna on both the transmitter and receiver? or can I just modify the transmitter to get a little bit of range boost?

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