Quote Originally Posted by RLBagley View Post
7-Element yagi for 433 MHz?

Eddy De Mol writes from Belgium to ask: "Will you improve the distance when using longer antennas as these on the following website?"



One of these long yagi antennas will extend your range in an unbelievable way. They narrow the focus and concentrate your unit's receiving power, yielding a stronger signal and giving extreme, pinpoint accuracy. If really you want to find whatever it is you've lost, you should have one of these. The only downside is the size.

Think of it like this: when searching for something at night you could use an ordinary light bulb, a flood light, or a spotlight. The ordinary light bulb is like an "omni-directional" whip antenna on your car -- it gives the same, weak illumination in every direction. A common 2 element yagi is like a floodlight -- it gives more range, but only in a certain direction. A 7 element yagi is more like a spotlight -- super bright in a very narrow beam.

The Marshall receivers has a 3 element yagi that is an excellent compromise between portability and performance -- good gain in a small package. But there is no limit to how big a yagi can get -- you can find units that have 60 or more elements. One of these is more like a laser beam and would increase your range by many times... Yagis like these are used by amateur radio people on 433 MHz to send signals to the moon and back. There is absolutely no reason why you can't use one of these high powered antennas with your Marshall receiver.

You can figure out the extra range of one of these long antennas by looking at the "gain" figure, quoted in dBd. The Marshall 3 element yagi has a gain of about 7.0 dBd. Every extra 6 dB will double your range. So the 10 element, 13 dBd yagi shown in the picture on your link will give about four times the coverage area when you're tracking, a pretty big advantage...

If it were me, I'd have one in the back of my car, or I'd go in with a bunch of friends and have a really big one back home which I could quickly get a hold of in an emergency.

The best place to find these big "guns" is on web sites of amateur radio ("ham radio") equipment.

Best of hunting,

Dave Marshall

By the way, there's another problem with these big antennas. They look... "unusual" to other people. I was using one in my favorite Arab country at night in hilly, desert terrain. I didn't know that I was near a military base which happened to be on alert at the time, and I found myself "detained" for the night. It turned out well, though. They brought out cookies and entertained me with football stories all night...
Hi Robert,

Thanks for posting this. I like the idea of being able to double the range for the price of an antenna.

I'm glad the gain of the Marshal antenna was specified in dBd instead of just dB. Some companies list the gain in dBi and it makes quite a difference.

Again, thanks.