The Bird Feeder hidden antenna
computer science crazy|
Joined: Dec 2008
28-11-2009, 06:24 PM
The Bird Feeder shortwave antenna is a vertical cage wire antenna.
A What? you might ask.
Imagine if you will eight flexible wires, evenly spaced in a circular pattern, much like a ground plane. Draw these wires vertically to form a wire 'tube' and connect them together with a ring at the top. Now imagine these wires inside a telescoping PVC mast. Top that off with a bird feeder. Now, instead of a ground plane system with radials you have to put in (the neighbours are watching), you have this 'wire tube' constructed as a vertical dipole. At 10m, the Bird Feeder antenna is a mere 17' tall when raised.
What would the neighbours say?
Or for that matter the manager?
"I raised it up for the birds to get into and it keeps the squirels out too. And look, I can take it out when I'm not using it or the weather is bad. Boy, I really like watching the birds from my window. Did you know that ..."
And then go on about some rare, but not unbelievable birds that frequent the feeder. Buy a book on the subject with some pages tagged to show them what you've seen so far. At worst, they'll think you're a flake and leave you alone. Next, go in and tune up 10m and catch some rare DX instead.
What do you have to actually put into the ground? Your coax and a PVC pipe to hold the mast up. Make it low in the ground and cap it so the mower doesn't take it off. For the most part, you can leave it up.
But do remember to put some seed in the feeder once in a while...
Bird Feeder Antenna - the details
This design sounds a bit far fetched, but it works. The vertical dipole, inside the PVC push-up, is invisible. It moves up and down and can be removed without drawing attention to the fact that it contains an antenna. The flagpole design has some problems. Not all PUDs, condos, or apartments allow flagpoles. They represent a permanent fixture. Not all associations or managers are that patriotic.
Although you can pack a good vertical in a flagpole, there is the problem of radials. You can run the vertical without radials, but that's another compromise.
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