antenna

I was fooling around with a 7dbi antenna. Attached a coax for use outside. I don't exactly how these wireless units operate, but was thinking about ground planes. I used a simple rf pickup device watching 10 hz pulses from unit. As I moved from top of antenna I went through nodes, but continued to get nodes on coax down a ways. I set the rf monitor out from antenna, and installed ferrite core around coax about 1/4 wavelength from connector. I think it improved overall radiation, and the rf did not go beyond the core. What you think?

Greg

Reply to
gregz
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Near field measurements are tricky. I'm not sure I'd trust them.

For RF, generally you coil up the coax like an inductor, and it makes a common mode choke. That takes the ferrite performance out of the equation.

There are some really high frequency ferrites these days. You can get

3GHz transformers if you want total electrical isolation. Coiled coax would be less loss though.
Reply to
miso

I'm using a 5 foot piece of coax about the size of rg58. Not much to work with. From what I can tell, these antennas do require either a ground plane, or a tube running over the coax to the connection a quarter wavelength.

I plan on placing the antenna on the outside of an aluminum screen, mounted in a toilet paper dispenser, horizontally polarized to help interference, sitting on the window ledge, about a quarter wavelength away from the screen. I was looking in Kmart for suction cups or something, and noticed the dispenser. Drilled out the ends, stuck antenna through.

Greg

Reply to
gregz

It sounds like you are making a reflector and not a ground plane.

Reply to
miso

There is a reflector involved.

Greg

Reply to
gregz

Have you considered building the biquad? It can easily be swapped from horizontal to vertical polarization. Taking a tip from Jeff, I built one using round loops rather than square. Just keep the circumference the same.

My point is you would probably get better results using a known design with a bit of science behind it rather than just hacking.

I built one very similar to the Marty design. Instead of messing with the pipe, I hacked an old N connector. Something like this would work:

Of course when push came to shove, I just bought a high gain antenna. But the hacked antenna was interesting, just to see what I could make.

Reply to
miso

I have looked at all designs. The project is currently in hold since I found another approach. I would like to try and make the biquad sometime.

Greg

Reply to
gregz

Was that n a good one, like brass underneath, solderable?

Greg

Reply to
gregz

Actually it was difficult to solder to the hack-sawed N connector. I used a small propane torch. You need to be careful not to melt the insulation in the N-connector. Maybe the pipe is a better idea if you have some pipe laying around. I doubt you could buy a foot of copper pipe, so you need to be able to transport the pipe, which is usually in

10ft sections. And you need a pipe cutter.

That's the problem with homebrew stuff. You need the tools.

I used the biquad wispying (like war driving, but with video) in Vegas. The biquad is pretty good for a little antenna. However the L-com panel antennas are relatively cheap and decent quality.

I trolled the net looking at reviews from WISP installers. They dissed quite a few antennas for leaking. L-Com was considered the best of cheaper products.

Hey, nobody was ever fired for buying Ubiquiti. Occasionally their gear shows up on ebay at reasonable prices. But for my money, a $40 L-Com panel goes a long way.

Reply to
miso

Looking at Martys page, I was wondering if I was getting ripped on rubber duckies. Claiming 7 dbi. No, I took one apart. There is multiple sections and a coil. So with some reflection I should get reasonable gain after all. I would have to use a screen on the biquad to remain more invisible. I had access to Copper screen, but not now.

Greg

Reply to
gregz

I'm dubious about some of these little duckies claiming 5dbi or 7dbi. You can't fight physics.

A reflector at the wrong distance can actually be worse. If you really want to add a reflector to a duckie, I'd look up corner reflector antenna.

Actually I'm drawing a blank here. You want what looks like a corner reflector, but it is on a ground plane. It looks like a V with the bottom solid. The corner reflector is just a plane V and usually used with dipoles.

Reply to
miso

I'm dubious about some of these little duckies claiming 5dbi or 7dbi. You can't fight physics.

A reflector at the wrong distance can actually be worse. If you really want to add a reflector to a duckie, I'd look up corner reflector antenna.

Actually I'm drawing a blank here. You want what looks like a corner reflector, but it is on a ground plane. It looks like a V with the bottom solid. The corner reflector is just a plane V and usually used with dipoles.

Reply to
miso

I can see the ground plane helping. It would probably make the curved cardboard/foil reflector work with a bottom plate. I didn't tell I was also fooling with it. Hard to test antennas around reflections.

I'm not going further yet. My preliminary test with flat reflector looked good in the near field. One inch spacing seemed optimal. I'm ordering another linksys router. I want to get that repeating a repeater working.

Greg

Reply to
gregz

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