Full Wave Length?

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tgardner

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I am home brewing a Scantenna that has only 800 band elements. Will it rx better if I cut it full wave length? I am using one I made that is quarter wave at 50’ but still not happy with the rx.

Also, do you tune it to the middle of the frequencies that you monitor they way you would for a CB antenna?
 

rescuecomm

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The elements should be either 1/4 or 3/4 wavelength on either side of the feedpoint. The 3/4 will perform the same as a 1/4 since the signal will cancel itself in the other 1/2 wavelength. I use a 18.5 inch antenna on a mag mount for 2 meters(146mhz) and it works as a 3/4 wavelength at 440mhz. Not as good as the dual band antenna that I never seem to have time to mount on the swingaway tire carrier bracket, but good enough.

Bob
 

tgardner

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Rescuecomm, thank you for your reply. You saved me a lot of climbing up and down to test different lengths. I will stick with the 1/4.
 

kb2vxa

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Hi T and all,

First of all you're not making a "Scantenna", what you seem to have in mind is a vertical half wave dipole. Such an antenna has unity gain so no wonder you're not happy with it and likely you're losing way too much signal in the coax. That's fodder for another thread so we'll leave it at that.

Making each element each side of center 9" or 3/4 wave won't buy you much, you still need more gain on that troublesome band. Many of us use 800MHz cell phone antennas, I use an Andrew 3dB gain colinear mobile trunk lip mount on a 4" square electrical box cover plate with 4 3" wires soldered on the corners as a ground plane type base antenna. Then there are high gain omnidirectional base antennas but they're very hard to construct and tune properly so all in all you're better off with a commercial product.

The long and short of it is leave the homebrew for the other bands since you'll have a lot less trouble with the "critical mass". A big part of that is tuning once you have finished construction so without the proper equipment that's out of the question. The idea is to stick with simple designs that are basically "cut and dried" and they're not the ideal on 800MHz.

Keep at it though, I admire people who go beyond casual listening and into the technical aspects of radio communications. Those are the ones who ask why and won't accept because it's so as an answer. We are HAMS. (;->)
 
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