Collinear Antenna element length

[biff44]

If I wanted to build a collinear receive antenna, similar to the one in this link:

http://www.rason.org/Projects/collant/collant.htm

But did not want it to be 7 feet long...
could I use dielectrically loaded quarterwave sections, maybe with er=9.9 loaded plastic dielectric, to shorten the resonators by the square root of 9.9? In other words, do the quarter wave sections have to be quarter wave in air, or in their own local media?

If I can do this, what do I give up? Poorer radiation resistance?

Rich

http://www.MaguffinMicrowave.com

Microwave and wireless design consulting

 

[VEBill]

The 'sections' should be halfwave long (vice "quarterwave").

Directionality and capture area are both related to real-world dimensions.

My way of looking at it (by way of extreme example to make the point clear) would be that if you made two collinear arrays, arranged them like a dipole and center-fed fed them out of phase (like a dipole), and then somehow shrunk them down to the physical size of a dipole, then it would function as a dipole. There should be a slight difference in that the current distribution would be flat-topped instead of sinusoidal, but the difference would be modest.

Interesting question...

 

[Higgler]

The bottom of the article hints you can make it shorter.

don't bother shrinking the elements, it won't be valuable.
Your loss will be based on the antenna size. If you're half size, you lose 3 dB gain. If you want to get that 3 dB gain back, put a reflecting wire it 1/4 wavelength (just a simple wire). You could rotate the wire and make it a directional antenna. Gain would be high away from the antenna.

bottom of article info regarding smaller antenna;

If the eight ½ wave coaxial elements result in an antenna too long for your liking (over seven feet), then it is okay to use four ½ wave coaxial elements but the SWR may be slightly higher (Attach four ¼ wave vertical ground radials at the antenna feed point to help lower SWR.). If