[NLRS] Fwd: VHF Antennas

[Dr. Gerald N. Johnson]

On 3/12/2011 9:15 AM, w0zq at aol.com wrote:
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> Hello NLRS land
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> Kirk, MWA member N0KK, has a new TS2000X and is looking for 2, 432, and 1296 antennas.  Please see his post below and if you can help him out drop him a note at n0kk at usfamily.net.  If anyone has somne experiece with the VHF Cubex Quad that Kirk references, drop him a note on that subject too.
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> 73, Jon
> W0ZQ
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> As you know I bought the TS2000X. Jon led me to Directive Systems for antennas.
> I have been looking them over but before I spend several hundred on antennas and feedlines and tower work I though I'd inquire with you.
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> Would you post to the Northern Lights group that I'm looking for antennas. They must be in great shape, able to be put up on a tower and forgotten for some time.
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> 2 meters should be in the 6-8 boom length. Center mount.
> 432 should be whatever...I'm considering the 11 element from DS.
> 1.2 I like the looks of the loop yagi but would consider something else.

Directive Systems hardware is spendy, but reliably good. M2 isn't bad 
but uses different schemes. Look at the 9 element for 2m SSB. And 
similar boom lengths for 432. I'm working up a stack of FO-9 for 2m and 
432 and will talk about them closely stacked at Aurora. A couple or 
three stacked gets decent gain (as much as a 5 wavelength yagi) without 
getting too directive in the azimuth plane for ordinary (as in HAM-M) 
rotor control. Long about 12' of boom on 2m.

Loop yagis at 1296 (actually 902 to 3456) have greater construction 
tolerances than regular yagies. Mount them elements down to cut down on 
bird damage.
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> Now for your opinions....Cubex Quad makes a 2/432 quad....What are your thoughts on a dual bander?
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The small one claims as much gain as a good 3 element yagi on the low 
band. I don't remember seeing one tested at a Central States or Aurora 
antenna measuring event. Its ultra easy to claim gains and I'm not a fan 
of quads. I'd wish for dimensions and to spend some time with a good 
mininec program (better for close spaced wires than NEC2, part of my 
Aurora presentation) seeing how much the coaxial antennas interact. I 
suspect more interaction than is desirable leading to considerable 
anomalies in the UHF pattern and efficiency. Compare antennas in free 
space the addition of ground causes too many complications, but the 
models indicate seriously increased gain over free space, even a dipole 
has lots of gain or the half space isotropic that's hard to believe. If 
you must compare gains over ground, compare to a dipole at the same 
height over ground, not the raw computed isotropic value. That will 
deflate most claimed gains to something more realistic.
> KK
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And finally, don't scrimp on feed lines.
> ______________________________________________________________
73, Jerry, K0CQ