Richard Clark wrote:
On Wed, 07 Jul 2004 17:44:58 -0400, Albert wrote:
How much gain (dbd) should I expect and about what take off angle will
I have?


Contrary to Wes' results, I do not find much more than 13dBi, and
certainly not from your proposed huge implementation running out
towards 50 wavelengths. In fact, I find antennas that are a tenth of
that (5M) have about as much gain as will be found.

My matrix of testing shows that doubling to 10 wavelengths and
doubling again to 20 wavelengths brings no further gain (except for
some opportunistic outliers).

[...]
Considering that common implementations of rhombics rarely go beyond a
couple of wavelengths to several, it seems that 20 or 40 or 50 has no
future.

Those findings of "no further gain" and "no future" are very strange. In
the real world, extreme-length rhombics on VHF do have high gain - and
also a very distinguished past.


The law of diminish returns must occur somewhere as you are
constantly losing power as it trucks down the length.

All types of antenna suffer from diminishing returns, in terms of gain
versus absolute size; and it is conceded that extreme-length V-beams and
rhombics take up a huge amount of real estate for the gain they
generate. But what you seem to be finding is a "gain saturation" effect
that is more severe than the normal diminishing returns.

This is a puzzle: would you care to share some antenna files?


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek