Hi Art,
You made the claim yagis can't have more than 20-25 dB F/B or
F/R, and that is not factual. My 40 meter antenna is an example,
and I'm sure there are countless others.
As a matter of fact with two driven elements in a phased array, I
can get a null that for all practical purposes goes to zero. BC
stations do that all the time, to protect other stations.
If you doubt my antenna or other three element yagis can have that
null depth, I can e-mail you an Eznec file showing they do.
I made no extraordinary gain, null depth, or bandwidth claims. My
antennas work like most other antennas in the world.
> I would like a yagi to have 'good'flat front to rear across the band.
> The same goes for flat gain and a flat realistic drive impedance The
> antenna I posed with 3 reflectors meets that target or goes along way
> towards that end. This antenna came up as a response to a post
> regarding extra reflecters and their physical length and we are
> certainly along way from that theme.
As I understand this, you are saying you have an antenna (with
three reflectors) that meets the goal of being very broadbanded by
virtue of having three reflectors.
It appears you are saying it has a deep wide rear null (more than
50 dB?) at useful angles, a flat and modest driving impedance
across "the band" (whatever band that is), and as I recall it has
comparable or more gain than other antennas the same physical
size (I believe you mentioned that in a prior post).
Many people would love to have an antenna like that!
I can't deliver one, it is far beyond my technical skills and meager
understanding of antennas.
> Does your 3 element yagi meet all YOUR goals with respect to
> performance across the band. Are there some areas YOU 'wish' you could
> improve upon, putting aside heavy emphasis on known resons why it
> CANNOT be done ?
It does everything I expect it to do, which is nearly all it can do
according to theory.
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|