Hi Mike,
To: <towertalk@contesting.com>
>Date: Sat, 02 Oct 1999 20:51:35 -0400
>From: "Michael J. Castellano" <km1r@snet.net>
>
>The best part about this site is the ongoing discussions
>(debates) that I find fascinating.
Ditto...
>My two and a half cents: The comparison of a log vs. yagi is
>like comparing a cargo ship to a passenger ship. They are both
>ships, but do different tasks.
There is a class of Yagi which it is valid to compare to the
LPDA. These are the parasitic arrays which attempt to cover 3 to
5 bands on a single boom with a single feedline. Against these,
the LPDA doesn't do badly if the boom length under consideration
is in the 30 or a bit more foot range (and longer).
>
>So I guess we can never really say one is better than the other.
Not without first defining what "better" means and what size
constraints must be met.
>Here: I use a HY-Gain Telex LP-1007A at 60 feet for one purpose:
>my work Involves multifrequencies and the requirement for faaast
>qsy. Gain is not important since higher than amateur powers are
>used. So here the LP is a great antenna and the yagi is not.
>
>HOWEVER; on 20, 15 and 10, there are 5 element monobanders...
>Hey: a lot of gain and reasoanable bandwith. For that purpose
>it is great and the lp stinks!
Yep, for coverage of a few hundred (or fewer if you insist on F/B
in excess of 20 dB) KHz, a multi element yagi is hard to beat.
But they are not without their limitations. However on the
whole, properly designed, installed, and tweaked in situ to
account for the site specifics, they are indeed the gain kings.
>
>So I guess I'm trying to say what everyone else has been
>saying... both are great for their intended purpose (assuming
>they have been built and tuned correctly!!)... and both are
>terrible when used for a non design intended purpose.
Tuned correctly is a key observation. But it includes a _LOT_
more than simply having a reasonable SWR somewhere in a ham band.
Very few tribanders actually end up installed with all of the
parasitic elements doing what the design calls for on all bands.
And the typical user has no way (other than the pattern stinks on
some bands) to determine that something is wrong. And even if he
does, he has no possibility whatsoever to make the required
"tweaks" for the affected band and then make the required "tweak
compensations" to keep the OK bands performing correctly.
OTOH, the LPDA only goes together one way and is somewhat self
compensating for unfortunate aspects of the site where it is
installed. They pretty much work as expected even considering
the large variation in the properties of their surroundings.
This is why Ward and Steve's comparison tests are so useful.
They are exposing the fact that the tribander's emperror is
relatively scantily clad. And this is why there has been so much
controversy surrounding their reports.
For a long time now, we have been choosing tribanders because
their _claimed_ performance was better than the LPDA's _claimed_
performance. Now we are forced to compare the tribander's
_actual_ performance with the LPDA's _claimed_ performance.
Soon, maybe we will be able to finally compare the tribander's
_actual_ performance with the LPDA's _actual_ performance. We
will finally have achieved the "apples only" comparison. My
guess is that once that is possible, the LPDA will not be shown
lacking when coverage of 3 or more HF bands is required and
performance on all the covered bands is insisted upon.
Just my $0.05.
73, Eric N7CL
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