[TowerTalk] Re: c3 vs tennadyne

[KI7WX@aol.com]

Apologies if this is a dupe, I think the previous reply which I sent from 
work bounced as I'm not subscribed to TT from that address.

KI7WX wrote:
>> FWIW, I've used a good log at W6EEN for the last few contest
>> seasons.  On 20M Don has "only" a 6L at 105 feet which is not
>> great for close in stuff, but killer on DX.  The Log is at 60 feet and
>> has an ~30 foot boom.

Lsica replied:
>Is this the 20 meter monobander at W6EEN that Lew McCoy talks about in
>his book "Lew McCoy Talks About Antennas"? 

Yes, there are some nice pictures of it and some of Don's other monster yagis 
in Lew's book. It is an excellent antenna for it's intended purpose which is 
working DX.  It is always a joy to operate from Don's station and I've been 
very fortunate to have that opportunity.  It really is an education to be 
able to flip from  antenna to antenna and appreciate in real time how 
different arrays function during different conditions.

And continued on with:
> I always thought the
>comparison between an LPDA and a 20 meter monobander was unfair enough,
>but to compare a 60 foot 6 element monobander at 105 feet to a 30 foot
>LPDA at 60 is completely ridiculous.

I must object to your tone and statement as being myopic. Particularly since 
your comment has been made without considering the actual meaning of what I 
wrote (but rather what you thought you read), nor the context of the 
discussion and how it applies to David's initial query.  Re-read my note to 
David, which he posted to the reflector, and see if you still dissagree with 
what was said and still feel my comments to be "ridiculous".  I will clarify 
below in case I was obtuse in my earlier writings.  However I do not think 
that was the case. 

First, I must say that to my way of thinking it's perfectly OK to compare any 
antennas at any time, determine the results of the comparison, and then 
comprehend what you have learned.  We all do that all the time and it is 
great fun.  Some folks model, some folks still even build and compare 
directly.  Sometimes we may even perform a valid comparison and learn 
something useful!!

That said, I didn't actually compare the two antennas in question directly as 
it's not important to the points which were being made. I would not suggest 
that a log periodic is a "better" 20M antenna than the 60 foot long, 
optimized six element yagi.  Rather, I clearly stated that the long boom 
monobander is a killer DX antenna (See the text you quoted).  If we look at 
raw numbers the monobander beats the LP hands down in every catagory.  One 
must comprehend, however, that those numbers are not the entire story.  Sharp 
beamwidth (footprint), high front to back ratios and suppressed higher lobes 
are not always desireable.  It depends on who you are trying to talk to.  
Bigger and higher are not always superior, despite what many have been 
conditioned to believe.

It's true in theory and in practice that a good long boom monobander (like 
Don's 20M 6L) at a height of 1.6 wavelength will have a significant low angle 
lobe which is great for working DX.  At the same time, however, the array 
which is optimized for DX will not work very well for short distance 
communications when the signals are arriving at a much higher angles. It 
simply cannot do both jobs. At 1.6 lambda the antenna has very little gain 
and may in fact have nulls at the higher angles. This is exactly what you do 
not want when you are trying to work domestic stations so using a high, long 
boom, yagi is a bad choice.  In my prior example for this situation, the log 
periodic at 60 feet will in fact significantly outperform the 20M monobander 
at 105 feet. It's an obvious and expected result. It doesn't mean the LP is a 
"better" 20M antenna and that was never implied. It does mean (as I did 
clearly state) that paper gain and patterns at arbitrary heights are not the 
only factors one must consider when planning an array and choosing antennas.  
Using the real world example where one antenna is something many of us would 
drool over and the other is rather ho-hum simply serves to illustrate the 
point that when you are planning arrays you must keep in mind the purpose of 
that array and choose the best antenna for the job.  Although many dream of 
monster yagis at high heights, they are not always going to be the best 
choice.

I hope that is more clear and would enjoy hearing the logic behind counter 
arguments as I firmly believe the above to be true.  If I'm wrong then I'm 
more than willing to learn something new.

Best,

Mark Curran
KI7WX


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