On Mon,5/30/2016 10:45 AM, Grant Saviers wrote:
My modeling (as G3TXQ comments) shows that max gain, min swr, and max
f/b all happen at different frequencies. So, "tuning" a beam with swr
seems like a trip to Vegas re what the performance will be. I think
it is at best a quick check that there are no gross assembly errors.
I've had the AutoEZ optimizer generate beam models with 1:1 swr, but
with reverse patterns, straight up patterns, no gain, etc.
One of the things I've learned reading what great antenna designers like
N6BT (the original Force 12) and G0KSC (InnovAntenna) have written is
that they work hard to optimize designs so that they are less sensitive
to height above ground and surrounding objects.
I also strongly agree with others that antennas should be tuned at their
mounting height. For most of us, that means temporarily rigging it so
that it can be adjusted where we can reach it, raised to see how it
works, and lowered for adjustment again if needed.
I also agree with Dan, Grant, and others that a GOOD model (meaning one
that accurately describes the antenna and follows the rules of the
modeling software for segmenting, etc.) is a pretty good predictor of
how it will work. That's been my experience.
73, Jim K9YC
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|