[TowerTalk] [Bulk] Change in Frequency As Antenna Height Rises

[Jim Brown]

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