This is why people stack antennas. There is no ONE sweet spot. 100' is almost 
too high for 10m but perfect for 30m. I say put it up, if you already have the 
tower. 
I'm planning my own installation. I have three crank up towers:  106', 89', and 
70'. The Steppir DB-36, which has three ele on 40m (6-40m) will go on the 106', 
a smaller Steppir on the 89' and a dedicated 6/10m antenna on 70'. I figure 
this will give me good, all around coverage. 
I can also vary the height on towers, if I'm aiming at any specific target. 
Crank up is the way to go, unless you have stacked antennas. 
Good luck.
Ed NI6S
> On Feb 14, 2017, at 03:06, Jeff AC0C <keepwalking188@ac0c.com> wrote:
> 
> I’m considering putting up an LPDA this summer to augment the existing stuff. 
>  The LPDA would serve two purposes:
> 
> 1. 30m/17m/12m DX chasing.   I suppose that really means 30/17 as I can’t 
> remember the last really solid 12m opening...
> 
> 2. Fixed-on-SA for 20/15/10m when contesting.
> 
> The problem is the usual tools for helping on height (HFTA) are more or less 
> band specific so what is the best height on (for example 20m into SA) is not 
> really a great height for another equally important (e.g. 30m DX into eastern 
> side of EU).   In playing around with HFTA clearly each height seems to 
> provide some benefit over another.  Higher band and higher height gives more 
> nulls but better low angle performance.  
> 
> I figured that something around 80-100’ overall but would greatly appreciate 
> any suggestions...
> 
> 73/jeff/ac0c
> www.ac0c.com
> alpha-charlie-zero-charlie
> 
> _______________________________________________
> 
> 
> 
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