[TowerTalk] LP vs SteppIR

Gene Fuller w2lu at rochester.rr.com
Fri Jan 22 14:04:09 PST 2010


Two comments :
 Back in the mid 90's W1KW stacked two fairly large LP's. From what I 
observed, including a contact wtih him while I was visiting TU2AA, It did 
very well - top of the pile ! Also, as you may recall there used to be 
stacked, tilted LP's for TV reception. Of course they would have been many 
wavelengths high.
 I'm a relative newcommer so it may have been previously discussed in 
detail, but what about the TH-11. Back when Hy-Gain was really Hy-Gain I 
talked with the guy who designed that and was quite impressed, but I haven't 
heard much about it's success or failure electrically or mechanically.

Gene / W2LU
----- Original Message ----- 
From: "jim Jarvis" <jimjarvis at optonline.net>
To: <towertalk at contesting.com>
Sent: Friday, January 22, 2010 4:19 PM
Subject: Re: [TowerTalk] LP vs SteppIR


>
> I made comments directly to Doug, at his first posting, and said that this 
> thread would
> again get legs.  :)
>
> So let me repeat some of my comment, for those who didn't see it the last 
> time.
>
> 1)  I've had several LPDA's,  the T8 being the best of them.    It's head 
> and shoulders
> above most trapped tribanders on short booms.  The F12 C3S may be an 
> exception,
> It's pretty good.
>
> 2)  I changed from LPDA to a 3 el SteppIR, and was extremely pleased with 
> its performance.
> It was a 3 el,  and sure enough, results were like going from a 2 el yagi 
> with the lpda
> to a 3 el with the steppIR.   No magic there.
>
>     Band change, with the Icom interface, was very fast.   It took 
> approximately
> 2-3 seconds for the computer to command the rig, amp, and antenna to 
> switch over.
> Barely enough time to get a sip of coffee, before calling the station I 
> was chasing.
> (I like to use the bandmap in small station contesting,  in a point & 
> click mode.)
>
> 3)  Stacking Log Periodics:
>
> An interesting topic.   And one which seems worth experimenting, to me.
> I started to, but got wrapped around the axle:
>
> With two T8's, each with  16' booms,  you can put the front elements half 
> wave apart
> at 28MHz,  and the rear elements half wave apart at 14 MHz.   The upper 
> antenna
> tilts downward and the lower antenna tilts upward.   I don't recall the 
> angle, at this point,
> something like 22.5 degrees.   My plan was to mount the lower antenna with 
> the longest
> 20m element at 36',  and the upper 20m reflector at 70'.
>
> I went so far as to buy two blank mast-boom plates from Tennadyne, and 
> have them
> locally drilled for the calculated tilt angles.    I was in process of 
> designing the In/Out of
> phase system,  which can be done fairly simply with a single relay, given 
> the transmission line boom
> feed system for the T8.
>
> Somewhere in there, I got bogged down trying to model the thing.   Cebik 
> also got
> bogged down modelling it.   Healthy discussion followed.   I was about to 
> buy the second
> LPDA and get on with my empirical approach,  when a hurricane blew 
> through,  took out
> a big oak tree, which took out my tower.   Then I got transferred.
>
> The feeling was that tilting the antennas would tend to raise the 
> radiation angle, at the
> heights we were talking about.   If I could have put the lower one at 70' 
> and the upper
> at 100, it might have been different.   That's what we had hoped to model.
>
> I still think this would be a worthy experiment--but not one I can pursue 
> in suburbia.
>
> N2EA
>
>
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