[TowerTalk] lp V stepIR

[Joe Subich, W4TV]

> 3 element stepir and the t8 will radiate almost the same 
> signal strength at the other end.

Both modeling and theory strongly disagree with this  ... 

The active portion of an 8 element 13-32 MHz LP on an 180 
foot boom is a small portion of the total boom length.  
Here are model data of an 8 element LP (18 foot boom), 
the SteppIR 3 element yagi (16 foot boom) and Force 12 
C3E (extra 10 meter director and 18 foot boom).  

The SteppIR/3 vs. 8 element LP vs. C3E (free space): 
---------------------------------------------------------
                   LP            SteppIR            C3E
    Band        Gain   F/R     Gain     F/R     Gain   F/R
     20          5.0   9.2      7.4     25       6.6   10
     17          4.9  12.3      8.3     25       3.0    2
     15          4.8  13.0      8.5     20       6.2   11
     12          5.0  14.9      8.8     15       4.4    5 
     10          5.1  14.5      9.0     11       7.4   23 
      6             n/a        10.1     20          n/a

The Log Periodic is a simplified model of an 8 element design 
on an 18 foot boom.  K9LA's work with the T-6 shows about .5 
dB less gain for a shorter (12 foot boom) antenna while   
Preliminary (unverified) results for a 10 element model (24 
foot boom) show about .8 dB additional gain and 1-2 dB better 
F/B (model data from AO). 

The SteppIR/3 vs C3E numbers closely parallel the field test 
data published by N0AX/K7LXC and SteppIR. 

One can see that the LP fails to come even close to the SteppIR 
- falling short my more than 3 dB except on 20 meters.  Further, 
falls one to two dB short of the typical gain of a two element 
(Reflector/Driven with 50 Ohm feed).  

An LP is a poor trade-off unless you have excess power and 
need to operate on any frequency instead of the relatively 
narrow amateur bands. 

73, 

   ... Joe, W4TV 
  


> -----Original Message-----
> From: towertalk-bounces at contesting.com 
> [mailto:towertalk-bounces at contesting.com] On Behalf Of anthony
> Sent: Saturday, January 23, 2010 9:45 AM
> To: towertalk at contesting.com
> Subject: [TowerTalk] lp V stepIR
> 
> 
> 3 element stepir and the t8 will radiate almost the same 
> signal strength at the other end.More to fail with the stepir 
> and did you see how much they cost??? WOW. big bucks. I would 
> put up the t-8 and high grade coax like davis bury-flex. If 
> done right this antenna will stay up without any maintenance 
> for 20+ years. No way the step ir will do the same. Also you 
> can buy two t-8's and one yaesu g-800s for what you would pay 
> for a stepir. Just a thought.
> 
> tony k2vi
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