[TowerTalk] antenna choices
Joe Subich, W4TV
lists at subich.com
Tue Apr 7 17:42:32 EDT 2015
Here are some model comparisons for various SteppIR models vs. other
"multi-monoband" yagis done at various times several (8 - 10) years
ago:
Here is a comparison of the three and four element SteppIR for a height
of 74' (22.5 m) above ground. A dipole will have about 8.2 dBi gain at
this height.
3 element 4 element elev.
Band Gain F/R Gain F/R
20 13.4 20 15.0 20 13 degrees
17 13.8 21 15.7 22 10 degrees
15 14.2 21 16.1 22 8 degrees
12 14.8 14.5 16.2 22 7 degrees
10 15.2 11 16.6 11 7 degrees
6 16.0 20 18.7 20 4 degrees
The SteppIR 4 element yagi vs. Force 12 C-31XR:
C-31XR SteppIR elev.
Band Gain F/R Gain F/R
20 14.0 20 15.0 20 13 degrees
17 n/a 15.7 22 10 degrees
15 14.3 22 16.1 22 8 degrees
12 n/a 16.2 22 7 degrees
10 15.6 21 16.6 11 7 degrees
6 n/a 18.7 20 4 degrees
The C-31XR numbers are Force-12 published specifications and
confirmed by modeling with AO. The SteppIR numbers are from
modeling in AO/YO (6 meter values use the optional passive
elements). Gain is given in dBi with antenna 74 feet (22.5
meters) above ground. At this height a dipole will have about
8 dBi of gain at the elevation angle shown above.
The SteppIR 3 element yagi vs. Force 12 C-3E
C-3E SteppIR elev.
Band Gain F/R Gain F/R
20 12.6 16 13.4 20 13 degrees
17 10.3 7 13.8 21 10 degrees
15 12.8 17 14.2 21 8 degrees
12 9.8 9 14.8 14.5 7 degrees
10 13.2 21 15.2 11 7 degrees
6 n/a 16.0 20 4 degrees
The C-3E numbers are Force-12 published specifications and confirmed by
modeling with AO. The SteppIR numbers are from modeling in AO/YO (6
meter values use the optional passive elements).
The SteppIR 3 element yagi vs. 8 element LP on 18' boom in free space:
LP SteppIR
Band Gain F/R Gain F/R
20 5.0 9.2 7.4 25
17 4.9 12.3 8.3 25
15 4.8 13.0 8.5 20
12 5.0 14.9 8.8 15
10 5.1 14.5 9.0 11
6 n/a 10.1 20
The Log Periodic is a simplified model of an 8 element design on an 18
foot boom. It should be comparable to the CushCraft ASL-2010 or the
Tennadyne T-8. K9LA's work with the T-6 shows about .5 db less gain for
the shorter antenna. Preliminary (unverified) results for a 10 element
(LP) model on a longer boom show about .8 dB additional gain
and 1-2 dB improved F/R.
Optibeam OB11-5 20' boom vs. 3 element SteppIR
Using Optibeam's claimed gain and Front to Back we have:
Optibeam SteppIR elev.
Band Gain F/R Gain F/R
20 12.7 22 13.4 20 13 degrees
17 13.0 22 13.8 21 10 degrees
15 13.2 20 14.2 21 8 degrees
12 13.4 19 14.8 14.5 7 degrees
10 14.5 19 15.2 11 7 degrees
6 n/a 16.0 20 4 degrees
Optibeam has a 6 meter (20' boom) vs. a 4.8 meter (16' boom).
Optibeam has 11 elements (three are "triple" elements) vs. three for
SteppIR. Optibeam has 15.8 sq. ft. wind load vs. 6.1 sq ft. for the
SteppIR and the Optibeam weighs 86 pounds vs. 42 pounds for the
SteppIR.
73,
... Joe, W4TV
On 2015-04-07 4:41 PM, Jim Brown wrote:
> On Tue,4/7/2015 1:25 PM, john at kk9a.com wrote:
>> That is very interesting data! Has anyone modeled a SteppIR with a
>> comparable boom length?
>
> Google found these. When I was making my purchase decision, I saw other
> work that looked like it was well done.
>
> http://p02.de/wp-content/uploads/2010/12/steppIR_Ms_ENGL_REV16DEC10.pdf
>
> http://www.k6sgh.com/antennas/steppir%20study.htm
>
> http://www.k6if.com/steppir/steppir_4el.html
>
> 73, Jim K9YC
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