It would be interesting to compare the 4el SteppIR and a 5 element 10m beam
with the same boom length. I think you would see a bigger difference on
10m, especially with F/B.
To: "'Bob Maser'" <email@example.com>,"'Joe Subich, W4TV'"
<firstname.lastname@example.org>,"'Carl Smidt'" <email@example.com>,
Subject: Re: [TowerTalk] SteppIR
From: "Dick Green" <firstname.lastname@example.org>
Date: Fri, 29 Jun 2007 13:34:17 -0400
I don't want to get in the middle of this, but I just ran EZNEC models
comparing the 4-el SteppIR and Force-12 EF-420 on 20m at 96'. The SteppIR
boom is 32'; the EF-420 boom is 30' (and presumably optimized.) Results:
4-el SteppIR Force-12 EF420
Elevation at max gain: 10 degrees 10 degrees
Forward gain: 14.36 dBi 14.29 dBi
Front/Back: 18.12 dBi 17.35 dBi
Front/Side: 18.12 dBi 17.35 dBi
Beamwidth: 60 degrees 60 degrees
It would be hard to tell the difference between these two antennas. I have
both installed, but the EF-420 is only at 72' on a tower that doesn't have
as good terrain as the tower on which the SteppIR is mounted. The SteppIR
consistently outperforms the EF-420, usually by as much as 5 dB. I attribute
that entirely to the difference in height and terrain.
I have not done models for 15m and 10m because I don't have data for any
4-el antennas for those bands. But I have compared the 4-el SteppIR with a
Force-12 515 (5-el on 15m, 24' boom) and a Force-12 616 (6-el on 10m, 24'
boom.) The gain figures are nearly identical, but the F/B on the SteppIRs is
lower, especially on 10m (a well-known characteristic of the SteppIR design,
resulting from inability to place the elements optimally on all three
bands.) The gain being comparable suggests that optimized 4-el monobanders
for 15m and 10m would outperform the SteppIR. But I don't know by how much.
73, Dick WC1M
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