Hi Allen,
There were some assumptions here, for sure--here are some specifics:
The SteppIR gain was modeled by a 4-element NBS Yagi (optimized gain) and
the LPDA was modeled by a 12-element LPDA design from the ARRL Antenna Book,
with gain calculated by EZNEC (we were looking at the T-12). The other
antenna we were considering was a TH7DX, which we did not simulate, but used
gain figures (measured) given by Roger WB0DGF here:
http://lists.contesting.com/_towertalk/2002-07/msg00739.html
The TH11DX looks like quite a different antenna from the TH7DX, being a sort
of hybrid Yagi-Uda and LPDA. It may give a bit more gain, or more flat gain
over frequency, than the TH7DX.
73, Chris KA8WFC
-----Original Message-----
From: Allen R. Brier [mailto:britech@earthlink.net]
Sent: Wednesday, June 28, 2006 10:57 PM
To: 'Christopher J Galbraith'
Cc: 'Tower Talk Reflector'
Subject: RE: [TowerTalk] Antenna comparisons
Chris,
Where did you get the gain figures? Just curious.
73,
Allen Ross Brier, N5XZ
Richmond, Texas 77469-2553
(281) 342-1590
(281) 342-0940 (FAX)
(713) 705-4801 (Cell)
-----Original Message-----
From: Christopher J Galbraith [mailto:cgalbrai@umich.edu]
Sent: Wednesday, June 28, 2006 11:55 PM
To: 'Allen R. Brier'
Cc: 'Tower Talk Reflector'
Subject: RE: [TowerTalk] Antenna comparisons
Hi Allen, group,
We are also considering a similar group of antennas. Here are some
thoughts, pros, cons:
SteppIR 4-element, 10-20m: Highest gain (by 2.5 dB at most), highest cost,
good reliability based on users' reports (only on the market for 2 years,
though), 30/40m kit (new) adds a rotatable dipole for these bands (about
$600 for this optional add-on). Other features, especially good for
contesting, include (1) the ability to create a bi-directional pattern, and
(2) flip your azimuth direction 180 degrees without rotating the antenna.
Tennadyne T-11 (or similar LPDA): Gain in between 2- and 3-element
Yagi-Ida, 2.5 dB down from SteppIR, mechanically robust (no traps or moving
parts), gets good reviews from users
Hygain big Yagi-Uda (THxx): Gain likely midway between LPDA and 4-element
SteppIR, mechanically complex and heavy, may require replacement parts and
service (trap covers) in several years, quality of Hygain products is
rumored to have decreased since the company was purchased by MFJ
We ruled out a Hygain, or other multiband Yagi-Udas that use traps and
focused on the SteppIR vs. LPDA debate. In the end, we were willing to
spend extra money on the SteppIR in large part due to the new 30/40m
rotatable dipole option as well as the additional contest-minded features.
But, if the extra money was not available, I believe we would have been very
happy with the LPDA. After all, 2.5 dB is not quite 1/2 an S-unit, which is
barely noticeable most of the time.
73, Chris KA8WFC
*Between these two options, another issue is out-of-band interference
rejection. An LPDA is matched well and has a nice pattern over a wide
bandwidth. So, a close-by interferer within the antenna's bandwidth (14-30
MHz, maybe a bit higher) will put a strong signal on your RX front-end. The
SteppIR, on the other hand, resonates on a relatively narrow bandwidth
(usually a bit smaller than the amateur band you are operating in) and
rejects most other frequencies, acting much like a bandpass filter. So, the
SteppIR has an advantage for multi-band contesting setups. It should make
one's receiving system more immune to interference from out-of-band signals.
On the other hand, a $50 bandpass filter on your RX will do the same thing.
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Allen R. Brier
Sent: Wednesday, June 28, 2006 9:23 PM
To: 'Chuck O'Neal'; 'Tower Talk Reflector'
Subject: Re: [TowerTalk] Antenna comparisons
My main interests are Contesting and DXing. I am looking for the best
performance in terms of gain. My favorite band is 10 meters (of course, when
there are spots!) I am looking for an antenna that will cover 20-10
including the WARC bands. I am undecided what I will use for 30/40 meters.
What other parameters should I include?
Allen Ross Brier, N5XZ SET
BriTech Systems Incorporated
NICET Fire Alarm Level IV
NICET Sp. Hazards / Sprinkler Systems Level I
1515 Windloch Lane
Richmond, Texas 77469-2553
(281) 342-1590
(281) 342-0940 (FAX)
(713) 705-4801 (Cell)
-----Original Message-----
From: Chuck O'Neal [mailto:cdoneal@comcast.net]
Sent: Wednesday, June 28, 2006 11:18 PM
To: britech@earthlink.net; 'Tower Talk Reflector'
Subject: Re: [TowerTalk] Antenna comparisons
This is an impossible question to answer unless you provide us with what
your operating requirements and expectations are.
Each of these antennas will outperform the others in specific areas.
Chuck...K1KW
----- Original Message -----
From: "Allen R. Brier" <britech@earthlink.net>
To: "'Tower Talk Reflector'" <towertalk@contesting.com>
Sent: Thursday, June 29, 2006 12:08 AM
Subject: [TowerTalk] Antenna comparisons
> I am trying to decide between three antenna types: the 4 el SteppIR, the
> T-11 Log Periodic and a TH-11 (or similar antenna). I would like to know
> your suggestions, recommendations and experiences with these antennas and
> especially comparisons between them. I plan to put it up approx 75 feet.
>
>
>
> Allen Ross Brier, N5XZ
>
> Richmond, Texas 77469-2553
>
> (281) 342-1590
>
> (281) 342-0940 (FAX)
>
> (713) 705-4801 (Cell)
>
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
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