[Top] [All Lists]

[TowerTalk] Re: [FCG] HF LOG-PERIODIC ANTENNAS Comments Please

To: "FCG" <>, <>,<>
Subject: [TowerTalk] Re: [FCG] HF LOG-PERIODIC ANTENNAS Comments Please
From: "Tom Jednacz" <>
Reply-to: Tom Jednacz <>
Date: Tue, 22 Jun 2004 14:05:39 -0400 (Eastern Daylight Time)
List-post: <>
 Hi Rich, I have a four element SteppIR and am very pleased. I replaced a
well designed 10 element triband yagi - Bencher Skyhawk (which by the way is
still for sale - $300 in excellent condition). The SteppIR is a four element
monobander on all frequencies. The element lengths are adjusted to make an
optimized 4 element design anywhere from 13.5 to 30 Mhz (it will do 6 meters
as basically a dipole if you want). Look at the yagi design equations and
you will see that boom length is not critical when you do not need to
consider bandwidth.

A log periodic antenna is a compromise in order to cover a wide frequency
range while providing an acceptable SWR in the ham bands. It takes many more
elements to produce the same gain as a monoband yagi. There is always some
interaction between elements which further reduces the performance of the
log periodic. According to Cushcraft their 8 element log periodic is 0.4 dBi
better than a 2 element center loaded yagi. Lots of unused aluminum. Not
much performance.

Government, commercial and military customers will replace their log
periodic antennas with the SteppIR as soon as they learn about the
performance improvement. Covering all frequencies at higher gain at each
frequency with four elements and low SWR instead of 20 elements is a good
deal both cost and performance.

Stacking monobanders: Let's say we want to stack 3 each four element
monobanders for 20, 15 and 10 meters. Before the SteppIR that would require
9 antennas and possibly several towers. Stack three each four element
SteppIRs and you get the same performance with a much lower cost. Three
SteppIRs will cost approximately $5,100 while 9 monobanders will be about $7
200 or more. 

I have used the SteppIR in several contests and it is wonderful. The SteppIR
changes frequency by listening to the logging program ask the transceiver
for the current frequency. No mistakes of transmitting on the wrong
monobander and tripping the amp. Never made so many contacts with such ease
with bad band conditions. The antenna is only up 48 feet - local
restrictions. After 50 years of hamming I finally was able to put together a
good station - Ten Tec Orion, Alpha 87A and the 4 element SteppIR. Now if I
only had the body of 30 years ago I would be able to do very well in
contests. HI 

The C3S is a very good antenna but it is still only a 2 element yagi. The
SteppIR design has the same performance advantages as the Force12 designs -
no traps plus it has the advantage of no extra aluminum to detract from
performance. The SteppIR design concept delivers the highest efficiency
currently available. Their attention to high performance is evident when you
look at their matching system. Most antenna manufacturers use a single balun
to match the driven element balanced load. The SteppIR antenna is designed
to have a feed point impedance of approximately 22+/-j0 ohms on all
frequencies and then use a balun plus a unun to get to 50 ohm load impedance
 22 ohm balanced to 22 ohm unbalanced with the balun and then 22 ohm
unbalanced to 50 ohm unbalanced with the unun. 

Needless to say I am impressed with the many aspects of the SteppIR design.
There are other important aspects of the design but they do not apply to the
performance of the antenna. If anyone is interested, send me an e-mail and
we can discuss. 

I have no connection with Fluid Motion or the SteppIR but I wish I did.

Tom, W7QF
-------Original Message-------
Date: 06/21/04 10:45:18
To: FCG; Towertalk
Subject: [FCG] HF LOG-PERIODIC ANTENNAS Comments Please
Hello to all,
I am wondering if a stack of three Log-Periodic Antennas is the way to go.
At best my single tower station will have three Tri-Banders on it. Possibly
a Force12 C3S around 90-60-30 feet.
I have been seeing allot of talk about the Stepper Antenna Systems.
>From what I am reading, the big advantage in this type of antenna seems to
be the antenna tuning to the frequency of use.
In the past I have heard negative comments that a Log-Periodic has allot of
aluminum not being used. These remarks may be true when compared to
Mono-Band antennas but is it true when compared to tri-banders.
I am wondering if anyone has any experience with the performance of
Log-Periodic antennas as compared to a Tri-Banders. Is this the type of
antenna to use for contest operations.
Any comments on the performance and quality of these antennas.
I am considering models:
T6---12 foot boom---6 elements
T8---18 foot boom---8 elements
I understand both these models can be side mounded on my tower.
Thanks for your help.
Rich AA2MF
FCG mailing list
Send mail -
Change/edit subscription info -
FCG Web site -
This message has been processed by Firetrust Benign.

See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>