[TowerTalk] Short Booms

[Bryan Rambo]

Howard and all,

I was just about ready to order a pair of those 4el SteppIR yagis when I
read on their web page that the 32ft boom was only 1-3/4 inch diameter.
Yikes!  My KT-34XA has a 32ft x 3in boom and I don't think it could manage
with less.  Granted, the SteppIR boom has a bit more wall thickness - but
wall thickness just can't make up for lack in diameter (if you believe the
moment formulas in my old college statics textbook).

Howard: After putting two of those beauties up, what do you think of that
skinny boom ???

73 - Bryan W4WMT

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]On Behalf Of Howard Klein
Sent: Thursday, September 11, 2003 7:03 AM
To: jimlux at earthlink.net
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Short Booms





----Original Message Follows----
From: Jim Lux <jimlux at earthlink.net>
To: Jerry Keller <k3bz at arrl.net>, Ward Silver <hwardsil at centurytel.net>,
Towertalk Reflector <towertalk at contesting.com>
Subject: Re: [TowerTalk] Short Booms
Front to Back (or Front to Rear) ratio is something that the SteppIR type
beam will excel at. Also, the SteppIR concept allows you to free one of the
parameters that otherwise you'd have to optimize: bandwidth.  You can set
the SteppIR up for performance at a single frequency.

As an interesting exercise try something I inadvertently found out about the
other day.  Take almost any 3 element 20m beam that has been optimized for
gain or F/B at a particular frequency.  Run a series of patterns at 100 kHz
steps covering from, say, 13.9 to 14.5 MHz.  Ignore the change in Z, and
look at the gain (which doesn't change with the reactive part of feedpoint
Z) The gain won't change all that much, but the back lobes change
dramatically.

I suspect that for the vast majority of situations, the beam works better
than the dipole or omni because it suppresses the stuff off the back and
sides, not because it ekes out an additional 3 dB of gain.

Jim,
I have a pair of 4 el SteppIR's and my real world impressions are exactly as
you describe. The patterns are much sharper than any of the monoband beams
or tribanders I have used over a span of 40 years. I optimize my beams for
gain at a given frequency most of the time. I am still refining the combo in
a stack since I have had them up for only a couple of weeks.
73,
Howard..K2HK

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