I can agree with most of your remarks excepting one : "the boom length has
been compromised slightly". I don't think that "slightly" is the right word
in this case.
73 & mni DX
----- Original Message -----
From: "Joe Subich, K4IK" <email@example.com>
To: "'4x1ad'" <firstname.lastname@example.org>; "'TowerTalk'" <email@example.com>
Sent: Monday, November 08, 2004 11:11 PM
Subject: RE: [TowerTalk] New antenna system
> > But what about F/B or F/S ratio? Aren't they of any importance?
> Of course they are. If you spend a little time working with the
> modeling programs (or reading the ARRL Antenna Book), you will find
> peak F/R is relatively narrow on most yagi designs and most fixed
> tuned antennas fail to achieve real pattern performance over even
> half of a given band. Often the F/R of an antenna set up for CW
> will fall to less than 10 dB on phone. For example, a three element,
> 16 foot boom 20 meter yagi might show F/R > 20 dB below 14.100 but
> at 14.200 it's down to 11 dB and only 7 dB at 14.300. Similarly,
> SWR is greater than 2:1 shortly above 14.100.
> > Personally, I can't take too seriously the manufacturer claim
> > that "a long boom is not needed to achieve near optimum gain
> > and front to back ratios on 20 - 10 meters since the SteppIR
> > can control the element lengths" !!!!
> The adjustable element lengths allow the SteppIR antennas to achieve
> a very nice balance between the gain available for a given boom
> length, F/R and SWR. Quite simply, modeling will show that, within
> limits Gain and F/R are nearly constant flat as one changes the element
> spacing (e.g., the position of the driven element in a three element
> yagi with a fixed boomlength) as long as the element tuning is
> adjusted to compensate.
> With the SteppIR antennas, the boom length has been compromised
> slightly in favor of higher gain on the low end of the range to
> the detriment of best possible F/R on 10 meters. That is a trade
> that many are willing to make.
> ... Joe, K4IK
See: http://www.mscomputer.com 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.
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