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[TowerTalk] SWR question

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Subject: [TowerTalk] SWR question
From: (Michael Tope)
Date: Fri Feb 28 02:07:38 2003
> option A - I have an SWR measured at the output of the amp of 1 : 1 and I
> have an indicated output power of 1 KW.
> option B - I have an SWR measured at the output of  the amp of 1.5 : 1 and
> have an indicated output power of 1 KW.
> At the DX location, will the option A signal be stronger or the same,
> everything else being equal.
> Bruce K1MY


The difference in gain due to mismatch will be inconsequential as long
as the VSWR is below 3:1. The low VSWR is a nice perk, but the real
key with the SteppIR antenna is the ability to optimize gain or F/B as
a function of frequency. In the case of a fixed monoband yagi, you can
get peak eletrical performance (F/B or forward gain), but only over a
fairly narrow bandwidth (probably around 2%). With the log yagi, you
extend the bandwidth, but at the expense of peak gain and F/B. The
steppIR allows you to optimize tuning for maximum F/B or Gain (
performance near the level of a monoband yagi having the same
boomlength) over a very wide bandwidth (~1 octave). The main
limitation with the SteppIR is the fixed boom length which eventually
catches up with you at the low-end (boom too short) and high-end
(boom too long) of the antennas operating range.

For the same boom length, the SteppIR should be capable of
deliverying a stronger signal at the DX location as compared to a
log yagi (offhand I would guess by 2 to 3 dB).

Although I haven't heard any complaints about the reliability of the
SteppIR antennas yet, the log yagi may prove more reliable over the
long haul as it doesn't have any moving parts or active components
(e.g. stepper motors, control electronics). If however I could convince
myself that the SteppIR is indeed reliable (based on the experience of
others who have had them up for a while), that would be my first choice.

73 de Mike, W4EF......................

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