On 4/13/2013 4:19 PM, Steve K7AWB wrote:
Anyone have any opinions on which one to use?
Hi Steve,
Some thoughts. First, the table is the result of a MODEL, not a
measurement. Second, gain is given as a single number, without
reference to bandwidth nor beamwidth.
Third, it's long been well known that given equally good (well
optimized) design, the primary influence on gain is the boom length. You
can tweak element lengths and spacing to trade a bit of gain for a bit
of F/B, beamwidth, or bandwidth, but I'd bet that most designers are
trying for close to the same set of compromises. In the table, you could
draw a pretty straight line on a scatter graph of gain vs boom length,
with no data point more than about 0.5dB off the line. I would tend to
view a table like this as "truth test" -- if the advertised gain doesn't
correlate pretty closely with boom length, someone's probably lying. :)
There is, of course, the issue of build quality, ruggedness, efficiency
of the matching system, support by the manufacturer, etc.
73, Jim K9YC
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