> There's probably some elegant mathematical proof (along the lines of
> Chu's and Harrington's) that says you can't get there with the
> constraint of all being on the same boom and interlaced (e.g. having
> a really long boom with a 20m 5 el Yagi, a 15m 5 el Yagi, and a 10m 5
> el Yagi, arranged end to end, probably isn't a "good" solution, even
> if the RF performance would be fairly good.
Arranging three monoband antennas end to end would violate the 95%
efficiency for the total boom length criteria but that was my point
from the beginning. Unless one is using tunable elements, the wind
load (extra elements) goes up significantly and/or the efficiency
goes down significantly in any triband antenna design.
Absent a rotating tower, monoband antennas for 40, 30, 20, 15, 17, 10
and 6 meters (or even 20-6) are out of reach for most single tower
stations. The SteppIR DB-36 and DB-18E (or original Yagis for 20 -
6 meters) are game changers in many cases.
73,
... Joe, W4TV
On 3/2/2011 8:46 PM, jimlux wrote:
> On 3/2/11 1:16 PM, Joe Subich, W4TV wrote:
>>
>> > The extra elements give you extra degrees of freedom. It's like
>> > building a filter. More sections gives you the ability to have a
>> > passband that's wider and flatter.
>>
>> I haven't seen a successful (95% efficient for the total boom length)
>> OWA design that covers 20/15/10 meters much less 20, 17, 15, 12, 10
>> and six meters.
>>
>>
>
> I was actually referring to a single band design.. if you have 4 or 5
> elements for a single band, you can simultaneously get flat Z across a
> wide band, good F/B, and good directivity.
>
> For a multiband design.. I doubt it. The F12 multiband 20/15/10 is
> basically a 3 element on each band, with a clever design to use a single
> feedpoint, and it's getting pretty cluttered on the boom with 9 or 10
> elements already.
>
> There's probably some elegant mathematical proof (along the lines of
> Chu's and Harrington's) that says you can't get there with the
> constraint of all being on the same boom and interlaced (e.g. having a
> really long boom with a 20m 5 el Yagi, a 15m 5 el Yagi, and a 10m 5 el
> Yagi, arranged end to end, probably isn't a "good" solution, even if the
> RF performance would be fairly good.
>
>
>
>
>
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