Thanks for clarifying that. It still seems to
me it would be easier to switch in reactances
at the center of the driven element that it
would be to have an additional element. A lot
of the 80M Yagi's are already doing this.
Also, on a 100 ft boom, my modeling experience
has been that 3 elements (one driven) have as
good gain and F/B as 4 elements (one driven).
What does your modeling show?
Rick N6RK
Don Moman VE6JY wrote:
> As others have correctly stated, it is an OWA style design so it is closer
> to a 3 element on 76 feet, which is a bit short still, but in in the 9
> 1/2
> years that it has been up, it has been a good performer. At 53 deg north
> (and way too close to the north magnetic pole) I need that much aluminum
> to
> keep up with guys with low dipoles just a few hundred km south! Some of
> the
> time, anyway.
>
> When the beam was built in the summer of 1998, weight was a big concern as
> the antenna would be installed "manually" with a winch line and gin pole,
> and leapfrogging the guys, to get it to the 160' level. So at an
> estimated
> 1300 lbs, this was plenty to handle in this fashion. A longer boom would
> have added more weight than I was equipped to handle at that time.
>
> Plans are under way for a 5 el OWA design on 100 feet of Rohn 80 boom.
> The
> boom is bolted together and weighed in at 1900 pounds. A finished target
> weight of 5000 lbs or less is the goal, the capacity of the crane that
> will
> be used to lift it to the 150 foot level. Progress has been slow, most of
> the raw materials are on hand, the tower anchors are in, but many hours
> are
> needed to put it all together. And summers are too short up here.
>
> Don
> VE6JY
>
>
>
>
> On Sat, Mar 29, 2008 at 9:25 PM, Richard (Rick) Karlquist <
> richard@karlquist.com> wrote:
>
>> The boom on this is only 76 feet. That would be
>> 19 feet on 20 meters. This seems way too short
>> to justify 4 elements. In fact you can do pretty
>> well with 3 elements up to a 26 ft boom on 20m.
>> IMHO, the "full size" moniker applies only to the
>> elements, not the boom.
>>
>> Rick N6RK
>>
>> Rob wrote:
>> > ... and then there is the 4 element full size 80m yagi.... (+ others
>> > on the website).
>> >
>> > http://alfaradio.ca/users/ve6jy/ve6jy-80m.html
>> >
>> > Rob
>> > VE6TR
>> >
>> >
>>
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