Interlaced Yagis suffer from undesired interactions.
The lower frequency director(s) act as inefficient reflectors
on the higher band. Several years ago I built a 3L15 inside
the parasitic elements of my Telrex 3L20. It worked, but
later computer analysis showed that at best, I could only
achieve about 2 dB less gain than would be available if
the 3L15 was up by itself. That is why Force 12 uses
forward stagger for their multi band beams.
Adding a second 10M director in front of the 15M director
will produce another 1 dB of gain on TEN. This is
basically what the TH6 does with a 10M director
followed by a 15M director and a trapped 10/20 director.
HyGain has a new 12/17M para-sleeve fed Yagi that
can also be tuned for 10/15M.
Force 12 has some 10/15M duo-banders using 4L on 10
and 4,5,or 6 elements on 15.
I have no affiliation with any antenna manufacturer or distributor.
de Tom N4KG
Am presently condidering combining a home brewed 4 element for 15
meters with a homebrewed 5 element for 10 still on design stages . on
a single boom. No great feat in itslef I'm sure. However here's is
the challenge: I have acquired a storm damaged th6dxx some parts and
the complete driven element still in tact. Wonder if any body has any
ideas about removing the 20 meter portion of the traps and using the
driven element as a 10/15 meter driver.
The other elements will all be full size on 10 and 15, as I see it
effective matching may be a problem , mechanically the hard ware is
already proven. needless to say , it is easier to keep one antenna
aloft than two, stacked one above the other. this would save an extra
boom loading and of course use only one run of coax.
What say you antenna gurus ? BTW am not interested in refurbishing the
th6. Already have monobander for 20.
Appreciate any comments.
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