[TowerTalk] Re: [DXR] beam (Tri-banders)

[T A RUSSELL]

The BEST way to combine monobanders on one boom is
with a FORWARD stagger as used by Force 12.

You can line up REFLECTORS by band / spacing because 
elements less than 1/2 WL at the operating frequency are
nearly invisible.   For example, 10M RF is "reflected" by the
first reflector and does not see the other reflectors.  15M
RF is not affected (much) by the 10M reflector and is "reflected"
by the 15M reflector.  20M RF is not affected by the 10 and 15M
reflectors and is" reflected" by the 20M reflector.

The Force 12  (2 element) tribander is an excellent example of
this principle.

The problem is with DIRECTORS where the lower frequency
directors act as inefficient REFLECTORS to the higher frequencies.
This is why most successful designs use traps or parasleeve
configurations to overcome the interactions among directors.

The new Cushcraft  X7 and X9 tribanders use individual driven
elements and reflectors with trapped 10 / 15 / 20 meter directors
to avoid the destructive interference caused by lower frequency
full size directors.

de  Tom  N4KG


On Sat, 26 Dec 1998 21:25:12 -0500 "J. Cronn" <cronnjwc@cftnet.com>
writes:
>Several years ago QST published a article describing a beam
>with 3 monobanders on one boom. Does anyone remember the
>year and month of this article?
>Thanks
>Jim Cronn
>W2GC
>
>Subscribe/unsubscribe, feedback, FAQ, problems 
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>

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