[TowerTalk] Stacking question

T A RUSSELL n4kg@juno.com
Tue, 24 Nov 1998 14:51:29 -0600

Re:   Sloping booms in stacked LP antenna systems

This technique was used at least as far back as the 1960's.
Such antennas were in use at the Collins Radio Company
Headquarters station in Cedar Rapids, Iowa and other locations.

While the sloping boom technique tends to maintain uniform
spacing, there is a pattern loss associated with sloped booms.

An upward sloping boom will increase radiation at the higher
incident angles, but suffer pattern loss at the associated ground
reflection angles.  The net result is LESS gain than a HORIZONTAL
boom which illuminates the incident and ground reflection angles

Similarly, a downward sloping boom will enhance the ground 
reflection angles but suffer pattern loss on the higher incident
angles.  Again, the net result is LESS gain than a HORIZONTAL

There is NO   FREE   LUNCH   in antennas or elsewhere.

de  Tom  N4KG

On Mon, 23 Nov 1998 14:08:12 -0700 Eric Gustafson <n7cl@mmsi.com> writes:
>I don't know how you'd do it mechanically.  But, as long as we're
>speaking hypothetically, you could mount the antennas so that the
>spacing increased from front to back.  Some of the wire zig-zag
>log periodic antennas were stacked this way.  This maintains the
>stacking distance to be nearly optimum for each operating
>frequency.  Only a small (usually 3 element) cell of the antenna
>is active on any one frequency.
>73, Eric  N7CL
>>From: owner-towertalk@contesting.com
>>Date: Sun, 22 Nov 1998 10:36:03 EST
>>Greetings, TowerTalkians --
>>       Let me pose a general hypothetical question; I'm going to 
>>takeoff angles for the moment (I don't know if this is possible with 
>>question - sorry).
>>      Suppose I had two non-LP multi-band yagi antennas that covered 
>>through 10M and was interested in contesting. In the overall scheme 
>of things,
>>is there a stacking distance that would allow the benefits of 
>stacking with a
>>minimum of compromises? For example, is 50 feet too far on 10M (and 
>15M?) and
>>too close for 40M? Intuitively I think it would be better to have the 
>>antenna on the top of the tower and drop the 40M from the bottom 
>antenna. This
>>would probably simplify the whole scenario. 
>>      I don't have and am not fluent with any antenna modelling 
>software so
>>I'm just trying to get a feeling for this proposed system. Any input 
>>Cheers,   Steve   K7LXC      
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