Hi Tom,
I haven't investigated this yet. But I'll bet that the effect is
very minimal given the H-Plane directivity (or lack of it) of
what is essentially a short boom 3 element yagi.
Do you have any idea about the quantity of "pattern loss" we're
looking for here? I'll be pretty shocked if it turns out to be
enough to drop the array below the performance of a single
antenna.
Lunch is going to seem free all next week anyhow. At least until
the turkey meat runs out.
I'll gin up a model and see how much of an effect this really
is. Stay tuned.
73, Eric N7CL
To: <towertalk@contesting.com>
>Date: Tue, 24 Nov 1998 14:51:29 -0600
>From: n4kg@juno.com (T A RUSSELL)
>
>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 equally.
>
>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
>boom.
>
>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:
>>
>>
>>Steve,
>>
>>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
To: <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
>>>ignore takeoff angles for the moment (I don't know if this is
>>>possible with this question - sorry).
>>>
>>>Suppose I had two non-LP multi-band yagi antennas that covered
>>>40 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 40-10M 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 greatly appreciated.
>>>
>>>Cheers, Steve K7LXC
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