jimlux wrote:
> Cqtestk4xs@aol.com wrote:
>
>> In a message dated 3/26/2009 5:39:51 PM Greenwich Standard Time,
>> nq4u@mtars.org writes:
>>
>> Plans are to add a stack match.
>>
>> Both antennas will be fed with 75 ohm hardline cut to proper length. Wire
>> antennas will also be located on this tower.
>>
>> Will there be some pattern distortion due to different antenna spec's?
>>
>> What are some problems that others have had in stacking two different
>> antennas such as these?
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>>
>>
>>
>> Anecdotal here:
>>
>> >From what I've heard stacking dissimilar Yagis has been met with mixed
>> success. I'm not sure of the reasons. Boom length and phasing problems
>> come to
>> mind.
>>
>> I've been stacking IDENTICAL antennas since the 80's and have always been
>> successful.
>>
>>
>>
>
>
> I think a way to summarize this is that stacking dissimilar antennas is
> trickier (i.e. less predictable from casual analysis) than stacking
> identical ones. Identical ones have easier analysis math to predict
> what they'll do. Dissimilar ones will have "different" patterns as you
> switch the various configurations. It will probably work (and
> realistically, you may not be able to identify any differences, since
> it's not like you can A/B it).
>
> You could probably, without a huge amount of trouble, run some models in
> NEC to see what you'd get, pattern wise.
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>
There is a good article on stacking dissimilar antennas on the array
solutions website.
w5ah
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