[Antennas] FW: Feeding stacked antennas

[Christopher Boone]

Actually with 4) 50ohm loads, you have other choices....u can use 50 ohm line throughout with some lengths being 1/2 wave long and some being 3/4 wl long or go with a 4 port power divider and same lengths of 50 ohm cable to each antenna...with the 50 ohm coax option, u will tie two together at a T making it a 25 ohm point then use a 3/4 wl piece to transform to 100ohms at the main T where both coupled will present a 50 ohm match.

Terry Conboy <n6ry at arrl.net> wrote:

>Jim,
>
>You already know how to do this!  You can just use another pair of 1/4 
>wavelength 75 ohm lines to combine the two pairs of Moxons into a single 
>feed at 50 ohms.  So in the end you'll need six total 1/4 wavelength 75 
>ohm sections for the four antennas.  If the any of the lines don't quite 
>reach physically (depending on your spacing and the 75 ohm line velocity 
>factor), you can add two equal lengths of 50 ohm line from each of the 
>two symmetric pairs, then combine those with the 75 ohm sections.  
>Should work like a champ.
>
>73, Terry N6RY
>
>On 2012-11-03 9:02 PM, Jim Miller wrote:
>>   
>> Subject: Feeding stacked antennas
>>   
>> How do I match four 50 ohm driven elements (in phase) to 50 ohm feed line?
>>
>> For years I have been considering placing a 2 meter directional antenna into
>> my attic (because that is the only place where I can have one).  I find that
>> for 2 meters that the Moxon antenna would rotate between my roof braces and
>> possibly even a pair that are two Moxons wide.  I want to make it 2 tall
>> first and later add another pair alongside the first ones later.  The two
>> tall stack would be about 78 inches tall overall not including rotor and
>> that will fit in my attic.  Two over two would be separated by 19 inches(or
>> so) horizontally and still be 78 inches tall.  The driven element to
>> reflector would be about 11 inches so if carefully placed may also be able
>> to turn between my 24 inch spaced roof braces.
>>
>> OK, so with the two Moxons vertically stacked, I would try the 75 ohm cable
>> to a tee and then 50 ohm to the shack for matching.
>>
>> The question, HOW do I feed the two over two stack and get to 50 ohms ????
>> If this isn't too stupid, can I just run all four together with same length
>> 50 ohm coax or short ladder line pieces and then a 4:1 balun or toroid?
>>
>> I am excited with the modeling results (I am in Kindergarten on modeling) of
>> this and the small size and ability to rotate inside my attic to give me
>> gain and directionality.  I have had the modeling results for over three
>> years and only started to build a prototype in that time.
>>
>> I intend to build these two vertically very soon (weeks-month) but want to
>> double the stack in the future.
>>
>> Comments please.
>>
>> Thanks es 73, de Jim KG0KP
>>
>
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