[Antennas] FW: Feeding stacked antennas

Sun Nov 4 13:26:57 EST 2012

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年11月03日 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
>