[50mhz] 5 over 5 stacking recommendations

[Lance Collister]

Ray Brown wrote:
> ----- Original Message ----- 
> From: "WD0T" <wd0t at mncomm.com>
> To: <50mhz at mailman.qth.net>
> Sent: Saturday, May 05, 2007 8:44 PM
> Subject: [50mhz] 5 over 5 stacking recommendations
>
>
> Greetings all, first time posting here!
>
> I have a question on recommended stack spacing, for using 2 cushcraft 5 element 6m yagis, looking to put 2 up on a short crank up
> tower for the June VHF contest.  By short tower I mean a 30ft to the lower 6m antenna. I am talking about stacking one above the
> other.
>
> What would you recommend for stack spacing using 2 of the CC 5 element, stock standard yagis?  Max gain would be nice, but also I
> need to not get crazy in terms of spacing distance.  I have seen in some places recommendations for .6 wavelength spacing for lower
> sidelobes, however I have also read that each type of antenna and height needs to be modeled to arrive at optimum spacing.
>
>
>
>   Howdy! Glad to see a question that I can answer! :-)
>
>   What I have at home is a pair of MFJ-1762 3-element 6m beams, in phase.
> Their manual gives instructions on how to construct a harness that can be used
> to feed the two antennas. The major trick is to space them 5/8 wave, or about
> 11'6" apart, then make sure you attach the center of one coax to the right side
> of the driven element (ground to the other side), while connecting the center of
> the other coax to the left side of the driven element on the other antenna.
> The instructions here are pretty clear...
>
> http://www.mfjenterprises.com/man/pdf/MFJ-1762.pdf
>
>   Good luck!
>
>                 _Ray_        KBØSTN
>
>
> Moderator: Ray Brown, KB0STN
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>   
Boy, WATCH OUT!  Normally (when you use equal length phasing lines, as 
most people do), you must remember to attach the center conductor of the 
phasing lines to the SAME SIDE of each yagi when the array is viewed 
from the front or rear!  Note that the only reason the MFJ instructions 
call for REVERSING the attachments is to correct for the fact that their 
phasing line lengths are NOT equal - they are 180 degrees out of phase! 

Since this is a mistake many first-timers make when trying to phase 2 or 
4 yagi arrays (when they often turn the upper yagis upside down) I felt 
I better clarify this unusual configuration, caused because of the very 
unusual difference in phasing line lengths. 

GL and VY 73, Lance

-- 
Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8)
P.O. Box 73
Frenchtown, MT  59834  USA
QTH: DN27UB
TEL: (406) 626-5728
URL: http://www.bigskyspaces.com/w7gj
2m DXCC #11/6m DXCC #815