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From: Don Moman[SMTP:ve6jy@freenet.edmonton.ab.ca]
Sent: Wednesday, July 22, 1998 10:11 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Another Stacking question
Don: I think that what you did has probably allowed good impedance match for
each of the antennas, however you need to assure that each driven element gets
power from the original feedline in phase with each other. Otherwise, you may
lose gain instead of adding it!
73/Mike, N7ML
PS some people forget to be sure that the baluns are all phased properly too,
that has left a lot of people scratching their heads when the gain was
evidently less than a single yagi.
I see comments on two methods of connecting antennas in a stack.
Most frequently, using equal lengths of cable from all antennas is
mentioned. The other way mentioned is using odd multiples of 1/4 wave
lengths of 50 ohm.
In my three high stack on 20, I went with the odd multiples. The upper and
lower antennas use 80' (7x) of RG 213, and the middle uses 34.3' (3x) and
all reach the WX0B stackmatch box near the center antenna. This approach
"wastes" very little coax. Using equal lengths would require an extra
45.7' to be used at the center beam.
I am in the process of planning the 15m stack, 4 high with .75 wave
spacing, and again plan to use the 1/4 wave approach which will minimize
wasted coax (and loss). A stack match type of approach will be used to
select various combinations. All antennas will the 6 el 48' boom OWA
design, which has a very flat and broad SWR curve. However I see frequent
comments about using equal lengths, which makes me wonder why. I am not
stacking tribanders, which is about the only reason I see for using equal
lengths. I am willing to believe both methods are fine, and perhaps the
equal length approach is simpler (no math) and that is why it is suggested
more frequently. Is one method better than the other? and why?
On a related matter, does anyone know if the DX Engineering 6 way box uses
equal length routing? I was planning to use one for the 15 and eventually
10m stacks, but not if I have to allow for different electrical lengths.
Thanks, 73
Don
VE6JY
VE6JY Don Moman email:ve6jy@freenet.edmonton.ab.ca
Box 127 Lamont, Alberta email forwarding: ve6jy@rac.ca
T0B 2R0 (403) 895-2925
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