[TowerTalk] Re:Stacking Distances (more info)
Jan.E.Holm@telia.se
Jan.E.Holm@telia.se
Mon, 22 Nov 1999 07:57:57 +0100
Hi Clive and all,
I can confirm this, it happend to me also. I have a 6/6 stack for
15
and 6/6 for 10 in the same tower and the low 15 and 10 ended up
3 meters from each other (10 below 15). When I cranked the 10
in place I noticed something happened since I had the network
analyzer connected but I didn´t bother with it at that time. After
investigating with NEC-2 I could see what was going on. Conclusion
was that I had to move away the 10 to atleast 5 meters distance.
(6 meters for virtually no interaction) That turns out to be a
problem since the low 10 will become kind a close to ground and
also the stacking distance towards the top antenna will be kind a
large. I ended up putting the low 10 4 meters below the 15 and have
to live with the interaction for the time being, at 4 meters I
thing I
loose about 0.7 dB gain but pattern stayed pritty much decent so
I have to live with it I guess. I will however move the 10 meter
antennas
to another tower at another date.
In any case the 10 meter 6/6 stack seems to work excelent, I have
the antennas at 24 over 11 meters so kinad a wide I guess but it
seems
to perform just right, or maybe anything works on 10 when the band
flips wide open.
Ofcourse this could be fixed by redesigning the 10 m antenna that
sits
close to the 15, can be done using NEC-2 or similar software
so maybe I even will try that.
Ofcourse any ideas on this subject are welcome.
73, Jim SM2EKM
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Från: clive@gm3poi.prestel.co.uk [SMTP:clive@gm3poi.prestel.co.uk]
Skickat: den 20 november 1999 14:39
Till: towertalk@contesting.com
Ämne: VB: [TowerTalk] Stacking Distances (more info)
Thanks for all the comments on my request re stacking. I have made
further
checks using Eznec and I have found the following. With a 4el 10m
lowest in
the stack with a 15m above it and both in line, the gain of the 10m 4el
not
necessarily F/B is reduced with all the separations I checked, that is
from
7ft to16ft.
At 7ft the gain is 2.62 db down on the 10m yagi measured on its own or
with
it turned 90 deg' to the 15m. With both antennas at 90 deg' there is no
drop
in gain with any separation calculated. With the two antennas in line
and
separated by even 16ft there is a gain drop of 0.72 db. At a distance of
what one might think of as reasonable ie 10ft the gain on 10m is down
1.83
db. I repeat that the patterns appear reasonable but the max gain is
down. I
suspect there are many stations out there thinking there antennas are
working well ie F/B but the gain is down by the equivalent to a 2nd yagi
phased. Is there anyone that has confirmed my results?. By the way I
used CC
4el designs for the yagis.
My thought is that the problem lies with the forward D2 on the 15m
absorbing
10m RF. any comments. 73 Clive GM3POI
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