I make it 4.6 dBd for the first one, +3 dB for the second one, plus 3 dB more
for doubling from 2 antennas to 4 => 10.6 dBd
This is borne out by my experience with a mixed stack of C3's and C4XL's at the
heights you mention. Going from 2 to 4 antennas seems to make more than 3 dB
of difference but I think that is psychology not electromagnetic theory.
Likewise, adding another pair for 6 should only add 1.5 dB or so, but it seems
to make more difference in operation than that.
This is all difficult to judge on HF because arrival angle makes such a
difference, and in fact is the real reason to have more antennas. I have seen
instances where the low pair is 10 to 20 dB better than all 6, and where using
the upper pair and lower pair without the middle pair (giving pretty high take
off angle) is better than any other combo.
The old W3AFM articles talk about the marginal cost of the next dB (at the risk
of sounding like an economist) and IMHO, stacking is worth the effort, after
you have done the "easier" stuff.
73 John N5CQ
-----Original Message-----
From: Josh Logan [SMTP:jlogan@bewellnet.com]
Sent: Sunday, October 18, 1998 5:17 PM
To: towertalk@contesting.com
Subject: [TowerTalk] A Question of GAIN
Assume a person built a 4 stack of C3 Force 12 multi band yagis
The C3 is given 4.6 dbd net gain for 20m
IF stacked at say 35ft, 65 ft, 95 ft and 125 ft
What would be resulting GAIN?
I would guess around 4.6 + 3.0 + 3.0 + 3.0 = 13.6 dbd net gain
Is this reasonable?? What is a good spacing ? 30 ft ?
assuming 20m performance is important.
Josh N7XM dreaming of Four Stack
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