A discussion has been raging on the TowerTalk Ham Internet
reflector about Log Periodics versus Yagi antennas.
I have tried to press for more fact than smoke but lack some of the
hard facts I need to know before making my own choice.
I have no interest in any trapped tri-bander, nor in the TH-7DXX or the
KT-34XA as I find them unwieldy and underperforming. I also have little
concern about beam performance on the frequencies in between the Ham bands.
Can you provide estimated figures so that I may contrast the Force 12
yagis with the Tennadyne LPDA's as I consider which to try here at our
new QTH, please? (I have entered the data I found on the Force 12
site, I still need the some missing data filled. I also need the
band-specific
data for all categories for the Tennadynes.)
As you can see I have shared this request with the good folks on the
TowerTalk list so that they might also learn from the information gathered.
FORCE 12: C3, C3S, C3SS versus Tennadyne: T-6, T-8 and T-10?
C3 C3S C3SS T-6 T-8 T-10
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----
SWR (worst case within band limits):
20m <1.6:1 <1.6:1 <1.6:1
17m ~2.8:1 ~2.8:1 ~2.8:1
15m 2:1 2:1 2:1
12m ~3.2:1 <4:1 <4:1
10m 2:1 2:1 2:1
Gain dBd*:
20m 10.4 10.3 10.1
17m 7.6 7.6 7.6
15m 10.6 10.5 10.5
12m 7.4 7.1 7.1
10m 10.2 10.2 10.2
F/B Ratio:
20m 15 14 18
17m 7 6 6
15m 18 17 17
12m 4 3 3
10m 18 16 16
F/S Ratio:
20m
17m
15m
12m
10m
Expected Pattern (mounted at 65 feet above sandy soil in west-central
Florida,
north of Tampa and 4 miles inland from the gulf)
20m
17m
15m
12m
10m
Thanks! & 73, DavidC K1YP
NOTES:
* I am using the following definition of "gain" from the Force 12 site.
Please offer an alternative that is applicable to both antenna types,
without a bias, if this one is deemed inappropriate.
"Gain at 74' includes ground reflection gain and is the computed maximum
forward gain of the antenna over real, average ground at a height of 74',
as
compared to a dipole in free space. To convert to dBi, add 2.14 (e.g.
11.8dBd
+ 2.14 = 13.14dBi). On dipoles, gain is shown as "n/a". Computations are
performed using state of the art modeling software: NEC-4, EZNEC, AO,
YO and are validated using consultants. FORCE 12 does not use traps, so
there are no assumptions needed about possible Q of the traps (coils)."
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