[TowerTalk] Questions Please?

[DavidC]

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
----------------------------------------------------------------------------
----
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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