On (25 Feb 97) Wayne Sarosi wrote to Ray Wade...
 WS> In a message to Wayne Sarosi  Ray Wade wrote:
 RW> The reason I asked about a different feedpoint is because my KLM
 RW> KT43-XA has a log periodic feed. Unlike a regular log periodic, only two
 RW> of the elements are fed, and I was thinking it was the rearmost of the
 RW> two that has the matching network and balun (4 KW PEP) and the next one
 RW> forward is cross fed (just like all the elements of your LPDA). This
 RW> makes the KT-34XA very broad. AAMOF it will cover *all* of 20 and 15
 RW> plus about 1.2 Mhz of the 10 meter band with less than 2:1 SWR.
 WS> Log-Yagi. It's a short LPDA with probably a reflector and a couple of
 WS> directors? I believe I've seen one a while back. KLM had another
 WS> monster yagi that had a 24 foot boom I believe.
Actually it is even more monstrous than that. Six total elements. From
rear to front; one reflector, then the two driven elements, then a
director, next a 10 meter-only director and finally the forwardmost
director. On 15 and 20 meters there are thus four active elements (two
of which are the driven ones) and 5 elements on 10. 32 foot boom!. It is
a *big* beam! Forward gain varies with frequency in each band (just like
your LPDA I would guess). On 20 the gain is 8.75 db at 14 Mhz, then
declines to 8.5 at 14.1, further declines to 8.25 at 14.2, rises to 8.5
at 14.3 then declines again to 8.0 at 14.4. The gain curve looks similar
on 15 and 10. Peak gain on 15 is 9.5 at 21.425 and is above 9 db for the
remainder of this band. On 10 meters the curve is flatter and runs from
11 db at 28 Mhz, then slightly up and back across 11 db at 28.7 where it
drops silghtly to 10.75 db at 28.85 then back up again to over 11 db at
29.0.
The SWR curve runs in opposition to the gain curve. At 14.0 it is about
1.2:1, then drops to *flat* at 14.050, back up to 1.3:1 at 14.2, then
down slightly crossing 14.4 at 1.2:1 then climbs rapidly to 2:1 at 14.45
(at this point, who cares since the top of the 20 meter band is 14.350).
However this allows lots of latitude for MARS operation above our 20
meter band.
Similarly 15 meters is all less than 1.3:1 up to 21.4 where it rises
rapidly to 1.5:1 at 21.450.
On 10 meters SWR ranges well below 1.3:1 all the way to 29 Mhz where it
crosses 1.5:1, then dips slightly, then rises rapidly crossing 2:1 at
29.2 Mhz.
This antenna is made in two versions. The KT-34A has a boom only 16 feet
long where the KT-34XA is double that. My antenna will outperform
*every* other tri band beam made, and *most* monobanders as well. As you
know, it is length of boom thay gives *gain*. These antennas are
also unique in that they all use so-called "linear loading capacitors"
in the L/C network that replaces the more convential "traps" found in
other tri band beams. The capacitors are formed of a tube-in-a-tube
arrangement where the outer (all parts are aluminum) tube has on each
end an insulator which supports the outer tube, concentricly, around the
inner tube. Other aluminum straps surround each of these capacitor
"elements" to create the inductance necessary to to "tune" each set of
L/C networks.
I have had this antenna up since 1980 and it performed flawlessly until
1992 when I took it down and installed an "upgrade" kit. The kit has
*better* plastic insulators for the "linear loading capacitors" which
had degraded slightly from sunlight on their top sides. Other slight
modifications in the kit included some new outer tubes for the
capacitors that have no "drain holes" in them, as the old design did.
The drain holes were there to allow any water condensation to drain out
but was discovered to be not necessary after many years of use by them
and the hams who own this antenna. Some hams reported that these
small (1/8 inch) holes allowed various "critters" to get inside them (I
didn't have that problem). Other minor physical adjustments of the
element assemblies broadened the 2:1 SWR limit edges slightly and
improved 10 meter SWR to well above 29.2 where the original crossed 2:1.
It is even better now.
It, along with several other antennas are mounted on my 70 foot ROHN 45G
foldover tower. Someday I might replace it with your, or some other, Log
Periodic array. Since I put the all band mobile in the car in late 1995
I have "discovered" 17 meters! I would like to have it available at my
"fixed" station.
... Egotists: People more interested in themselves than in me
--- PPoint 2.00
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