In a message dated 6/26/01 8:36:06 PM Pacific Daylight Time, n4kg@juno.com
writes:
<< A current fed Long Wire is an OK antenna, but probably NOT at 20 ft.
There will be DEEP NULLS broadside to the wire and lesser nulls
off the ends of the wire.
I installed a 2L wire beam composed of an inverted VEE plus
Reflector with 150 degree apex angles and 21 ft of separation
supported by a rope boom between two 50 ft high light poles
for adjacent baseball fields. The ends were tied off 200 ft from
the center of the antenna. This beam was aimed due NORTH
from North Alabama (K4BFT 5A AL). Performance was AMAZING -
we had W1's answering CQ's an hour before sunset and VE1,2,3,
5,7, KL7, and even a few Europeans after dark. With a single inv vee
we usually work far fewer W1's and VE's. For the West Coast,
we use a vertically polarized Delta Loop which is usually about
6 dB stronger to W6 / 7 after 11 pm. It was interesting to note
that we still had many Tex, NM, Ariz, CA stations call after
CQing on the 2L wire beam aimed North. Some FL stations
were somewhat weak but still called in and were worked off
the back of the beam. We have used this antenna for the last
2 years and both times beat the 20 / 80 CW station for the first
and second time. Peak 10 QSO rate was 140, our best ever.
BTW, we also used the 40M wire beam on 15M and worked all
over the country, jumping from W1/2 to W6/7 to W4. A 3/2 WL current
fed Long Wire (e.g. 40M straight dipole used on 15M) has 6 lobes.
If the ends are dropped SLIGHTLY (15 to 30 degrees), the nulls
are filled in. If the ends are dropped too much (45 degrees) it
becomes much less effective.
K4BFT 40 / 15 / 10 CW station results using 100W output:
40M CW QSO's 738 2L40 Inv Vee + Vert Polarized Delta Loop
15M CW QSO's 355 40M Inv Vee
10M CW QSO's 15 40M Vertically polarized Delta Loop)
Total station QSO's 1108
On Tue, 26 Jun 2001 EDT N4CW@aol.com writes:
> Out of curiosity, what antennas were truly outstanding during Field
> Day this > year? I used a full-wave, fed a quarter wave from one end
(up 20
> feet!) and it performed "just okay", judging by how long it took me to
get
> responses to my CQ's.
> You can E-mail your responses directly to me to save on bandwidth.
> 73, Bert N4CW (N4CW@AOL.COM)
>
The inverted vee beam does indeed work very well. In support of the the
above report, some time after my first article on the inverted vee in 8/60
QST, someone came out with a phasing box that would phase and match 2 similar
inverted vees about .2 WL apart with separate coax feed. You could reverse
the pattern, adjusts for max gain or F/B or the 8JK configuration. For
someone in the Midwest this would be a great FD or anytime antenna to meet
all the different conditions. I used it on 160-40M and will use it again.
Another favorite "Hard Butt Kicker" for year around base use and for Field
Day, I have used horizontally oriented quads on 160,80&40M .1-.2 WL high.
Their vertical and broadside "figure 8" pattern uses the ground as a
reflector to give the RF a "jump start" up to the reflecting medium in the
sky and back down to the receiving antennas "Without Passing Monopoly Ground"
again with very very good strength out to 3000 miles much to my surprise.
The high angle pattern is fairly broad and the very low loss path seems to
make up for reduction of gain at say 45 degrees. I call it the "Slam Dunk
Antenna." There is a lot of signals on 40M all over the country on FD night
on (also160&80), so a good signal is needed to work the East coast and
Midwest from Seattle on 40M. It's a great antenna locally 24 hours a day
I've used 100 ohm balanced coax into a Match Box for example on a 40M quad
loop on 40,20,15&10M. It's a great match on all 4 bands and fairly quiet
also with balanced 100 ohms coax and the selectivity of a Match Box. I've
also used a 1/2 wave of 450 ohm open wire line cut for and Grid Dipped at 7.1
MHz into the Match Box for all these bands and it repeats the quads Lo-Z at
the end of the feedline which the Match Box matches on all bands--only if you
try it.
An interesting concept occurs on 75M--not needing the Match Box. The 40M
quad loop is a 1/2 wave long on 80M presenting a very high Z at the balanced
feedpoint. It's a bit lower Z at about the right value if a 2 wire loop is
used spaced about 6" to simulate a fatter dipole and the Z was about 4050
ohms. The open wire line is now a 1/4 wave long on 80/75M and inverts the
Hi-Z to a Low Z. Guess what the Lo-Z was? Are you setting down? It was 50
ohms--I lucked out. If it wasn't I'd have adjusted the spacing of the 2 wire
quad loop so the Z there inverted down to 50 ohms. I could also adjust the
spacing of the open wire line to fine tune the Z seen at the end of the
feedline--but I didn't have to. Now using a technique I used in another
application I hooked one wire to my IC-720 50 ohm input and the other lead to
a 3 gang BC variable stator and the rotor/frame to the rig ground lug. The
variable has a plate bent over so that when it's closed it's shorted out. As
you go higher in frequency the inductive reactance reflected at the end of a
1/4 wave feedline is canceled out by the right setting of the Xc depending
what frequency you are on above the lower resonant frequency of the loop and
open wire line--all the way to 4 MHz. Resonant low and tune high. The
remaining Rt value doesn't change much all the way to 4 MHz allowing one to
operate the entire 80/75M band-even with no tuner other than the BC 3 gang
variable. It's a great concept. I've never tried a typical rigs tuner on
this as when I first did this they didn't have them internally. It works
great even though it's a balanced feedline into an unbalanced xmiter output.
If you talk to the RF it will behave.
The pattern and gain of a 40M loop in Eznec is hardly different on 80/75M
than a 80/75M WL quad loop is on 75M. So a 40M horizontally oriented loop
operates on 80/75/40M with high/medium angle and on 20,15&10M end fire/low
angle with progressive gain. It's a great FD antenna. There is more. I
struck a "RF Gold Mine."
On 30,17&12 the 40M quad loop has a Hi-Z feed and the feedline is an odd
number of 1/4 waves which inverts the 40M loops Hi-Z to a Lo-Z at the end of
the feedline for the Match Box and easy matching. When I get time I'll write
this up with all the patterns and Z's. There is more.
A lower frequency version does the same on 160&80/75M. In SD 3 years ago I
had a 75M horizontal quad 20' high over the street fed with a 1/2 wave of 600
ohms Zo open wire line cut for 3.56 MHz into the Match Box. This Match Box
really gets a work out if you know how to use it. It would put a 20/9 signal
into Seattle on 75M running 100W. That's not exactly high angle.
On 160M a Match Box made just for 160M I'm sad to say--finally failed.
Using a UnUn mobile toroid with Z steps all the way down to 6 ohms, I
inserted it in one leg and it matched 1:1 at 17 ohms at 1.8 MHz and 23 ohms
at 2 MHz. That's too low for the Match Box. I used my trusty 1936 BC
variable once gain (everyone should have one) and it tuned out the reactance
all the way to 2 MHz. Now this is only the 2nd 160M antenna I've been able
to "use across the entire band" with a low SWR to coax. I calculated the 75M
single wire quads Z at about 21,000 ohms. The band width is very narrow due
the 1247/1 Z step down ratio but it sure worked well at 20' high. I will
make a "2 wire version" to decrease the Z to about 7000 ohms to give 50 ohms
using 600 ohm open wire line. I have a model of this in Eznec. That's only
a 144 ohm step Z down and should give much better bandwidth and no step
matching xformer is needed--just the BC variable.Xc. Very simple indeed. I
calculated that a 1025 Zo open wire line would have matched the 21,000 ohms
to 50 ohms. Unfortunately the Zo of open wire line tends to top out at about
660 ohms with reasonable spacing wider than 6".
75M quad loop presents a Lo-Z on all bands now and a 1/2 wave open wire line
cut and grid dipped for 3.562 MHz will be a 1/2 wave or multiples on all
bands (close enough) reflecting the 1 WL quads Lo-Z at the end of the
feedline for easy matching into most any tuner in particular with a "2 wire
quad" to simulate larger diameter. Unbalanced tuners can even be used with
toroids on the coax. This is a great FD or Base antenna. Now this and the
previous 40M quad only works if you actually try it.
I want to erect again a 1 WL horizontal quad loop hung between the baseball
light poles at home in SD cut for 900KHz (292'/side). It's not for the BC
band but to have an "end fire pattern" on 160,80,40M with "progressive gain."
There are football fields with poles the right spacing that aren't used on
FD (baseball fields will be) that would be absolutely great FD sites. If the
football field light poles aren't wide enough make it rectangle. I'd like to
take that new Yaesu 5W rig to Safeco Field with the big roof during a game
and do some gamma matching with a tuner on 160,80,40M. Big bridges are
potential 160,80&40M antennas anytime as are water towers if there are no
other RF Service antennas on it. Those big cranes used in shipyards are
potential antennas with some "creative feedline matching" using a tuner and a
wire with a vice grip pliers to make a connection. I'd like to try the Space
Needle or the Narrows Bridge on 160M. Awesome! K7GCO
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