<< In a message dated 9/18/01 6:02:31 PM Pacific Daylight Time,
ve9aa@nbnet.nb.ca writes:<<
Frank, et al
Guess I missed the original post and the subsequent ones, but FWIW, I've
tried hundreds of antennas over the years
for all bands 70cm-160m, many of them on 160m.
Specifcally for 160m, in no real order:
Alpha-Delta DX-A twin sloper
Low dipole (apex @ 48')
Inverted Vee (variation of same)
Carolina Windom 160
Full wave loop (rectangle) (not horizontal loop, but perpendicular to the
Earth) Shuntfeeding a 48' Delhi tower (with 20' mast & LOTS of antennas
on top) 1/4-WL inverted L wire (top 'corner' @ 50')
5/16th-WL Inverted L wire with series cap
The last antenna BAR none kicked the others butts BIG TIME.
I strung 170' of insulated #12AWG as an inverted L over some tall Poplar
trees in my yard, with a large series air variable ~800pF and it really
works well. I have about 30-some full length 1/4wl radials)
It ain't no 4-square but it is amazing. I rarely get on 160m anymore but in
a year and a half or so I worked 150+ countries
on 160m running either 100w or 1kW.(usually the latter)
I almost always had 2 or 3 antennas on the go at any one time so always did
the "A-B" comparison thing.
I can assure you, the 5/16th inv-L cracked the pileups 8 or 9 times out of
10, the first call. Now, I live in a swamp so have great soil for 160m but
this antenna REALLY works.
Save yourself some time (AKA blood/sweat/tears) and install an inverted L.
1000' unterminated BEV for RX @ times
FWIW
Mike VE9AA
Michael, Coreen & Corey Smith
(VE9AA, VE9AAA & Baby-VE9)
271 Smith Rd
Waterville, NB
E2V 3V6
Canada
http://members.tripod.com/~ve9aa/index.html
http://www.geocities.com/RainForest/Vines/2174/ >>
Mike: This is a very good report. The L has been a very good antenna even
back in the 30's. I started a trend of making it longer than a 1/4 wave and
adding a variable BC variable in series to tune out the XL from being too
long. It also raises the Rr closer to 50 ohms or even above for 70 ohms
coax. Another concept is to make it long enought to a "Create 160 Ohm" Rr
feedpoint and match it with 90 ohm coax. This improves the ratio of Rr/RLoss
for the same radial system and that is always beneficial. The vacuum
variable is nice but is a problem to adjust from the shack. The 1000 pf BC
variable does its thing in less than 180 degress across the whole 160 or 80m
band. One suggestion is to adjust the length and orientation of the L so
that 50 ohms is obtained say at 3.6 MHz. This way the Rr at 3.5 MHz is less
than 50 and above 3.6 MHz it's above 50 rather than 50 ohms at 3.5 MHz The
idea is to get the best average SWR curve from 3.5-4 MHz or 1.8-2 MHz or the
range of frequency you will use. This procedures should be obvious but there
are still some that can't grasp the idea.
I've had great success with the horizontal quad loop for local and a fair
ways out with no skip zone like a vertical. I've worked some 4000 mile DX on
75 SSB also. A quad loop say .15 WL high uses the ground as a reflector
giving it a "kick start" up up up and away not even passing over ground
before it hits the receiving antenna. I call it the "Slam Dunk Antenna." It
has a very efficient path.
I use a couple of ways to load a 80M quad loop 20' high on 160 (or a 40M loop
on 80M) with a way to get low SWR (50 ohms) over the entire 160 or 80M band
using 600 ohm open wire line with virtually no feedline loss. I loaded a 40M
loop on 160M one time (15 KHz bandwidth) with 35W and beat a local with a
KW-1 on AM using an L in signal to another AM station 25 miles away. High
angle does far more than most are aware of throughout the entire 11 year
cycle and over 24 hours. I consider the horizontal loop a must for every
ham.
Your having 2 to 3 different antennas up for a A/B/C test is a great idea
that few do. I've worn out a couple coax switches over the years. k7gco
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