Posted by
Peter Chamalian on
Jan 05, 2012; 3:22pm
URL: http://elecraft.85.s1.nabble.com/Horizontal-Delta-Loop-Questions-tp7154769p7154802.html
I have a full size 80 meter delta loop that is vertical, hung from a support
on my tower at the 75 foot point. The shape is not ideal (too much
horizontal but I can't do any better). I feed it with 450 ohm line at the
0.64 wave point down from the top. The antenna is then tuned with an
AT-Auto (Palstar) and I've used other tuners as well. This antenna does not
tune at all well on 160. The Q is out of sight (very sharp) and if you can
get a match (I would with an old Murch but not the AT-Auto) it was only good
for a few kHz before you had to retune and tuning was very touchy.
I never tried lengthening the feedline -- I just put up a true 160 meter
antenna, a Double-L which works OK. After three years of very casual
operating, I made DXCC on top band.
Pete, W1RM
-----Original Message-----
From: Rick McClelland, AA5S [mailto:
[hidden email]]
Sent: Thursday, January 05, 2012 10:14 AM
To:
[hidden email]
Subject: [Elecraft] Horizontal Delta Loop Questions
Hi,
I'm a CW operator who dwells in the lower end of the HF bands. My current
antenna is a 200' horizontal delta loop 40' high, fed with 87' of 450 ohm
ladder line. This connects to a 4 to 1 balun (common mode choke?) which is
attached to my Dentron Jr. Monitor tuner via 5' of RG213. Looking at a
spreadsheet, I see that a full wave loop for 80 meters is 287' and 143.57'
for 40 meters.
A hypothetical question to the wise ones on this list is would I expect any
practical improvement in performance of my antenna system (on 40 meters and
above) by reducing my 200' delta loop to 143.57' and feeding it with 71.78'
of ladder line so that the sum of the antenna length plus twice the ladder
line length is 287'? This seems to make theoretical sense since the
entire system would be resonant at 7mhz and integral multiples thereof.
However, the performance of my current 200' loop appears to be quite good
from 80 to 6 meters and my small tuner matches whatever impedance this
system is presenting to it so I'm hesitant to take a pair of snippers to my
antenna.
I would like to increase the length of the loop to 287' feet and feed it
with 71.78' of ladderline but that is another story. Also, would I expect
to be able to tune any of the these three antennas on 160 meters if I were
to purchase either a KXAT100 or KAT500 tuner which presumably have a wider
tuning ranges than the Dentron Jr. Monitor tuner?
Rick McClelland, AA5S
Fort Collins, CO
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