Delta RX Antenna used by FO0AAA
from
Earl, K6SE
on
June 1, 2000
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Several subcribers inquired about the Delta 160-meter receiving antenna
used at FO0AAA.
It is a close relative of the Pennant and Flag antennas, which are
ground-independent relatives of the Ewe. The Delta is a modification of
the "delta-shaped Ewe loop" shown in figure 7-66 on page 7-51 of ON4UN's
new Low-Band DXing book.
I took John's Delta-Ewe and, with the feedpoint and termination located
at the bottom corners of the triangle, I used EZNEC to optimize the
design for best F/B and zero reactance at 1.830 mHz. This is the design
that was built by ON4UN for use by FO0AAA.
It is a delta loop-shaped antenna with a 28-foot (8.537m) bottom
horizontal wire and the apex 17 feet (5.183m) above the bottom wire.
That means there is a total of about 72 feet (21.951m) of #14 AWG wire in
the triangular loop.
The EZNEC design had the bottom horizontal wire 3 feet (0.915m) above
ground, therefore the apex was 20 feet (6.096m) above ground. It is a
ground-independent antenna, without the ground-related shortcomings of
the Ewe.
The termination resistor, which goes in one of the bottom corners of the
loop, is 950 ohms non-inductive. The feedpoint is at the other bottom
corner and the feedpoint impedance is 950 ohms with zero reactance at
1.830 mHz. An impedance matching transformer such as those previously
described on the Topband Reflector for use with the Pennant or Flag
should be used with the Delta antenna.
The F/B ratio in the EZNEC model is greater than 40 dB and the cardioid
pattern directivity of the antenna is in the direction of the feedpoint
end of the antenna (the same as with the Pennant, Flag, or Ewe). The
gain of the antenna is about -34.5 dBi, so a receive preamp should be
used with the antenna.
The primary reason this design was chosen by the FO0AAA team was that it
was an easily-erected and easily-rotated directional receiving antenna.
Only one support at the apex is needed (which must be non-metallic). The
bottom corners of the antenna can be attached and pulled taut with rope
to tent stakes driven into the ground. To change directions, it is a
simple matter to relocate the tent stakes to the desired direction and
re-attach the corners of the antenna.
Unfortunately, this design was done too late to make it into an article
about Flags and Pennants I wrote for QST (which will probably appear in
the July 2000 issue).
73, de Earl, K6SE
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Delta RX Antenna used at FO0AAA
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by K6SE on June 4, 2000
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I was mistaken when I wrote that the Delta rx antenna used at FO0AAA for 160-meters would not be covered in the article about Pennant & Flag rx antennas which will appear in next month's (July) QST. I was able to add the info about the antenna just before the publishing deadline.
73, de Earl, K6SE
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Delta RX antenna used at FO0AAA
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by N2TK on June 5, 2000
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I have built one of these receive antennas pointed at Europe. The base is 6' above ground.
I have a EWE antenna, 15'H X 38'L also pointed at Europe. It has an insulted wire on the ground connecting the two ground rods together.
Only have data for two months. The trend is that on 80m the EWE hears better. On 160m the delta loop hears better. Not a huge difference, but noticeable listening to European stations. Not sure if the difference is more to the value of the terminating resistors (optimized for each band?) or the antenna itself.
Need to try changing the value of the resistor with a noise source off the back for both 80 and 160m to see the difference for both antennas to see if the terminating resistor makes a difference.
Tony
N2TK
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RE: Delta RX antenna used at FO0AAA
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by VE6WZ on June 8, 2000
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Earl, Could i not make this antenna switchable by inserting a switch box with a DPDT relay on each end of the loop which would switch in either the terminating resistor or xformer matched feed-line. Feedlines and control lines all with good current baluns of coarse. I realize this antenna design was meant to be rotatable, but i am thinking of trying one strung up in the woods. Two directions from one loop would be best. I have read that one support and two 90 deg. loops will couple/ interact...??? true?? if not i can see 4 directions with one support, two loops and some relays, diodes...etc. etc.
de Steve. VE6WZ.
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