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Topband: Flag Antenna Report

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Subject: Topband: Flag Antenna Report
From: (George Maroti)
Date: Thu, 25 Nov 1999 10:10:46 -0500
As a shortwave and medium wave DX'er, I've been following this list
with great interest the past couple of months.  It is an excellent
forum for discussing different rx antenna designs.

After reading the many postings on flag & pennant antennas, I built a
flag 2 weeks ago.  My flag was built to the exact dimensions specified
by Earl K6SE, (14 feet high by 29 feet long, mounted 6 feet above
ground).  I used a 950 termination resistor.  For the impedance
matching transformer I used an FT114-43 toroid, with 35 turns of #24
insulated solid copper (telephone) wire to the antenna, and 10 turns of
#24 to the coax (75 ohm RG-59/U).

My QTH is Mount Kisco, approximately 40 miles North of New York City.

For my first test, the flag was oriented to receive signals from the
N-NW, at an approximate
330 degree bearing.  During my local morning (1300 UTC) on the MW band,
and in comparison to my dipole and T2FD antennas, the results were as

1. Several times the flag heard stations which were completely
inaudible on the other antennas.

2. I was able to almost completely null WLUX 540 kHz 60 miles to the
South-South East.  This station was about S6 on my Drake R8B with a 30
meter dipole, and only S1 with the flag.

3. On frequencies with 2 stations audible, the flag was able to either
null one of the stations, or bring the station that was in the
background out in front. 

Tests were also conducted with the feedpoint and termination reversed,
essentially at a 150 degree bearing. This time during my local evening
(2300 UTC), I was able to receive stations in Cuba, Columbia, Venezuela
and St. Kitts.  Although these are not considered tough DX catches by
MW DXers, the quantity of these stations as received by the flag far
exceeded my other antennas. 

I'm convinced that my flag is performing as a directional antenna on MW
frequencies.  At SW frequencies however, my results are quite different
and disappointing.  My main interest was to use this antenna for the 90
and 60 meter tropical bands.  At these frequencies however, the antenna
was quite deaf.  Above 6 Mhz, gain returned somewhat, but
directionality was lost.  Gain was not equal to the dipoles or T2FD,
but the flag could be used up to 20 Mhz or so.

I'd greatly appreciate any input on what I need to do to improve
performance in the 60 and 90 meter bands.  I realize the flag and
pennant were optimized for 160 meters; perhaps those with modeling
software can determine what the optimum dimensions should be for the
tropical bands.  I'm considering replacing the fixed 950 ohm resistor
with a Vactrol to see what effect varying the termination resistor has.

Finally, this was my first attempt at winding an impedance matching
transformer, so I'd like some reassurance that I did this right.  I
wound the 35 turns on one side of the toroid, and the 10 turns on the
opposite side of the toroid.  I believe this was suggested by others,
but it is not consistent with previous designs I've seen.  I'm used to
seeing the larger (primary) winding covering the entire diameter of the
toroid, with the smaller winding wound over the primary.

Thanks in advance, and Happy Thanksgiving to all!

George Maroti

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