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Great
antenna, easy to build
By
George Maroti
Flag
and Pennant list, October 12, 2000
Back in November, 1999, I summarized my experiences with my first
Flag antenna.
The entire article can be found here.
At that time, I felt my antenna was useful for MW BCB, as gain and
directivity were acceptable.
However, I was disappointed with its performance in the 60 and 90
meter SWBC bands. The antenna was quite "deaf". Many Topband Dxers
offered advice, and the consensus was that my problem may be due
to my hand wound impedance transformer, or common mode currents
on the coax.
With the DX season upon us, I decided to give the Flag another
try, but with a different impedance transformer.
Rather than wind my own using a different toroid, I bought a Mini-Circuits
16:1 transformer from Nebraska Surplus Sales. More info on this
product may be found at Mini-Circuits'
web site.
With the new transformer, things improved on the SW tropical bands.
The gain is still a bit low as compared to a resonant dipole, but
adequate; comparable to my K9AY loop.
I also have directivity in the 75 meter band, where on 3905 kHz
I'm able to reduce stateside ARO activity to better hear either
Radio New Ireland in PNG or Radio Merauke in Indonesia. The F/B
is still not as dramatic as on MW however.
On medium wave, my nulls are comparable to my K9AY Vactrol
terminated loop. Recently, auroral activity has been such that on
a non-directional antenna, Central and South American stations have
been dominant between 550 and 1000 kHz. With the Flag pointed North,
the Latin stations were completely eliminated, revealing US and
Canadian stations to the North that were completely inaudible on
non- directional antennas.
Unfortunately, neither my Flag nor my K9AY loop displays such dramatic
results in the SW tropical bands. For me, the antennas are still
useful in these bands as I'm able to reduce or eliminate noise,
and my S/N ratio is improved. Claims have been made that the Flag
has a good F/B even on 40 and 80 meters. I've yet to observe a situation
where I can nearly eliminate a co-channel station in those bands
as I can with the MW BCB.
To me, the Flag has several strengths, particularly if you're
primarily interested in DX from one direction.
The antenna is simple to construct, is relatively small, and has
no direct connection to ground (and thus can be suspended in the
air).
It's main shortcoming, particularly as compared to a K9AY Vactrol
terminated loop, is that it's more involved to rotate a Flag, Pennant
or Delta if several directions are desired. |
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