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Topband: Phasing Flag antennas?

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Subject: Topband: Phasing Flag antennas?
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Date: Sat, 20 Nov 1999 11:32:28 -0800
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From: Earl W Cunningham <>
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On Thu, 18 Nov 1999 18:32:11 -0600 "Mike Knowlton"
<> writes:
"I have built a Flag antenna, it has a cardiod pattern.
Antenna info at--

I live in the panhandle of Florida and pointed my antenna about 40*
(towards Boston), the antenna nulls out a lot 
of noise and Mexican MW stations."
 Pleased to hear your Flag is doing its job.  The Flag and the Pennant
were devised to be better and easier antennas to build than the EWE or
K9AY because they are ground-independent.

"I want to add a second flag and phase the two, probably using an
MFJ-1026.  I'll be putting the second Flag broadside, maximum spacing is
150 to 200 feet. I'll be looking from 540khz to topband."

The answers to my questions probably depend on the frequency, but I'm
looking for some discussion.
The MFJ-1026 is used to null noise, will it phase my antennas and sharpen
the lobe?"
Having no experience with antenna noise cancellors, I can't answer about
the MFJ-1026.

In the broadside configuration, yes, the azimuth lobe will be sharpened
significantly with in-phase feeding if the spacing is at least 1/4 wave. 
In the end-fire configuration, very little sharpening of the azimuth
pattern will occur.
What kind of pattern can I expect?
The azimuth pattern of a single Flag is about 145 degrees wide at its -3
dB points on both 540 and 1830 kHz.  

With 150-foot broadside spacing, it's 140 degrees wide at 540 kHz and 103
degrees wide at 1830 kHz.

With 200-foot broadside spacing, it's 134 degrees wide  at 540 kHz and 84
degrees wide at 1830 kHz.

Best spacing for 1830 kHz is 315', where the pattern is sharpened to 54

"How many degrees can I rotate the lobe?"
In the broadside configuration with 150-foot spacing, at 1830 kHz the
lobe can be rotated by changing the phasing in one of the Flags.  With
90-degree phasing, the single lobe will be shifted 34 degrees from its
normal (in phase) direction.  With 180-degree phasing, there will be two
main lobes, each + and - 23 degrees from the normal direction.

In the end-fire configuration, no directional control is available by
varying the phasing.

"Do I aim the two antennas in the same direction?"
Definitely yes.  Build the second Flag as an exact duplicate of your
existing Flag, including termination resistor value and matching
transformer.  Use equal-length feedlines to each Flag.  Antenna output to
the receiver will be 3 dB greater than with a single Flag.  The S/N
improvement will be even more significant due to the sharpening of the

73, de Earl, K6SE

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