Proper Phasing of two Andrew DB224 Antennas
 

I would like to install two Andrew DB224 4-element colinear antennas as a
DB228 (8 element). When the antennas were ordered to replace a Celwave P654, I
was told that two 224 and and the proper phasing harness would be the same. The
antennas and harness were ordered but I have a problem. The antennas were
shipped but I'm now told the phasing harness for the amateur frequencies (-007)
is no longer available. I have received some information on the phasing harness
but from the drawings provided, the two outputs are not the same length
therefore will not be in phase. Since the antennas are the same, wouldn't the
two outputs of the phasing harness be in phase or is it normal to provide some
downward tilt. Unless I'm badly mistaken,the antenna element should be fed
in-phase giving maximun gain in the horz.direction.
Don AF4Z

right me old Hubert, don't know what the grief is for? The bloke asked a
simple antenna question!

If you take and erect at ground level, two 1/4 wave vertical antenna
elements,
spaced 1/2 wavelength apart.
Install a good radial earth.
Fit both vertical elements with 1/4 wavelengths pieces of 50 ohm coax cable,
Take both cables to a, 2 female / 1 male, pl259 T piece, in the middle at
1/4 wavelength .
The T out cable goes to rig.
Then take a 1/2 wave piece of coax with a PL female plug on one end, and a
male on the other.
Insert this 'stub' between the vertical element and the T piece.
this make one side of the array feeder, 1/2 wavelength longer, making it 3/4
wavelength,
this will alter phase and direction from end fire, to broadside.

Clear as mud?

Did you order DB224-A (150-160MHz) or 224-E (140-150MHz) range models? The
harnesses on the antennas are for their proper range....the harness between
the two antennas can be easily made up of 75 ohm RG11 coax cut in ODD
multiples of 1/4wavelength (taking Velocity Factor into account!). The
lengths would be the same on each side of the T to the 224 feedpoints. Easy
to do....the harnesses on the antennas are made to match 100ohm elements
down to a single 50 ohm point.....but as long as both antennas are the same
range, you only need to worry about the harness between the separate 224s

Chris
WB5ITT

Don Winn wrote:
I would like to install two Andrew DB224 4-element colinear antennas
as a
DB228 (8 element). When the antennas were ordered to replace a
Celwave P654, I
was told that two 224 and and the proper phasing harness would be the
same. The
antennas and harness were ordered but I have a problem. The antennas
were
shipped but I'm now told the phasing harness for the amateur
frequencies (-007)
is no longer available. I have received some information on the
phasing harness
but from the drawings provided, the two outputs are not the same
length
therefore will not be in phase. Since the antennas are the same,
wouldn't the
two outputs of the phasing harness be in or is it normal to provide
some
downward tilt. Unless I'm badly mistaken,the antenna element should
be fed
in-phase giving maximun gain in the horz.direction.
Don AF4Z

Chris;

I have two of the DB224E antennas: In my case, I have the plan to mount the original antenna as-designed, so it will be mounted ABOVE the four-foot side-mounted standoff, and the top-most DB224 will be completely in the clear.

The SECOND DB224 will be mounted UPSIDE-DOWN below the top DB224. The lower DB224 will be mounted on the same stand-off bracket. -Is this CORRECT?? (OK to be mounted upside down?)

QUESTION #1: I need to make a POWER DIVIDER so I can feed both antennas. In tour comments above, I see that you mention that the phasing harness (power divider?) can be made up of 1/4 wave (calculated) lengths of RG-11; If the two legs of the power divider are the same, will this mean that the lower antenna will be fed OUT OF PHASE? (The lower DB224's elements will be "upside down...) -If needed, I could rotate the elements on the lower DB224, so they "hot side" is UP, just like the standard configuration.

QUESTION #2: Is the lower DB-224 to be mounted upside-down, under the top-most DB224? (I am concerned about moisture being trapped in the elements.)

QUESTION #3: What are the possible patterns for the elements? (I now have the top DB-224 set up with two elements facing North, and the other two elements facing South. The LOWER DB224 would be in an omni-directional pattern.)

Thank you!! -Mike- K0JTA