Good day, John (KF0M) and others;
I was away all last week, and part of the previous, so I was unable
to give you a PROPER reply to your comments. Others had comments to add
to my situation, but yours seemed to cover a lot, so I will direct my
comments to ALL, via YOU! My THANKS to all of you that offered comments.
Your comments were as follows:
" I put up a DB228 about 4 yrs ago. The lower antenna was mounted upside
down
so that both upper and lower feed lines came together at the center.
The DB products harness to join the two DB224 sections together had one side
1/2 Wl longer than the other side to keep the element phasing correct.
If you use a standard 2 port 50 ohm power divider you will need to make sure
one of the feed lines from the power divider to the antenna is 1/2 wl longer
than the other."
From your data on my "assembly" of two DB224 antennas as a DB228
array, I will make the phasing harness up with a 1/4 and a 3/4 wave
(after the velocity factor computation of my RG-11 coax).
I have several other related questions; -If you would please
reference to each "numbered" point below, it will be easier for me and
others to follow.
MY QUESTIONS to you, and others:
1. Is the FACTORY-MADE harness made up as with the RG-11 type coax
cables MOLDED onto the coax cables? -Or, are the cable "legs" simply
made up, then attached to a coax-TEE? (I want to make my own harness,
you see. It is my plan to solder the RG-11 coax directly to the
required type N connectors.))
2. It is my desire to have the top-most DB224 act as a bi-directional
antenna. As such (with no real info), I have arranged the top-most two
elements so that they are directly in line with each other. The lower
two elements are also directly in line with each other, but they are are
on the opposite side of the mast. (Elements 1 and 2 face North; Elements
3 and 4 face South.)
Or, should elements numbered 1 and 3 be facing North (as an example)
and elements number 2 and 4 be facing South?
-I have NOT put the new DB224 up, yet.
3. I have no concrete plans for the lower DB224; It could remain as a
360 degree coverage, or I could set it up with elements 1 and 4 at North
and South, respectively; Elements 2 and 3 would then "span" one side of
the mast, soas to offer more of a carderoid (sp) pattern. -In this
case, the elements would face 0, 60, 120 and 180 degrees. (Your
suggestion, please?)
4. It is my ASSUMPTION that the top-most DB224 be "right side up," and
the lower DB224 be mounted upside-down. Is this correct?
If this is the case, the lower DB224's elements will be "hot side
down," which is opposite from how the top-mounted DB224 has the elements
arranged.
If I mount the lower DB224 upside-down, will this retain water,
which will freeze and damage the antenna? (Yes, the 1/4 and 3/4
wavelength phasing harness will insure a proper phase, so I will
actually realize GAIN.)
5. The SPACING of the elements is far from "even; In my case, as well
as other reported element arrangements, I see from 60 to just over 70
inches of center-of-element to the next like point. I had fully
expected to see an exact measurement! I have a Cushcraft 4-bay antenna,
whose setup has all four elements at a fixed, and EQUAL number of
inches, +/- 1/8 inch!! (I cannot locate the instruction manual for my
HyGain 4-bay J-Poles, but I am assuming that the element-to-element
spacing is the same (equal), and exact; These examples are so very much
different from what the DB224 units seem to all be set up as. So: What
is correct??? Is there some hidden magic from the phasing harness and
the seemingly inexact element placement that actually allows a focus of
the RF energy where it is needed? -Or, is this really an important factor??
6. In looking at the pictures and diagrams of the DB228 documentation,
I see that the images (as an example) show that the top-most DB224's
four elements are .75 inches center-line-to-center-line. I see the
exact same for the four elements on the lower DB224. But, the
centerline spacing of the fourth element (lowest one) to the now-upper
element of the lower DB224 is somewhat more than 1.2 inches. (?????)
Is this actually correct? -Or are the pictures and the drawings simply
made up by someone other than an engineer? Here again, I had assumed
that the element spacing "should be" even, and exactly the same!
Thank you in advance for your time and effort!!
73!
-Mike-
K0JTA
