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DSEFO222-22 Rev 2/21
22)
Assemble the front boom sag by placing the boom sag support bracket over the rear of
the front boom section (marked with green), placing the bracket so that it is against the next
boom section. Complete the assembly as you did for the rear. Once the boom is adjusted for
no sag, tighten
the ¾” hose clamps securely.
23)
If you are installing multiple antennas, mark each boom sag so it stays with the antenna
it came off of.
If you are installing multiple antennas, please be sure that you build each
antenna with the same T-match wire orientation. In the above drawing, the center pin
goes to the right hand side of the antenna as viewed from the back of the connector.
Make sure both antennas do the same! Proper phase relationship is very important
here!
If you wish to check your work, now is the time to apply power to the antenna. Any
workaround RF energy should be done carefully. We do not recommend standing next to an
antenna with many watts of 222 MHz energy radiating around it. The best method involves
using a low power return loss bridge and SWR indicator along with a signal generator.
A power level of 1milliwatt is all that is required. The
T-arm shorting bars
may be adjusted with
power applied and the point of best match can be found quickly, easily and more accurately
than that with an amateur transmitter and wattmeter connected. Generally, good watt meters
can reliably indicate SWR down to about 1.2:1. A high directivity bridge or coupler can
increase accuracy, but 1.2:1 is more than adequate for any installation.
The aperture of this antenna is large enough, so that you must elevate the antenna a
minimum of about 8 feet or 2.5 m above the ground. Point the antenna so that there are no
"reflectors" or obstructions for 100 feet directly in front of the beam. A better method would be
to point the antenna straight up toward the sky. Support the antenna on a wooden or metal
pole or tube, and tie or guy the antenna boom with very light string or line. Now the driven
element will be at arm level, and ground effects are removed. Most locations are pretty clear
straight overhead as well!
Install a short length of coax (1/2 wave is ideal ...The antenna impedance will
repeat each half wave from the antenna regardless of coax imperfections) between the coax
connector and your bridge or wattmeter. If you utilize your 222 MHz transmitter as an RF
source, apply power and observe the reflected power. Turn off the power and adjust the T-
Match bars equally in small increments - 1/8" or 3 mm. is a good starting point. Apply power
again and observe results. If it got better, keep going. If it degraded, change the direction of
your T-Match movement program and recheck your SWR. At some point, you will observe a
null in reflected power.
When you have found it, tighten the set screws on both the driven
element and the T-arms with the supplied hex wrench.
Brass, copper and tin lead solder will oxidize in the weather and o
ver the year’s performance
can degrade. It is a good idea to spray your handiwork with a good grade of clear paint
sealant. As a general rule, the slower drying sprays tend to be more enduring. Rustoleum
"Clear Seal" or Krylon clear sprays are recommended. A few light coats work better than one
big one.
Be sure to cover the connector before spraying.
DO NOT, UNDER ANY CIRCUMSTANCES, APPLY ANY TYPE OF SEALANT OR COATING TO THE DRIVEN
ELEMENT, T-ARMS OR CONNECTOR ASSEMBLY, OTHER THAN KRYLON
®
CLEAR COAT. ANY OTHER
COATING WILL ADVERSELY AFFECT THE SWR AND VOID YOUR WARRANTY.
