DH Satellite Gibralter Gemini Sectional Antenna Mount - Manual (Page 11)

Heavy Duty Feed Strut________________________
We have developed a new feed strut and collar for the
heavier 4 Port Seavey feed assembly. This utilizes the
rectangular aluminum tube for the feed strut. Figure
#12 right shows the sketch of this feed assembly; it is
very simple to install. Each strut has 2 ‐ 5/16 x 2 1/4”
bolts to attach to the feed collar. Now attach one of
the angle brackets (2" x 2") to the antenna with the
1/2" x 3" bolts. Notice that angle bracket has two
holes. You will use the bottom hole. The top hole is
for an optional Chaparral type feed. Next, attach the base
of the strut to the angle brackets with the 5/16 x 1 1/2"
bolts supplied. Align the feed to point directly at the center
of the antenna. Now measure the focal length to the front
of the scalar rings. (Seavey recommends f/l is measured to
front of scalar ring.)
Ku Band Feed Assembly-----------------------------
When using the Ku only feeds, you will be using the C14F feed plate and tri‐collar. See Figure #13. First, attach the flat
tri‐collar to the feedhorn as follows: attach the first two pieces by using the 8‐32 x 1" screws provided. Now slide the
collar onto the feedhorn and add the third piece; tighten evenly. Attach the tri‐collar to the larger horseshoe collar by
the 8‐32 x ¾” bolts and nuts; tighten down. You can adjust polarity by loosening these nuts and rotating feed. Finish by
assembling the struts to the feed collar as shown in Figure 14. (Fig#14 shows single Ku feed inserted in collar)
Figure #13 Figure #14
Fine Tuning the Antenna--------------------------------
After the assembly is complete, we recommend you "string the antenna." Simply run a string from a back brace across
the front of the antenna to the brace 180 degrees apart. Now do this with each brace. If the strings all meet in the
middle and no pressure is on any of them, the antenna is perfect and no further work needs be done. If one of the
strings is not close to the others, then step back and sight across the dish and see where you will have to push with the
back braces. Only make small adjustments at a time and remember to start with all braces loose. After you are sure
the antenna surface is flat, you should double check to see that the feedhorn is set at the proper distance, then
check
to see that it is pointed at the center of the antenna. In our years of setting up antennas, these three items
seem to cover over 98% of all problems of picture quality.
PAGE 11
Feed Strut Length
2.4m & 2.7m with a 39” mount is 36 5/8”
3.0m with a 48” mount is 41 3/4”
Figure #12
½” x 3” Bolts