[amsat-bb] Fw: 23 cm Loop feed
kc6uqh at cox.net
Wed Sep 27 22:17:20 PDT 2006
Here is a modification to a standard conifer type 2.4 GHz grill antenna. The loop gives it a feed for L Band used here to receive ATV 1.253 GHz while transmitting on 2.441 GHz. Filters are required on both bands to reduce white noise from the Xmit PA and leep power out of the receive preamp. Those interested in Pictures request via E-Mail and I will forward them.
Subject: 23 cm Loop feed
Dave, Ted and Gary,
Here are some pictures.
#1, & #2 show the feed mounted on the dish from both sides, #3 shows the Split Feed balun.
Clamp tight one end 12" length of # 12Ga house wire in shop vise, pull hard until straight, then strip off insulation with a box cutter. The loop is 2.64 " square center to center, formed from the # 12 hard drawn house wire with the insulation removed.
Using a 3" length of 1/8 " copper hobbie tubing, cut two .025" wide slots one on each side for 2.4 " long. Trim back the braid 2.9 " on a piece of R/G 142, Strip 0.2" of the center dielectric from the end of the cable. Slide the copper tube on to the coax unsplit end first, fan out the braid, and bend over the center conductor and solder to one of the split ends, Each side of the loop connects to a split end of the tubbing. Silde a piece of 1/4" heat shrink tubbing over the copper tubbing and solder the braid to the unsplit end You can also solder a bracket to this end to support the cable, and in the center of the opposite side use a piece of acrylic plastic 1/16 thick, heated and bent to support the other side of the loop. After connecting the loop, shrink the tubbing and coat the matching section and connections with liquid electrical tape or yellow weatherstrip adhesive. Cable is then wire tied to the boom. The loop is 2.75 " from the center of the reflector where it is screwed to the 2.4 GHz antenna cover.
This is a living document and comments about omissions, changes etc are welcome in the intrerest of maintaining an accurate documentation.
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