|928 5 element colinear
1" aluminum tubing was used for the large sections. 12 gauge stranded copper wire with ring connectors for the small wire sections. The ground plane wires are from brass rod. Ring connectors were soldered on to the brass rod. The rods were riveted to the base section of tubing. All stranded wires were riveted to the larger aluminum tubing. The coax used was Radiall-Larsen Dual shield RG-58.
Peformance is much better than the three quarter wave below. A station that had quite a bit of QSB on them with the 3/4 wave was Q5 with this antenna. With the SMA3 they could not be heard and they couldn't hear me either.
I really need to go back and rebuild this antenna. After revisiting Ross's site below, I realized that my first element is improperly built. I should be feeding the first fat element in the center. I also did not utilize the 75ohm quarter wave match that he does.
I built a similar 3 element colinear for VHF. I tried the techinque of feeding it through the bottom section to act as a decoupler trick and it doesn't appear to work all that great. I'm going to try it out again with a 75ohm quarter wave match.
This site was the inspiration for this antenna. I just sized things for 928Mhz.
|928 3/4 wave
This antenna was built with all scrap box parts.
The top piece of aluminum tube was left over from an antenna trimming/conversion project. The bottom piece of tube was from scrap that was cut off of another antenna. The RG-58 a/u with molded BNC was another piece of scrap. As well as the PVC tub that serves as a support. The ends of the coax had ring connectors soldered on them. Both piece of aluminum tubing were drilled through the pvc support. Then the coax ends were connected to the aluminum tubing with aluminum rivets. (The tape is added for waterproofing and aesthetics.)
It performs better than the Comet SMA 3 it replaces.