From ki6ds@dpol.k12.ca.us Mon Nov 1 13:36:47 1999 Mon, 1 Nov 1999 10:15:40 -0800 From: ki6ds@dpol.k12.ca.us (Hendricks, Doug) To: Subject: NorCal Doublet for 10 - 40 Meters Date: Mon, 1 Nov 1999 10:34:24 -0800 George Heron posted to the list about his giving away several NorCal Doublet antenna kits at the NJ QRP meeting Saturday. A neat way to say Trick or Treat, George!! Several have emailed and asked about the construction details so here it is guys. The NorCal Doublet evolved from work done on the St. Louis Doublet designed by my good friend Dave Gauding, NF0R. His work was the inspiration for my efforts. Thanks Dave. It is designed to satisfy the following criteria. 1. It must be capable of making casual contacts, or qrp contest type qsos. 2. It must be cheap. 3. It must be light weight. 4. It is designed to be used with the SD20 fiberglass telescoping pole, and one of the goals is to NOT bend the top section over. 5. It must be multiband. 6. Use of a tuner is ok (I use a ZM-2) 7. It must be deployable in less than 5 minutes. 8. It must tear down in less than 5 minutes. This antenna is NOT: The end all to all antennas. While it may be used as a home station antenna, (I am presently using one version cut for 20 meters), it is mainly a portable or "in the field" type of antenna. There are certainly a lot better antennas out there, but none of them meet my criteria as well as the NorCal Doublet. I know that regular ladder line is superior to the ribbon cable, but it is nowhere nearly as light and managable. Ok back to the antenna. I looked at Dave's original article in QRPp, and decided that you didn't have to use magnet wire for the dipole portion as Dave did. If you had a 50 or 60 foot piece of ribbon cable, you could eliminate the connection of the magnet wire to the ribbon cable!! That takes out a weak point, the soldered connections. I also remembered the antenna that Jim Cates, WA6GER, told me that he made out of zip cord back in the early 70's. So, I got a piece of ribbon cable 50 feet long and did the following: 1. I separated two conductors from the cable, and had a two conductor strand that was 50 feet long. 2. I measured 26 feet and marked with a marker. 3. I then took one nylon cable tie, put it through the eye of a small fishing snap swivel, and then tighten it around the cable. This would become the center support of the doublet. I would use the snap to hook to the eye at the top of the SD20 fiberglass fishing pole. 4. Next, I split the two strands to the 26 ft. mark and the nylon cable tie. (It not only attaches the snap swivel, it also keeps the cable from splitting farther.) I now have a NorCal Doublet with two 26 ft. legs, and a 24 ft. feedline of 2 conductor ribbon cable that acts as twin lead. 5. I attach a ten ft. piece of heavy string, actually it is nylon cord, to each end of the legs. I use 20 penney nails as anchors if there is nothing to tie off the Doublet to. 6. The last thing is to attach the feedline to my ZM-2 Tuner and I am ready to rock and roll on 10 - 40 meters. Now for the cost. 100 ft. of 10 conductor ribbon cable from Mouser Mouser #571-1570403 $9.36 (Enough material to make 10 antennas) Ribbon Cable - $.94 Nylon Cable Tie - $.02 Snap Swivel - $.25 20 Ft. Nylon Cord - $.02 2 #20 Nails - $.05 Total cost of antenna: $1.28 !! How does it work? Well, I have about 150 qso's on my NorCal Doublet cut for 20 meters (legs are 16.5' long) and it has served me very, very well. I have worked 40 states, 3 DX countries, and have been able to hold a frequency and call CQ in three different qrp contests using the NC20 and running 5 watts. I encourage you to give it a try and let me know how it works for you. If you think of improvements, please share with us. Enjoy, 72, Doug, KI6DS