PAC-12 Rigid vertical
2020-07-04 Something caused me to think about this antenna this morning. I had to hunt all over to find it! But I found it and all the bits and pieces and assembled it. Then I poked its spike in the ground in the front yard and connected it to my nanoVNA. I was able to tune it pretty easily on 40, 30 and 20 meters. So with it set to 20, I quick grabbed my x5105 QRP rig and connected it to the ten foot coax coming from the antenna. After about five minutes tuning around I heard K3PA on 14.030 from Kansas calling CQ MMC. It was clearly some contest but I didn't care, I just wanted to record a QSO with this quickly thrown together setup. To my surprise he came back and gave me a 559 report. He was also 559 so I feel pretty sure his was legitimate.
The antenna was stuck in the ground in my front yard using it's own sharpened spike. I attached a 15' counterpoise laid out on the grass. The coax was a ten foot piece of RG-58.
I had to look up online to find out that MMC stands for Marconi Memorial Contest. The website says, "The Marconi Memorial contest HF commemorates the II Century of Radio and its father: Guglielmo Marconi. It’s a World-Wide competition: everybody can work everybody, only CW." So unknowing I entered the honor role of those recognizing "our father"! How fitting that should happen using this obviously compromised and largely forgotten antenna. A couple hours later I returned to the antenna but could raise no one!
2020-01-26 It's been several years since I even thought about this antenna, other then it's been in a plastic bag in the way Under my bench! But preparing for Winter field Day yesterday I got to thinking about it. Actually it had come to mind after a QSO with KW4JM who was doing a SOTA activation on a mountain in Western North Carolina last week. I was QRP using my 29ft EF wire. He had to struggle to copy me so I emailed him afterward and told him I appreciated his sticking with me. That resulted in the exchange of a couple emails in which I asked him about his antenna, rig, etc. He sent me a link to a YouTube video describing his DIY No-Stick Buddy-Stick Antenna. That inspired me to get out this Pac 12 and think about using the coil to duplicate his antenna. (Since writing this I've built his. Click to see my description.)
Then today I thought I'd just put this thing together and see what it looked like on my NanoVNA which I have set to show the SWR curve all the way from 6mhz to 30mhz. So after a few minutes I had it together, found an old 12 ft piece of speaker wire to use as a counterpoise, leaned the thing up against the couch and took a look. I had multiple taps on the coil and found the one for 40 meters. With just a little tweaking of the collapsible whip it had a great SWR on 40. Same on the 30, 20 and 15 meter taps!
That inspired me so I quick got my xiegu x5105 and hooked it up. Nothing heard on 40. Nothing heard on 20. But tuning across 30 meters I heard N5XE in QSO with another station which I couldn't hear. But Carl was S8! Wow. After he signed he called CQ and I replied. That resulted in a nine minute solid-copy QSO. He gave me a 559 and he was a steady 589. He was running 50 watts to an inverted vee 35 feet up.
It takes quite a bit to get me really excited. But that did it! Thanks Carl for a highlight in my ham radio life! After shivering my butt off in the unheated, detached garage yesterday for Winter field Day, what fun to have "arm chair" copy, in the living room, with the antenna sitting on the floor leaned up against the couch and the radio on the coffee table! That's Ham Radio for you! The Pac 12 is back in my good graces!
What is a pac 12 antenna? Click this link to see a PDF about it. The photos below show mine. It's fully extended length is 9 feet. It consists of a collapsible whip, three 12 inch 1/4 inch aluminum rods threaded on both ends and one additional 12 inch rod which is threaded on one end and sharpened on the other to be used as a ground stake to hold it up. I made a PVC pipe thing with a SO239 coax jack on the side as shown. The SO239 Center pin goes to a 1/4 inch brass bolt on the top end. The SO239 ground-side goes to a 1/4 inch brass bolt on the bottom end. The sections are all held together with 1/4 inch couplings.
The loading coil is wound on a PVC pipe with 1/4 inch brass bolts in each end. The top end of the coil is connected to the top bolt. The bottom end is open, not connected to anything. A pigtail with alligator clip is connected to the lower brass bolt. It can be connected to any of the taps on the coil. I made the taps by simply forming a twisted loop at the appropriate points along the coil.
The inductance of my entire coil (from top bolt to bottom tap) is 42uh. Next tap up is 35uh, 3rd is 30uh, 4th is 14uh, 5th is 7uh, top tap is 1uh. I share those just as ball park figures. The exact values may be different in your situation. The major factor will be the fully extended length of your antenna. I actually made an additional 117uh coil so I could tune it on 80 meters. I can't recall whether it is used in addition to or in place of the main coil.
My main point is simply to inspire whoever reads this to play with antennas. I find great fun and fulfillment out of making and trying different antennas and want to share the fun.
Several years ago I ran across the PAC-12 vertical and had some success with my home built version. If nothing else it is an interesting project to build and you get quite a thrill when you make a contact with it.