Folks, this has been a fun and hilarious winter project. Yesterday, when I built this air cannon antenna launcher it was -4 degrees outside and this was a perfect evening project to put together. For years, me and my two ham radio buddies (WR8S Bill Shultz and WV8TG Tom Graf), have enjoyed ARRL Field Day activities and usually used a slingshot and a 3/4 ounce fishing sinker weight and an old Zebco fishing reel (with 20 pound test line) to shoot and suspend our doublet dipole antennas high into the trees. Certainly, the slingshot worked pretty much flawlessly… but… boys will be boys, and the idea of an air cannon / spud launcher / potato gun type system seemed to be a new desire. (Most people, our wives included, wouldn’t trust our 3-man team with a slingshot, let alone a potato gun! But I digress.) Actually, our local ham radio club (Monongalia Wireless Association) had a version of a potato gun antenna launcher, so we decided we needed one of our own… and to make some design modifications in the interest of… “science”… plus our own sadistic pleasures. (Make sure you read below WV8TG’s initial “pressure test” experience.) The following pictures hopefully provide the basic concept and parts we used. Tom and I split the cost of the parts needed to make launchers and each built our own version, but they both are the same basic design with only length dimensions of the air chamber and barrel being the difference.
All parts where sourced from our local Lowes store in their plumbing department, except the Schrader valve which can be purchased at an automotive store. Total cost about $40 but you could make a couple of them as a joint project with a friend and reduce that cost per launcher a bit. I got a small rubber gasket for the outside nipple of the Schrade valve to act as another seal on the exterior of the air chamber. You will need to drill holes for Schrader valve, barrel slug stop and projectile slug caps to attach the screw eyes to attach the fishing line. I used 3 inch PVC for air chamber, 1.25 inch PVC for the barrel and short sections to mate the air chamber, trigger valve and threaded barrel. The projectile slugs were made from 3/4 inch PVC and caps and I filed off the nubs on the caps with a Dremel tool for a smooth fit into the barrel. I used PVC Prep on each joint before applying the glue. When gluing joints together, insert the sections together and twist a quarter turn for a solid adhesion. Let all glue set up for 24 hours before testing air pressure chamber. I will pressurize the chamber inside and let it sit overnight to see if it loses any pressure. It’s too cold right now to take outside in -4 degree temperatures to test, but I will use a bicycle pump with a pressure reading valve, and start at 40 psi… then 50 psi… and then 60 psi for test shots to see how it functions and check for any air pressure leaks. We use 60 psi for our club launcher.
WV8TG (Tom) charged his air chamber (barrel not attached) and let it set overnight to test for chamber air leakage. When he opened the trigger value… there was NO leakage… but there was a sudden LOUD release of 60 psi air gush out of a 30 inch long, 3 inch wide fully charged air chamber. He indicated the compressed air release was… impressive. However, his wife was not impressed… nor was she aware of the scientific test that was taking place. #surprise! #WHOOOOOOOSH #loudwifeexpressions I have no reason to doubt Tom will find his projectile slugs in the next county using his design. The club chamber was 12 inches long versus his 30 inch air chamber. #overkill? I designed my air chamber for 14 inches and will conduct all tests… outside. #potentialmeanwife
Well… the 2015 ARRL Field Day adventure is in the books… the logbooks, that is. Having experienced decades of Field Day excursions, this one takes the cake! What started out as a hot, sunny, humid Friday afternoon setting up our station high atop Chestnut Ridge, ended on Sunday afternoon having operated under conditions of torrential rains, a downward shift of 40 degrees in temperature, one antenna failure, one operator unable to man a station due to illness, a generator choked-out by all the moisture in the air and eventually walking around in a literal cloud! We had three layers of clothes on and could see our breath on Sunday morning! To say the least, it was a unique set of challenges to overcome.
Plan A was to slingshot and hang 3 doublet antennas, run 2 KX3’s for CW and PSK31, and run an Icom 7200 with a new Heil Pro 7 headset on voice. We had a 5500 watt generator and 25 gallons of fuel to keep us purring along. With 4 operators we had a good chance to keep all rigs racking up points for the duration. Laptops were ready to log and the plan sounded solid. The goal was to beat our score from Field Day 2014 and thought a good mix of voice and data would do the trick.
Our usual set-up has us mooching off of WR8S’s generosity when he goes to the trouble of of hauling his camper to the top of the mountain. We extend the awning and set up a table or two to operate from. Field Day 2014 was done via battery power and QRP mode.
The video below is a typical contest exchange using CW (Morse Code) and in the ARRL Field Day Contest an exchange of information would be the call sign of the other station, your operating mode (how many radios are you running and what sort of power and station are you running), followed by your section of the country. Then you return your own exchange to the other station and move on the to next contact by calling “CQ FD CQ FD de WT8WV WT8WV” and hope for a return of your call sign for a confirmed contact to log. CQ means “calling anyone”… FD means your are calling for the “Field Day” contest… de is French and means “from”… and WT8WV is our station’s “identifying call sign”. (You will see Bill (WR8S) make a contact and then write down the exchange from the other station on the log paper… then he begins calling CQ FD CQ FD de WT8WV using a memory keyer that he can program with the CQ message, our contact information and a thank you good bye message. He just needs to use the keyer paddles to send the other stations call sign during a contest.) Our return message to the other station to enter into their own log was, “WT8WV 2A WV”.
The pictures below tell the story of our challenges and our solutions. I have to admit I thought we were DOA when the generator croaked at 4:30 am on Sunaday… but we quickly came up with Plan X and realized WR8S had a converter in his truck! Back to battery power to finish of a good run of PSK31 and CW for 2 points each!
The original team plan was to use my new call sign WT8WV and be “3 Alpha West Virginia” but Jay got sick on Friday so we were now down 1 team member and 1 radio. Then we had a balun issue with 1 doublet antenna. So now we are WT8WV 2A WV with 2 Elecraft K3’s and 1 antenna. We decided to salvage our potential scores by focusing on PSK31 and WR8S’s speedy left hand on CW… and forgo voice comms.
Any one who has EVER coiled wire, coaxial cables, audio cables or even a hank of rope knows UNCOILING it has at one time or another created a “rats nest” of tangled mess that will increase your blood pressure, makes you exceedingly cranky and often has caused Tourettes-like symptoms. Fighting an unruly coil of coax or audio cable wastes a lot of time when setting-up a gig, a Field Day site or even coiling a power chord at home! Having spent years working in television studios, control rooms, and other audio gigs on a daily basis, I learned early on from the engineers that there is ONE way to coil cabling… W2AEW shows that in his video! (P.S. Engineers can be especially grouchy if you don’t coil correctly and THEY get to untangle YOUR improperly coiled rats-nest from a previous gig tear-down as they work on an important production. Time is money.)
CQ Contest… CQ Contest… CQ Contest !!!
Ham radio contesting is exciting and fun to participate in regardless if you are a Rookie Contester or a Seasoned Pro-Contester! As with any big project, proper prior planning makes all the difference in your final score. This QRZNOW.COM article about developing a Pre-Contest Checklist will add to your QSO tally! Click link below for the full article…
I have helped build and used two of these Doublet Antennas during the 2014 Field Day Contest and they worked great! Worked many stations on CW, Phone, and PSK31. Works great across many HF bands. A little over 120 feet long. WR8S (Bill Shultz), WD8WQK (Tom Graf) and I are going to make one for my ham shack as soon as I order the parts. Take a look at Ray Heffer’s explanation of the Doublet Antenna and a diagram by N4UJW below.
I had the pleasure of playing with two Elecraft KX3 radios during ARRL Field Day 2014 running CW and PSK31 modes. Both radios worked like a charm off of battery power and we racked up some excellent contacts during the hours of the contest. I want to thank Bill (WR8S) and Tom (KD8WQK) for letting me get may hands on their toys! Definitely on my WISHLIST!
The KX3 HF Radio is pictured above. The optional 100 Watt Amplifier is pictured below.
Watch the Elecraft KX3 Demo Video below…
Connect the KX3 to an iPad…