Portable PVC Antenna Mast
I created this portable PVC antenna mast for Reach the Beach relay. The relay race covers 200 miles in New Hampshire starting 6AM Friday morning at Cannon Mountain and ending by Saturday evening on Hampton Beach. Each relay transition area is staffed by an amateur radio volunteer to coordinate transition area opening/closing, penalties, and emergency information. This year I operated a station at the transition area in Sandown, NH.
My portable station consists of an Icom IC-2200H mobile 2m radio powered by an Optima Yellow Top deep cycle 12V battery. The battery has more than enough capacity to power the radio for the 8 hour transition area shift. The antenna mounted on the PVC mast is an Elk Antennas 2m/440 Log Periodic. For this event I was operating on the 2 meter VHF band.
The Elk Antennas log periodic has a fitting that accepts a 1" PVC mast. The mast must be made out of an insulating material. I built the portable mast out of several sections of 1-1/4" and 1" PVC pipe. The portability criteria was that it must fit in the back of my Honda Accord. I limited the longest sections to a maximum of five feet and used 1-1/4" Schedule 40 PVC for strength.
The base consists of an "H" shape constructed from 1-1/4" pipe. Each section of pipe is approximately a foot long with tee fittings between and caps on the exposed ends. In the center of the "H" is another tee fitting pointing up with a short stub of PVC and a threaded female fitting on the end. This provides a threaded socket which will accept five foot main sections. The base is weighted with two 60lb bags for "tube sand" although I could have used lighter sand bags, or cinder blocks, or other weight.
Each main section is 1-1/4" PVC, five feet long with threaded male and female fittings cemented onto each end. I used two five foot sections. I constructed an additional section but found that the mast was "floppy" and very difficult to lift into position and attach to the base single handed. I haven't tried using it with a partner, but I do think the design can support at least a third section once it is in place and guyed.
The top section is 1" PVC, and has a threaded male fitting and a 1-1/4" threaded reducing fitting. Midway up the two foot top section is a T fitting which extends more 1" PVC about a foot out to support the coax feed line. This is needed with the log periodic so that the feed line extends orthogonal to the elements for a short distance before curving downward. The antenna simply friction fits onto the 1" vertical.
Four guy cords are used. The guy line is just thin purple rope tied around the reducing fitting with a round turn and two half hitches. A taut line hitch is used to attach the guys to four ground stakes and adjust the tension. The mast is self-standing without the guys, but they provide considerable stability.
To set up the mast I attach all of the threaded sections together and slip the antenna onto the end. Next I lift it up and place it into the threaded base fitting and twist it until it is stable. At this point the guy cords can be attached. Since the log periodic antenna is direction it is necessary to aim it. Once the guy cords are attached the threaded base fitting can actually be rotated through a full 360 degree rotation without affecting stability. This will cause the guys to wrap somewhat as the mast is rotated but it does not seem to significantly affect the guys.
The mast sustained gusts of 35 mph without dangerous flexing. During my initial testing once the mast was guyed I could slap the PVC and get a massive amount of flex out of it without issue. The threaded fittings hold up fine. Time to setup the entire station was around 15 minutes, similar for bringing it back down again.
The antenna performed flawlessly at Reach the Beach (although the Transition Area in Sandown is not a particularly difficult area). I received the repeater (25 miles north) at S9 and had good signal with 10 watts of transmit power. If you build a similar mast, please consider dropping me an email at firstname.lastname@example.org, I would love to see your design!