I noticed a clever antenna mount on another ham’s roof, so I built one myself. Putting my VHF/UHF antenna at the highest point of the roof has really improved my ability to copy some of the far-flung participants in our weekly ARES/RACES net.
A cradle built from two-inch ABS DWV (drain, waste, and vent) pipe sits across the ridge of the roof. Legs two feet long go down on each side and a two-foot section is a vertical antenna mast.
My antenna is a Diamond X50NA, same as the X50A, but with a weatherproof Type N connector. I did additional weatherproofing with 3M Temflex 2155 rubber splicing tape and Scotch Super 33+ electrical tape.
I had spotted an antenna mounted like this and contacted the ham at that address. Rolf Klibo, N6NFI, replied with an article he’d written for the SPARK newsletter describing the mount (here is a PDF of that article). With that, I was off to the hardware store.
I used two-inch ABS DWV (drain, waste, and vent) pipe in two-foot sections. I cut up two of them to make the four pipe sections that go along the ridge of the roof.
The X50NA mounting hardware fits masts up to 2 3/8 inch, which is why I used two inch pipe. For coax strain relief, I used a conduit hanger that fit. Zip ties attach a loop of coax to the hanger so the full weight of the feed line isn’t pulling on the connector. That can rip the coax right out of the connector, or harder to diagnose, pull just one of the shield or center connector loose.
For a commercial version, I’d look at the Rohn NPPK, a steel frame that fits over the roof peak. It is designed to have a rubber mat underneath and four 18 pound concrete blocks holding it down. I’m sure it is far more secure than my DIY plastic pipe mount.
Excellent idea and easy to construct. Well done Walter.
For wind resistance, I would fill the pipes with sand then glue on pipe caps.
I had exactly the same thought, to weight it with sand. Rolf also had the same idea, but hasn’t done it yet. His mount has been up on the roof for years with no problems.
Another option, maybe better than sand, would be to loop a rope around the middle of the mount and tie it down to the eaves on each side.
Interesting article and good ideas in the comments as well… thanks Walter, Andrew and AC9DN.
I’m going to be living in class a motorhome & that gave me ides fixing one for my j-pole & talking with cb shop tech he said it work better with a sheet of rolled tin as a reflector but run a ground wire to ground-stake & add a trap from coax about 12″ from pl-259 wrap coax in loop 5 turns 4″ in diam. ! Just thought i toss the info along hes a master tech with 50+ years in same shop !
A trap or choke is a good idea.
A J-pole is a half-wave antenna, so it does not need a ground plane underneath it. That could even detune it. A reflector would be off to one side and would make it directional. That reflector would need to be the right spacing and size, because it would be part of a two-element Yagi.
A ground stake is for lightning protection, not for RF. I’d add a lightning arrestor at the antenna or on the feedline if you are in lightning country.
For a dual-band (2 m and 70 cm) J-pole, I’m a big fan of the antennas designed by Ed Fong, WB6IQN. The base antennas are inside a PVC pipe, so they look like a roof vent. His DBJ-1 is $30, a real deal.
Hi Walter, love the idea of this. Do you have a link to the original article? I did search for it but cannot find it. I can probably eyeball your pictures and get a good enough idea of how it goes together but would be great to see the original source plans. Thanks
The original article was in the June 2002 newsletter for the Southern Peninsula Amateur Radio Klub (SPARK). That club has closed down and their newsletter archives stop in 2000. The author mailed me a copy directly. I’ll see if I can upload it somewhere.
It has a bit more detail, basically fit it all together on the roof, then glue it. His was up for five years before he wrote the article, so it seems like a long-term solution. He started with a 2 m ground plan but has been using a (larger) Diamond X50 like mine since 2002.
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Thanks for the rapid response Walter, that would be awesome if you can find it but not a big deal if not for sure. I had run through the various options in my head and glue it together up there made sense, safely wrestling a PVC spider up the ladder without breaking it or me feels unlikely 🙂
I’ve uploaded the PDF of that article and linked to it. Thanks for asking about it, that article has some construction details that I didn’t mention.
Fantastic, thanks so much Walter. That’s my project for next weekend sorted. I had already decided to remount my ABS-B antenna somehow, I think this is the ideal solution for me.