Urban Rooftop Ham Radio Antenna
by bekathwia in Circuits > Gadgets
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Urban Rooftop Ham Radio Antenna
I recently put a ham radio antenna on my roof, so I could get better signal inside my apartment, which isn't on a high floor.
As an ultra beginner without a lot of investment in the hobby, it was perfectly acceptable to have to climb onto the roof to get any signal on my portable radio's antenna. But the benefit of this larger, roof-mounted antenna is that now we can leave the radio on all the time and listen to it inside, which leads to more opportunistic connections and overall more time spent enjoying.
What follows outlines the process we used. I have previously written a guide about getting started in ham radio, in case you're interested.
The antenna I got is a VHF/UHF antenna that mounts on top of a pole. My friend David, my boyfriend Smokey, and I put up one of these on David's roof and on our own roof, and the two had different mounting situations. At David's place, we used a mounting kit with metal straps and special brackets to hold the pole to a chimney. At our place, there was an unused analog TV antenna pole that we planned to repurpose.
Important note about safety: if you don't know what you're doing, consult someone who does (and who knows your local regulations, too). Putting an antenna on your roof brings the risk of a lightning strike which, if not properly grounded, can cause fire and other damage, as well as loss of life. I'm not an electrician or an expert.
Supplies
Everything I used to connect to my Baofeng UV-5R radio:
- Tram 1411 Broad Band Discone/Scanner Base Antenna
- Outdoor-rated PL259 coaxial cable (aka UHF SO-239)
- Coaxial lightning arrestor
- PL259 coax to SMA adapter
- SMA extension cable
- Ground wire
- Pipe grounding clamps
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Pole Prep
Starting from scratch at David's place, we attached the pole brackets to the chimney with the kit's included metal straps. It took some adjustments to get the pole straight up and down, then clamped on tightly when we turned the final adjustment nuts.
To prep a previously-used antenna pole, we had to remove what was still left of the old analog TV antenna. Some of its pieces broke off easily, while the final connection was so rusted that it needed to be cut free with an angle grinder.
Assemble Antenna
We put together the antenna by following the included instructions. Basically we needed to screw in all the radials to the center piece, then tighten the nuts against the center piece to help prevent the radials from backing out when they wobble in the wind.
The last step was to add the long radial that sticks off the top of the antenna, at which point the whole thing became difficult to set down anywhere.
Run Cable Up Through Pole
We ran our cable up through the pole, and caught it at the top opening. This was easiest to do with two people. The cable is stiff enough to stay straight in the tube when pushed up from below.
Plug in and Mount the Antenna
We brought the antenna close to its mounting position atop the pole, then plugged in the cable, securing the screw collar tightly. Threading the remaining cable slack back into the pole, then we seated the antenna atop the pole and tightened the set screws.
Test It!
Before running our giant cable all around the building, we tested the antenna to be sure everything was working as expected. We could hear and be heard by the Bronx repeater very clearly.
Run Cable
Then it was time to run the cable where we wanted it to go, and attach it to things. For us that meant going around the roof railing and over the edge, following a bundle of existing cables down to our apartment window.
Ground the Antenna Pole and Cable
The next very important step is to connect both the antenna pole and the signal cable to ground, in case of a lightning strike. I ordered some ground bronze clamps online but got the wrong size. The clamps I ordered were too big for both the antenna pole and the electrical conduit I planned to attach to, so flipped one of the pieces around to allow the clamp to fit a smaller diameter pipe. The downside here is it looks a bit silly and if you overtighten the screws, you could deform the pipe. Electrically, I don't think the flip has any effect (but feel free to explain why that may be wrong in the comments).
The ground clamp has another opening designed for the ground wire to connect. I hooked up some 10 gauge copper wire to the clamp connected to the antenna pole, and routed it to another clamp attached to an electrical conduit for a rooftop appliance, which in theory is all grounded through the building's electric. I'm not an electrician, and I don't have the access to drive my own ground pole into the actual ground, so please consult with a local expert to find the best way to ground your own antenna.
On the other end of the signal wire, I used a grounded coupler to connect another piece of the 10 gauge wire to a ground clamp connected to the same electrical conduit, just a couple floors lower. The coupler then connects to an adapter and wire to my Baofeng radio.
Use It!
I hope you found this guide useful, and thanks for following along! You might be interested in some of my other articles:
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