Height Is Everything
Getting the antenna 20 ft higher often beats doubling your power. A ridge or a summit turns a 5 W handheld into a 100-mile station. That's why 2 m on SOTA is so much fun.
KENTUCKY PORTABLE CLUB • ANTENNA GUIDES
VHF & UHF ANTENNAS
2 meters, 70 centimeters, 6 meters and 220. J-poles, Slim Jims, roll-up J-poles for SOTA, ground planes, a tape-measure yagi, mobile antennas and rubber-duck upgrades, with a calculator that cuts them all for any band.
THE BASICS
What's Different Up Here?
VHF and UHF signals mostly travel in straight lines. They go a little past the horizon, but they don't bounce off the ionosphere the way HF does. So different things matter.
Vertical or Horizontal?
FM, repeaters and packet: vertical. SSB, CW and weak signal: horizontal. Use the wrong one and the signal can drop 20 dB. Satellites need both, or circular polarization.
Antennas Are Tiny
A full-size 2 m antenna is under 5 ft. A 70 cm yagi fits in a backpack. Building your own is cheap, quick and very forgiving. A great first project.
Coax Loss Is Real
100 ft of RG-58 throws away about 75% of your power on 2 m and over 90% on 70 cm. At these frequencies the coax matters as much as the antenna. See the numbers
PICK ONE
Which VHF/UHF Antenna?
Every one of these can be built at home for a few dollars. The calculator below cuts most of them.
J-Pole
A half-wave radiator on top of a quarter-wave matching stub. No radials, no ground plane. Usually built from copper pipe or aluminum. Hang it from a tree or mount it on a mast.
| GAIN | About like a dipole (0 dBd) |
| BEST FOR | Home, camp, repeaters |
Slim Jim
A J-pole folded back on itself with a small gap. It's a little lower angle and cleaner pattern than a J-pole. It's easy to make from 450 Ω ladder line or a piece of copper wire.
| GAIN | About a dipole, lower angle |
| BEST FOR | Hanging in a tree, attic |
Roll-Up J-Pole
A J-pole made from 300 Ω twin-lead. It rolls up in a pocket and hangs from a tree branch or a trekking pole with a string. A huge upgrade over a rubber duck.
| WEIGHT | A couple of ounces |
| BEST FOR | HTs, SOTA, emergency kit |
Quarter-Wave Ground Plane
One SO-239 connector, five pieces of stiff wire or welding rod. One goes straight up, four slope down as radials. Build it in 30 minutes.
| GAIN | Close to a dipole |
| BEST FOR | Home base, first build |
Yagi (Beam)
Point it where you want to talk. Even 3 elements gives about 7 dBi, about 5× the power toward the other station. Great for SOTA, satellites, far repeaters and fox hunts.
| GAIN | 3 el: ~7 dBi · 5 el: ~10 dBi |
| BEST FOR | Summits, simplex DX, satellites |
Mobile Whips
A ¼-wave on a mag mount or NMO mount is the simple workhorse. A 5/8-wave gives about 3 dB more on 2 m. Either way, the vehicle roof is the ground plane, so mount it in the middle of the roof.
| ¼ λ 2 M | ~19 in, no matching |
| 5/8 λ 2 M | ~48 in, needs a base coil |
CALCULATOR
VHF/UHF Antenna Calculator
Pick the antenna and the frequency. Dimensions are starting points: cut a little long, then trim and slide the feed point for the lowest SWR.
Measure between the inside edges of the metal where pieces join. Tune outdoors, away from metal and people.
HOW THEY'RE BUILT
J-Pole & Slim Jim
The letters match the calculator. Both are fed a little way up the matching stub, with the coax center on the long side and the shield on the short side.
Copper Pipe J
Copper pipe J-poles use ½" pipe with a 90° elbow, a tee and a cap, all sweat-soldered. Hose clamps make a good adjustable feed point: slide them up or down D for the lowest SWR.
Folded with a Gap
The gap goes in the side with the shield connection, at the top of the ¼-wave section. Ladder line makes it easy: cut a small notch in one wire for the gap, and short the two wires together at the top and the bottom.
SOTA & GO-KIT
Roll-Up J-Pole from Twin-Lead
About $5 of 300 Ω TV twin-lead. It rolls up into a pocket and turns a handheld into a real station on a summit or at a campsite.
Steps
- Cut the twin-lead to the total length from the calculator (Roll-up J-pole), plus an inch.
- Short the bottom: strip the two wires at the bottom end and solder them together.
- Cut the notch: at the stub length (C) up from the bottom, cut a 1" piece out of one wire. Everything above the notch on the other wire is the radiator.
- Feed it: about D up from the bottom, carefully expose both wires and solder thin coax (RG-174 or RG-316): the center to the wire that continues up to the radiator, the shield to the notched wire.
- Choke the coax: wind 4–5 turns of the coax, about 1" across, right below the feed point. Without it the coax becomes part of the antenna.
- Hang it: a hole and a string loop at the top. Tie it to a branch or a pole, and keep it straight and away from metal.
Make It Work
- Height wins. Even 15 ft up a tree beats a rubber duck at chest level by a mile.
- Tune it once with an analyzer or the HT's power meter, sliding the feed point an inch at a time. Then seal it with heat-shrink and glue.
- Use "slotted" window twin-lead if you can find it. It's a bit less affected by rain.
- Store it loosely rolled, not folded sharp. Kinks change the tuning.
- 2 m SOTA: call on 146.52 MHz simplex, and post an alert so chasers know to listen.
POINT IT
The Tape-Measure Yagi
A famous 3-element 2 m beam (designed by WB2HOL) with elements cut from a steel tape measure, on a PVC boom. The elements fold when they hit a branch. It costs about $15 and is used for SOTA, fox hunting and satellites.
Layout (146.5 MHz)
The calculator scales these lengths to other frequencies. Below about 144 MHz or above 450 MHz, use a real yagi design program instead of scaling.
Tips
- Boom: ¾" schedule 40 PVC with two crosses and a tee. Elements are clamped with hose clamps. As built: about 7" of pipe between reflector and driven element, and 17½" from driven element to director.
- Cut the tape with tin snips and round the ends. Cover them with tape or end caps. The edges are sharp.
- Sand the paint off the driven element halves where the coax and hairpin connect. Solder fast, since the tape is steel.
- Tune by sliding the driven halves closer or farther apart. Many work at 1.2:1 or better right away.
- Vertical for FM (elements up and down), horizontal for SSB. Hold it by the boom behind the reflector.
- Choke the coax with a few turns at the boom so the coax doesn't skew the pattern.
HANDHELDS & VEHICLES
HT & Mobile Upgrades
Tiger Tail
A ¼-wave wire (about 19" for 2 m) attached at the base of the HT antenna and left hanging. It gives the antenna the counterpoise your hand was faking. It's often worth several dB. A ring terminal under the antenna, or a clip, works.
Longer HT Antenna
The stock rubber duck is a short, lossy compromise. A 15–18" flexible whip, or a half-wave telescoping whip, can make a big difference. Check your connector type (SMA male vs. female) before you buy.
Get It Outside & Up
Inside a car or a building, a handheld loses a lot. A mag-mount on the roof with a short run of good coax, or a roll-up J-pole in a tree, beats any antenna on the radio.
Mounting
- Center of the roof gives the most even pattern.
- NMO through-hole mounts beat mag mounts for loss and reliability.
- Dual-band (2 m/70 cm) mobiles are convenient and usually worth it.
- Check SWR after mounting. Trim ¼-wave whips a little at a time.
Getting It Up
- A J-pole or Slim Jim on a 20–31 ft fiberglass pole at camp
- Short coax: the shorter, the better up here
- Choke at the feed point
- Clear of the trailer, the truck and the trees, if you can
Commercial Options
Fiberglass base collinears give 3–6 dB of gain for a home station. Satellite stations use handheld dual-band yagis. Build the J-pole first. It'll teach you more than any purchase, and it works.
CALCULATOR
Coax Loss on VHF/UHF
How much of your power actually reaches the antenna (perfect match, dry coax).
Typical published loss figures. Old, kinked or water-soaked coax is worse, and every connector adds a little more.
FIELD NOTES
VHF/UHF Tips
- Choke the coax on J-poles and Slim Jims. A J-pole is famous for putting RF on the coax. 4–6 turns of coax about 3" across, right at the feed point, fixes it.
- Tune it where it lives. A J-pole tuned on the garage floor will shift once it's up the mast. Tune it at least a few feet up, out in the open.
- Seal the coax connection outdoors with coax seal or self-amalgamating tape. Water in the coax is the #1 VHF antenna killer.
- Connectors matter more up here. PL-259s are fine on 2 m. On 70 cm and up, N or BNC connectors are better.
- Simplex frequencies: 146.52 MHz (2 m) and 446.0 MHz (70 cm) are the national calling frequencies. See the frequency guide.
- Higher beats bigger. A J-pole at 30 ft usually beats a gain collinear at 10 ft.
- Fox hunting? A yagi plus an offset attenuator is the standard kit. See the fox hunt page.
- RF exposure: keep high-gain antennas away from people, especially on 70 cm with 50 W. Check with the RF exposure tool.
Further reading: M0UKD Slim Jim & J-pole calculator · Tape-measure yagi build · CVARC Slim Jim build (PDF)
Get Outside. Get On The Air.
GET IT HIGH. KEEP THE COAX SHORT.
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