Double Bazooka Antenna
The Double Bazooka builds each half of a dipole from a length of coax cable instead of plain wire — the shield forms the conductor, and the center conductor is shorted to the shield at the outer (far) end of each quarter-wave section. It's been a popular QST-era design since the late 1960s, built on the claim that the coax sleeve reduces feedline radiation and common-mode noise pickup without needing a separate balun, and gives somewhat wider bandwidth than plain wire. This guide builds it properly and gives you the honest, more measured engineering picture alongside the traditional claims.
How the coax-sleeve construction works
Each dipole leg is a section of coax cut to a quarter wavelength (adjusted for the coax's velocity factor), with the center conductor soldered to the shield at the far end — shorting the coax into a shielded quarter-wave sleeve. At the feedpoint, both legs' shield-and-center pairs connect to the feedline, similar in spirit to a plain dipole but with the coax shield acting as the actual radiating conductor near the feed.
Feedpoint: both legs' shield+center pairs connect to the transmission line
The traditional claims
The design has long been promoted as offering wider SWR bandwidth than a plain wire dipole and reduced susceptibility to common-mode feedline current and RF noise pickup near the feedpoint, without needing a separate balun — explaining its long-running popularity in ham literature since it first appeared in QST.
What independent modeling and measurement have found
Later NEC modeling and measured comparisons by antenna analysts, including work published by L.B. Cebik, W4RNL, have generally found the Double Bazooka's real-world bandwidth and noise performance to be very close to a plain wire dipole fed through a good common-mode choke balun — not the dramatic improvement the original claims suggested. This site presents the design honestly: it's a legitimate, workable dipole variant with an interesting construction method, not a proven step up in electrical performance over a well-built plain dipole.
- What's real: it performs as a competent half-wave dipole, and the coax sleeve does provide some shielding right at the feedpoint.
- What's overstated: the magnitude of bandwidth and noise improvement over a plain dipole with a proper choke balun, according to independent modeling.
Why build it anyway
It's a solid, working dipole with genuine historical interest, and coax is a readily available, weatherproof, mechanically robust material for the legs. Build it expecting dipole-class performance with an interesting construction method — not a mystery-antenna upgrade.
Installation options
- Flat-top between two supports: the standard install, identical footprint to a plain dipole of the same band.
- Inverted-V from a single mast: works the same as with a plain dipole, with the usual modest gain and impedance shift any inverted-V brings.
- Areas with harsh weather: the coax jacket's durability is a genuine practical advantage over bare or lightly insulated wire in icy or high-UV climates.
| Band | Design freq (MHz) | Coax leg length (VF 0.66) | Notes |
|---|---|---|---|
| 80m | 3.75 | ~43.3 ft (13.2 m) | Each leg, center shorted to shield at the far end |
| 40m | 7.15 | ~22.7 ft (6.9 m) | — |
| 20m | 14.15 | ~11.5 ft (3.5 m) | — |
| Coax type | — | RG-58/RG-8X typical | Use the actual velocity factor of your specific coax for best accuracy |
Double Bazooka Dimension Calculator
Materials for Double Bazooka
Building the Double Bazooka
The construction is straightforward coax prep and soldering — the only unusual part compared to a plain wire dipole is shorting the center conductor to the shield at each far end.
Cut both coax legs to length
Use the calculator above with your coax's actual velocity factor, and cut two equal lengths of coax.
Prepare the far end of each leg
Strip back the jacket at the outer end of each coax section and solder the center conductor directly to the shield braid, shorting them together.
Weatherproof the shorted ends
Cover each shorted joint with heat-shrink tubing and seal it, then fit an end insulator/cap for mechanical support.
Prepare the feedpoint ends
Strip the near (feedpoint) end of each coax leg, keeping the center conductor and shield separate and ready to connect to the feedline.
Assemble the center feedpoint
Connect each leg's shield-and-center pair to the corresponding side of your feedline at the center bracket — one leg's braid+center to the feedline's center, the other's to the feedline's shield.
Raise the antenna
Hoist the antenna flat-top or as an inverted-V, same as any ordinary dipole install.
Connect the feedline and sweep SWR
Connect your feedline to the center bracket and sweep across the band to check the resonant dip.
Trim if needed
Because the legs are coax rather than wire, trimming means carefully cutting a small amount off the far end and re-shorting center to shield, rather than simply snipping a wire tip.
| Symptom | Most likely cause | Diagnosis | Fix |
|---|---|---|---|
| SWR is off from the calculated frequency | Used a generic velocity factor instead of your coax's actual VF | Check the VF used in the calculator against your coax's actual spec sheet | Re-run the calculator with your coax's actual velocity factor and re-trim |
| Performance doesn't seem noticeably better than a plain dipole | Expecting the traditional claims rather than the more measured, independently modeled performance | Compare against a plain dipole with a good choke balun, not an idealized dramatic-improvement claim | Not a fault — treat this as dipole-class performance with a different, weatherproof construction method |
| Shorted end joints failing or corroding | Incomplete weatherproofing at the far-end short | Inspect the heat-shrink and sealing at each far-end joint | Re-seal or redo the heat-shrink and weatherproofing at the joint |
Does the Double Bazooka really reduce noise more than a plain dipole?
Independent NEC modeling and measurement have generally found the difference to be small compared to a plain dipole with a good common-mode choke balun — the traditional claims of a dramatic improvement aren't well supported by that more recent analysis.
Is it still worth building?
Yes, as a solid, weatherproof dipole variant with genuine historical interest — just go in expecting dipole-class performance rather than a mystery upgrade.
Do I still need a balun?
The design is traditionally built without one, relying on the coax sleeve itself; adding a choke balun anyway is a reasonable, low-risk step many builders take regardless.
Does coax velocity factor really matter that much?
Yes — since the leg length calculation depends directly on it, using the wrong VF for your specific coax will shift your resonant frequency noticeably.
Can I use any type of coax for the legs?
Most standard 50-ohm coax types (RG-58, RG-8X, RG-8) work fine — just use that specific cable's actual velocity factor in the calculator rather than an assumed generic value.
How is this different from a plain coax-fed dipole?
In a plain dipole, coax is only the feedline running to the antenna. Here, sections of coax actually form the radiating dipole legs themselves, with the center conductor shorted to the shield at the far end of each section.