Eggbeater Antenna
The Eggbeater takes the classic crossed-dipole turnstile idea and bends each element into a loop shape, then adds a reflector screen or rod set below - reshaping the pattern to favor straight overhead (zenith) rather than the horizon, and providing circular polarization that stays usable regardless of how a satellite is oriented as it passes. Because it needs no rotator or tracking, it's a favorite fixed antenna for FM satellite work (SO-50, AO-91, and similar) and APRS satellite digipeater access, where a pass goes from horizon to zenith and back in a matter of minutes.
Two crossed dipoles, fed in quadrature
Like a plain turnstile, the Eggbeater uses two half-wave dipoles crossed at 90 degrees to each other, fed with a 90-degree phase difference between them. That quadrature feed is what produces circular polarization - useful because a satellite's own orientation relative to your station changes constantly during a pass, and a circularly polarized ground antenna avoids the deep signal nulls a purely linear (horizontal or vertical) antenna would suffer as that relationship rotates.
How this differs from the plain Turnstile already on this site
The Turnstile antenna uses straight crossed dipole elements and favors a broad, near-horizon omnidirectional pattern - good for general VHF coverage. The Eggbeater bends each dipole into a loop shape and adds a reflector screen or rod set below the elements, which reshapes the pattern to concentrate more energy toward zenith and less toward the ground - exactly what a satellite ground station wants, since satellites pass overhead rather than along the horizon.
- Turnstile: straight elements, no reflector, horizon-favoring omnidirectional pattern.
- Eggbeater (this guide): bent/looped elements, reflector screen below, zenith-favoring pattern for satellite passes.
Why bend the elements at all
Bending each dipole into a loop-like shape lets the antenna self-support more compactly than a straight crossed-dipole structure of the same electrical length, while also broadening the pattern usefully toward higher elevation angles - both practical benefits for a fixed satellite antenna that needs to work across an entire pass without moving.
Why a reflector screen below the elements
Without a reflector, a crossed-dipole pair radiates roughly equally up and down, wasting half its energy toward the ground. A wire mesh screen or a set of rods spaced below the elements reflects that downward energy back upward, concentrating the pattern where satellites actually are.
Installation options
- Fixed mast, no rotator: the entire point of this design — a simple fixed mount handles the whole pass without any tracking hardware.
- Rooftop or tower-top mount: keeping the antenna clear of nearby obstructions matters more here than for a tracked beam, since you can't steer around a blockage.
- Paired with a tracked Yagi: some satellite stations run an Eggbeater for easy near-zenith passes and a tracked crossed Yagi for lower, more distant passes where extra gain matters more.
| Parameter | 2m (146 MHz) | Notes |
|---|---|---|
| Each bent dipole (total wire length) | ~42.4 in (1.08 m) | ~5% longer than a straight half-wave due to the bend geometry |
| Reflector screen/rod-set diameter | ~28-33 in (0.7 lambda) | Wire mesh screen or radial rod set below the elements |
| Screen spacing below elements | ~9.8 in (0.2 lambda) | Adjust slightly during tuning for best pattern |
| Phasing line length difference | ~9.8 in electrical (0.25 lambda x VF) | Sets the 90-degree quadrature phase shift between the two dipoles |
Eggbeater Dimension Calculator
Materials for Eggbeater
Building the Eggbeater
Bending the two elements accurately and getting the quadrature phasing right are the two details that matter most here.
Bend both dipole elements
Bend each dipole's total wire length from the calculator into the loop-like eggbeater shape, keeping both elements as close to identical as you can.
Cross-mount the elements at 90 degrees
Mount both bent elements to a non-conductive center support, crossed at 90 degrees to each other, at a common feedpoint height.
Build the reflector screen or rod set
Assemble the wire mesh screen or radial rod set to the calculated diameter.
Mount the reflector below the elements
Space the reflector below the crossed dipoles at the calculated distance using non-conductive standoff arms.
Build and connect the quadrature phasing feed
Wire the phasing line/power divider so one dipole is fed a quarter-wavelength (electrically) different from the other, producing the 90-degree phase shift needed for circular polarization.
Connect coax and mount to a fixed mast
Connect your feedline and mount the assembled antenna to a fixed mast - no rotator or elevation tracking is needed for this design.
Sweep SWR and verify on a satellite pass
Sweep the feedpoint for a clean resonant dip, then verify real-world performance by working an actual FM satellite pass from horizon to zenith.
| Symptom | Most likely cause | Diagnosis | Fix |
|---|---|---|---|
| Weak signal during low-elevation passes | Design inherently favors zenith over the horizon | Compare signal strength at low vs. high elevation during a pass | Expected behavior; use a tracked, higher-gain crossed Yagi for consistently strong low-elevation performance |
| Works on some satellites but not others | Mismatch between the antenna's circular polarization sense and the satellite's | Check the sense of polarization your phasing feed produces against what each satellite uses | Most FM satellites tolerate either sense; a mismatch mainly costs some margin on weaker passes |
| SWR is off from the calculated frequency | Inconsistent bend geometry between the two elements | Compare the bend shape and dimensions of both elements | Correct the bend so both elements match; bending is more sensitive to variation than a straight dipole |
How is this different from the plain Turnstile on this site?
The Turnstile uses straight crossed dipoles and favors the horizon; the Eggbeater bends the elements and adds a reflector screen to favor zenith instead, which is what satellite work needs.
Do I need a rotator?
No - that's the design's main advantage. Its wide, zenith-favoring pattern covers most of a satellite pass from a fixed mount.
Will it work for low-elevation passes?
Less well than for high-elevation passes - a tracked crossed Yagi outperforms it near the horizon, which is a real tradeoff of going rotator-free.
Does the sense of circular polarization matter?
Most FM satellites tolerate either sense with some signal margin loss if mismatched - it's worth getting right, but a small mismatch usually isn't a dealbreaker on strong passes.
Can I use this for APRS satellite digipeaters?
Yes - this is one of the design's common uses, alongside general FM satellite voice work.
Can I build this for other VHF/UHF bands?
Yes, the calculator scales all dimensions to your chosen design frequency, though 2m and 70cm are the most common bands this design is built for.