The eggbeater antenna is constructed of two circular loops made of 16 AWG (1.29mm) copper-clad steel wire insulated with heatshrink tubing. The circumference of each loop is equal to one wavelength, adjusted for the velocity factor of the wire. A quarter wavelength (again adjusted for the velocity factor) phasing line made of 93-ohm RG62 connects the two loops. The impedance of the loops is about 100 ohms so the RG62 is a close match. With the two loops connected in parallel, the resulting impedance is about 50 ohms which matches well with most RF receiver or preamp inputs.
FREQ CIRCUMFERENCE DIAMETER PHASING LINE
310MHz 36 inches 11-1/2 inches 8-3/8 inches
315MHz 35-1/2 inches 11-5/16 inches 8-1/4 inches
418MHz 26-3/4 inches 8-1/2 inches 6-1/4 inches
426MHz 26-1/4 inches 8-3/8 inches 6-1/8 inches
433.92MHz 25-3/4 inches 8-1/4 inches 6 inches
X-10 uses 310MHz in North America and 433.92MHz elsewhere. RF-capable programmable touchscreen remotes (e.g. Philips Pronto, Universal MX3000) use 418MHz in North America and 433.92MHz elsewhere.
For a receiving antenna, dimensions need not be exact. Ring terminals crimped to the ends of the coax along with triangular eyelets, formed by bending the ends of the antenna elements, simplify connections.
For clarity, the schematic representation above shows the loops separated but they are assembled perpendicular to each other with one loop inside the other as shown below.
Cut the antenna elements 1-1/2 inches oversize to allow 3/4 inch for forming eyelets on each end. The copper-clad steel wire tends to retain the curvature from the coiling operation which makes measuring the length awkward. The easiest method is to cut the heatshrink tubing to size, slip it over the antenna wire and then cut the wire so it is 1-1/2 inch longer than the heatshrink. To form the eyelets, lay the heatshrink covered loop on a flat surface. Using 6 inch long nose pliers, bend 1/4 inch at each end up 120°. Move in 1/4 inch and bend up 120°. Move in 1/4 inch and bend down 30°. You want to end up with a triangular eyelet with 1/4 inch sides as shown in the schematic representation at the top of this page.
The elements are mounted to the top of a Polycase LP-11F enclosure using stainless steel hardware:
6 ea. insulated ring terminals
4 ea. 6-32x5/8 phillips or hex head machine screws
8 ea. internal star lockwashers
4 ea. 6-32 hex nuts
8 ea. flat washers
4 ea. 6-32 locknuts (nylon insert type)
Remove the top cover from the enclosure. Drill 4 holes in it for the 6-32 screws. The holes are in a symmetrical diamond pattern with about 1-1/4 inches cross corner. The elements can also be mounted atop the MR26A or MR26E.
Assemble as shown in the photo and hardware sketch. Tie the elements together at top center with a small tie-wrap.
The best location for the antenna is usually the one that is most central (both horizontally and vertically) to your transmitters but slight variations in location and/or angular orientation can make a difference. We recommend rotating the antenna in 30-45° increments to find the optimum orientation with your mix of transmitters.
Copyright: No part may be reproduced except as authorized by written permission. This restriction extends to reproduction in all media.