RADIO HABANA CUBAYou can obtain more antenna gain, and of course a narrower beam pattern, if you add elements to the basic 2-element CBQ. For the average CB station, a 2-element CBQ is more than enough. It provides ample gain, a reasonable front-to-back ratio and is both lightweight and easy to build. Nevertheless, for those wanting still higher gain, here are the dimensions for CBQs with 3, 4 and 5 elements.
THE CBQ ANTENNA, Part 2:
A LOW-COST, EASY-TO-BUILD, COMPACT QUAD ANTENNA
FOR THE 27 mHz CITIZENS' BAND
BY ARNIE CORO
Host of "Dxers Unlimited"
SEND YOUR COMMENTS, QUESTIONS AND IDEAS DIRECTLY TO ME AT: firstname.lastname@example.org
Adding more elements to the basic 2-element CBQ
The separation between the Reflector and the Driven Element changes dramatically when you add a Director element, so the 3-element CBQ needs a much longer boom, and thus is much bigger and difficult to handle.
The 4- and 5-element antennas provide still more gain.... tests at a typical installation proved that the 4-element CBQ cut for the slightly higher amateur 10-meter band, provided 10 dB gain... a ten-fold increase in effective radiated power. The 5-element version tested showed about 12 dB gain...
Similar antennas built for the 2-meter amateur band provided the same results. I assume that you are now familiar with the CUBICAL QUAD configuration, so I will only give a table of dimensions for the 3-, 4- and 5-element CBQs.
REFLECTOR 11.44 m. 37 ft, 6 in (same size for all antennas)
DRIVEN EL. 11.17 m. 36 ft, 8 in (same size for all antennas)
DIRECTOR 1 10.63 m. 34 ft, 10 in (same size for all antennas)
DIRECTOR 2 10.08 m. 33 ft
DIRECTOR 3 9.55 m. 31 ft, 4 in
DISTANCE BETWEEN ELEMENTS:
For the 2-element CBQ (already described in part one):
Distance between Elements: 1.00 m. 3 ft, 4 in.
For the 3-element CBQ:
Distance between Reflector and Driven Element: 1.6 m 5 ft, 4 in Distance between Driven Element and Director: 2.6 m 8 ft, 6 in
Please notice that the antenna is not symmetrical, so this requires finding the center of gravity before installing in on the mast.
For the 4-element CBQ:
Distance between Reflector and Driven Element: 1.6 m 5 ft, 4 in
Distance between Driven Element and Director 1: 2.0 m 6 ft, 8 in
Distance between Director 1 and Director 2: 2.0 m 6 ft, 8 in
Please notice that this is also a non-symmetrical antenna, so the center of gravity does not fall at the center of the boom; you must either calculate it, or determine it experimentally before installing the antenna on the mast.
For the 5-element CBQ:
Distance between Director 2 and Director 3: 2.00 m. 6 ft, 8 in.
An almost perfect 1-to-1 SWR can be achieved by moving the REFLECTOR slightly back and forth, toward the driven element or away from it, until the SWR meter reads 1 to 1, or maybe 1.1 or 1.2 to one.
There are many factors involved, so don't worry of at your particular installation the minimum SWR that you can achieve is say 1.3 to 1 or something similar. This is absolutely not significant at the power levels involved, and certainly irrelevant for receiving!
Use fiberglass spreaders if you can afford them. Select their diameter for a compromise between antenna overall weight and mechanical resistance. A well built QUAD will last many years, while a poorly built one may break down at the slightest wind that goes past 20 mph!
WARNING: When erecting this or any other antenna, follow all established safety rules, including your personal safety equipment, adequate procedures, and staying away from power lines. You don't want your hobby to bring your life to an end!!!
Just e-mail me at: email@example.com
02 March, 1998
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