Unadilla W2AU 4:1 Balun for Wire Antennas - Voltage Balun
W2AU Series Baluns have long been the standard of the industry
The W2AU Balun is the preferred Balun of Radio Amateurs worldwide. W2AU’s operate at a low VSWR from 1.8 to 40 mHz, and handle powers up to 2 KW PEP (at SWRs of less than 3:1).
The W2AU Baluns are transformer designs with ferrite cores to provide 95% minimum coupling efficiency. Each has a built-in lightning arrestor, hang up hook, and 600 lbs of pull-apart strength in a weatherized, rugged package using only stainless steel hardware and quality materials.
Two models are available. The 1:1 matches 50 (or 75) ohms unbalanced coax to 50 (or 75) ohms balanced dipoles. The 4:1 matches 50 (or 75) ohm unbalanced coax to 200 (or 300) ohm folded dipoles.
- 200-Ohm / 50-Ohm or 300-Ohm / 75-Ohm
- Transformer Type 1.8 - 40 MHz
- Transition: to Coaxial Connector (SO-239 / UHF-Female)
Understanding Baluns by W4ULD
Baluns - ARRL
The matchbox is a tuner and all it does is make the transmitter believe it has an antenna with a lower SWR than it really has. This way it will introduce more power to the antenna than it can typically radiate.
A random length antenna, one not tuned to any one frequency is a compromise antenna. Anywhere it is not resonant it will produce significant SWR’s above 3:1.
With 200 watts of continuous key down CW it would heat up the core of the W2AU balun, at the feed point,and damage it, but that is the extreme example. Many Hams understand this and do it anyway with care.
Also, note that new solid state equipment further limits your operating options never contemplated over 50 years ago when these instructions were made. The equipment manufacturer dictates the parameters of your operating ability.
It is suggested that if using ladderline, no balun, because a balun at the feedpoint, would interfere with the radiation that the offset antenna needs from the ladderline.
Instead use a ” W2AU 4:1 Ladder Line Balun ” at the end of the ladder line transitioning the ladder line to a coax entry into your shack. A 4:1 extends resonances available. Some hams use a 1:1.
These are some ideas in using an offset antenna.
Remember your ABC’s – ALWAYS BE CAREFUL
Other DetailsSee warranty details above
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Well made easy to use, good instruction sheet. Works great on a 20 meter dipole.