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It is optimized for 3.5/7/10/14 MHz but will work reasonably well on all amateur bands from 80 meters thru 10 meters with a 135 foot length of wire and a short connection to ground. (Adjustments to the length for your particular installation can move the resonance point to your preference).
Recommended wire lengths and Installation Notes for Unun models 4932, 4935, 9130, 9132 & 9135. Table shows typical SWR relative to installed wire length. SWR will vary based on topography, proximity of nearby structures, configuration of the antenna wire and choice of ground or counterpoise.
If the transformer is used with an external tuner in conjunction with a single wire antenna typically 130-135 feet in length, power should be reduced on those bands that show an SWR above 1.6 to 2:5 without the tuner. A level of 500-600 watts is the maximum with a further reduction on any band measuring above 3:1.
This EFHW antenna (patterned after one by Steve Ellington N4LQ, with notes by K1RF), if built carefully, will serve you for many years, and at up to 200 watts. The heart and engineering of its design is in its 49:1 impedance matching transformer, or unun (connects an unbalanced
We recommend minimum height of 20 feet at any or all points of our EFHW-8010 antenna models or 10 feet for EFHW-4010 models. This height applies also for Inverted “L” and Inverted “U” configurations where vertical side(s), starting at minimum 3 feet or 1 meter above ground, should be minimum 20 or 10 feet long.
High Impedance UNUN for EHFW antenna The UNUN has a high impedance ratio (49:1 to 64:1) – not feasible to use transmission line transformers whose practical limit is about 16:1. It is a conventional transformer. Uses a ferrite toroidal core or cores (usually Type 43 or type 52 material). Most 1:4 and 1:9
22 lut 2021 · The following is a list of materials required to make a 49:1 unun impedance transformer for an end-fed half wave antenna. You will also need a half-wavelength length of wire (14 or 12 gauge typically) in order to construct an antenna radiator for whichever ham band you choose.
