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This project assembles a 49:1 ferrite-core (“FT”) type #43 transformer that matches 50 ohm input to 2500 ohm end fed antenna. 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.
An 80-10 end-fed half-wave antenna can be a very good performing part of an HF station. But its performance depends heavily on a well-designed and carefully constructed 49:1 unun, which matches the long wire impedance to within tuning range of operation. But the perfor-mance of an end-fed antenna is also very dependent on height above ground.
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.
The "9:1 UNUN" are for random length wire antennas fed at the end. 49:1 or other high ratio transformers are for resonant "cut to frequency" antennas like the traditional zepp/fuchs antenna.
antennas for HF. Transformer Construction: Assuming 49:1, I start with a good 6 feet of 18ga. enameled wire. I fold up about 7 inches of one end and place the loop created in a pair of pliers with padded jaws to protect the wire coating from scars. I then hand-twist the wire, leaving an inch or two for the short end. This is the primary winding.
21 mar 2024 · I was looking at what my Nano VNA graphs would reveal about the MyAntenna (commercially sold) End-Fed 1/2 wavelenth long (135 ft) with the MyAntenna 49:1 UNUN. The 49:1 UNUNS are fairly recently available devices.
7 lut 2024 · Yes, use a 9:1 Unun type transformer. You can also use an antenna called an End Fed Half Wave (EFHW) that is about 66 feet long and uses a 49:1 Unun. With either antenna try and get it up as high as possible for best effect, but even if it ends up being low it will work great for NVIS around the UK and into Europe, so you'll have fun regardless.
