49:1 / 64:1 End-Fed HF Antenna Impedance Transformer
These passive HF antenna transformers provide a 50-ohm coax input and a high-impedance connection for end-fed wire antenna experiments. The listing uses the term “balun”; for this end-fed application, the device functions as an impedance-transforming unun between an unbalanced coax feed and a single-wire antenna.
Choose the ratio and build state
- 49:1 balun kit: DIY version for users who will wind and assemble the transformer.
- 49:1 balun finished: assembled 49:1 transformer board.
- 64:1 balun kit: DIY version for a higher transformation ratio.
- 64:1 balun finished: assembled 64:1 transformer board.
A 49:1 transformer is commonly used to transform an approximately 2.5 kOhm end-fed antenna feed point toward a 50-ohm coaxial system. A 64:1 version targets a higher feed-point impedance. The best choice depends on the antenna wire length, height, ground/counterpoise arrangement and operating band.
Connections and tuning
- The board is labeled 50 OHM INPUT for the coaxial feed and Half Wave for the end-fed wire connection.
- The printed wire-length chart is an approximate starting point only. Final resonance and SWR depend on installation height, nearby structures, ground conditions and counterpoise arrangement.
- Use an antenna analyzer or SWR meter to verify the finished antenna before transmitting.
- These products do not provide automatic tuning. Adjust the antenna system or use a suitable external tuner if the measured match is not acceptable.
Important operating notes
- This is a passive antenna component, not a transmitter, receiver or antenna tuner.
- Power capability varies with frequency, match quality, duty cycle, installation and thermal conditions. Start at low power, verify SWR, and increase only within the limits of the completed assembly.
- End-fed antennas can develop high RF voltage at the feed point. Keep the antenna clear of people, buildings and power lines, and operate only in accordance with local radio regulations.
- Kit versions require RF construction, winding and soldering experience. Inspect the completed transformer before connecting radio equipment.
Package contents
Contents depend on the selected kit or finished option. Antenna wire, coaxial cable, analyzer and radio equipment are not included unless explicitly shown in the selected option.