LDG RU-9:1 Unun, 9:1 Impedance Transformer, 1.8–30 MHz, 200W PEP

The LDG RU-9:1 Unun is a 9:1 impedance transformer designed to interface vertical and end-fed antennas with LDG automatic antenna tuners — or to operate standalone with resonant verticals where no tuner is required. By transforming the high impedance of an end-fed or random wire antenna down to a level closer to 50Ω, it allows your tuner to achieve a match far more efficiently than it could without the Unun in line.

Rated at 200W PEP and covering 1.8–30 MHz, it's suitable for HF operation across all amateur bands from 160m through to 10m. The weatherproof-ready construction makes it equally suited to permanent outdoor installations.

Key Features

• Configuration: 9:1 Unun (impedance transformer)
• Frequency coverage: 1.8–30 MHz (160m–10m)
• Power rating: 200W PEP
• Designed for LDG automatic antenna tuners — also operates standalone
• Suitable for vertical and end-fed antenna installations
• Easy to weatherproof for outdoor use

Technical Specifications

• Configuration: 9:1 Unun
• Frequency: 1.8–30 MHz
• Max power: 200W PEP

Frequently Asked Questions

What is a 9:1 Unun and why do I need one?
A 9:1 Unun (unbalanced-to-unbalanced) transformer converts the high impedance of an end-fed or random wire antenna (typically 450–900Ω) down to approximately 50Ω. This brings the antenna impedance within the matching range of most automatic tuners, resulting in a more efficient and reliable match.

Do I need an antenna tuner to use the RU-9:1?
Not necessarily. With a resonant vertical antenna, the RU-9:1 can be used standalone without a tuner. However, for end-fed random wire or non-resonant antennas, pairing it with an LDG automatic tuner is recommended for best results.

Which LDG tuners is it compatible with?
The RU-9:1 is designed specifically to complement LDG automatic antenna tuners, including popular models such as the AT-100Pro, AT-200Pro, and Z-11Pro series. It can also be used with other tuners that accept a 50Ω input.

What bands does it cover?
It covers 1.8–30 MHz, spanning all HF amateur bands from 160m (1.8 MHz) through to 10m (28 MHz).

What is the maximum power it can handle?
The RU-9:1 is rated at 200W PEP, suitable for most HF transceivers used in amateur radio.

Can it be used outdoors?
Yes. The unit is easy to weatherproof and is well suited to permanent outdoor antenna installations. Ensure connections are sealed against moisture for long-term reliability.

What type of antenna is it best suited for?
It is ideal for end-fed wire antennas (EFHW or random wire) and vertical antennas with a high feedpoint impedance. It is not intended for balanced antennas such as dipoles — a balun would be more appropriate in those cases.

What connectors does the RU-9:1 use?
The unit uses standard SO-239 (UHF) connectors for the coax side, compatible with PL-259 plugs used on most HF coaxial feedlines.