A high-ratio impedance transformer wound 46:6 on a mix 75 ferrite core, giving a 59:1 impedance transformation. It matches a short end-fed wire — typically 25' or 31' — to the 50 ohm input of your receiver or SDR.
This transformer lifts your receiver's 50 ohm input up to approximately 2,950 ohms at the wire — right in the region a short wire wants to see. The weak, high-impedance signal from the wire is transferred efficiently into the receiver instead of being lost to mismatch.
Why it works so well on receive
Below roughly 15–20 MHz, atmospheric and man-made noise set the noise floor — not your antenna's efficiency. That means a short wire, properly matched, delivers all the signal-to-noise ratio the band has to offer. You don't need a huge antenna for excellent MW, 160m and LF reception; you need a short wire and the right transformer. This is it.
Why mix 75
Mix 75 ferrite has very high permeability, so the 46-turn winding has plenty of magnetising inductance even at 1 MHz and below. The transformer presents a high shunt impedance right across the medium wave band and down into LF, so it doesn't short away your signal at the bottom end — a common failing of transformers wound on lower-permeability material intended for HF.
Built using
Fair-rite FT140-75 core, 46:6 winding ratio
IP65 case
5mm stainless steel connectors
SO239 gold plated connector
All drilled holes are sealed from the inside to prevent water ingress
Typical use
End-fed wire of 25' or 31' (also works well with other lengths), 25' aluminium flag poles
Medium wave broadcast band, 160m, and LF/VLF listening
Ideal for SDRs, communications receivers and vintage sets with 50 ohm inputs
Receive only
Tips for best results
Connect a ground rod or a few metres of counterpoise wire to the ground side of the transformer — a short wire worked against a decent ground picks up noticeably less noise.
Ideally add a mix 31 or 75 common-mode choke stop your coax dragging household noise into the receiver — often the single biggest improvement you can make.
Route the wire away from the house where possible; most MW-band noise is local.