Antennas

The stock whip is fine for FM and a strong local AM station. On shortwave it is fighting physics: a quarter wavelength at 6 MHz is about twelve metres, so a 60 cm whip is a tiny capacitive stub. The radio is built around exactly that. Its antenna input is deliberately high-impedance, not a 50-ohm port, and tuned for a short whip rather than a coax feed. Almost everything useful about upgrading the antenna follows from those two facts.

The cheapest shortwave upgrade costs almost nothing: a counterpoise wire. The whip borrows your hand and body as a ground reference, which is why the radio often sounds worse in a stand than held in your hand. Clip a few metres of wire to the radio’s ground and the signal and SNR on the low bands climb further than extra whip length will take them.

Start cheap: a longer whip and a ground wire

A longer telescopic whip is a real win for FM and strong MW, where it can approach a resonant quarter-wave near 100 MHz. On shortwave the counterpoise does more than the extra length, and the clip-on ground lead below is the highest-value upgrade on this whole page. For a quick boost in the field you can also clip a reel extender onto the whip — use its alligator clip, not the 3.5 mm plug, because that jack on the ATS Mini is audio out, not an antenna input. Get a whip with an SMA male base so it screws straight in.

Where to clip the ground wire: the radio’s ground is the outer metal of the SMA socket the whip screws into, and the knurled nut at the base of the whip that screws onto it. Clip there, not onto the whip’s rod or its hinge — wire on the rod only makes the antenna longer, which is the reel-antenna trick, not a counterpoise. Any insulated wire works, 2 to 5 metres of it: a double-ended crocodile lead on the radio end, the rest trailing loose on the floor away from chargers and power supplies. Connect the far end to nothing, least of all a mains earth, which usually brings more noise than it removes. Then compare SNR on a weak station with and without the wire, and try a different length or direction; it costs nothing.

Compact loops

A small loop is quiet and directional, which helps indoors: rotate it to null out local noise. The cheap printed-circuit "donut" is pocketable but inconsistent, and some have a measured coil flaw that leaves them working at only a handful of sharp frequencies. The passive YouLoop is the one to trust: balun-coupled, no power, and it cannot overload the radio. Its output is low, so it rewards a quiet location more than a crowded daytime band.

Active antennas: more signal, more noise

An active antenna puts an amplifier right behind a small probe, so it can lift weak shortwave out of a tight space. The Mini Whip is the classic E-field plate; a broadband active whip covers the whole HF range; the MLA-30+ is an active loop that trades a whip’s noise pickup for a loop’s quieter, directional reception on a balcony. All three need DC power fed up the coax, usually a bias-tee, often over USB. All three can overload the SI4732’s modest front end and throw ghost signals across the bands, and all feed 50-ohm coax into the radio’s high-impedance jack, so a small inline attenuator or a matching transformer can tidy things up. When strong signals start swamping everything, the radio’s own attenuator and AGC are the first thing to reach for.

Powering one is where the cheap traps are. The DC has to travel up the same coax that carries the signal, which is what a bias-tee does: the MLA-30+ ships with one, a bare Mini Whip does not. Read the frequency span rather than the price. The common ten-dollar modules start at 10 MHz, so they quietly delete longwave, mediumwave and everything below the 31 metre band — exactly the range you bought an active antenna for. A unit that starts in the kilohertz costs more and is the one that matches this radio.

Going bigger: a longwire

When you can string out a few metres of wire outdoors, an end-fed random wire through a 9:1 matching transformer is the cheap classic, quieter and stronger than any whip. One caution is specific to this radio: it overloads easily on long wires, so keep the wire modest, add a counterpoise, and lean on the attenuator if images start to appear.

Two cheap parts make the experiment painless. A pigtail with an SMA plug on one end and crocodile clips on the other gets bare wire onto the radio without soldering a connector first, and a 1:1 balun at the feedpoint stops the outside of the coax braid picking up the flat’s electrical noise and delivering it straight to the receiver.

The 27 MHz CB antenna

This one is sold for citizens band, and it is a resonant 27 MHz element, not a broadband shortwave antenna. On receive the radio is forgiving of mismatch, so it works as a longer outdoor element that hears other shortwave bands better than the stock whip. Think of it as a bigger whip that happens to be tuned for 11 metres, not a catch-all.

Which one for your situation

A rough guide. If you only want better FM, a longer whip is enough. If you listen indoors in a noisy flat, the YouLoop and a ground wire beat anything amplified. If you have a balcony or a garden and want maximum shortwave, the MLA-30+ or a longwire with the 9:1 transformer is the way up. Whatever you hang on it, the jack is SMA female, so the antenna end has to be SMA male. For a fuller situation-by-situation matrix, see best antenna for the ATS Mini.

Unplug an external antenna in a storm and when you are not listening. A static discharge through the jack can quietly deafen a portable’s front end, and clipping a lead straight onto an active antenna’s amplifier can kill it.