The mAT-125S is a general use external automatic antenna tuner for use with any HF transceiver. Automatic RF-sensing tuning mode. RF-sensing means no external control cable is needed. No internal rechargeable batteries, direct power from 12-14 vDC source. Connect a 50 ohm coax cable between the radio and the tuner and you are ready to use. 

1.8-54 MHz, 5-1500 ohms matching range, internal monostable relay instead of latching relays.

The differences between the mAT-125E and mAT-125S are described here:

mAT-125E:  Internal latching relays draw zero power after initial tuning and will allow the tuner to be used with as little as 100 mW of input power. No bypass mode; the tuner must be taken out of line when not in use as it will retain last SWR setting with latching relays when power is off. Uses internal rechargeable batteries for power instead of 12 vDC, can be used for very long periods of time from a single charge,s

mAT-125S:  No internal latching relays. mAT-125S uses a monostable relay, requiring DC power be present for tuner to be used. QRP power level to use the tuner actuated must be 5 watts or higher  Bypass or power off modes resets to open default bypassing the tuner, no need to reove it from the signal path between the radio and antenna to NOT use it. Monostable relay also allows for a lower overall SWR match with simple on/off logic. mAT-125E uses a microprocessor to control latching relays, once a close suitable match is found (generally 1.8:1 SWR or lower) the tuner will stop the tuning sequence. 

Superior build quality with machined, black oxidized aluminum case and excellent multi-layer circuit boards.

Specifications:

- 0.1-120 watts SSB/CW power, 30 watts on keydown digital modes.  100 watts max above 50 MHz.

- 1.8-54 MHz continuous operation.  Built-in frequency sensor.

- Tuning time 0.1-3 second for full tune cycle

- Tuning range 5 to 1500 ohms impedance

- Monostable relay instead of latching for faster tuning time to an overall lower SWR than mAT-125E

- Requires external 12-14 vDC source

- Dimensions 7 7/8" deep, 5 1/8" wide, 1 5/8" height (20 x 13 x 4 cm)

- Weight 1 lb 9 oz (0.75 kg)

Click here to read the operation manual