MLA-S (portable RT)


MLA-S (portable RT)

The MLA-S (portable RT) is probably one of the most economically viable commercially produced plug-and-play magnetic loop antennas directly designed for remote tuning (RT).


499.00 €


in stock


MLA-S (portable RT)is probably one of the most economically viable commercially produced plug and play magnetic loop antennas that are directly designed for remote tuning (RT). The portable suffix reflects the fact that the MLA-S (portable RT) is expandable and can be carried in a small backpack. The method of use on site is by means of a three-legged tripod with 1/4" universal fitting. Tripod not included.

Bands and power

The MLA-S (portable RT) is operable on amateur radio bands from 60m to10m with a maximum power of 40W. When transmitting with this maximum usable power, it is not advisable to sit at the wake-up antenna less than 5m away. The antenna is not safe for operators with a pacemaker! The switching of the band segments is done by three external JUMPers according to the table below.

Red - 60m
Blue - 40m
Grey - 30m and 20m
without jumper - 17m to 10m.

Tuning within the above segments is provided by a DC motor, which is connected to the CB4M MINI driver box via an audio cable with 3.5mm JACK connectors. As the converted variable capacitor has no stops (it rotates continuously 360 degrees), this significantly simplifies the electronics of the CB4M MINI driver. By nature, however, the arrows on the CB4M MINI controller cannot be labeled as FRQ UP and FRQ DWN, which may not be an ideal solution, but when comparing the benefits associated with the controller's single-endedness, it is an acceptable compromise. The CB4M MINI driver is included in the package. A more detailed description of the driver is below. The appearance of the MLA-S (portable RT) and the CB4M MINI driver can be seen in Figure 1 and Figure 2.


CB4M MINI is a CONTROL BOX for remote tuning of magnetic loop antennas. It extends the range of previously used CB4M, CB4M DUO, CB4M UNI controllers, which were created gradually with the continuing development and expanding type range of magnetic loop antennas produced by BTV and LOOPER SYSTEMS.

The CB4M MINI is the simplest of the range of drivers. Because it uses knowledge accumulated over several years, it performs the remote MLA tuning function very well even without the PWM control previously used. Unlike the CB4M, the CB4M DUO has an integrated internal 9V replaceable battery to power the controller electronics and to control the DC motor that turns the magnetic loop antenna capacitor, significantly reducing interference caused by poor quality power adapters.

Unlike the CB4M, the CB4M DUO is not equipped with a DC turnout (biast -T). Therefore, an additional cable is required to control/tuning the MLA-S (portable RT). To connect the MLA-S (portable RT) and the CB4M MINI, a standard audio JACK/JACK cable is used, possibly supplemented with a 5m or even 10m extension cable. Both the MLA-S (portable RT) and CB4M UNI are equipped with a stereo (femal) 3.5mm JACK connector. The 3.5m cable and 9V battery are included.

CB4M MINI control - MLA-S (portable RT) tuning

For remote tuning of the MLA-S (portable RT), the CB4M MINI is equipped with three buttons on the top panel of the cabinet. Two buttons provide FORWARD/BACK functions, the third button switches the tuning speed - coarse/soft. This function of the CB4M MINI is solved by changing the voltage for the DC motor. In the fast detuning mode, the rotational speed of the DC motor can be factory set using the internal R-trimmer. In fine tuning mode, the voltage and speed are constant. The two outermost LEDs on the top panel indicate FORWARD/BACK capacitor movement, the middle LED indicates the tuning speed in color. Green - slow mode, orange - fast mode.  The CB4M MINI controller is shown in Figure 1.   

Technical parameters

  • Bands: 5.3-7-10-14-18-21-24-28 MHz
  • Maximum usable power: 40 W
  • Loop diameter: 80 cm
  • Antenna weight: 1.2 kg