DIY Medium Wave Antenna for TEF6686 DSP Radio

In order to enable the TEF6686 DSP radio to receive medium wave (MW) broadcast signals, a new antenna has been homemade to further improve the packaging, following the production of the LC matching MW antenna last time.

DIY Tips:

1. Material preparation:

one 10mm*120mm green-painted medium wave magnetic rod, one MUTSUMI PVC-2LXT16B7 variable capacitor (CBM-444HF or PVC-224C/F can also be used instead), two hollow protective rubber rings with 10mm inner hole, one PVC pipe with a length of about 130mm and a diameter of 20mm, two adapter pipe covers and clamps with 20mm PVC pipe, one 22mm or 25mm potentiometer dial, and one SMA female connector.

2. Homemade instructions:

Wind the medium wave antenna coil, and connect the tuning end to the variable capacitor with about 70-100 turns. Wind about 10-15 turns on the other end to connect to the radio antenna port. There is no strict limit, but use multi-strand enameled wire (at least 7 strands), and try not to use lacquered wire. It is recommended to position the coil in the center of the magnetic rod. To protect the magnetic rod antenna, it needs to be covered with two rubber rings on both ends, and then put into the PVC sleeve. The variable capacitor is inserted into one of the PVC pipe covers, and the wall of the cover should be shaved off before insertion to create four slots for the variable capacitor to fit in. For easy installation and removal, an SMA female connector is added to the other PVC pipe cover, making it easy to connect to the TEF6686 radio when listening to medium wave. Finally, pour some epoxy resin or 904 silicone gel into the PVC sleeve to further fix the magnetic rod and variable capacitor.

3. Actual test:

Continue to listen to MW and FM synchronous broadcast radio indoors, adjust the TEF6686 radio frequency to MW 1170kHz, and observe that the worst reception level is 19dBμv by adjusting the variable capacitor. The best reception level is 82dBμv when finely tuning the variable capacitor to the optimal reception point. The same effect is achieved when listening to other medium wave broadcasts at different frequencies. Using a DeSheng PL36X series magnetic rod antenna at the same position, the received signal level is 47dBμv.

4. Conclusion:

The principle of this DIY is to match the LC to "tune in" to the most suitable frequency point. The medium wave magnetic rod antenna of a regular radio is fixed and cannot achieve the best reception effect for each frequency point within the entire frequency band. This is the advantage of a "tunable" medium wave magnetic rod antenna.