RMS Antenna

This is a two band antenna working on 20mtr and 40mtr Amateur Radio bands.

The two band antenna (20m and 40m) radiating elements are fed on the single coaxial cable and the plastic spreader are shown in the below figure .

Two 34 Feet long wires are taken for the 40m antenna and two  17 Feet long wires for 20m antenna. Both the live wires are joined at the connector hot end and the return wires are soldered to the ground terminal of connector.  The 40m and 20m radiating wires are separated by the insulating material. Here we have used the plastic spreader of length 5.5 Inch.

After erecting the antenna the radiator wire length need to be adjusted for best SWR. Typically 1.2:1 is achievable.

We will be adding photos soon after tuning.

SMPS 14V@20A

SMPS (Switch Mode Power Supply) is an electronic power supply. These are classified into four types based on the input and output voltages.
• DC to DC
• AC to DC
• AC to AC
• DC to AC
In this post we will concentrate only on AC to DC (also called off-line DC power supply) converter. The input voltage is normal AC mains and the output rating is 14V@20A. The main blocks in this SMPS are Controller card and Switching Circuit . The functionality of the card is to Sense the output Voltage and Current. We used N-Channel Power MOSFETS (IRFP460) for Switching purpose. It has HY3845 which is fixed frequency current mode PWM controller.
The preview of controller card schematic and image is given below:-

                                                             a. Schematic of Controller Card

                                                                  B. Picture of Controller card
Pictures of the SMPS is given below:-

This power supply can also be used for SSB Transmitter.
We shall keep updating the post for more information. Suggestions are most welcome.