DC DC CONVERTER FIELD TEST

We have tested the DC DC converter in field yesterday in SALEM. The two units are working more satisfactorily than we expected. We connected two solar panels of 100Watt in series to get the 40Volts on no-load and 36Volts on load (Battery). The test is continued till the shade falls on the panels at 5:30. For 2hrs the battery gets fully charged.

Improvements in the 2^nd unit:-

There was a high frequency humming sound in the transformer. To reduce that we increased the turns ratio from 7:5 to 8:6. We added two high voltage capacitors (1000uF & 0.1uF) at the input to remove spikes. We relocated the diode to improve the heat dissipation. The MOSFET and Diodes are placed in the front and back panel respectively. The raise in temperature of panels is less than the previous unit.

The pictures of 2^nd unit are given below.

The schematic diagram is shown below.

For more details please feel free to contact us.

BATTERY BOOSTER

This project was originally published in November 2004 QST. We have made the simplified version as shown in the below schematic.

Performance verified at 5A continuous load current to prove the design. For further details feel free to contact us.

DC to DC converter

It is a simple DC to DC converter. The input is from two solar panel with minimum Voltage of 24V, typical voltage of 32V and maximum Voltage 40V.The Output current is 10A @13V.This seem to be highly efficient. No heat sinks are used for the MOSFET and diodes. Only 3mm thick aluminium sheet is used for front panel on which power devices are mounted. We tested it for 2 hrs with output current of 4 A @ 13V, the temperature of front panes raises only by 2 degrees Celsius.  For other details please feel to contact us. 

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.

RF AMPLIFIER 16NF06

Happy New Year Greetings to Every One,

              Today we tested an RF amplifier with 16NF06 mosfet the performance is really superior than IRF510. Normally we used to set 3.3 volts bias for IRF510 but this mosfet requires some more bias to conduct 3.9 Volts. This amplifier drawns 2.1 ampere at 13.8 volts. Output RF power is 25W PEP with 0dbm INPUT.

Instruments used:
1. Standard HP RCT 8900A.
2. 30 Mhz GW INSTEK oscilloscope.
3. Power supply 10 AMP Range.

Regards,
R&D Team.

SB-7 TRANSCEIVER RX BOARD FULLY ASSEMBLED AND TESTED

ASSEMBLED SB-7 RX BOARD:

BACK SIDE VIEW RX-BOARD WITH SURFACE MOUNT COMPONENTS:

Dear all,
           We are happy to announce that our SB-7 Rx Board is fully assembled and tested in our R&D Lab.The performance was really good comparing to previous receivers.The A.G.C circuit and audio filter is doing the job very good. Noise level is less. We heard lot of dx stations in 40 meter. All tests are done with standard HP 8920A RCT and oscilloscope. Signal level feeded and checked from -107dbm to -67dbm. Sensitivity and gain is good.

Regards,
R&D Team.

SB-7 TRANSCEIVER RF AMPLIFIER SCHEMATIC

RF AMPLIFIER SCHEMATIC:

RF AMPLIFIER COMPONENT SIDE LAYOUT:

RF AMPLIFIER SOLDER SIDE LAYOUT:

FUNCTIONAL DIAGRAM:

Dear all,

              I would like to share the RF amplifier schematic of our SB-7 Transceiver project. This is an simple RF amplifier which amplifies the 1 Volt RF to 12 to 15 watts RF Power (PEP). This circuit uses simple transistors & Mosfets. Biasing is made using a 7808 voltage regulator with 10 K POT control. Low pass filter is used in the final stage to eliminate the unwanted signals. The PCB Size is 145 X 73mm.

Regards,
R&D team.

SB-7 TRANSCEIVER TX SCHEMATIC

SB-7 TX SCHEMATIC:

SB-7 TX SOLDER SIDE:

SB-7 TX SILK SCREEN:

SB-7 TX COMPONENTS LAYOUT:

Greetings Every one.

                    I would like to share the TX side of our SB-7 Transceiver Project. This circuit is simple and straight forward.

1. It uses TLO82A as mike amplifier.

2. Double balanced mixers using diodes.

3. If Amplifier.

4. 12 MHz crystals for Ladder Filter.

5 . Broad Band Amplifier

FUNCTIONAL DIAGRAM:

Regards,
R&D Team.

SB-7 SINGLE BAND TRANSCEIVER 7MHz

I would like to share some inside views and also like to have some critics to comment on our new upcoming project SB-7 Transceiver which is a single band 40 meter transceiver in S.S.B. mode (LSB only).

This upcoming Transceiver project is an improved version of our previous TRx project - JOTA TRx. The changes and enhancements for this TRx. would be: AUDIO FILTER, AGC CONTROL,S-METER & Mike Gain adjustments.The MAX Power of this Transceiver is 15 Watts.We will be updating this page and blog quite often so please take time and keep checking in for updates. 
 
A small preview of the schematics and components used have been shown below:

SINGLE BAND RX SCHEMATIC:

LAYOUT RX( SB-7):