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):

AUDIO FILTER

Audio filter in Jota 40 receiver Testing Mode:

Schematic Diagram:

Greetings Everyone,

               We are Happy to share this experiment result of this audio filter. Basically this is not our original design. Our sincere thanks to our good ham friends OH2NLT and OH7V for this beautiful circuit which is used in JUMA Receiver.

                We constructed this circuit in a general purpose PCB for simplicity and also modified the circuit
                 in input side adding some external capacitors to achieve good performance.Half voltage of the
                 given supply voltage is required to the pin no 3.

                 Our testing process begins in the evening tuning for some time no stations heard.After a break
                 we received a strong station with call sign VU2MBU giving General CQ CQ Hi. At the time with
                 out using the filter we heard a lot of  hissing noise in the background.The audio filter is                                    connected in the audio chain suddenly performance increased.Hissing noise level reduced to very
                 minimum SIGNAL to NOISE Ratio improves by 2.5db that is measurable.

                  All components are locally available in Bangalore market for Less than 50Rs/-

                  After this improvement we tested the audio filter continously for 2:30Hrs with the following
                  stations received in good quality audio with less noise.

                   1.VU2MBU
                   2.VU2PLL
                   3.VU2LSR
                   4.VU2KSJ

         Warm Regards,
         RnD TEAM.(MIPL)

               

               
               

WSPR - Successful

Hello Everyone,

We were successful using the WSPR technology to connect with another Amateur Radio Operator.

Our setup consists of a Raspberry Pi (Single Board Computer) as a transmitter. For more information on how to use Raspberry Pi as WSRP Tx., please Click Here

We are transmitting using our Engineers callsign: VU3PWT at 10.14015MHz.

WSPR Tx. info: VU3PWT MK32 25

MK32 is the grid location and 25 is the power in dBm. Tx. Freq: 10.14015MHz

From the Raspberry Pi we connected to a very small amplifier (350mW) and then to a Low Pass Filter which is then connected to a very good antenna.

Using this setup we connected with VK6ZT, Australia. We will be running this setup for some more days to get more propagation signals and more research.

Few pics of the setup:

WSPR (amateur radio software)

Hello Everyone,

Lets check out a new software used the Amateur Radio World. Its called WSPR which is pronounced as WHISPER. The abbreviation of WSPR when expanded is "Weak Signal Propagation Reporter"

Some facts about WSPR

Developer(s)	Joe Taylor, K1JT
Initial release	2008
Development status	active
Written in	Python (GUI), Fortran, C [1]
Operating system	Cross-platform
Available in	English, Italian, Spanish, French, German, Japanese, Polish, Portuguese, Russian
Type	Amateur radio and DSP
License	GPL
Website	physics.princeton.edu/pulsar/K1JT/wspr.html

"Courtesy: Wikipedia"

WSPR was developed by Nobel Winning Astrophysicist JOE TAYLOR in 2008 under University of Princeton. 

WSPR is a piece of software that enables you to participate in a world-wide network of low power propagation beacons. It enables your radio transceiver to transmit beacon signals, and to receive beacon signals from similarly-equipped stations in the same amateur band. Participating stations usually upload spots that they receive in real time to a web server, you can find out within seconds of the end of each transmission exactly where and how strongly it was received, and even views the propagation paths on a map.

How to use it:

•       There are two modes

•       Receiving & Transmitting

•       Here we are discussing about Receiving mode

Required things

1. SSB Radio

2. Personal computer with a sound card and WSPR 2.0 software

3. Working Internet connection

How to Listen:

1. Connect SSB Receiver  with sound card

2. Connect PC with internet and sync the internet time

3. Run the WSPR 2.0

4. Select receive mode

5. Wait for even minutes and identify the signals in waterfall display

Format of Data:

 After receiving the signal, WSPR software will decode it and will display the data

1. Call sign

2. Location of transmitter

3. Power used for transmission

4. After reception WSPR software will upload the location in to WSPRnet server and it will generate a MAP

Technical Specification:

•       1. Modulation used : Continuous FSK

•       2. Channel Bandwidth : 6Hz

•       3. Baud Rate : 1.4648 bauds

•       4. Total time taken for transmission 1.54 minutes

•       5. Length of data send over channel : 50bits

•       6. 28 bits for call sign

•       7. 15 bits for location

•       8. 7 bits for power in dbm

More info can be found at: http://physics.princeton.edu/pulsar/K1JT/wspr.html