64 WATTS AMPLIFIER

Greetings Everyone,

               Today we tested an RF Amplifier constructed on a 6.3mm copper plate with dimension of 175X150. Continuous output measured in our standard HP RCT for more than 5 minutes like FM..This copper plate RF amplifier added with extra heat sink for better dissipation.

Tested Frequency-  14MHz.
Continuous Power- 64 Watts For more than 5 minutes.
Transistors            - 2+2 IRF510

Regards,
R&D Team.

RF AMPLIFIER ON COPPER PLATE

Greetings Everyone,

               Today we tested an RF Amplifier constructed on a 6.3mm copper Plate with dimension of 175X150. Continuous output measured in our standard HP RCT for more than 10 minutes like FM. Heat transferring is happened equally in copper because copper is good conductor of heat.

Tested Frequency-  14MHz.
Continuous Power- 35 Watts For more than 10 minutes.
Transistors            - 2+2 IRF510

Regards,
R&D Team.

SWR BRIDGE

Greetings Everyone,

Today we tested a SWR Bridge in our R&D Lab.The SWR Bridge is made by using 6mm toroids winded with 10 turns of 26 SWG copper wire. And also we used 3mm copper tube as shown in figure with wires shorted in two ends. The above circuit is taken from the RF publication issued in 1985. We have only implemented the circuit. The standard SWR's measured are: Zo, Zo/2 and Zo/3.


The below formula is used to measure the SWR:
SWR = (Vforward + Vreverse)/(Vforward - Vreverse)

Schematic diagram is shown below.

 The Results are satisfactory with 7,10 &14MHz Frequencies.

13.56MHz ISM BAND AMPLIFIER USING 7NK30Z

Greetings Everyone,

Today we tested an ISM Band amplifier of 13.56 MHz with our standard R.C.T. ,Oscilloscope & Bird 500 Watts Dummy Load. It draws 10A at 33V D.C. That is 330W input and output of 200W. Upon calculating the efficiency more than 60%.

This time we have used a different MOSFET: STP 7NK30Z.  It can withstand up to 7A and maximum voltage of 300V. 7N stands for 7A rating and 30Z for 300V.  

BIRD's 8325 Tenuline Coaxial Attenuator

Greeting's,

First feast your eyes on the pictures below before I explain what this monster machine is.

 

This is a monstrous 500W, 50 Ohms, 30 dB Attenuator. We got this unit for testing our RF Amplifiers.

The following the specifications for the unit:

Impedance: 50 ohms nominal
Connectors
                  Input    : Bird “QC”, Female N normally supplied
                  Output : Bird “QC”, Female N normally supplied
Power Rating: 500W
Frequency Range: 500 MHz
Attenuation: 30 db ± ½ db, dc-500 MHz
Cooling Method: Dielectric and air convection currents

The Attenuator was tested with our amplifier and we are were exceptionally happy with the results.

The manual for the above unit can be downloaded for further reference from this link: Click Here. 

50 WATTS @ 12VOLTS HF AMPLIFIER USING 16NF06

Greetings to Every one,

We tested another one amplifier in our R&D Lab using 16NF06 mosfet.The results in 14MHz are amazing.We measured 50 watts output in 14MHz and more than 50 Watts in 7MHz using standard test Equipments HP 8920A RCT and GW-INSTEK 30MHz oscilloscope.It drawns 6Amp at 13.8VDC.The efficiency of this amplifier is 60%.  Below is the Photo and circuit details.

Note: T.S Means test select to adjust Minimum 10ma current in each MosFet.

1.) Input Transformer:

This is a step-down transformer. Primary is 4-Turns and secondary is 2-Turns wound on a TV balun core because maximum input power is 5 Watts only 26 SWG is sufficient. We have used 4-Turns primary with 26 SWG and 2-Turns secondary using 24 SWG.

2.) OUTPUT TRANSFORMER:

3.) Output Transformer:

This transformer was constructed using reference from Motorola book (R.F. Device Data -Vol. 2)

Primary consists of single turn copper tube of 4 mm diameter. Secondary consists of 2-Turns of Teflon coated wire.

Here we can see the copper tubes are shorted at one side. TV balun cores are slipped over the  copper tubes and secondary winding is completed last. The primary inductance of one turn copper tube should be 1uH. If the inductance is higher, this amplifier can works at lower frequencies. 

The above picture shows the PCB used to short the two copper tubes.

Here we can see the balun cores slipped over copper tubes.

Regards and Nice Home brewing,

R&D TEAM.

H-Bridge Motor Driver using MOSFET's and Transistors

In this post, we shall be covering on how to construct a H-Bridge Motor Driver circuit using simple MOSFET's and Transistors. The main feature of this H-Bridge is that the motor can be driven in both directions.  

An H-bridge is a circuit that allows a voltage to be applied across any load, like a motor in our experiment, in dual directions. The 'H' here just represents the formation of the circuit and has no reference to anyone.

 The H-Bridge can be realized using simple switches first:-

The H-bridge arrangement is generally used to reverse the polarity of the motor and to let the motor 'free run' to a stop, as the motor is effectively disconnected from the circuit. The following table summarizes operation, with S1-S4 corresponding to the diagram above.

S1	S2	S3	S4	Result
1	0	0	1	Motor moves right
0	1	1	0	Motor moves left
0	0	0	0	Motor free runs

 Now let us realize the actual circuit using MOSFET and Transistors:

 To download Schematic: Click Here (JPEG) & Click Here (PDF) 

We have used IRF9540 for P-Channel MOSFET and IRF510 for N-Channel MOSFET. Respective NPN and PNP Transistors are used to drive the MOSFET's which can be seen in the circuit diagram. We have used Arduino to give the logic signals to the pins to turn on and off the MOSFET's. The diodes are provided to prevent back EMF generated by the motor. 

Direction 1:
Pin1: Logic 1
Pin2: Logic 1
Pin3: Logic 0
Pin4: Logic 0

Direction 2:
Pin1: Logic 0
Pin2: Logic 0
Pin3: Logic 1
Pin4: Logic 1

After reading the above, you  might be wondering why not short the respective PIN's with the same logic. Well you can, that's what we have implemented and its easier to drive the motor in both directions with using only two I/O pins from the Arduino.

 This is the implemented circuit tested in our RnD lab. Below you can see the Working video.
   

Now you can view the motor in slow motion:

LPF (LOW PASS FILTER) FOR 20METER

Greeting's Everyone!!!!!

We built a Low Pass Filter for 20-meter H.F. band which is used in BITX designed by our good friend Farhan (VU2ESE). The inductor coil is made by using 9-turns of 22-S.W.G. on a Teflon former. This L.P.F. worked beautifully and was tested with R.C.T. HP 8920A. We fed only  -7db to take care of mismatch.

Below we have included the picture of the circuit we constructed in the RnD Lab. Also we have included the schematic for home-brewing purpose.

Communication between two PC’s through the Serial Port:

                                         

Hello Everyone,

We set up a half duplex communication between two PC’s through the serial port. The CPU needs a serial port for communicating with each other . To connect these serial ports we need:

1. Two DSUBSCF female jacks and
2. Three equal length wires.

DSUBSCF1 Txd (3^rd pin) is soldered with a wire to the DSUBSCF2 Rx (2^nd pin). Similarly the DSUBSCF1 Rx (2^nd pin) is soldered  with a wire to the DSUBSCF1 Txd (3^rd pin) and the 5^th pin is grounded. Join these two pins with a wire or don't use the pin.  Make sure that all the three wires are of same length. Now your cable is ready, and you can connect the two female jacks to the respective PC’s.Hence they can communicate with each other.

To transmit or receive the data we need to follow few  simple steps which are given below:

1. Open the Hyper Terminal as shown in the below picture.

     2.  Give any icon name (E.g.:- test).

     3.  Select the communication port as COM1.

     4.  Select the Baud rate or Bits per second as 19200 or 19.2K, Data bits ­­­- 8, Parity - None, 

           Stop bits – 1, Flow control – None. Then click APPLY and later OK.

       

           

     5.  Finally you will see the blank screen.

     6.  Follow the same steps from (1 to 5) for the other PC also.

NOTE:For sending the data click on send button, For transmitting click on the BROWSE button and also select any one of the protocol..

For receiving the data follow the same protocol as in transmitting one.

L.P.F. (Low Pass Filter) for 40 Meter R.F. Systems

Greeting Everyone!!!!!!!!!!!!!

We built a L.P.F. (Low Pass Filter) design published in 1987 ARRL  hand-book in chapter 2 (2-44).

The circuit performs very well in 7Mhz freqency. The ARRL Hand-book has given the test chart as below:

Filter No.	Fco	3 dB	20 dB	40 dB	Max. SWR	C1, C5 (pF)	L2, L4 (uH)	C3 (pF)
87	7.54MHz	8.61	11.5	17.0	1.327	470	1.45	820

This filter works as it is with out any changes and modifications.

Below we have show the tested circuit without any modifications from the original circuit which is also show below.