RF Power Amplifier Module S-AV10H TOSHIBA

Here's an interesting S-AV10H TOSHIBA RF Power Amplifier Module circuit. It can deliver over 14W with as low as 100-200mW input power. The system is tuned for 50 ohm input and output. The frequency can be 150-175MHz. This is how the Module looks like.

To the left is the power input pin. Then comes power control, main power line and to the right is the output power. As you see there are quit many components inside and both input and output are matched to 50 ohm.


RF Power Amplifier Module S-AV10H TOSHIBA Schematic
The main part of this project is an oscillator which you will find on the left side. It is an oscillator based around Q1. L1 and C1 forms the tuned oscillating unit. The unit can easy be set from 100 to 200MHz by changing C1 and spacing/compressing the aircoil L1. You can see the air coil at the botoom left corner on the first photo at this page. Q2 works as a booster and amplify the power to 150mW.

The RF signal then enter the Module at pin 1. Pin 2 is a power control unit of the Module. The voltage at this pin will set the output power of the Module. A voltage stabiliser LM317 is added to generate a variable voltage from 1.25V to 12 V. You can see it in the middle of the PCB and in front if it is a 10 turn potentiometer (P1). An inductor blocks RF from the Module to pass out to the power line of the LM317. Pin 3 of the module is the main power input which also is RF blocked by an inductor. Theses inductors are not critical in any was, make sure they can handle high currents since the module will consume high current.
Pin 4 of the module is the power output matched to 50 ohm system.

You must use a dummy resistor of 50 ohm else you will destroy the module. Make sure you choose a good resistor which can handle 30-50W. Make sure you have placed the Module to a heat sink becasue it will be hot.

RF Power Amplifier Measurements
The output power from this module could be set from a few mW to about 18 W by the voltage at Control pin. The unit was stable down to 145MHz and current was about 2.2A at max output power.

Source: RF Power Amplifier Module

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Simple RF Field Meter

This circuit is a simple RF field meter. It will be in great help to tune transmitters for best performances. Not everyone has a power meter, and how can you know that the antenna you connect is purely 50 ohm. The next block diagram show you one easy way to measure the RF field strength. To the left you find a dipole antenna.

The antenna should be cut to match the receiving frequency. The length of antenna is not a critical at all.

Length = 0.95*300/(4*freq) <= (freq = MHz) 

The RF signal is then rectified in a diode and the DC voltage is then amplified in an OP-amplifier. To display the voltage I use a panel meter. The amplifier gain can be set with a potentiometer and I have also added a bias voltage to set the zero level of panel meter.

How To Use RF Field meter

• Place the RF field meter 5 meter away from my transmitter.
• Then put all variable capacitor to middle.
• Switch on the transmitter and go to my RF filed meter.
• Then set the gain (with potentiometer) so I get half of max reading on the panel meter.
• Then switch off the transmitter and set the offset (with other potentiometer) so I get zero reading on the panel meter.
• Repeat this tuning process unit it looks good.

Now I can start tuning the transmitter and watch the panel meter. All I need to do is to tune for max reading on the panel meter. Then I know the RF field is at max strength. I also advice you too receive the signal you are transmitting to check that it sound good. I also check the current to the transmitter so it don't get to high.

Usually the current go down when good tuning has been done and you got max power. Another good thing to monitor is the temperature of the transistors. Don't let them go to hot.

I find my RF field meter to be a very simple and powerful too. This RF filed meter works from 30mW to several watt.

RF Field Meter Schematic
At the bottom left corner you will see a voltage divider. This divider is to produce a virtual ground of 4.5VDC. Above you will find the dipole antenna. The dipole antenna will pick up some radiated energy and the diode will rectify the RF signal to a DC voltage at VRF. This voltage is still quit low and needs to be amplified before it can control the panel meter.

The signal then enter the OP which amplifies the voltage to suitable level set by the "Gain" potentiometers". The second OP acts as a voltage follower and set the offset (zero) for the panel meter. The panel meter is connected to the board via two wires (5meter long).

To prevent any RF signal to be induced in this long wire I have added 2 ferrite block which will act as high impedance units. You can use any ferrite block or large inductor (10uH).

Source: RF Field Meter

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1W VHF RF Amplifier 2SC1970 88-108 MHz

This RF power amplifier is based on the transistor 2SC1970 and 2N4427. The output power is about 1.3W and the input driving power is 30-50mW. It will still get your RF signal quit far and I advice you to use a good 50 ohm resistor as dummy load. To tune this amplifier you can either use a power meter/wattmeter, SWR unit or you can do using a RF field meter.

RF Amplifier Assembly
Good grounding is very important in a RF system. I use bottom layer as Ground and I connect it with the top with wires to get a good grounding. Make sure you have some cooling at the transistor. In my case I put the 2SC1970 close to the PCB to handle the heat. With good tuning the transistor shouldn't become hot.

RF Amplifier Printed Circuit Board
You can download a pdf file which is the black PCB. The PCB is mirrored because the printed side side should be faced down the board during UV exposure. To the right you will find a pic showing the assembly of all components on the same board.

This is how the real board should look when you are going to solder the components. It is a board made for surface mounted components, so the cuppar is on the top layer. I am sure you can still use hole mounted components as well.

Grey area is cuppar and each component is draw in different colours all to make it easy to identify for you. The scale of the pdf is 1:1 and the picture at right is magnified with 4 times. Click on the pic to enlarge it.

Low-Pass Filter
Some of you might want to add a low-pass filter at the output. I have not added any extra low pass filter in my construction because I don't think it is needed. You can easy find several homepages about low pass filter and how to build them.

Source: 1.3W Power Amplifier

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28W RF Amplifier for FM Broadcast 88-108 MHz 2SC1946

This RF Amplifier designed for FM broadcast using a single 2SC1946 VHF Power Transistor. This 10-30W RF amplifier circuit provides an appropriate power boost with an input of 1-3 watt. Tower are 30 meters high will send signal surrounding air should be around 15 km.

RF Amplifier Artwork
The layout of the 2SC1946 28 Watts FM broadcast RF amplifier has been created with sPRINT Layout v3.0. You can get a Shareware copy at: http://www.abacom.de. The pcb outline is 100 x 50 mm (width x height), all bitmaps have a resolution of 600dpi.Use FR-4 single sided photoresist epoxy pcb material for best results.

RF Amplifier Parts List
All component values are drawn on the .comp and .silklayer bitmaps, with the following exception(s);
all four (4) coils (in the lowpass filter section) are: 3.5 turns, 8 mm DIA., 1.2 mm CuL closewound i.e. no wirespacing.

Note:
CuL = magnetwire, enameled copper wire, insulated (rigid) copper wire e.t.c..
2 mm equals approx. to #12 A.W.G
1 mm equals approx. to #18 A.W.G
1.2 mm equals approx. to #17 A.W.G
0.8 mm equals approx. to #20 A.W.G
0.3 mm equals approx. to #28 A.W.G.)

• all diameters are measured from the inside of the coils, i.e. 'internal' diameter.
• make sure to mount the rf-transistor on a appropriate heatsink and use some thermal heatsink compound between the flange of the transistor and heatsink! (Thermal resistance heatsink at least 6°C/W.)

Source: http://www.3-mtr.info/shareware/Amplifier%2028Watt%20MicroStripline%20(2SC1946A)/

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20W VHF Linear Amplifier 2SC1946 50 MHz

This VHF linear amplifier works for 50 MHz frequency using 2SC1946A with power output about 20 Watt. It needs input 30mW and output 25W for 150 Mhz. It seems can be used for 144 Mhz without modification. There are Power IC and 2SC1946A with low-pass filter on the board.


Some Experiences
I have checked Mitsubishi Catalogue and found it is 175 Mhz(ft), 3W input - output 30W(at 13.5Vcc), Gp10dB. I reffered Linear Amplifier Hand Book for deciding capacitors and coils. I made PCB with cutting by cutter knife and removing by heat with solder tool.

After mounted all parts on the board, I tried to adjust SWR for input. Connect SWR meter between rig and linear amplifier and connect 50 ohm dummy load. Without power source for linear amplifier, I have to adjust SWR as it becomes lower (at least less than 1.5).

With adjusting TC, I could get about 20 Watt. And then I connected Omron Relay (G5V2) for input/output circuit and I adjusted again, after that I noticed power was less about 10W-12W.

I tried to adjust SWR to be 1.0 by changing coils. I have changed input/output coils from 2 turns to 3 turns and I could get SWR 1.0. After I got SWR 1.0, output power becomes about 25Watts but moduration was not good and seems self oscillation. I have changed input ATT with 6dB and after that moduration becomes good with 20W output.

Author: JO1ACW
Website: http://www.geocities.co.jp/Technopolis/7222

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30W VHF RF Amplifier for 88-108 MHz

This 30W RF amplifier circuit provides an appropriate power boost with an input of 4-6 watt operating on the VHF FM Broadcast Band with 88-108 MHz frequency. However, the circuit is very stable and provides a clean-output through 7 element Butterworth low-pass filter (LPF).

Circuit Explanation
This VHF RF power amplifier circuit uses 2SC1946A VHF RF power transistor. The transistor is specifically designed for operation in frequencies up to 175 MHz, with very good results.

As you can see, the power line is well decoupled. The amplifier current can be over 5 amps. All the coils are made from 16 gauge laminated wire (or Silver copper wire can do best) and the RFC can be of HF toroid core or 6 holes ferrite bead.C3 and R1 forms snubber circuit while R2 and C6 prevent the RF amplifier from self-oscillation at VHF, sometimes you need to add 180 ohms in parallel with L7.That will cause the amplifier to dissipate "undesirable VHF" thereby reducing spurious level.

Using multiple power design, by combining two power transistors, can lead to more responsibility compared to a single power, especially in the UHF and VHF bands. It may result to great interference because of the out of phase operation of the two amplifiers. To amplify the output at its operating frequency, it simply involves connecting the output to a good antenna with a 50 ohms transmission line. With this, the amplifier can be adjusted easily.

The photo above is 60Watts VHF power amplifier using the above circuit. Two of 2SC1946A transistors are arranged at 90 degrees to each other and their outputs are combined using "Power Combiner Network”. It is quite difficult to combine powers at VHF and UHF bands.

However, I recommend that hobbies should stick to single power design due to its complicity and large rate of Intereference. (in attempt to go for double transistors which involves power combiner network). Since the two amplifiers are operating in different phase (out of phase).

Tuning:
Tuning of the amplifier is not hard at all. You just have to connect the output to a good antenna with a transmission line (RG214) of 50 ohms. First match the output network, and then do the same to the input network for a maximum power output. By way of adjustment, you can increase the output at its operating frequency.

Note:
Operating unlicensed transmitters is illegal in some countries, including the UK. The circuit presented here is for educational purposes only.

Author: David Celestin, Ghana, West Africa
e-mail: mightycelestin@yahoo.co.uk
Website: www.zen22142.zen.co.uk

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I've finally made my peace with (Pendrive) Linux!

I suppose I am about to admit that I've been wrong all along, that I didn't really understand what Linux is all about, etc, etc.

Undoubtedly that's true.

What has changed my view is the fact that I've been using for some little time now a "Pendrive Linux" Ubuntu distro, and that has served me very well. So well that I really ought to be grateful and revise my opinions about Linux in general.

With this software, which as has been hinted at above, is installed on a USB "PenDrive", I have been able to (for example) surf the Internet using my "work laptop" (fairly well locked down by my company's IT department) whilst working away from home, staying in hotels, and so on.

This distro has performed without any problems for several months, other than running out of space, and that was down to me not setting it up with adequate space to start with, rather than it being a problem with the software itself.

I can connect to my POP3 Email accounts at will, and even do other arcane stuff such as analyse configurations of whatever WiFi network I am connected to as required and work around them if possible.

For a piece of free software, this has to be a Good Thing!

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