Broadband RF Amplifier 470-860 MHz with BLW32-33

This Broadband RF Amplifier for 470-860 MHz taken from Philips Aplication Note (AN_BLW32_33). Please download file in PDF format.The broadband rf amplifier for TV Transposer band IV/V designed with transistor BLW32 and BLW33. In this case, my RF Amplifier design replaced them with 2 pieces BLW34 have good result.

Download combine two BLW34

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RF Power Meter

The RF Power Meter presented is based on the AD8313 Log Detector manufactured by Analog Devices. The IC can be ordered as a sample direct from ADI, or you can search for it in some disabled GSM mobile phones available on the market. In GSM phones AD8313 is used as a Log Detector, part of the Power Control Loop circuit. Generally could be easy identified near the Power Amplifier module.

AD8313 is a Logarithmic Detector which can accurately convert an RF signal at its input to an equivalent decibel-scaled value at its DC output.

The DC output is “linear in dB” with a basic slope of 20mV/dB. The slope can be adjusted in a range from 18mV/dB to 30mV/dB. The linear input range of AD8313 is between -60dBm and 0dBm, which corresponds to a DC output between 0.6V to 1.6V (pin 8).

The following operational amplifiers (LM324) are translating the DC output range of AD8313 (0.6V to 1.6V on Pin nr 8) to a scaled range read by the Voltmeter (-6V to 0V). The scaled range has a resolution of 100mV/dB.

For example the minimum input value (-60dBm) corresponds to a read voltage value of -6.0V, -59dBm corresponds to -5.9V, -58dBm corresponds to -5.8V, and so on up to 0V that corresponds to 0dBm (as in the table below).

The frequency range of AD8313 is between 100MHz to 2.5GHz, but the range that not requires a dynamic slope adjustment is between 100MHz to 1.4GHz. The resolution of the RF Power Meter is better than 1dB; only near 0dBm input is approximately 2dB. The RF input has an impedance of 50 ohms provided by the 53 ohms resistor in parallel with the internal impedance of the AD8313.

For calibration inject first at the input an 800 MHz signal at -60dBm and adjust P2 for -6V reading on the output Voltmeter. After that increase the input level up to 0dBm and adjust P3 for 0V reading on the output Voltmeter. The slope can be adjusted by the P1 semi-resistor.

Careful design of the RF input layout should be done for minimizing parasitics which can produce un-wanted resonances that affects the linearity vs frequency of the log-detector.

Tolerance of the resistors is +/-1%.

A calibrated attenuator at the input can be used to increase the maximum input power, without damaging the detector.

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FM RF Power Amplifier For FM Broadcast 40W

This amplifier was built based on Marconi's website, A Design for a 40W broadband VHF RF Power Amplifier for FM broadcast. A few minor tweaks were made to the schematic and a few parts were changed to what I had available (mostly surface mount components). The heatsink is from an old Motorola Mostar 800 MHz radio, and has the perfect heatsink island to match the MRF171A. Also used is a Progressive Concepts external LPF7002 low pass filter because it was also on hand. Since the MOSFET uses 28 VDC, I had to homebrew a 28 Volt / 5 Amp power supply using the schematic found in the ARRL handbook.

Tune up went exactly as stated in the how-to, with the RF power output hitting 57 Watts when driven with a stock Broadcast Warehouse 1 Watt LCD PLL transmitter at 98 MHz. Liberal use of ferrite beads and feedthru capacitors are on all RF detector, fan control and SWR control circuits.

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FM Power Amplifier 1.2W

The following is a very easy to build amplifier that was designed to follow a Ramsey FM-10 and FM-25 transmitter. It is built on top of a simple PCB board surface style (all parts tacked on top, no holes in PCB.) The performance is excellent with power levels of up to 1.5 watts acheivable and harmonic suppression greater than 50db. Using this amp in conjunction with an Ramsey FM-10/25 can provide you with the ideal micro power radio station with usable range of up to 2 miles or more. If you use this unit to amplify a Ramsey FM-25, build the FM-25 in the low power output configuration.

I feel this is a much better alternative than the Ramsey LPA-1 because it provides much lower harmonic output and it is relitivly bullet proof to antenna mismatches which has been known to destroy LPA-1s without the slightest warning.

The PCB board is a single sided copper board etched or grinded out to the shown layout. The board size is 3 3/8" x 1 3/8" but anything close that can accomidate the parts without any lengthing of the lead lengths is fine.

I recommend that if you don't have a good way to make the PCB that you buy the Radio Shack PCB Etching Kit, this kit works very well for this type of application. We've used laser printer iron ons for this board, but we've found that electrical tape or the resist pens work fine.

Design and Schematic:

Old Schematic

New Schematic

The amplifier is a 2 stage design. The first stage uses a high gain microwave transistor amplifier running class-A to boost a 10mw signal to about 150mw.

In the first stage the resistor R1 (1.5K) gives Q1 (mpf-901 or mrf-901) and the Ramsey transmitter a nice stable input/output load to look at that should smooth out missmatches between the transmitter and the amp (note that this type of matching is only workable at flea power levels.

Printed Circuit Board (PCB):

3 3/8" x 1 3/8"

Construction Tips:
Solder all the small low lying parts first; resistors, L3, L4, L5, L6. Then mount all the small capacitors; C5-C10, and C12. Next Q1, C1,C2,C3,C4, followed by L1, L2 and Q2. Finally add C11 and attache the input and output with coax to the connectors and/or transmitter.

Part's Layout:


For tune up you should simply tune C1, C2, C3, C4 and L1 for maximum output. This amplifier doesn't like to ocsillate, but this is always a possiblility. You can check for oscillation by tuning a FM radio up and down the FM radio band, if you hear multiple images of your broadcast your amplifier is in oscillation (not good).

Updates and Modifications
I would change the design slightly if I were to build more of these amplifiers. The input is not DC isolated. I would add a .001uh cap between the input and Q1. This is a must do mod if the amp is to be used as a stand alone device (ie not hardwared ont a FM-10).

I would get rid of C12, it is not necessary since C2 blocks the DC between stages. I would move C1 to the other side of C3, this allows C2 to be adjusted without effecting the C1/L1 low pass filter. I would add another 5-50pf cap from the input side of L2 to ground, thus adding an extra element and more flexibility to the output/matching filter (I would and have done this addition on every amp that I have built with an output power of under ~3 watts, cannot get -50db down on harmonics without it.)

The modifications listed above can easly be made to the existing circuit board if done during the assembly stage. Basically you would shift Q1 and its associated parts one pad to the right on the circuit board (since C12 is no longer necessary), and add a .001uf cap between the first pad and the base of Q1 pad. C1 can easly be moved to the pad on the output side of C2. And another 5-50pf variable cap fits nicely on the input side of L2.

L6 mostlikly can be optimized, but is most likely not that critical to the overall performace of the amp.

Parts List

Resistors:
R1 1.5K ohms
R2 20K ohms
R3 300 ohms


Capacitors:
C1, C2, C3, C4, (C14) - ~5-50pf
C12,(C13) - .001uh
C5, C7, C9 - .01uf
C6, C8, C10 - .1uf
C11 - 10uf


Inductors:
L1- .2uh adjustable digikey...
L2 - .2uh fixed coil...
L3,L4,L6 - 10uh Moulded Inductor
L5 - 3 turns of #22 enamel wire through Ferrite Bead.

Transistors:
Q1 - mpf901 -or- mrf901
Q2 - 2sc1970

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MRF317 FM Amplifier Circuit for 88-108 MHz

FM amplifier is used for amplify signal from exciter in broadcast radio station. In this page, RF FM Amplifier uses solid state material with minimum gain 9dB. Input FM Amplifier needs 5-10 watt with power output about 100 watt.

The Block schematic and datasheet

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WLAN High Linearity Power Amplifier

The SST11LP12 is a high-power, high-gain power amplifier based on the highly-reliable InGaP/ GaAs HBT technology. The SST11LP12 can be easily configured for high-power, high-efficiency applications with superb power-added efficiency while operating over the entire 802.11a frequency band for U.S., European, and Japanese markets (4.9-5.8GHz). It typically provides 35 dB gain with 16% power added efficiency @ POUT = 23 dBm.

The SST11LP12 has excellent linearity, typically ~4% added EVM at 21 dBm output power which is essential for 54 Mbps 802.11a operation while meeting 802.11a spectrum mask at 23+ dBm. SST11LP12 also has wide-range (>20 dB), temperature-stable (~1 dB over 85°C), singleended/differential power detectors which lower users’ cost on power control.

The power amplifier IC also features easy board-level usage along with high-speed power-up/ down control. Ultralow reference current (total IREF <3 style="font-weight: bold;">802.11a WLAN transmitter and access point applications.

Figure 1

The SST11LP12 is offered in 16-contact WQFN package. See Figure 1 for pin assignments and Table 1 for pin descriptions.

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Low Power RF Amplifier for 88-108 MHz

This application use a common NPN RF transistor called 2SC1970. You can also use other transistors like 2N4427 and some others. Check datasheets to se how much power the transistor can handle. 2SC1970 will handle 1.3W and 2SC1971 up to 6W. Most transistor has a power gain of 10dB meaning 10 times power amplification.

This is the reason why you must use several stages to achieve a strong transmitter. In this construction we are getting higher power then ever and you must be careful with the transistor. A 50 ohm dummy load MUST be used while testing, else the final transistor will break. An antenna can be used but the antenna must be properly made else the transistor will break.


Hardware and Schematic
In all RF system and specially in RF amplifiers, it is very important to have a stable power supply and making sure you won't get any RF out on the power line. The Capacitor C12 and C13 will stabilise the DC power supply. L1, C10, C11 and L3 with C8, C9 will also prevent RF from leaking out to the powerline and cause oscillation or disturbances. L1 and L3 should be ferrite chokes or inductance's about 1 to 10 uH.


Transistor Q1 will act as a buffer amplifier, because I don't want to load the previous stage to much. The input RF signal is passin C1 and F1 which is a small ferrite pearl where the wire just passing through. F1 with C2 will act as an impedance matching for Q1. F1 can be substituted with a coil as L4, but in my test I found that the ferrite pearls gave best performances. L2 is nit a critical component and any coil from 2-10uH will do the job. Q1 will amplify the input signal from 50mW to about 200mW. Q1 can amplify much more, but It doesn't need to do that because 200mW is good for the final transistor. If you want higher power you can decrease the resistor R2.

If you look at Q2 you will also find a ferrite pearl F2 at the base to emitter. This ferrite pearls is to set the DC voltage to zero and be a high impedance for RF signals. I wounded the wire 4 times around this small ferrite pearl. You can substitute it with a coil of 1uH or more.

C4, C5 and L4 forms an input matching unit for the transistor. Not much we can do about that…
At the output of the final transistor Q2 you will find 2 coils L5 and L6.
Together with C6 and C7, they form an impedance unit for the antenna and also for the transistor.

Printed Circuit Board (PCB) - Download
Above you can download a (pdf) filer 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.

RF power
This amplifier is based on the transistor 2SC1970 and 2N4427.
The output power is about 1.3W and the input driving power is 30-50mW.
You can use other transistor as 2SC1971 and get much more output power.
1.3W will still get your RF signal quit far and I advice you to use a good 50 ohm resistor as dummy load.
Make sure it can take up to 5-10W, else it will be a hot resistor.
You MUST use an antenna or 50 ohm dummy resistor while testing else you burn up the transistor.

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