Electronic Transmitter Guide

Cable-TV Amplifier with 5 Outlets

noreply@blogger.com (Quick Zone) — Fri, 09 Oct 2009 17:29:00 +0000

Here's the design of a cable TV distribution amplifier (CATV). This cable TV distribution amplifier has 5 outlets. This amplifier boosts the TV cable signal with 18dB before the signal is split into 5. The design is based around a MAR-6 MMIC. This Integrated Circuit amplifies DC to 2GHz with about 18dB, uses only 15mA and costs around 4,5 Euro.

The CATV distribution amplifier circuit is built on a piece of double sided circuit board with one trace cut out with a sharp hobby knife. It is housed in a standard metal housing, that holds the 6 F-connectors for the HF. A 7805 is used to stabilise the electrical power.

The electrical power (8..30 VDC - 50mA) enters the housing via a (1n) feedthrough-Capacitor. A single diode protects the circuit from reverse polarity voltage. A 7805 soldered to the housing (GND) stabilises the voltage at 5 Volt. Two 100nF capacitors prevent the generation of spurious signals and noise by the 7805

The HF signal enters via a F-connector. An optional attenuator (0,75 - 20 dB) gives the ability to decrease the signal strength in case you should experience interference by intermodulation products. In my situation, I ended up adjusting the attenuator at the maximum level…

After the attenuator, the signal passes through a 1nF capacitor to block DC voltages and goes into the MAR-6. The input to the MAR-6 is indicated by a dot on the body and a chamfer to the input leg.

Power is supplied to the output of the MAR-6 through a 100 Ohm resistor and a 6 hole ferrite choke (1uH). DC current will be about 15mA (3,5 Volt DC at the output of the MAR-6). Another 1 nF capacitor blocks DC and only HF signal is sent to a passive resistor splitter, made from 51 ohm carbon film resistors. Input impedance is 50 Ohm for the MAR-6. Output impedance will be a little less than 75 Ohm. The splitter is build as a 'spider web' floating over the circuit board. Each output is has a female F-connector. All F-connectors are soldered directly to the housing.

After closing the lid of the housing, the circuit should be reasonably immune to the 5 x 1.5 kW Digitenne (DVB-T) transmitters built less than 3 kilometre from my house L

Safety ground
I placed the amplifier right where the cable enters our house, and routed coax to all outlets. The housing is connected to safety-ground with a copper wire.

CATV Amplifier Power supply
For power supply, I use a non stabilised adapter. Unloaded, the output is 8,5 Volt DC, just enough for the 7805 to do its job.

Source: Cable-TV distribution Ampplifier

25W Broadband RF Amplifier 88-108 MHz

noreply@blogger.com (Quick Zone) — Sat, 19 Sep 2009 05:58:00 +0000

This RF amplifier for FM 88-108 MHz with no tune (broadband) needed to cover all the FM Band. This RF Power amplifier is equiped with the famous Mosfet transistor the BLF245. Depending on the output power level you are able to provide with your FM synthesizer, you can use or not the 2N3866 driver stage included in this amplifier design.

Impedance matching network file(PDF)

All the impedance networks (Input-Output) of this RF amplifier have been determined by using the softwares: Mimp.EXE and Genesy.

Low pass filter measurements file(PDF)

This RF Amplifier need a 9 elements low pass filter ensures that its harmonic frequency meet at least a 60 dB rejection from the carrier.(RF Simulation with RFSIM99)

Gain and Ros measurements file(PDF)

The RF FM amplifier has a 27 dB gain (with driver stage) and provides 25W with a 58% efficiency.

RF Power Amplifier PCB Layout

Source: 25W MOSFET FM AMPLIFIER

Frequency Converter 2.4 GHz to 700 MHz

noreply@blogger.com (Quick Zone) — Fri, 24 Jul 2009 11:53:00 +0000

It's theoretically possible to convert a 2.4 GHz wireless LAN signal to a much lower frequency to help overcome non line-of-sight issues. Many UHF television frequencies in some areas are currenty unused. Those would be great to hijack. You could then use common directional UHF TV antennas for your links. This current design is theory only.

It might even be possible to hack the local oscillator out of an old 2.5 GHz MMDS down converter and use that to drive an external frequency converter.

This might help overcome non line-of-sight issues most people are facing today. Fairly high antenna gain and RF output power should reduce the multipath conditions which degrade wireless data links.

The theory is to mix 802.11b channel 9 (2451 MHz) with a local oscillator frequency of 1536 MHz. The resulting IF frequency is 915 MHz, which is the new transmit/receive frequency. You then will do a little dance to the Gods to keep pagers and cellphones from destroying all your hard work.

The actual bandwith of the RF signal of the final direct sequence spread spectrum signal is 22 MHz wide, between 904 and 926 MHz - centered at 915 MHz.

You should also lower the data rate, say to 1 Mbps, this reduces the TX/RX switching times a bit.

It might also be possible to transvert down to the unused 600 to 700 MHz UHF TV frequencies. You could use those cheap, high gain UHF TV antennas and scrap cable TV hardline.

This design is for reference only, it hasn't been built completely yet. There are several quirks that will need to be worked out: the use of resistive isolation pads at various points, diplexer on the mixer's IF output, PLL loop filter values, and various switching voltages. It can be used as a start to the TAPR Summer 2003 PSR callout for 802.11b transverters.

Since in most urban areas the 900 MHz band is actual worse than the 2.4 GHz band in terms of interference, it may be possible to use this as an IF rig for lowering long coax losses, or even further transverting to the 440 or 1.2 GHz bands.

Source: 2.4 GHz to 700 MHz Converter

Designing RF Filter Faster

noreply@blogger.com (Quick Zone) — Fri, 24 Jul 2009 11:40:00 +0000

How to design RF Filter Fast? A Windows® electrical filter design and analysis program designed to expedite the design of lowpass and highpass filters using Standard Value Components (nearest-5% values). You can view your spectrum analysis filter design.

SVCfilter™ is a program designed to expedite the design and analysis of lowpass (and highpass) filters with nearest 5% component values.

Here are some pertinent features:

SVCfilter is 32-bit Windows® electrical filter design software nicely written to help the radio amateur, technician or engineer design and analyze lumped-element lowpass and highpass filters.
Order, topology and family are all entered by clicking on buttons.
If the Chebycheff or Cauer family is chosen then three options for passband ripple (.01, .044 and .200) are available.
If the Cauer family is chosen then four options for stopband depth (30, 40, 50 and 60 dB) are available.
Cutoff frequency is entered in the usual text box and can be from audio through UHF.
Cutoff frequency can be as low as 0.1 Hz, allowing the value of .159155 [ i.e., 1/(2*PI) ] to be used. This, in conjunction with a termination value of one ohm, yields parts values for the textbook classic "normalized" design.
System impedance by default is 50 ohms but a textbox allows entry of any value of your choice, for example 600 ohms for audio.
Inductor Q values are set by default to a value of one million. A textbox allows entry of any value of your choice in the range of 10 minimum to one million maximum.
The graphic output draws the schematic of the filter you have designed, and also plots the responses of that filter (both transmission and reflection). It selects the nearest 5% values for the capacitors and shows those values as well as the exact values and overlays the response plots for the nearest values on top of the original exact-value plot.
Tuning buttons allow stepping the cutoff frequency up or down in 1% steps and immediately seeing the new performance of the redesigned filter on the plot.
Place the cursor anywhere on the plot and see the transmission, reflection, VSWR and envelope delay values for that frequency.
Inductors are retuned as necessary to maintain the response of Cauer filters after nearest capacitors are chosen.
To maintain the high level of quality of the graphic output, the outputs to the printer are not "screen dumps" but instead are from a set of dedicated routines which write directly to the printer. The quality of the graphics as delivered by the printer will be limited only by that printer, commonly several hundred pixels per inch. The printer output on one sheet contains the schematic with parts values along with the set of responses.
Click on the "Write Elsie File" button to write a file to drive Elsie the filter design and analysis program for followup filter examination in even greater detail.
Click on the "Write Spice schematic" button to write a file to drive the LTspice simulator. (Tonne Software has no connection with Linear Technology Corporation.)
This program was written to simplify the sometimes difficult task of lumped-element lowpass (and highpass) filter design by automating or setting as default some of the more frequently-encountered options. But it also includes analysis, uncommon for such an application.

Download SVCFilter - How To Design RF Filter Faster in detail

Source: How To Design RF Filter Faster

RF Test Probe

noreply@blogger.com (Quick Zone) — Fri, 24 Jul 2009 11:16:00 +0000

Like the Classic RF Probe, this RF test probe is used in conjunction with a high-impedance-input Voltmeter or Digital Voltmeter Meter (DVM). What makes this probe unique is?

What makes this probe unique is that it's built inside the shell of a regular ol' ballpoint pen. Besides being conveniently compact, the unit sports a needle-probe suitable for use in probing surface-mount circuits, and good overall shielding. The pen cap protects the needle probe when not in use.

When measuring sinusoidal signals, it should provide RMS-corrected readings, using a 10 or 11-Meg input impedance VTVM or DVM. With a 1-Meg DVM, it reads 25% of the sinusoidal RMS voltage. Reasonable accuracy (+/- 10%) can be expected over the HF/VHF range (2-150 MHz), although this hasn't been verified. When used to measure non-sinusoidal signals, the accuracy will be unknown, but it still affords good relative measurements, and most of the time, that's all that's required. It makes an excellent, compact, and portable accessory for troubleshooting or homebrewing QRP equipment with peak voltages less than 50 Volts (most solid-state equipment)

RF Test Probe Construction
The figure below shows the parts required to build the Ballpoint RF Probe. Click on the image to open an larger, annotated image with parts labled, and construction notes. Pick a ballpoint pen with a non-metalized plastic body, and plenty of room inside. The Papermate Flexgrip model I used had an inside diameter a little over 1/4-inch. We'll use an itty-bitty scrap of double-sided printed-circuit-board to mount the electronic components. Trim the PC board to about 2-12" long and 3/16" wide; don't make it too wide, or it won't fit inside the ballpoint pen. Notch or file a little out of the middle of the pc board, so the 1N34A diode will fit easily inside the pen body. then, on one side only, groove in two places, so as to create 3 lands on the "top" side of the board.

In addition to the rf test probe parts shown, you'll need a 2-1/2" piece of heat-shrinkable tubing to cover the electronic assembly (although electrical tape would do instead), and about a foot of 1/4"-wide adhesive-backed copper tape, commonly available in rolls of 200-300 inches at large hobby stores. Although a chip capacitor is shown in the photo, a very small disc capacitor will do as well.

Source: N5ESE's Ballpoint RF Probe

MP3 FM Transmitter Circuit

noreply@blogger.com (Quick Zone) — Tue, 14 Jul 2009 16:40:00 +0000

Here's a simple VHF FM transmitter that could be used to play audio files from an MP3 player or computer on a standard VHF FM radio. The circuit use no coils that have to be wound. This FM transmitter can be used to listen to your own music throughout your home. When this FM transmitter used in the car, there is no need for a separate input to the car stereo to play back the music files from your MP3 player.

To keep the circuit simple as well as compact, it was decided to use a chip made by Maxim Integrated Products, the MAX2606 [1]. This IC from the MAX2605-MAX2609 series has been specifically designed for low-noise RF applications with a fixed frequency. The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors
for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency.

It is possible to fine-tune the frequency by varying the voltage to the varicap. Not much is demanded of the inductor, a type with a relatively low Q factor (35 to 40) is sufficient according to Maxim. The supply voltage to the IC should be between 2.7 and 5.5 V, the current consumption is between 2 and 4 mA. With values like these it seemed a good idea to supply the circuit with power from a USB port.

A common-mode choke is connected in series with the USB connections in order to avoid interference between the circuit and the PC supply. There is not much else to the circuit. The stereo signal connected to K1 is combined via R1 and R2 and is then passed via volume control P1 to the Tune input of IC1, where it causes the carrier wave to be frequency modulated. Filter R6/C7 is used to restrict the bandwidth of the audio signal. The setting of the frequency (across the whole VHF FM broadcast band) is done with P2, which is connected to the 5 V supply voltage.

The PCB designed uses resistors and capacitors with 0805 SMD packaging. The size of the board is only 41.2 x 17.9 mm, which is practically dongle-sized. For the aerial an almost straight copper track has been placed at the edge of the board. In practice we achieved a range of about 6 metres (18 feet) with this. There is also room for a 5-way SIL header on the board. Here we find the inputs to the 3.5 mm jack plug, the input to P1 and the supply voltage. The latter permits the circuit to be powered independently from the mains supply, via for example three AA batteries or a Lithium button cell. Inductor L1 in the prototype is a type made by Murata that has a fairly high Q factor: minimum 60 at 100 MHz.

Take care when you solder filter choke L2, since the connections on both sides are very close together. The supply voltage is connected to this, so make sure that you don’t short out the USB supply! Use a resistance meter to check that there is no short between the two supply connectors before connecting the circuit to a USB port on a computer or to the batteries.

P1 has the opposite effect to what you would expect (clockwise reduces the volume), because this made the board layout much easier. The deviation and audio bandwidth varies with the setting of P1. The maximum sensitivity of the audio input is fairly large. With P1 set to its maximum level, a stereo input of 10 mVrms is sufficient for the sound on the radio to remain clear. This also depends on the setting of the VCO. With a higher tuning voltage the input signal may be almost twice as large (see VCO tuning curve in the data sheet). Above that level some audible distortion becomes apparent. If the attenuation can’t be easily set by P1, you can increase the values of R1 and R2 without any problems.

Measurements with an RF analyzer showed that the third harmonic had a strong presence in the transmitted spectrum (about 10 dB below the fundamental frequency). This should really have been much lower. With a low-impedance source connected to both inputs the bandwidth varies from 13.1 kHz (P1 at maximum) to 57 kHz (with the wiper of P1 set to 1/10).

In this circuit the pre-emphasis of the input is missing. Radios in Europe have a built-in de-emphasis network of 50 μs (75 μs in the US). The sound from the radio will therefore sound noticeably muffled. To correct this, and also to stop a stereo receiver from mistakenly reacting to a 19 kHz component in the audio signal, an enhancement circuit Is published elsewhere in this issue (Pre-emphasis for FM Transmitter, also with a PCB). Author: Mathieu Coustans, Elektor Magazine, 2009

MP3 FM Transmitter Parts List
Resistors (all SMD 0805)
R1,R2 = 22kΩ
R3 = 4kΩ7
R4,R5 = 1kΩ
R6 = 270Ω
P1 = 10kΩ preset, SMD (TS53YJ103MR10 Vishay Sfernice, Farnell # 1557933)
P2 = 100kΩ preset, SMD(TS53YJ104MR10 Vishay Sfernice, Farnell # 1557934)
Capacitors (all SMD 0805)
C1,C2,C5 = 4μF7 10V
C3,C8 = 100nF
C4,C7 = 2nF2
C6 = 470nF
Inductors
L1 = 390nF, SMD 1206 (LQH31HNR39K03L Murata, Farnell # 1515418)
L2 = 2200Ω @ 100MHz, SMD, common-mode choke, 1206 type(DLW31SN222SQ2L Murata, Farnell #1515599)
Semiconductors
IC1 = MAX2606EUT+, SMD SOT23-6 (Maxim Integrated Products)
Miscellaneous
K1 = 3.5mm stereo audio jack SMD (SJ1-3513-SMT
CUI Inc, DIGI-Key # CP1-3513SJCT-ND)
K2 = 5-pin header (only required in combination with 090305-I pre-emphasis circuit)
K3 = USB connector type A, SMD (2410 07 Lumberg, Farnell # 1308875)

Notice. The use of a VHF FM transmitter, even a low power device like the one described here, is subject to radio regulations and may not be legal in all countries.

RF Power Amplifier 80W 2SC2782

noreply@blogger.com (Quick Zone) — Wed, 15 Apr 2009 19:46:00 +0000

This is a conventional FM RF power amplifier design, using bipolar transistors in a tuned class C circuit. Thanks to the use of two stages, the amplifier can be driven to full power with less than 1 watt driving power, so that a large gain margin results in this FM transmitter.

Bipolar VHF power transistors have a severe affinity for low frequency self- oscillation. To obtain stability in this amplifier, I employed several techniques, such as placing the resonances of base and collector chokes far apart, damping the chokes with resistors, using RC combinations for absorption of unwanted frequencies, using feedtrough capacitors for bypassing on the board, etc. It took some tweaking, but the amplifier ended up unconditionally stable.

The impedance matching network between the two transistors calls for such a low inductance, that it would be impractical to make it with actual wire. So I used a micro stripline etched on the PCB. Also, the power and SWR sensor at the output was made with micro striplines.

This amplifier has a low pass filter at the output, resulting in a signal clean enough to be directly connected to an antenna. The SWR meter was placed before the filter, in order to clean out the harmonics produced by its diodes. In any case, while the signal is clean enough to easily satisfy usual legal and technical requirements, this transmitter should not be used at a multi-transmitter site without further narrowband filtering! This is so because any other strong signals on nearby frequencies would be picked up by the antenna and coupled to the power transistor, which would mix it up with the own signal, creating a wide array of intermodulation products, some of which would be re-radiated! This is a common and very big problem in many multitransmitter sites. In such places, NOT EVEN ONE FM transmitter should be allowed on the air without narrowband filtering! Such filtering is easily accomplished by means of a single tuned cavity, which can be constructed from copper tubing or sheet.

RF Power Amplifier 80W parts overlay without parts identification!

Here is the PCB layout, including the microstrips. The board is 20cm long and is double-sided, with the backside being a continuous groundplane except for two small pads at the driver transistor base and collector. I cut out these pads with a knife, rather than making a whole computer drawing for that!

Source: 80 Watt FM stereo broadcast transmitter

See more: RF TV Modulator - Audio Video RF Modulator - TV Modulator

High Fidelity FM Stereo Modulator

noreply@blogger.com (Quick Zone) — Mon, 17 Nov 2008 13:09:00 +0000

This circuit is a stereo encoder for FM transmitter. It is used for generating a high quality FM stereo multiplex signal that is suitable for driving mono FM transmitters. This version features improvements to the audio mixer stage, better gain adjustments in the audio filter stage and a rework of the multiplexer stage. When it is adjusted properly, the Rev E design produces an FM stereo signal with excellent fidelity.

In addition, It is a good idea to have a stereo compressor between the signal source and the transmitter, when properly set, it can save the operator from having to "ride" the volume level between the point of good modulation and the point of distortion. This circuit does not perform pre-emphasis (high frequency boosting), a graphic equalizer in front of the compressor can be used if desired.

This is a fairly high-level project, it should only be attempted by someone with a fair amount of electronics experience. A decent oscilloscope and an audio signal generator are necessary for aligning this circuit.

It is the operator's responsibility to run the transmitter in accordance with the frequency regulating authority of their country, it may be necessary to use an output attenuator on some fm ransmitters.

High Fidelity FM Stereo Modulator authorized by Forrest Cook

See more : 2.4 GHz Power Amplifier - RF Power Meter - UHF Power Amplifier

30W VHF FM Amplifier BLF245

noreply@blogger.com (Quick Zone) — Tue, 28 Oct 2008 22:08:00 +0000

This FM amplifier has been designed to take place on a heatsink microprocessor PC equipped with its fans, the advantage of this method of cooling has been selected for the fact that it is not very common and expensive. The Power out of the VHF FM amplifier can be achieved by 30 Watt.

The size of the printed circuit of the amplifier will adapt quite easily to the type of heatsink as you have available, if possible, because in many cases, those of recovery, the fans have already lived and the price of a model remains very affordable. The dimensions of the circuit must be respected at best because of the presence of lines granted strip-line. These dimensions are 73 mm wide and 63 mm in height.

The method of amplification is Class AB. Below is a description of mounting image. The layouts are made of carnations, but it is also possible to achieve with simple crossings "legs of resistance", for example .. The printed circuit will be achieved with double-sided glass epoxy, 0.8 mm thick.

Source: 30W VHF FM Amplifier BLF245

See more : Power Amplifier - RF Meter - UHF Amplifier

Designing a Combiner for VHF/UHF

noreply@blogger.com (Quick Zone) — Tue, 30 Sep 2008 04:36:00 +0000

Here's is one way of combining several antennas on VHF/UHF is by using a power combiner (or power splitter if you prefer to look at it from that angle). Using the principle of impedance transformation in a quater wavelength transmission line, a proper matching can be made between antennas and the downlead cable.

To build a RF combiner you need to design a coaxial quaterwave line, having a characteristic impedance Zo, determined from Zo^2 = Z1*Z2, where Z1 and Z2 are the impedances being matched. This is normally done by using tubing - round or square - with air as dielectricum.

Simple impedance calculation
The characteristic impedance for the two types of lines are:

a = the diameter of the inner round conductor.
b = the inner diameter - or side lenght - of the outer conductor.

Combiners for 144, 432 and 1296 MHz
2-way combiner for 144 MHz.
4-way combiner for 432 MHz.
2-way combiner for 1296 MHz.

Exact impedance calculation

See more : 2.4 GHz Power Amplifier - RF Power Meter - UHF Power Amplifier

VHF Video Transmitter 60-200 MHz

noreply@blogger.com (Quick Zone) — Tue, 23 Sep 2008 09:18:00 +0000

Here's a simple video transmitter for VHF TV channel will accept baseband video input, hence it can be driven by most CCD cameras and VCR video outputs. It ouputs roughly 80mW and when used with a 40cm telescopic antenna over 100 metres range is possible.

The transistor of the video transmitter can be a BC108, BC546, BC337 or a 2N2222. L1 is wound on a 10 mm air former. Use 6 turns 24 SWG for frequency 60-80 MHz, 4 turns for 150-180 MHz, and 2 turns for 180-200 MHz

You can use this with a monochrome or color video signal. To transmit sound just build the wide band FM transmitter and tune it to the audio channel.

See more : Audio Video RF Modulator - PLL FM Transmitter - Circular FM Antenna

FM Bandpass Filter 97.5 MHz

noreply@blogger.com (Quick Zone) — Wed, 03 Sep 2008 16:13:00 +0000

This type of filter circuit is a bandpass filter for FM band 88-108 MHz. This bandpass filter is in fact a combined highpass and lowpass filter. The first stages are a high pass and the last stages a low pass. We ripped it out the newsgroup alt.radio.pirate too bad, we can't remember who posted it. We tested the schematic with a simulation in MicroSim PSpice A/D Analog/Digital Simulator, Version 6.2 - April 1995. You find the output on this page.

This is An overview with PSpice from 10 MHz to 400 Mhz :

An overview with PSpice from 70 MHz to 150 Mhz looked like the next picture. Too bad PSPice didn't interpolate the points more detailed, this is why the curve is angled and not bowed!

Source: FM Bandpass Filter 97.5 MHz

See more : Audio Video Modulator - FM Transmitter - Ring FM Antenna

Tunable Dipole Antenna For FM Broadcast

noreply@blogger.com (Quick Zone) — Sat, 30 Aug 2008 06:07:00 +0000

This is a simple dipole antenna for FM broadcast. It can be tune for 88-108 MHz frequency range. It's very clear and easy to build. For more gain it can be stacked (2 or 4 antennas and used power divider for distributing RF energy).

How to construct:

Solder all copper pieces before attaching to the 1/2[inch] plastic T.
The aluminum tubing is attached to the copper fitting with 2 self-tapping #6 screws, 1/2[inch] long, one on each side.
The antenna element to which the ground side of the SO239(=PL259) is attached always points downwards.
Tune the antenna by adjusting the lengt of the adjustable elements. Length in inches is equal to 2952 divided by the frequency in MHz

Visit Free Radio

See more : Video Modulator - PLL FM Transmitter - FM Antenna

5W PLL FM Transmitter from Pira CZ

noreply@blogger.com (Quick Zone) — Tue, 22 Jul 2008 13:23:00 +0000

Here's a new Phase Locked Loop (PLL) FM Transmitter from PIRA CZ. This PLL controller is programmed by PIC PIC16F627A with a single I2C TSA5511 (TSA5512/SDA3202).

The transmitter includes RDS/SCA input and Audio/MPX input with optional preemphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons.

The transmitter can work also without the LCD display.

Pira CZ 5W PLL FM Transmitter Documentation

Visit PIRA CZ

See more : FM Transmitter - LCD FM Transmitter - PLL Transmitter - Audio Video Modulator

Stereo Compressor Limiter with Clipper for FM Broadcast

noreply@blogger.com (Quick Zone) — Tue, 22 Jul 2008 12:51:00 +0000

This application circuit is stereo audio compressor limiter with clipper for processing your FM audio signal. Limiter is a device, which weakens loud signals and intensifies silent signals. On its output there is signal with constant level. Signal clipping on the limiter output allows to increase the signal level without exceeding maximum frequency deviation limit 75 kHz. It's very suitable since preemphasis is used.

Be careful if you want to buy any simple compressor/limiter board available on the market! Although a big list of features is mentioned, some of these toys have no signal overshooting protection and have no precise preemphasis with HF clipping option. With these devices it's not possible to keep loud sound AND meet the frequency deviation limit. So there is no reason why to pay for them.

Circuit Schematic:

Left Channel Schematic

Right Channel Schematic

Printed Ciruit Boards (PCB):

Part list:

Left channel:
R1, R3 - 10k
R2 - 1k
R4, R5 - 1M
R6 - 18k
R7, R8, R15-R17, R19 - 33k
R9 - 1M5
R10, R12, R14, R18 - 470R
R11 - 270R
R20, R23, R25 - trimmer 5k
R21 - trimmer 5M
R22 - trimmer 1k
R24 - trimmer 500R

C1 - 4n7 (EU) or 6n8 (USA), plastic
C2 - 470n plastic
C3 - 4n7 plastic
C4 - 330n plastic
C5, C7, C8, C12 - 10n ceramic
C6 - 22n ceramic
C9 - 330p ceramic
C10 - 470p ceramic
C11 - 82p ceramic
C13 - 10u/25V tantalum
C14 - 470u/25V electrolytic
C15, C16 - 220u/10V electrolytic

U1 - TLC272
Q1 - BC557B
Q2 - BF245C
D1, D2 - Red!!! LED diode 5 mm, medium luminance (eg. 200 mcd)
J2 - jumper

Right channel:
R1, R3 - 10k
R2 - 1k
R4, R5 - 1M
R6 - 18k
R8, R15-R17, R19 - 33k
R9 - 1M5
R10, R12, R14, R18 - 470R
R11 - 270R
R20, R23, R25 - trimmer 5k
R22 - trimmer 1k
R24 - trimmer 500R

C1 - 4n7 (EU) or 6n8 (USA), plastic
C2 - 470n plastic
C3 - 4n7 plastic
C4 - 330n plastic
C6 - 22n ceramic
C7, C8, C12 - 10n ceramic
C9 - 330p ceramic
C10 - 470p ceramic
C11 - 82p ceramic
C14 - 470u/25V electrolytic
C15, C16 - 220u/10V electrolytic

U1 - TLC272
U2 - 78L05
Q1 - BC557B
Q2 - BF245C
D1, D2 - Red!!! LED diode 5 mm, medium luminance (eg. 200 mcd)
J2 - jumper

Tips:
Following steps are recommended for the stereo version:

1. If you have a possibility to measure static current gain of the transistor (h21e), find a pair of Q1's with similar h21e from about 5-10 pieces.
Place a temporary 3-pin IC socket piece instead of Q2's. Set the same input level value for both channels. Find a pair of Q2's from about 5-10 pieces which results in the same output level in both channels (you may follow the LED luminance if clipping is set). Then remove the sockets and solder the Q2's found.

Transistor Q2 temporarily placed in socket.

Visit Pira.CZ Site

See more : Transistor FM Transmitter - Stereo Encoder - FM Transmitter Antenna

Ring Circular Polarized Antenna for 88-108 MHz

noreply@blogger.com (Quick Zone) — Mon, 23 Jun 2008 04:26:00 +0000

This simple antenna called Ring Circular Polarized Antenna. You should construct this antenna with .5 inch copper. With a little experiment I did, antenna can be tuned in 88-108 MHz FM frequency range with only changing the vertical elements. The secret is a ratio of vertical and horizontal dimensions.

In FM transmitter you need signal transmitted to any direction so you need antenna type that transmitted with polarized circularly. Antenna Gain -3.2 dB, bandwith 500 KHz with maximum power handling 500 Watts. In order to use antenna on 88-108 MHz, broadband antenna type must be designed with no tune involved.

How to double Your Transmitter Power
Amplification of signal to transmit based on antenna gain in Decible. Power from transmitter be able to doubled, tripled or even become more power. The value is called ERP (Emmittion Radiating Power). For Doubled your transmitter power to be ERP Power need stacked 4 antennas (3.12 dB gain antenna), 6 antennas (5.12 dB), 8 antennas (6.4 dB).

How to stack your antenna?

See more : FM Transmitter - LCD FM Transmitter - FM Transmitter Antenna

Low Power VHF TV Transmitter

noreply@blogger.com (Quick Zone) — Mon, 23 Jun 2008 04:10:00 +0000

One of the most useful gadgets a video enthusiast can have is a low-power TV Transmitter. Such a device can transmit a signal from a VCR to any TV in a home or backyard. Imagine the convenience of being able to sit by the pool watching your favorite movie on a portable with a tape or laserdisc playing indoors. You could even retransmit cable TV for your own private viewing. Videotapes can be dubbed from one VCR to another without a cable connecting the two machines together.

When connected to a video camera, a TV transmitter can be used in surveillance for monitoring a particular location. The main problem a video enthusiast has in obtaining a TV transmitter is that a commercial units are expensive. However, we have some good news! You can build the TV Transmitter described here for less.

Download Description and Construction Details

See more : FM Encoder - FM Transmitter - FM Stereo Transmitter

80mW FM Transmitter with Dipole Antenna

noreply@blogger.com (Quick Zone) — Mon, 23 Jun 2008 04:01:00 +0000

This electronic circuit is a fm transmitter circuit that suitable for beginners for stereo encoder testing. Provided the input stage is designed to accommodate line input levels i.e. approx. 2Vrms into 50kOhm. The transmitter output power is approx. 80mW, which is sufficient to cover an area of about one hundred meters.

The RF portion consists of a totally screened oscillator which is operated by a stabilised voltage and a loosely coupled buffer stage. With this two-stage lay-out a good frequency stability and low harmonic interference radiation is achieved. The frequency of the oscillator can be adjusted in the commercial range (88-108MHz) by a trimmer capacitor Cl.

The FM-modulation of the transmitter is achieved by a varicap BA138. The frequency ratio can be adjusted by the capacitor C6.

To enlarge the transmission range, the output circuit which is tuned with capacitor C14, can be terminated into a full wavelength antenna.

RF filters (RFC1-3) minimize power supply hum in the transmitted signal.

Specifications:
Operating voltage: 9-12V
Operating current: 8mA
Frequency (adjustable): 88-108MHz

Inductors:
L1: 3 turns, 5mm coil diameter (air-core), 1mm copper wire with a tap-off at a wire length of 12 mm, measured from ground terminal.
L2: 2 turns, 5mm coil diameter (air core), 1.5mm copper wire.
RFC1-3: 5 turns, 6-hole ferroxcube, thin Copper wire.

Antenna construction:
The antenna consists of a full wavelength dipole configuration. The construction details are indicated in figure below.

See more : FM Stereo Encoder - FM Transmitters - Stereo Transmitter

FM Stereo Encoder for Beginner

noreply@blogger.com (Quick Zone) — Mon, 23 Jun 2008 03:48:00 +0000

This circuit is a simple fm stereo encoder. A method commonly used in (double side-band suppressed carrier) DSB-SC modulation to provide synchronisation between modulator and demodulator is to transmit a sinusoidal tone (pilot tone) whose frequency and phase are related to the carrier frequency. This tone is positioned at 19 kHz, outside the pass-band of the modulated signal. The carrier frequency is 38 kHz, double that of the pilot tone. The receiver circuitry detects the pilot tone and translates it to 38 kHz, which is then used to demodulated the encoded signal.

In stereo broadcasting it is necessary to transmit and receive both left (L) and right (R) audio channels while also providing the sum (L+R) to monophonic receivers. To serve both stereophonic and monophonic receivers, the (L+R) signal occupies the normal audio spectrum in the frequency range 20 Hz to 15 kHz and the (L-R) signal, also in the same frequency range, is shifted in frequency using DSB-SC modulation. The carrier frequency used in this process is 38 kHz. A typical block diagram of a FM stereo encoder is shown in figure 1 (a) and figure 1 (b) indicates the resultant composite spectrum.

In the receiver, the pilot tone is filtered out and is doubled in frequency which is then used to synchronise the demodulator to the modulator. Finally an addition and subtraction (matrixing) of the two signals yields the desired L and R audio signals.

Subtractor:
The subtracter consists of an op-amp configured as a one-to-one subtracter. The subtraction process yields the (L-R) signal which is the modulated with the carrier at a frequency of 38 kHz.

Adder:
The adder consists of an op-amp configured as a one-to-one adder. The addition process yields the (L+R) signal which is used in monophonic receivers.

Multiplier (modulator):
The multiplier consists of an analogue switch which chops the (L-R) signal at a frequency of 38 kHz.

Band-pass filter:
The band-pass filter is centred at 38 kHz and yields the desired DSB-SC signal.

Pilot tone generation:
An astable consisting of a 555 timer is set to generate a frequency of 76 kHz. This frequency is divided using two F/F's to produce 38 kHz and 19 kHz.

Carrier generation:
The carrier is generated by dividing the 76 kHz signal by two.

Low-pass filter:
The 19 kHz is passed through a low-pass filter to produce a sinusoidal pilot tone.

Mixer:
The final stage is the mixer. The mixer, by using an addition process, combines the monophonic (L+R) signal, DSB-SC (L-R) signal and pilot tone.

Specifications:
Input impedance: 47kOhm
Input level: less than 2Vrms
Output level: maximum 2Vrms into 50kOhm

Tuning and calibration:

Adjust your FM receiver to the frequency of your transmitter.
Select Mono reception mode.
Adjust POT1, POT2, POT3, POT4 and POT5 to minimum.
Connect a TAPE or CD player Left (L) channel to the encoder.
Play a sound track.
Adjust POT3 to 3/4 of the value.
Adjust POT1 until the signal distorts on your monophonic receiver.
Turn POT1 back until there is no distortion.
Disconnect the (L) channel and connect the (R) channel.
Adjust POT2 until the signal distorts on the monophonic receiver.
Turn POT2 back until there is no distortion.
Adjust C7 until the frequency output (PIN3) of the 555 is 76 kHz (here you'll need a frequency counter).
Select Stereophonic reception mode on your receiver.
Adjust POT5 until the pilot tone indicator switches on.
Adjust POT4 until there is no signal on the left (L) channel and there is a signal on the right (R) channel of the receiver.
All adjustments required are now done.
Re-connect the left (L) channel to the encoder.
Should the callibration be correct you will hear the sound track in stereo on you receiver.

See more : FM Encoder - FM Transmitter - FM Stereo Transmitter

TV RF Power Amplifier 470-860 MHz with BLW32-33

noreply@blogger.com (Quick Zone) — Mon, 26 May 2008 19:49:00 +0000

TV Linear Power Amplifier for 470-860 MHz taken from Philips Aplication Note (AN_BLW32_33). Please download file in PDF format.The Wide-Band UHF Power 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

See more : Stereo Transmitter - Simple TV Transmitter - Stereo Encoder

UHF TV RF Power Amplifier 100W

noreply@blogger.com (Quick Zone) — Mon, 26 May 2008 19:41:00 +0000

The TV amplifier has been tuned under class-A small-signal conditions and characterised under large signal class-AB conditions from band IV - V in UHF. (All Datasheets)

Amplifier Circuit
The total description of the amplifier is given in Figs 6 and 7 and Table 8 (in datasheet). The amplifiers input and output matching networks contain mixed microstrip-lumped elements networks to transform the terminal impedance levels to approx. 25 W balanced.

The remaining transformation to 50 W unbalanced is obtained by 1 : 2 balun transformers. The baluns B1 and B2 are 25 W semi-rigid coax cables with an electrical length of 45° at midband and a diameter of 1.8 mm, soldered over the whole length on top of microstrip lines. To keep the circuit in balance two stubs L1 and L8 with the same length have been added. For low frequency stability enhancement the input balun stubs are connected to the bias point by means of 1 W series resistors. Large capacitors (C4 and C11) are added at the biasing points to improve the amplifiers video response.

Printed Circuit Board (PCB)
The printed-circuit board laminate utilised is PTFE-glass with an er = 2.55 and a thickness of 0.51 mm (20 mills).

A complete TV transmitter and amplifier has been designed and characterised based on the BLV861, capable of operating in full band IV and V with flat gain and high output power in class-AB. BLV861 is able to generate 100 W CW power and a power gain compression below 1 dB in band IV and V. Overall gain of the amplifier is >8.5 dB and an efficiency of ± 55%. TV-measurements have been carried out showing a 1 dB compression point above 120 W PO, SYNC at VCE = 28 Vand 150 W at VCE = 32 V.

Amplifier shows an agreed linearity performance in class AB operation both under two tone and three tone conditions.
Biasing the amplifier at a VCE = 32 V results in a higher output peak sync power and a better linearity response.

See more : FM Stereo Transmitter - TV Transmitter - FM Stereo Encoder

UHF TV Linear Push-Pull Power Amplifier with BLV859

noreply@blogger.com (Quick Zone) — Mon, 26 May 2008 19:35:00 +0000

A broadband linear power amplifier design is presented, suitable for application in TV transposers operating in band IV and V (470 to 860 MHz). The design is based on two BLV859 bipolar transistors combined with quadrature hybrids. Typical results at the recommended class-A bias point (25.5 V/9.1 A) for the total module include 40 W peak sync output power at -54 dB three tone IMD level (fvision = -8 dB, fsound = -10 dB, fsideband = -16 dB) and an average gain of 10.5 dB in the (470 to 860) MHz range.

The BLV859 is a bipolar linear push-pull power transistor designed to operate in the 460 to 860 MHz range. With a specified output power of 20 W peak-sync in class-A it is the largest device in the new generation of transposer transistors. The intermodulation distortion level is -54 dB (fvision = -8 dB, fsound = -10 dB, fsideband = -16 dB) and power gain >10 dB at 860 MHz. For application in TV transposers for Band IV/V (470 to 860 MHz) a wideband linear power amplifier has been designed with two BLV859 transistors in class-A.

The amplifier consists of 2 balanced circuits (datasheet), both equipped with a BLV859 and coupled in parallel by means of a wideband 3 dB -90 degree sagewireline coupler at the input and output.

For good thermal contact, heatsink compound should used when mounting the transistors on a heatsink.

See more : FM Stereo Transmitter - TV Transmitter - FM Stereo Encoder

Broadband UHF Power Amplifier For TV Transposers 3W

noreply@blogger.com (Quick Zone) — Mon, 26 May 2008 19:25:00 +0000

A broadband RF power amplifier design is presented, suitable for application in TV transposers, operating in UHF band IV and V (470 - 860) MHz, with simple printed circuit board.

The RF power amplifier design is based on a BLW898 bipolar transistor. Typical results at the recommended class-A bias point (25 V/1.1 A) for the total module include a 3-tone IMD level of -64 dB (fvision = -8 dB, fsideband = -16 dB and fsound = -10 dB) and an average gain of 10.5 dB at 3 W peak-sync output power in the (470 - 860) MHz frequency range.

The BLW898 is a bipolar linear power transistor designed to operate in the (470 - 860) MHz range. The transistor is encapsulated in a SOT171A 6-lead rectangular flange package with a ceramic cap. The specified output power is 3 W peak-sync in class-A. The intermodulation distortion level (IMD) < -63 dB (fvision = -8 dB, fsideband = -16 dB and fsound = -10 dB) and gain >10 dB at 860 MHz. For application in TV transposers for Band IV/V (470 - 860) MHz a wideband linear power amplifier has been designed operating in class-A. It is suitable for driving higher power stages in TV-transposers.(datasheet)

See more : PLL Transmitter - TV Transmitter - FM Amplifier

TV RF Power Amplifier 14W #2

noreply@blogger.com (Quick Zone) — Mon, 26 May 2008 19:09:00 +0000

From #1 TV RF Power Amplifier 14W

BIAS CIRCUIT
Below is the RF power amplifier's components part list and bias circuit for supply feeding.

C1, C2, C4, C5, C6 = 1nF LCC Chip + 10nF LCC Chip
C3 = 100µF Sprague
C7 = 10µF Sprague
D1 = 1N 4001
L1, L2 = 5 Turns , Diameter 0.5 mm, W Diameter 3mm
P1 = 1k.
R1 = 56 ohm/ 1/2W
R2 = 5600 ohm, 1/2W
R3 = 2.2 ohm, 3W
R4, R5 = 56 ohm, 1W
R6 = 4,7 ohm, 1/2W
T1 : BDX 54 B/BD139

Printed Circuit Board
you can Click image for enlarge and see more deatil of printed circuit board and component layout.

See more : PLL Transmitter - Audio Video RF Modulator - UHF TV Power Amplifier

TV RF Power Amplifier 14W #1

noreply@blogger.com (Quick Zone) — Mon, 26 May 2008 18:59:00 +0000

This RF power amplifier works in frequency 470 - 860 MHz UHF Band IV and V with power out 14 Watts with input power 1.5 Watts. The power amplifier is suitable for amplifying rf signal your tv transmitter with 0.5 - 2 watts power output.

TV Power Amplifier Schematic
RF power amplifier circuit is taken from Philips transistor application note, as you can see below.

Part Lists:
C1 = C6 = C16 = 4,7 pF (500 V) multilayer ceramic chip capacitor
C2 = C3 = C20 = C21 = 33 pF multilayer ceramic chip capacitor
C4 = C9 = C13 = C19 = 1,2 to 3,5 pF film dielectric trimmer
C5 = C7 = C15 = C17 = 100 nF multilayer ceramic chip capacitor
C8 = C10 = C11 = C12 = 220 pF multilayer ceramic chip capacitor
C14 = C18 = 6,8 mF/40 V solid aluminium electrolytic capacitor
C22 = C23 = 1 pF (500 V) multilayer ceramic chip capacitor
L1 = L2 = L13 = L14 = Coax. 50 Ohm with diameter 2,2 mm; lenght 29,0 mm, soldered on striplines
75 W (1,1 mm ´ 28,0 mm). inner L1 dan L13 not connected
L3 = L4 = 52 W stripline (2,0 mm ´ 16,5 mm)
L5 = L8 = 470 nH microchoke
L6 = L7 = 39 W stripline (3,1 mm ´ 8,0 mm)
L9 = L12 = 1 Turn (1,0 mm); diameter 5,5 mm; lead space 2 ´ 3,5 mm
L10 = L11 = 39 W stripline (3,1 mm ´ 34,0 mm)
L3, L4, L6, L7, L10 dan L11 are striplines on PTFE fibre-glass PCB wirh dielectric (Îr = 2,74); w 1/32".
R1 = 10 W carbon resistor

Continue: TV RF Power Amplifier 14W #2

See more : PLL FM Transmitter - Audio Video RF Modulator - UHF Power Amplifier