to view documentation in PDF formatFirst, a word from our legal department:
For educational purposes only. These kits are offered for the furtherance of one's knowledge regarding radio frequency design and principles. At all times during operation the assembled unit must be connected to a dummy load. Part 73 of the FCC rules prohibits the unlicensed operation of these transmitters when connected to an antenna. All responsibilities for the ultimate use of these kits are born solely by the builder and/or operator.
All kits are complete and come with professionally manufactured, drilled and tinned PC boards. All coils are pre-wound. Amplifier kits require either 12-14, 28 or 48 volts DC for proper operation. Full instructions and diagrams included. Required tools include: a 25-30 watt soldering iron with a fine tip; diagonal cutters; needle nose pliers; assorted screwdrivers and other small hand tools. Full assembly diagrams and instructions are included with each kit. Antenna construction diagrams are provided with each transmitter or amplifier order. Download our Micropower Broadcasting Primer for a complete technical overview. Our "Build A Radio Station" DVD is available for $15 plus $5 S&H. Check out our newest publication, A Popular Guide To Building A Community FM Broadcast Station. Available for $6 plus $1.25 postage.
Certain kits are designed to work with each other. For example, the 40 watt amplifier is designed to be driven to full power with about 1 watt of input power - hence it works very well with the 1 watt PLL transmitter. An amplifier only increases the output power of a given input signal, it can not produce an FM signal whereas a transmitter or an exciter creates the FM signal at a suitable power level for possible further amplification by an RF amplifier.
| FM EXCITERS | AMPLIFIERS | ANTENNAS |
| FILTERS | DUMMY LOADS | ANTENNA KITS |
| POWER SUPPLIES | METERS | COAXIAL CABLES |
| ENCLOSURES | LIMITERS | MIXERS/MICROPHONES |
| VARIOUS & SUNDRY ITEMS | ORDERING INFORMATION |
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1 to 1.5 Watt No Tune PLL Transmitter/Exciter - $110
Our standard PLL kit design. Using wideband monolithic components from Minicircuits, this PLL covers the entire broadcast band by setting the 8 position dip switch. This kit comes partially assembled with the surface mount components soldered on. It is available fully assembled for $195. Please note: this is a mono transmitter and requires an external stereo generator for stereo broadcast applications. Audio input is high impedance, line level. The RF output transistor is a heavy duty TO220 type, not the lighter duty TO18 type found in most comparable kits.
10 Watt No Tune PLL Transmitter/Exciter - $165
Our newest PLL kit design. Using wideband monolithic components from Minicircuits, this PLL covers the entire broadcast band by setting the 8 position dip switch. This kit comes partially assembled with the surface mount components soldered on. It is available fully assembled for $250. Please note: this is a mono transmitter and requires an external stereo generator for stereo broadcast applications. Audio input is high impedance, line level. The kit includes a heat sink and a 7 X 7 aluminum mounting plate for the transmitter and all connectors. A matching 7 X 7 box chassis is available for $25 to mount the plate on and enclose the transmitter. This yields a self-contained 10 watt transmitter.
VHF/UHF Cable TV Modulators - $150
These form the basis for a low power 25-50 watt TV transmitter when combined with the appropriate broadband VHF TV amplifier. Available in VHF channels 2-13 and UHF channels 14-44. Please specify the channel you wish to broadcast on. Download our Low Power TV Primer
Unless specified otherwise, these amplifiers are designed to operate within the standard FM broadcast band of 88 to 108 MHz. If you have need of operation on other frequencies, pleaae contact us because we can possibly modify an existing design to meet your requirements.
1 watt No Tune Broadband Amplifier - $40
1 watt output for an input power of 10 mw or 50 mw. Great for boosting lower power VFOs, and low power Ramsey FM-10 type kits. Very compact size, 3 1/2 X 1 1/2 inches.
6 watt No Tune Broadband RF Amplifier - $40
Uses a rugged, high gain RF FET transistor. to boost a 200 milliwatt watt input to 6-8 watts. Input attenuation pad included for reducing input levels of 1 watt or so. A very small and compact circuit measuring 2 3/4 by 4 1/2 inches. Easy, quick assembly with no tuning needed. Requires 12-14 volts DC at 3/4 to 1 amp for operation.
15 watt RF Broadband No Tune Amplifier - $65
Uses a high gain RF FET transistor to boost a 200 milliwatt watt input to 15 watts. Input attenuation pad included for reducing input levels of 1 watt or so. Measures 2 3/4 by 4 1/2 inches and fits into a 6 inch brick enclosure (available punched and drilled). Easy, point to point surface mount assembly. Requires 12-14 volts at 2 amps for operation.
30-40 Watt No Tune FET Broadband Amplifier - $95 / 70 Watt No Tune
FET Broadband Amplifier - $125
Both amplifiers operate at 12-14 volts DC. The 30-40 watt amplifier requires 1 watt of drive power and the 70 watt amplifier, a 2 stage design, requires only 200 milliwatts of drive power. Current requirements at 13.8 volts - 5 amps for the 30-40 wattand 9 amps for the 70 watt. Output power is adjustable with a variable bias voltage control.
30-40 Watt Modular No Tune Broadband Amplifier - $130
30 to 40 watts of output power for an input of 50 milliwatt. Uses a hybrid RF power module covering a frequency range of 88 to 100 MHz. A very good companion amplifier for FM stereo cable system modulators (available from FRB). 7 element filter included on the circuit board. Easy, large surface mount type assembly. Can be driven from the 50 milliwatt section of the 1 watt FRB PLL transmitter. Requires 6-7 amps at 12-14 volts DC.
150 Watt No Tune FET Broadband Amplifier - $165
A high power RF FET broadband no tune amplifier. It requires the PS500 (24 volts DC, 500 watts) power supply for properation operation. 10 watts of drive power is needed for full power operation. Use in combination with the 10 watt PLL. A complete enclosure kit including heat sink is available for $170. This is a 12 X 12 chassis with a mounting plate that supports the 10 watt PLL, 150 watt amplifer, voltage regulator (included, for reducing 24 volts DC to 13.8 volts DC) and all connectors. Matching power supply (PS500) is $225.
VHF and UHF TV Broadband Amplifiers
25 Watt High Band (channels 7-13) VHF - $150
25-30 Watt Low Band (channels 2-6) VHF $150
25 Watt UHF (Channels 14-30) - $150
These amplifiers use broadband power modules and are very easy to assemble. They are driven directly by the cable TV modulators listed above. Even though the power levels are not high, given the proper combination of antennas and amplifier, very respectable effective radiated power can be achieved. For example: two amplifiers can be driven with the same modulator by using a signal splitter; the output of each amplifier is fed to its own two element antenna, one stacked above the other; the two element antenna has a gain of 4.5 dB, stacked together the total gain is 9 dB; with a total gain of 9 dB and a total input power of 50 watts, the effective radiated power is about 400 watts.
It is absolutely imperative to use a filter to prevent interference from harmonics generated by the transmitter. Both these filters are low pass types which start to attenuate the signal at 108-110 MHz or so. Not using a filter will create problems and give the FCC ammunition to use against us.
7 Element Output Filter Kit - $15.00
A seven element low pass filter, composed of 4 coils and 3 capacitors, to flatten those harmonics. This one works well with the 6 watt and 15 watt amplifiers. Enclosure is $12.00
9 Element Heavy Duty Filter Kit - $40.00
A nine element low pass filter which will handle power levels to 250 watts. Use this for 40 watt and above amplifiers. Enclosure is $15.00
Always use a dummy load when testing and tuning transmitters and amplifiers. A dummy load is a non-inductive resistive load which simulates an ideal antenna impedance of 50 ohms. Never use an antenna for testing and tuning transmitters.
20 Watt Dummy Load Kit - $15.00
Essential for tuning up and testing transmitters and amplifiers. Will handle 20 watts without any strain, higher powers for a briefer period of time. Presents a 50 ohm impedance. to the transmitter.
100 Watt Dummy Load Kit- $50
500 Watt Dummy Load $75
Fully assembled commercial unit. The 500 watt load is a "can antenna" style with the resistive element suspended in a bath of mineral oil in a one gallon can.
An FM broadcast stationâs signal strength is extremely dependent on having a properly tuned and positioned antenna. Tuning an antenna requires changing the length of one of more elements and/or the cable attachment point. An SWR meter is needed to properly tune the antenna.
Comet Antenna - $125.00
A commercially made antenna for the FM broadcast band. It is a 5/8 ground plane design that assembles quickly and easily. It tunes by sliding the inner element up and down. Has a gain of 2.
Dipole - $40
Easy and quick design. Includes the aluminum antenna elements.
2 Element Yagi for either FM or TV - $75, low VHF version $100.
Provides a gain factor of 3-4 with a 120-150 degree pattern of coverage. Specify whether for the FM band, low VHF (2-6), high VHF (7-13) or UHF (13-27). Can be stacked for higher gain
Unless you are planning on operating from a 12 volt lead acid battery or from the lighter socket in a vehicle you will need an AC operated DC power supply. Wall adapter units cannot be used. We have the following units available. Small switching type supplies for mounting inside the enclosure are available as well, see the no-tune PLL section. 2 amp 12 volt switcher - $30, 3 amp 24-28 volt switcher $40.
PS-3 - 2.5 Amp 13.8 VDC power supply - $40
PLL with a 6 watt Use this to power either the 1/2 watt PLL transmitter or a 1/2 watt amplifier
PS-7 - 6 Amp 13.8 VDC power - $50
Use this to power the the 15 watt amplifiers.
PS-14 - 12 Amp 13.8 VDC power supply - $80
PS-20 - 20 Amp 13.8 VDC power supply - $110
Use this to power the 40 watt amplifier The above are Pyramid brand power supplies, We have higher quality Astron 13.8 volt DC power supplies available as well.
Switching power supplies for higher power amplifiers
PS28-1 - 5 Amp 28 VDC power supply - $95
PS28-2 - 15 Amp 28VDC power supply - $150
PS48-1 - 6 Amp 48VDC power supply - $250
PS48-2 - 12 Amp 48VDC power supply - $450
Switching 13.8 V 12 amp DC power supply - $125
A very compact lightweight power supply that is 1/4 of the weight of the PS-14. Ideal for overseas shipments.
Power & SWR Meters
These are essential to the proper tuning and setting up of both transmitters and antennas. An antenna has to be fine tuned so that it accepts the full power of the transmitter and reflects the lowest amount possible back, that ratio of forward power to reflected power is known as the standing wave ratio (SWR). The various stages of both transmitters and amplifiers have adjustable capacitors which are used to tune the unit to the frequency of operation. A power meter allows you to see the effect of these adjustments on the power level and to set everything at an optimum level.
Daiwa Meters - Model CN-101 - $100 / 100 Model CN801H - $140
Dual cross needle meters that shows both forward and reflected power on the same meter face. Makes tuning up very easy, no need to switch back and forth between these two functions. The model CN801H has a large meter face that is very easy to read.
FREQUENCY COUNTER - $80
To accurately maintain your operating frequency a digital frequency counter is highly recommended. This unit is a 6 digit unit usable to 350 MHz.
A coaxial cable is a special type of wiring that has an inner conductor surrounded by an insulating plastic sheath which is covered by a braid of copper wire that is then covered by a plastic jacket. The 75 ohm video cable used in home TV applications is one type of coaxial cable. For most RF purposes, 50 ohm cable is used. Quite a number of 50 ohm coaxial cables are available ranging from the rather small to cables over 1" in diameter. Regardless of the type, all such cables exhibit a loss that increases with frequency of operation and the length of the cable. For most purposes we will concern ourselves with RG213 and RG8x (mini version of RG8). In very short runs RG58 can be used, but we prefer RG8x due to its lower loss and ability to stand a bit more abuse. RG213 has the lowest loss of the group. Under no circumstances should the cables be twisted, kinked or crushed, this will cause major problems. We supply both RG8X and RG213 in the following lengths. Each end is terminated with a PL259 plug.
RG8X: 25 feet - $15, 50 feet - $25, 75 feet- $35, 100 feet - $40
RG213: $1 ft in 25, 50, 75 and 100 ft lengths
BOX7
7 x 7 aluminum chassis punched and drilled for 1watt PLL transmitter with or without the 6 watt amp - $25
The Brick Enclosure
15 watt size -$45, 20-40 watt size -$70. 75-100 watt size - $80, 150 watt size - $110. Combined heat sink and enclosure made from extruded aluminum. Will support a 1 watt PLL on a slide-in plate in combination with the 15, 40, 80, 100 or 150 watt amplifiers.
Rack Enclosure - $75
Will work for a 1 watt with or without stereo generator, 1 watt PLL & 6 watt amp with or without stereo generator, 1 watt PLL and 15 watt amp with or without stereo generator. Please specify which combination. Compact switching power supply for internal mounting - $50.
A limiter is required to prevent over modulation of the FM signal. Over modulation will cause spurious emissions and interference with other signals plus sound very distorted. It is extremely important to prevent this.
Berhringer Autocom Limiter/Compressor - $125.00.
Professional audio limiter/compressor with lots of features.
We offer the entire Behringer and & Samson audio line including mixers. Please inquire for catalog and pricing.
Samson Mixpad 4 - $175
A good choice for portable and field operations. It features two XLR low impedance inputs with one stereo input for a CD player or tape unit. Power source is either AC or 9 volt batteries.
Gemini DJ1000 Mixer- $250
3 XLR microphone channels, 3 turntable channels and 6 line level stereo inputs.
Samson S-12 hypercardoid microphone - $60.
An excellent low impedance unit for the broadcast studio. 25 foot XLR cable is $18.00
Tweak stick - $2.50
Essential to tuning transmitters and amplifiers. Non-conductive body with tiny metal blade at end. In tuning these transmitters and amplifiers a metal screwdriver will cause false tuning to happen due to the interactive effects of the metal and the holder of the screwdriver with the circuit. A plastic TV tuning tool kit can be found at Radio Shack as well
Seizing the Airwaves - $13.00
A Free Radio Handbook by Ron Sakolsky and Stephen Dunifer. Let us conjure up a vision of a Wild Radio Stampede disrupting the territorialized lines of Authority artificially drawn in the air surrounding Mother Earth..... Within this book, the myriad voices of the Free Radio Movement come alive with the same urgency that has challenged both corporate and governmental control of radio-activity. If seizing the airwaves is a crime, then welcome to the millennial police state. Add $4 for shipping
Build your own Radio Station DVD - $15
A video guide to setting up a micrpower broadcasting station. Add $4 for shipping
Free Radio, the Documentary by Kevin Kyser DVD - $15
An excellent documentary on the Free Radio movement. Add $4 for shipping
Proceeds from the sales of these kits go to the furtherance of micropower broadcasting, bringing a voice of empowerment to every community. Please add $6.00 for handling and shipping for 1-2 kits and $3.00 for each additional kit. $6.00 for the 2.5 & 7 amp power supply and for each brick enclosure and $15.00 for the 14 amp power supply. Normal shipment is either UPS ground or priority mail depending on size and weight. COD orders add $8.00. Air mail to other countries, $12.00 per kit. We ship within 2-3 weeks after receipt of order, sometimes sooner depending on the work load. Payment to be made out to Free Radio Berkeley. Foreign orders please pay by money order drawn on US bank
Free Radio Berkeley
Suite 406
1442 A Walnut St
Berkeley, CA 94709
510-625-0314