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First, 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. View our Micropower Broadcasting Primer (in English or Spanish) for a complete technical overview. Several Publications and DVDs are available for purchase to help you get started.
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 TRANSMITTER KIT PACKAGES | FM EXCITERS |
| AMPLIFIERS | ANTENNAS |
| FILTERS | DUMMY LOADS |
| COAXIAL CABLES | POWER SUPPLIES |
| METERS | TRANSISTORS |
| ENCLOSURES | VARIOUS & SUNDRY ITEMS |
| ORDERING INFORMATION |
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These packages include everything needed to build a transmitter in the wattages indicated. All include PLL kit, Amplifier kit, voltage regulator, enclosure, and assembled power supply. Additionally, you will find a selection of cables and antenna below to complete your transmission station. Image displays a fully assembled 150 watt transmitter.
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.
Frequency Agile Cable Analog TV Modulator - $200
These form the basis for a low power 25-50 watt TV transmitter when combined with the appropriate broadband TV amplifier. Fully frequency agile, 54 MHz to 800 MHz.. Select a channel with the up and down buttons on the front panel and go. Available for either NTSC or PAL B/G transmission formats. Make sure to 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.
Heat sink for 40 Watt Amplifier $20
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 proper operation. 8 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 Amplifier Kits
This kit includes all components and instructions to build a very easy to assemble amplifier that uses broadband power modules. They are driven directly by the cable TV modulators listed above. Even though the power levels are not high (30 watts), 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! Please contact for international shipping costs. An extruded aluminum enclosure with integral heatsink as shown in the photo is available for an additional $75. Available in one of these option: 25 Watt High Band (channels 7-13) VHF, 25-30 Watt Low Band (channels 2-6) VHF, 25 Watt UHF (Channels 14-30).
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 / 100 Watt Dummy Load Kit $50
Essential for tuning up and testing transmitters and amplifiers. Will handle 20 or 100 watts without any strain, higher powers for a briefer period of time. Presents a 50 ohm impedance. to the transmitter.
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.
FM broadcast station 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 Kit - $40
Easy and quick design. Includes the aluminum antenna elements.
Assembled 2 Element Yagi for either FM or TV - $100.
Provides a gain factor of 3-4 with a 120-150 degree pattern of coverage. Specify the channel and/or frequency
whether for the FM band, high VHF (7-13) or UHF (13-42). 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
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.
PS-20 - 20 Amp 13.8 VDC power supply - $110
Use this to power the 40 watt amplifier.
PS28-1 - 5 Amp 28 VDC Switching Power Supply For Higher Power Amps- $95
PS28-2 - 15 Amp 28VDC Switching Power Supply For Higher Power Amps - $150
PS48-1 - 6 Amp 48VDC Switching Power Supply For Higher Power Amps - $250
PS48-2 - 12 Amp 48VDC Switching Power Supply For Higher Power Amps - $450
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
LMR400 type: $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.
RD30HFV1 - $22
Mitsubishi RF FET Transistor used for the FRB 30-40 watt FM Broadcast Amplifier
RD70HFV1 - $35
New RD70HFV1 Mitsubishi VHF 70 Watt RF Power Transistor
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 - $15
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.
Build your own Radio Station DVD - $15
A video guide to setting up a micrpower broadcasting station.
Free Radio, the Documentary by Kevin Kyser DVD - $15
An excellent documentary on the Free Radio movement.
Check out our Book and DVD Page for More!
Proceeds from all sales go to the furtherance of micropower broadcasting, bringing a voice of empowerment to every community. Check/Money Order customers can send payments made to Free Radio Berkeley at the address below. Foreign orders paying in this manor may only use a money order drawn on a US bank. Shipping and Handling $10.00 for the first kit, $3 for each additional. International Air Mail: $15 for the first kit, $5 for each additional. COD orders add $8.00. Please email for shipping rates on all other Check/Money Order purchases and International Orders. Items typically ship within 7 days of payment receipt but custom designed and assembled items can take upwards of 3 weeks, sometimes sooner depending on the current work load.
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