YOU CAN ADJUST THESE TRANSMITTERS
TO ONLY TRANSMIT 200 FEET
FM Stereo Radio Transmitter LCD PLL
The newer version of software for this fm transmitter
allows you to limit power in .010 watt steps
The field strength of this transmitter can be adjusted to the proper level.
Where to buy this FM transmitter, its worth it, this is not junk like so many others
Frequency - 87-108MHz
Tuning Step - 10kHz
RF Power Output - MAX setting 0.31 Watt
Spurious Emissions - Better than -45 dB ref to carrier
Frequency Stability - PLL Typ +/-0.5KHz
SWR Ruggedness - can withstand a 30:1 mismatch
RF Output Connector - BNC or "F" type
Audio Input Sensitivity - 0.8V rms for +/- 75 KHz
Signal To Noise - Ratio 60 dBu
Frequency Response - Flat from 20 Hz to 15 KHz
Stereo Separation - >40dB
Audio Distortion - Better than 0.2 % THD
Audio Input Connectors - Phono/ RCA
Power Input - 8 ~ 17Vdc Regulated 250mA
Printed Circuit Board Dimensions - 4" x 2 1/2"
Information about this transmitter
Virtually indestructible - don't worry about high SWR it can with stand a 30:1 mismatch
The transmitter can be powered by a REGULATED 8v to 17vdc power supply
tunes across entire FM band, in 10kHz tuning steps.
Modulation level , frequency , Mono/Strereo mode and other parameters are set using two buttons and LCD.
This unit works right out of the box no special tools or knowledge needed
just set the desired frequency and connect the output of your computers sound card to it and go.
Modulation level , frequency , Mono/Stereo mode and other parameters are set using two buttons and LCD. The transmitter is easy to use because of built-in AGC (Automatic Gain Control), normal input signal should be anything from 100mV to almost 5V p-p, AGC has fixed attack about 0.5s and user programmable recovery time from few seconds to few minutes True sine wave pilot. Filtered MPX. Filtered audio - each channel has Butterworth 4th order Low Pass Filter (TLC14) Filtered RF.Continues tuning across entire FM band. PLL lock detector. RF shutdown if PLL can't lock.
To do the tuning: push left button to activate or to move cursor(blinking symbol), push right button to change value, Menu number is displayed in lower right corner, new settings stored if right button pushed while menu number is blinking. Settings are stored in EEPROM, on power-up the transmitter set at last used frequency, it remembers what is was set at.
Seven element Low Pass Filter is integrated , transmitter has clean output , there are
no harmonics ! this just means it won't not bleed over onto other channels.
so your neighbors won't be listening to your Christmas music on their TV sets
For "normal" usage of the transmitter:connect antenna, audio source and power.
turn volume high within couple seconds the transmitter supposed to set proper modulation
by itself, if the transmitted sounds are too loud, then just set L lower to a lower setting.
if the transmitter used for talking set R to 0 for (no recovery)
For best performance use 12-14 vdc power supply, use RG6 cable, (input audio level 2V p-p, just means don't over drive it.)
Frequency |
87-108MHz 10kHz Typ 0.31 Watt - this should be set for the proper field strength * Better than -45 dB ref to carrier PLL Typ +/-1KHz Withstands 30:1 mismatch BNC or "F" type 0.8V rms for +/- 75 KHz 60 dBu Flat from 20 Hz to 15 KHz 40 dB 75uS or 50uS if shipped to Europe Better than 0.2 % THD Phono/ RCA 7 ~ 17Vdc Regulated 250mA 4" x 2 1/2" inches |
Look up Radio Stations in your area - so you don't interfere with them
HOMEMADE FM ANTENNA
Matching your antenna to your transmitter is the single most important link in your transmitter set-up - and a good antenna and match is the secret to getting maximum range. Matched means an electrical impedance match, if the proper impedances are not maintained between transmitter and antenna, power is then reflected back away from the antenna and back into the transmitter! This can cause the final amplifier stage to be damaged, not to mention a spurious signal and lousy range. Its not hard to make your own antenna....see below.
Design your own J pole Ant. - ( Cool design )
Beginner's Guide to Low-Power FM Broadcasting
Design your own J pole Ant. - ( Cool design )
doubling the height above ground is equivalent to increasing power 4 times
so keeping your antenna at ground level will help limit its power.
In the United States, this is how the FCC regards an unlicensed FM transmitter :
Licensed FM broadcast stations and their listeners have ALL the rights! You may have some limited privileges in locally-unused band space, but your non-licensed use of a transmitter has absolutely NO rights at all over the rights of licensed broadcast operators and the rights of their listeners to interference-free reception. If your operation of a device interferes with ANYBODY'S use or enjoyment of an FCC licensed transmission of any kind, your only choice is to IMMEDIATELY terminate or change the operation of your low-power transmitting device so as to cause no more interference. That's it! No discussion, no exceptions - if you persist in causing interference to other folks,
you’re asking for trouble!
Unlicensed operation of small transmitting devices is discussed in "Part 15" of the FCC Rules. These Rules are published in 100 "Parts," covering everything imaginable concerning the topic of "Telecommunications." It is a fascinating read and well worth the modest cost. The six books containing the FCC Rules are section 47 of the complete Code of Federal Regulations, which you are likely to find in the Reference section of your Public Library. If you have questions about the legal operation of your FM transmitter or any other kit or home-built device which emits RF energy, it is your responsibility to study the FCC regulations. It is best if YOU read (and consult with a lawyer if you are in doubt) the rules and do not bother the understaffed and busy FCC employees with questions that are clearly answered in the rules.
Here are the primary "dos and don'ts" picked from the current FCC Rules, as of May, 1990. This is only a brief look at the rules and should not be construed to be a complete legal interpretation! It is up to you to operate within the proper FCC rules.
1. In the past, no "two-way communications" use of the 88-108 MHz FM broadcast band was permitted. This prohibition does not appear in the current edition of Part 15. Previous editions of Part 15 discussed "wireless microphones" while the June 23, 1989, revision eliminates this discussion in favor of more detail regarding computer and TV peripherals and other modern electronic conveniences. However, it is not immediately clear that the 1989 revision of the FCC Rules Part 15 necessarily "cancels" previous regulations. Laws and rules tend to remain in force unless they are specifically repealed. Also, FCC Rule 15.37 discusses "Transitional Provisions for Compliance with the Rules," and states in item (c): "There are no restrictions on the operation or marketing of equipment complying with the regulations in effect prior to June 23, 1989." It is up to you to read the rules yourself and understand them.
2. It is the sole responsibility of the builder-user of any FM broadcast-band device to research and fully avoid any and all interference to licensed FM broadcast transmission and reception.You need to do a good job of finding a clear frequency, see if a channel is clear and available in your area.
this is the key to avoiding trouble find a clear channel!
3. For some frequency bands, the FCC sets 100 milliwatts (0.1 watt) as the maximum permitted power output for unlicensed, home-built transmitting devices, and that the combined length of your antenna and feedline (coaxial cable or other) must not exceed 10 feet. But the technical standards for 88-108 MHz are very different, and are primarily concerned with band width and RF field strength.
4. FCC Rules pertaining to field strength do not differ for "stereo" or "monaural" transmissions.
5. Broadcasting on the grounds of a school using the AM broadcast band is specifically permitted and encouraged between 525 and 1705 KHz under Part 15.221.
6. FCC Rule No. 15.239 specifically addresses operation in the 88-108 MHz FM broadcast band for which your FM transmitter kit is designed. However, this Rule does not, by itself, tell you everything you need to know about using a device of this kind. Therefore, we are noting a series of Part 15 regulations which should be observed: The "bandwidth" of your transmission is limited to 200 KHz, centered on the actual operating frequency. This is a "generous" limitation designed to accommodate cruder FM devices. Its signal should sound no "wider" than any other FM station when listening on an ordinary FM radio.
FCC Rule 15.215(a) says: "Unless otherwise stated, there are no restrictions as to the types of operations permitted under these sections." This general provision appears to leave you free to use your FM stereo transmitter in a manner similar to operations of an FM broadcasting station, or to use it for any other non-interfering, practical application.
FCC Rule 15.5: General conditions of operation: "(b) Operation...is subject to the conditions that no harmful interference is caused and that interference must be accepted that may be caused by the operation of an authorized radio station, by another intentional or unintentional radiator, by industrial, scientific and medical equipment, or by an incidental radiator. (c) The operator of a radio frequency device shall be required to cease operating the device upon notification by a Commission representative that the device is causing harmful interference."
The most specific FCC regulation of 88-108 MHz FM Broadcast band unlicensed operation is that the " RF field strength" of the signal must not exceed 250 microvolts at a distance of 10 feet from the transmitter (FCC rule 15.239). If you have any concern about this emission limit, have your device checked by a technician with accurate measuring equipment. Remember that the "field strength" of a signal is determined as much by the antenna as by the RF output of the transmitter itself.
Since radiated output power depends on antenna type, height above the ground, cable loss, and transmitter power, it's almost impossible to calculate.
*The best thing is to limit its operation just enough to transmit to the car radio,
thats is all you really need.
NEWER smaller type
FM Stereo Radio Transmitter LCD PLL
RF Power Output 25mW to 0.5Watt
0.5w not pictured, $180/ea
Where to buy this FM transmitter, its worth it
Frequency 86-108MHz
Tuning Step 10kHz
RF Power Output 25mW to 0.5Watt
Spurious Emissions Better than -45 dB ref to carrier
Frequency Stability PLL Typ +/-1KHz
SWR Ruggedness Withstands complete mismatch
RF Output Connector "F" type or BNC
AGC range 0.8v to 4v p-p
Signal To Noise Ratio 60 dBu
Frequency Response Flat from 20 Hz to 15 KHz
Stereo Separation >35 dB
Pre-emphasis 75uS or 50uS if shipped to Europe
Audio Distortion Better than 0.2 % THD
Audio Input Connectors 3.5mm
Power Input 9 to 25Vdc 0.5A
Frequency, AGC, Mono/Strereo and other parameters are set using two buttons and LCD.
. Filtered MPX. Filtered audio .Filtered RF. Continues tuning across entire FM band.
Unlocked PLL RF shut-down. The transmitter comes with built-in seven element Low Pass Filter to suppress harmonics.
Using built-in antenna analyzer make wire or even small hard-to tune helical(coiled wire) antenas in minutes, no SWR meter needed.
Just change antenna length and/or shape till impedance fall into 20-100 Ohm range.
LCD shows realtime data while the transmitter is in analyzer mode which makes tuning very easy - no RF experiance needed !
Having matched resonating antenna fed with 0.5w is the same as using 10watt transmitter with non-resonant antenna.
Cover about 1 mile radius using "junk" antenna, safe $$$ !
If range is too high or to safe battery life set lower RF power using buttons and LCD
RF power output continuously monitored for overload, short or open circuit.
It is OK to reconnect antenna cable while the transmitter run at full power.
The transmitter powered by filtered power supply or 9v or car battery,
DC coax power plug, 2.1mm I.D., 5.5mm O.D., center positive,