MPX2000 DIGITAL FM STEREO TRANSMITTER

The MPX2000 Digital FM stereo transmitter is a PLL synthesized FM Stereo transmitter that is microprocessor controlled. It covers the 88-108 MHz FM Broadcast band in 100 kHz increments. (Extended frequency coverage and/or 50 kHz spacing available for export use). It has a built in Stereo generator and a LED digital readout displaying transmitter frequency, and a bar graph modulation indicator. It operates from a 15 to 20 volt DC supply or 16 to 20V AC supply, and is intended for low power FCC Part 15 operation. Unlike some other units in this price range the circuit boards contain everything you need except power supply and optional external antenna. No extra stereo generator or external metering is necessary.

Specifications and Features of the MPX2000 are as follows:

• Microprocessor controlled, LED display shows transmitter frequency.
• Phase Locked Loop (PLL) synthesized, 100 kHz steps, 88-108 MHz coverage (USA models).
• Extended coverage 87.5-108.5 MHz, 50 kHz or 100 kHz steps option available for export use
• No frequency drift, 100 Hz frequency accuracy, crystal controlled.
• Keypad frequency entry, no tuning, just punch in desired frequency.
• Complete stereo multiplex generator on board.
• 19 and 38 kHz MPX subcarriers are crystal controlled
• Stereo generator has adjustments for optimum separation
• Bar graph 10 segment deviation (Modulation) indicator
• Overmodulation indicator LED included.
• PLL Lock and SCA indicator LEDs.
• RF output adjustable 1 to 10 mw, (10-100 mw for export use).
• Built in audio limiting for good "punch" without exceeding deviation limits.
• Accepts line level audio inputs from most CD players, tape decks, and other audio equipment
• 75 usec audio preemphasis with 15 kHz lowpass active filter.
• SCA capability for third audio channel, with external SCA adapter.
• Audio frequency response 20-15000 Hz.
• Built in RF harmonic filter
• Spurious and harmonic outputs better than -55 dBc.
• RF shutdown circuit disables transmitter if PLL is unlocked.
• Operates from DC supply of 15 to 20 Volts at 350 milliamperes (DC supply, batteries, wall wart, etc) or 16 - 20V AC supply
• DC supply polarity protection and voltage regulation on board.
• All signals accessible for educational and service purposes
• For export use only, can cover a village or community with our 1 Watt amplifier
• On board audio generator (1187 Hz) crystal controlled, for testing
• Fully compatible in mechanical and signal interfaces with our AM88 AM Transmitter
• Excellent learning tool
• Display board separate from main board for maximum packaging flexibility.
• Can be operated without display board for dedicated or fixed frequency applications.
• PC board sizes: Main board 4 X 7 inches, Display board 2 X 7 inches.
• Rugged epoxy fiberglass .062" thick G-10 PC boards used
• Mounts in our NC225 case 6 X 8 X 2.5 inches for a compact unit.
  
  A Block Diagram of the MPX2000 FM stereo transmitter can be seen by clicking here
  
  The MPX2000 will be useful anywhere a short range low power FM audio link is needed. The MPX2000 is far superior to free running FM transmitters and will not drift off channel, and is perfectly compatible with digitally tuned FM receivers. It is also useful as a teaching aid, unlike low end units using a BA1404 or other black box IC. The MPX2000 allows access to all MPX signal waveforms and allows the observation of the signal generation process . The MPX generator circuit is adjustable for optimum performance, and if no test equipment is available, works well with default settings, so anyone can get satisfactory results with only a VOM or a DVM. In the USA and certain other countries, signal radiation must be kept to a level low enough so as not to exceed specific field strength levels and not to interfere with other stations using the FM broadcast band. Check with the applicable laws in your nation, such as the FCC or DOT rules and regulations. In the USA Part 15 of the FCC rules and regulations applies. Having no easy way to measure field strength, keep the power as low as you can and use only a simple antenna, as short as possible. The MPX2000 will provide a +10 dBm signal (10 milliwatts) into 50 ohms. This is more than adequate for covering an average property and only a 12 inch antenna is needed for this. This will give a useable range of 50 to 200 feet with a typical pocket stereo receiver.

  For best results a relatively clear channel is necessary. The PLL helps tremendously by keeping the signal on frequency. In large metropolitan areas it may be difficult or impossible to find a clear channel. In this case try using an in between channel ie. even 100 kHz in the USA, odd 100 kHz in areas using even channel allocations. Also, you might try to get between two weak stations if possible. However, this can be impossible for digitally tuned receivers, but analog (continuously tuned) receivers will have no problem. Many lower end pocket stereos are still analog. It is best to operate between 88 and 92 MHz as this part of the band is used by lower powered stations. The MPX2000 may be mounted in our NC225 case . A Complete Case Package including everything needed to produce a finished unit as per our website photo is available. Typical applications of the MPX2000 include but are not limited, as follows:
  

• Home audio systems. Listen to your CD player, tape deck, etc on a pocket stereo receiver while not in same room as audio equipment, or outside the house, garage, deck, etc
• Other applications such as private or in-house broadcast systems for schools, real estate, health clubs, stores, offices, museums, etc.
• Use as a short range FM station in remote areas where no other FM reception is possible, or no suitable stations can be received.
• For entertainment of groups where a foreign language is spoken. Two languages can be carried, one on each channel, for a bilingual PA system, using small pocket stereo receivers. Useful for churches, shows, etc. The AM88 can also be used along with the MPX2000 for additional channel capability
• The MPX2000 can be used with our Voice Messenger and Identifier to make a "talking sign" for sales purposes, such as real estate, entertainment, flea markets, etc. A sign can be posted instructing one to tune their radio to the FM channel that the MPX2000 is set to, and hear the message.

Export operation

For export use, where regulations permit (NOT IN USA) 100 mw or more output is possible but this amount is not guaranteed in any way. In this case a matched antenna should be used. This may allow up to a mile or more range, depending on local terrain, if a properly matched antenna is used. Optional extended frequency coverage fron 87.5-108.5 MHz is available as an option for Non-USA use, with 50 kHz channel spacing available on special order. However, the MPX2000 is strictly an entertainment device and is not meant for commercial broadcasting, therefore no guarantees of any kind can be offered nor technical assistance be given for export use, details of which must be worked out by the user.

For export applications only a 1 Watt amplifier is available for boosting the power output of the MPX2000. This enables coverage of a village or community and is useful where regulations permit as a low cost alternative to a commercial FM transmitter. This is NOT LEGAL IN THE USA

For applications requiring an AM broadcast band transmitter, see our AM88 PLL synthesized Low Power AM Transmitter

AVAILABLE EXTRAS:

• Complete Case Package includes NC225 case, drilled and lettered front and rear panels, all necessary hardware, all connectors, wire and cable to finish kit per website photo. Includes necessary instructions.
• Whip antenna Collapsible multi-section 20 or 29 inch whip antenna
• Extended Frequency coverage for export use 87.5-108.5 MHz, with either 50 kHz or 100 kHz spacing . Call or email for information.
• Extended Frequency coverage retrofit kit for existing MPX2000 models is available. Call or email for information.
• Hardware package All connectors, switches, wire, LEDs, fasteners, and spacers for mounting in typical enclosure.
• Case only NC225
• Power Supply 16V AC transformer 1100 mA