PHLMIRA250FM BROADCAST RADIO TRANSMITTER

BLOCK DIAGRAM Audio Input FM Modulator Bandpass Filter Low Voltage Power Supply RF Coupler Control & Power Metering Circuits Solid State Power Supply Solid state RF am p lifie r 250 watts

May 20, 2004 THEORY OF OPERATION—MIRA250 The overall theory of operation for the MIRA250 is provided on this page. Detailed theory of operation is outlined in the technical manual for each major sub-assembly (synthesizer, power amplifier, etc.) The audio signal comprised of left and/or right channel audio, and any subcarrier generator audio is fed to the audio processing board. The audio processing board contains the necessary pre-emphasis should that be required for the audio signal employed. The composite audio signal is then fed to a limiter to prevent overmodulation and sent to the voltage controlled oscillator (VCO). The VCO creates a linear FM waveform on the actual RF channel to be transmitted as programmed by the synthesizer. The synthesizer generates the proper frequency for the designated frequency channel and it uses a temperature compensated crystal controlled oscillator to control the carrier frequency to the prescribed FCC frequency tolerance. Once on the correct frequency, the RF driver amplifies the RF signal to a level that can drive the RF power amp. The RF power amp receives the RF signal from the driver and amplifies the signal to 250 watts. At the output of the RF PA, a filter is employed to prevent harmonics from reaching the output connector. Each one of the subassemblies mentioned in this paragraph uses a DC voltage. The DC voltages are generated by the switching power supply that receives its control signal from the controller assembly. The controller assembly provides a user interface and sends the appropriate voltages to the various subassemblies to program the correct mode of operation, the frequency of operation, the output power level, etc. The controller also monitors specific parameters of the subassemblies and displays that information as selected from the front panel. Greg Best Consulting, Inc. 9223 N. Manning Ave. Kansas City, MO 64157 816-792-2913

May 24, 2004 The parts list and tune-up info for the MIRA250 are contained in the technical manual. Respectfully, Greg Best President Greg Best Consulting, Inc. 9223 N. Manning Ave. Kansas City, MO 64157 816-792-2913

May 24, 2004 The schematics for the MIRA250 are contained in the technical manual. Respectfully, Greg Best President Greg Best Consulting, Inc. 9223 N. Manning Ave. Kansas City, MO 64157 816-792-2913

1 TEST REPORT ELETTRONIKA S.r.l FM TRANSMITTER TECHNICAL REPORT INTRODUCTION The following information is provided to verify the technical performance of the MIRA250 FM transmitter. The following information is supplied for FM broadcast service according to applicable portions of Part 2 and Part 73 of the FCC rules and regulations 1. Power Output Measurements as indicated by FCC Rule Part 2.1046 and. 2. Frequency stability measurements associated with variations in ambient temperature and with variations in line voltage as specified by 73.1545. 3. Demodulated Amplitude versus Frequency response measurements of the transmitter compliant with the Engineering charts identified in 73.333. 4. Occupied BW of the FM signal as specified by FCC Rule Part 73.297, 73.317, 73.319, 73.322, and 73.1570. 5. Measurement of conducted harmonics and spurs outside its assigned channel as specified by FCC Rule Part 73.317. 6. Measurement of cabinet radiation of spurs and harmonics as specified in FCC Rule 2.1053 and 2.1057. 7. Measurements of voltage and current to final amp stage as outlined in FCC Rule 2.1033. Measurements were conducted at power output levels of 250 watts and 50 watts and constitute the range of power for which type certification is sought. FIGURE 1--TEST EQUIPMENT CONFIGURATION The test equipment used for the measurements on the next few pages is listed at the back of this exhibit. All test equipment had been calibrated prior to the use of the equipment by the supplier of the test equipment. RF Power Output Stability vs Line Voltage The equipment was configured as shown in Figure 1. The loss through the RF output cable and directional coupler and attenuator was calibrated at the carrier frequency of 98 MHz. The audio generator was not energized. The transmitter was energized at room temperature at an initial power output of 250 watts. Power was read on the Bird 4391A Power Meter and a reference level was established on the Advantest R131 Spectrum Analyzer. The line voltage was varied from 94 volts to 126 volts using a variac to adjust Audio Generator (Part of Mod Analyzer) 6 dB Matrixing unit (Part of MIRA250) MIRA250 Directional Coupler Power Meter Modulation Analyzer Spectrum Analyzer Voltage Measurement RF Load 2 the voltage. The test was repeated at an output power of 38 watts. The data is tabulated on the next page. RF Power Power Supply RF Power Power Supply 248W 94V ac 38W 94V ac 248W 110V ac 38W 110V ac 248W 126V ac 38W 126V ac RF Power Output Stability vs Temperature The equipment was configured as shown in Figure 1. The loss through the RF output cable and directional coupler and attenuator was calibrated at the carrier frequency of 98 MHz. The audio generator was not energized. The transmitter was energized at room temperature at a power output of 290 watts. Power was read on the Bird 4391A Power Meter and a reference level was established on the Advantest R131 Spectrum Analyzer. Next the temperature was varied from 0 C to +50 C. Data at the extreme temperature limits and at room temperature was recorded regarding power output. The transmitter was adjusted to 48 watts and the procedure was repeated. FRQUENCY STABILITY The equipment was configured as shown in Figure 1. The loss through the RF output cable and directional coupler and attenuator was calibrated at the carrier frequencies of 98 MHz. The audio generator was not energized. The transmitter was energized at room temperature at a power output of 250 watts. Power was read on the Bird 4391A Power Meter and a reference level was established on the Advantest R131 Spectrum Analyzer. The line voltage was varied from 94 volts to 126 volts. The output frequency was read on the spectrum analyzer. The results are tabulated below. RF Frequency Power Supply 98,0000009MHz 94V ac 98,0000009MHz 110V ac 98,0000009MHz 126V ac CONDUCTED EMISSION Two configurations have been considered: Stereophonic and Monophonic STEREOPHONIC MODE The pilot was set to 9% (6.75 kHz deviation) and 15kHz was injected into the Left (or Right) input with the main channel and the stereo channel at 28.5kHz deviation. The transmitter was energized at 250 watts RF output power and the conducted emission levels were recorded on the Advantest R131 Spectrum Analyzer. RF Power Temperature RF Power Temperature 292W 0°C 48W 0°C 291W 25°C 47W 25°C 293W 50°C 48W 50°C 3 As can be seen in the above graphs, in the stereophonic mode, the emissions meet the requirements as outlined in FCC Rule 73.317. The rule stipulates emissions between 120 kHz and 240 kHz from the carrier frequency are -25 dB or better, emissions between 240 kHz and 600 kHz from the carrier are -35 dB or better, and emissions greater than 600 kHz from the carrier are at least 43 + 10 log P o , or -67 dB referenced to the unmodulated carrier (top of the screen for these graphs). STEREOPHONIC MODE PLUS SCA In this case, an SCA channel has been added to the stereo channel. A frequency of 67 kHz is applied to the SCA input and its sub-carrier is modulated at 15% (11.15kHz). The 15 kHz applied to the left (right) channel is adjusted to obtain 70% modulation (52.5kHz). 4 As can be seen in the above graphs, the combined stereo and SCA channel emissions meet the requirements as outlined in FCC Rule 73.317. The rule stipulates emissions between 120 kHz and 240 kHz from the carrier frequency are -25 dB or better, emissions between 240 kHz and 600 kHz from the carrier are -35 dB or better, and emissions greater than 600 kHz from the carrier are at least 43 + 10 log P o , or -67 dB referenced to the unmodulated carrier (top of the screen for these graphs). Monophonic Mode For the Monophonic case, 15kHz has been applied to the Mono input with 85% modulation (63.75kHz deviation). 5 As can be seen in the above graphs, the monophonic mode emissions meet the requirements as outlined in FCC Rule 73.317. The rule stipulates emissions between 120 kHz and 240 kHz from the carrier frequency are -25 dB or better, emissions betwe…

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