Broadcast Electronics' single tube FM-30A thirty kilowatt transmitter evolved from the field proven design of a well known predecessor - the FM-30!  The FM-30A incorporates features suggested by the over one hundred and twenty-five FM-30 users nationwide.

    Included in the FM-30A standard design are state of the art enhancements such as the modular slide-out IPA’s, a modular Automatic Power Control, a super quiet air cooling system, and the optional Microprocessor Video Diagnostic system (MVDS).

 INNOVATIVE POWER AMPLIFIER

   The power amplifier section of the FM-30A employs a patented folded half-wave cavity.* This unique design innovation completely eliminates troublesome plate blocking capacitors and sliding contacts.  The result is exceptional reliability and lower maintenance costs.

   A patented second harmonic suppressor is also integrated into the folded half-wave cavity.  This minimizes second harmonic energy at the source without wasting fundamental frequency power.  An external low pass filter (with directional output couplers) ensures compliance with FCC, Canadian DOC, and CCIR recommendations.

   All PA adjustments are performed through smooth operating front panel controls with counters.  A grounded bellows provides the fine tuning adjustment while a grounded loop couples to the antenna.  This careful attention to grounding yields the added benefit of improved lightning immunity.

 EFFICIENT SINGLE TUBE DESIGN

    The FM-30A uses a single, high gain Eimac 8990/4CX20,000A tetrode to produce 30 kW of RF power on any frequency between 87.5 and 108 MHz.

    The 4CX20,000A tube has been used in 30 kW FM transmitters since 1980.  Its reliable, consistent performance is well established by the more than 150 units presently in service.  Tube life in excess of 20,000 hours is not uncommon at the 25 kW to 30 kW output level.  At output levels below 25 kW, the overall tube life of the 4CX20,000A in the FM-30 transmitter has been phenomenal.

    The high plate efficiency at the 30 kW output level results in surprisingly low power consumption.  This single tube design saves money in both operation and maintenance.

     A new grid circuit optimizes the impedance transformation between the solid-state IPA and the power tube grid.  This novel design takes advantage of the power gain capability of the Eimac tetrode while providing maximum signal bandwidth.  Installation or removal of the power tube is easily accomplished from the front of the transmitter.  Thanks to a broadband screen neutralizing technique, neutralization re-adjustment is normally unnecessary when changing tubes.

 BROADBAND SOLID-STATE DRIVER/IPA

    The output of the FX-30 exciter is boosted to approximately 60 watts by a solid-state Power FET pre-driver stage.  A hybrid splitter network feeds two identical solid-sate IPA modules designed and manufactured by Broadcast Electronics.  The outputs are combined to produce the drive level necessary to power the PA stage.

 ELECTRICAL/MECHANICAL

 AC Input Power

208 V WYE/240 V Delta, 60 Hz, three phase. (Taps for 196 to 252 V. Other voltages and line frequencies are available upon request.)

 Primary Power Consumption

Typically 51 kW (@ .94 pf) at 35 kW RF output.

 Overall Efficiency

Typically 68% (AC line input to RF output).

 Size

(Transmitter) 56.5" W x 31.5" D x 70" H (143.5 W x 80 D x 177.8 H cm).

(Power Supply) 34.5” W x 31.5" D x 70" H (87.6 W x 80 D x 177.8 H cm).

 Weight & Cubage

(Transmitter) 1500 lbs. (682 Kg); packed 1750 lbs. (795 Kg) 72 cu. ft. (2 cu. meters).

    (HV Power Supply) 1750 lbs. (794 Kg); packed 1800 lbs. (816 Kg) 44 cu. ft. (1.25 cu. meters).

 Altitude

     7500 ft.

Ambient Temperature Range

-10 degrees C to +50 degrees C.

Sound Level

61 dB (A-weighted), 48 dB (SIL), (Ref. 0 dB = .0002 microbar) @ one meter front center.

 Finish

B/E blue with anodized aluminum control center panel and anodized aluminum trim.

 *MONAURAL OPERATION

 Audio Input Impedance

 600 ohms balanced, resistive, adaptable to other impedances, 50 dB common mode suppression.

 Audio Input Level +10 dBm nominal for +75 kHz deviation @ 400 Hz.

 Audio Frequency Response

+0.5 dB, 30 Hz to 15 kHz, selectable flat, 25, 50, 75 microsecond pre-emphasis.

      Harmonic Distortion

0.08% or less (.04% typical).

      Intermodulation Distortion

0.08% or less, 60 Hz/ 7 kHz, 4:1 ratio.

 Transient IMD

   0.1% or less (square wave/sine wave).

 FM S/N Ratio 72 dB below ±75 kHz deviation @ 400 Hz (75 dB typical) measured in a 30 Hz to 15 kHz bandwidth with 75 uS de-emphasis.

 *WIDEBAND COMPOSITE OPERATION

 Composite Inputs

 3 total, (1) unbalanced and (1) balanced plus front panel test.  All connectors BNC.

 Composite Input Impedance 10K ohm, nominal, resistive.

 Composite Input Level  3.5 V p-p nominal, for +75 kHz deviation.

 Composite FM SIN Ratio 72 dB below +75 kHz deviation @ 400 Hz (75 dB typical) Measured in a 30 Hz to 100 kHz bandwidth with 74 uS de-emphasis.

 Composite Harmonic Distortion 0.08% or less .04% typical).

 Composite Intermodulation Distortion 0.08% or less (.04% typical).

 Composite Transient IMD  0.1% or less (square wave/sine wave).

 Composite Amplitude Response +0.1 dB, 30 Hz to 100 kHz.

 Composite Phase Response +0.5 degrees from linear phase, 30 Hz to 53 kHz.

 Composite Group Delay 390 nanoseconds, +25 nanoseconds 30 Hz to 53 kHz.

 Composite Slew Rate 12 V/microsecond (symmetrical).

 *STEREO OPERATION

 Audio Input Impedance 600 ohms balanced, resistive, floating. (Adaptable to other impedances).

 Audio Input Level +10 dBm, ±1 dBm, for 100% modulation @ 400 Hz. (Adaptable to other input levels).

 Audio Input Filters 15 kHz LPF with delay equalization for minimum overshoot.

 Frequency Response +0.5 dB, 30 - 15,000 Hz, 75 uS pre-emphasis (flat, 25 or 50 uS pre-emphasis selectable).

 Total Harmonic Distortion 0.08% or less.

 Intermodulation Distortion 0.08%, 60 Hz/7 kHz; 4:1 ratio.

 Transient Intermodulation Distortion 0.1% (square wave/sine wave).

 FM Noise 72 dB or better below 100% modulation @ 400 Hz, 75 uS de-emphasis.

 Stereo Separation

45 dB or better; 30 - 15,000 Hz (sine wave).

 Dynamic Stereo Separation

40 dB or better; 30 - 15,000 Hz (normal program content).

 Linear Crosstalk

Main to Sub/Sub to Main due to amplitude and phase matching of left and right channels,

30 - 15,000 Hz, 45 dB minimum below 100% modulation.

 Non-Linear Crosstalk

Main to Sub/Sub to Main due to distortion products. 70 dB minimum below 100% modulation.

 

Pilot Stability

+0.5 Hz, 0 to 50 degrees C.

 

Modes

Stereo, Mono L&R, Mono (L) and Mono (R) remote controlled. (See FS-30 data sheet for full details).

 

*SCA OPERATION

 

Modulation

Direct FM

 

Subcarrier Frequency

67 kHz (39 to 95 kHz to order).

 

Subcarrier Frequency Stability

±0.5% (330 Hz @ kHz), 0 to 50 degrees C.

 

Subcarrier Harmonic Content

Less than 0.3%.

 

Subcarrier Envelope Decay

Greater than 100 msec. from 90% to 10% subcarrier levels.

 

Modulation Capability

+20% of subcarrier frequency.

 

Audio input Impedance

600 ohm balanced, resistive.

 

Data Input Impedance

75 ohm unbalanced, resistive, DC coupled.

 

Input Levels

(Audio) adjustable +10 dBm 10 -10 dBm for +6 kHz deviation @ 400 Hz (Data) adjustable 1.0 to 4.0 V p-p for +6 kHz deviation (DC coupled).

 

Pre-emphasis

(Audio) 150 microseconds standard (75 uS with internal jumper) (Data) no pre-emphasis.

 

Frequency Response

(Audio) +05 dB, 10 - 10,000 Hz, exclusive of audio low pass filter, (Data) +0.5 dB, DC – 10,000 Hz.

 

Audio Low Pass Filter

Sixth order, -3 dB @ 4.3 kHz, standard (resistor changes for other values).

 

Data Low Pass Filter

Same as AF filter or may be bypassed.

 

Total Harmonic Distortion

Less than 0.5% throughout AF pass band.

 

Intermodulation Distortion

Less than 0.5%, 60 Hz/7 kHz; 1:1 ratio (audio preemphasis and LPF bypassed) Typically 0.1%.

 

Crosstalk, SCA to Stereo

-60 dB or better below 100% modulation of left or right. 75 uS de-emphasis.

 

Crosstalk, Stereo to SCA

-50 dB or better below +6 kHz deviation of SCA using 150 uS de-emphasis and FS-30 stereo generator.

 

FM Noise

72 dB below ±6 kHz deviation @ 400 Hz (150 uS de-emphasis).

 

Auto Muting Level

Adjustable from 10 to 30 dB below program level.

 

Auto Muting Delay

Adjustable, 0.5 to 10.0 seconds.

 

*Through FM-35A Transmitter using model FX-30 Exciter, model FS-30 Stereo Generator, and model FC-30 SCA Generator as applicable.