Blonder Tongue AM Series Agile Modulators

Discounting all Blonder Tongue gear, Open to offers on the lot.  

This is an earlier version of the currently available AM 60-550.  The primary difference appears to be in the dipswitch control for the channel assignment.  The version we have available has a mono audio interface.  

This is a description of the current model from BT:

"AM series is a family of frequency-agile analog audio/video modulators. AM-60-860, the flag-ship model, is available in NTSC channels 2-135 (54-860 MHz), and the PAL B, G, and I channels in the same frequency range. More economical models are available in NTSC for the frequency ranges 54-550 MHz, or 54-806 MHz. EAS (Emergency Alert System) is standard on all models. Stereo Audio, SAP (Secondary Audio Programming), and several other optional features are also available."

DESCRIPTION

AM Series frequency agile audio/video modulators provide visual and aural RF carrier outputs on any Broadcast or CATV channel over the full 50 to 450 MHz (AM xx-450) or 550 MHz (AM xx-550) frequency range. The Modulators feature a clean output signal with an exceptionally low out of band noise floor that permits the construction of multiple channel headends without auxiliary filtering. They are available in either 60 dBmV (AM 60-xxx) or 40 dBmV (AM 40-xxx) output versions. A selection of options are available to suit the product for a wide range of requirements. The modulators accept standard (sync negative) polarity video from any common source, such as a satellite receiver, TV demodulator, video tape recorder or TV camera. DIP switches for setting the output frequency are accessible from the front panel as are the level controls and modulation indicators.  An external IF loop-thru enables the replacement of the standard internally generated IF signal with an alternate source of composite IF (such as an "all call" system) or the insertion of IF scrambling equipment.

ELECTRICAL
All modulator functions are carried out on two printed circuit boards.  The A/V Modulator PCB generates the visual and aural carriers at IF and modulates them with processed video and audio signals.  The Output Converter PCB converts the IF signals to the final RF frequency and amplifies the selected channel to the required output level.   On the A/V Modulator PCB the video signal is passed thru a low pass filter, buffered and DC restored. A LED overmodulation indicator lights if the video signal exceeds a calibrated preset level, corresponding to 87.5% modulation. The audio signal is first pre-emphasized (to 75 microseconds) and then it frequency-modulates a 4.5 MHz oscillator.   A preset comparator samples the audio and lights a LED when a level required for 25 KHz deviation is reached.   A high quality MC 1374 modulator chip generates a crystal controlled 45.75 MHz visual carrier that is modulated with the processed video signal in an integral balanced modulator. Concurrently the visual carrier and the 4.5 MHz audio subcarrier create a 41.25 frequency-modulated aural IF carrier. The combined IF carriers are amplified and passed thru a SAW filter that produces a near-ideal bandpass response for a true vestigial sideband output.   In the Output Converter PCB the IF signal is applied to a CATV type up/down converter. There is a 1st LO (nominally held at 567 MHz by a PLL, but capable of small frequency offsets, set by DIP switches) produces a 612 MHz IF. A 2nd PLL oscillator, also controlled by DIP switches, then converts the signal to the selected output frequency. An appropriate broadband amplifier gives the final RF output level.

SPECIFICATIONS (Typical)
RF
Output Frequency Range:   AM 60-550:   All channels 50 through 547.25 MHz (channel PPP)

(Channels Selectable by front panel DIP switch in .25 MHz increments)
F.C.C. Offset:                              +12.5 KHz and +25 KHz. (Selectable by front panel DIP switch)
Output Level:
AM 60-xxx:                         +60 dBmV
AM 40-xxx:                         +40 dBmV
Output Level Range:                         S10 dB, continuously adjustable by the front panel output level control
Aural/Visual Carrier Ratio Control:             -9 dB to -30 dB, continuously adjustable by the front panel A/V ratio control
Video Frequency Response    (Fv - .5 to Fv + 4.2 MHz):                 ±1 dB
Spurious Outputs:                           >58 dB below output of visual carrier level
Carrier to Out-of-Channel Noise:              75 dB, more than 73 dB in a 4.0 MHz bandwidth
Frequency Accuracy/Stability (meets FCC Docket 21006 Specifications): ±5 KHz Aeronautical offsets, ±20 KHz Non-offsets
Aural Intercamer Stability:                    4.5 MHz settable within ±1 KHz
IF
IF Loop Output                         +28 dBmV@45.75 MHz
VISUAL
Video Input for 87.5%
depth of modulation:                     Factory set for 87.5% modulation for a video inputofl.OV P-P
Differential Gain @ 87.5% Modulation:         0.5 dB
Differential Phase @ 87.5% Modulation:        1.5°
P-P Video to RMS Hum Ratio:                60 dB
Visual Carrier to Noise Ratio
in 4 MHz Inband Bandwidth:              68 dB
Video Modulation Depth Indicator            Set @ 87.5%, adjustable to 90%
AURAL
Audio Input for 25 KHz Peak Deviation:        140 mV RMS
Input Impedance:                         Hi-Z
Audio Frequency Response
20 Hz to 20 KHz:                       ±0.75 dB Ref. to Std. 75 usec pre-emphasis (exceeds 100 KHz with
pre-emphasis defeated)
BTSC Stereo/Mono (*):                      Field defeatable audio pre-emphasis for BTSC baseband inputs
Aural Overmodulation LED Indicator:          25 KHz ±2 KHz
GENERAL
Power Requirements:                      105-125 VAC, 60 Hz, 3/8 A Fuse, Slow Blow
Temperature Range:                      0° C to 50° C
MECHANICAL
Dimensions:                               19" Wx 1-3/4" H x 14-1/4" D (AM60), 19" Wx 1-3/4" H x 9-1/2" D (AM40)
Shipping Weight:                           7 Ibs. (Approximate)
Signal Connectors
RF Output:                           Type "P
IF Input:                                 Type "F"
IF Output:                               Type "F"
Audio Input:                            Phono Jack
Video Input:                             Type "F"
(*) NOTE : Clip out of R4 on A/V Modulator Board defeats pre-emphasis for stereo capability.