Model 8000 Radio

General Description


General Description

The series 8000 modular design concept permits a wide variety of configurations of low density links in the 960 MHz and 2 GHz microwave communications bands. Future changes and expansions are readily accomplished with a minimum of field rework or down time. Systems can be optimized for particular applications with optional transmitter powers and receiver bandwidths. In Series 8000, Nutel can provide one-way or duplex terminals and repeaters in unprotected, protected, and space/frequency diversity systems.

In the 790 to 960 MHz range, Series 8000 can carry up to 36 fequency division multiplex channels plus a service channel. RF power options are 0.5,1.5, and 6.0 watts minimum. Receive bandwidth options are 35 kHz, 100 kHz, 200 kHz and 800 kHz.

In accordance with the United States FCC Rules for private microwave systems operating within the 952 to 960 MHz band, emission bandwidth is limited to 200 KhZ. Within this limitation, Nutel Series 8000 can carry up to 12 voice channels plus a service channel. In addition, The radio is also capable of operation in the 932.5 to 935 MHz / 941.5 to 944 MHz bands for the proposed government/private shared point to point service.

In the 1700 to 2500 MHz range, Series 8000 systems can carry up to 36 frequency division multiplex channels plus a service channel. RF power is 1.0 watt minimum. Receiver bandwidth options are 200 kHz, and 800 kHz.

Radio Equipment

Frequency Control and Modulation

Series 8000 transmitters and receivers use direct crystal controlled oscillators; no AFC or phase-locked loop circuits are used. Oscillators are temperature-compensated so as to eliminate temperature stabilized ovens. Modulation is a combination of FM and PM. The transmitter oscillator frequency is directly modulated for frequecies from 20 Hz to 4kHz, and phase modulated by frequencies above 4 kHz. This results in flat deviation below 4 kHz and deviation preemphasis above 4 kHz.

Transmitter Frequency Multiplication

Series 8000 oscillators operate in the vicinity of 13 MHz. For both 960 MHz and @ GHz, the multiplier chains are identical up to 320 MHz. Multiplier stages are X3, X2, X2 and X2.

The 960 MHz equipment uses a transistor tripler which yields exceptional efficiency. The 0.5 watt transmitter requires less than 5 watts DC power, and the 1.5 watt unit less than 13.4 watts DC. The optional 6 watt amplifier needs 15.6 watts DC power.

The 2 GHz transmitters use a 320 MHz power amplifier followed by a single step recovery diode multiplier of either X6, X7 or X8.

Transmitter model numbers, power output and frequency ranges are summerized in Table 1.

Receivers

The Series 8000 receivers have internal preselectors so that there is no need for external bandpass duplexers for image rejection or out of band interference protection. For close TX-RX frequency spacing (3.6 MHz) at 960 MHz, notch type duplexers are used. For TX-RX spacings on the order of 50 MHz at 2 GHz, ferrite circulators are used for duplexing.

Series 8000 receivers employ dual conversion with intermediate frequencies of 30 MHz and 5.4 MHz. Bandwidth options are provided by replaceable IF filters.

Receiver model number, IF bandwidths, and thresholds are summarized in Table 1.

Signaling Options

Series 8000 transmitters and receivers have space for one optional plug in subaudible module in each direction. In addition, the type 830X service channel has space for three plug in signaling modules in each direction. The frequencies used are above the service channel, at 3375 Hz,3600 Hz, and 3825 Hz. In band service channel tones can also be supplied

System Characteristics

Baseband Impedance

Transformer coupled port 75 ohm bal. or unbal.
600/150 ohm optional
Direct coupled port  600 ohm unbalanced

Frequency Response

Transformer coupled port 300 Hz to top BB freq. +/- 0.5 dB
Direct coupled port 20 Hz to top BB freq. +/- 0.5 dB

Transmitter

Spurious Outputs More than 60 dB down

Receiver

Spurious Response More than 60 dB down
Selectivity 3/6 dB 60 dB
35 kHz 35 kHz @ 3 dB 140 kHz
100 kHz 100 kHz @ 6 dB 400 kHz
200 kHz 200 kHz @ 3 dB 1800 kHz
800 kHz 800 kHz @ 6 dB 3200 kHz

Environmental

Specification and operating -35 C to + 65 C
Storage -40 C to +70 C
Humidity 0 to 95% noncondensing

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