Model MCX-1 Coaxial Modem

Coaxial Modems

Model MCX-1

FEATURES

Phase-continuous FSK modulation and coaxial cable connection provide reliable data transmission in high-noise environments

30 dB dynamic range permits operation on any point on cable without the need for amplifiers or attenuators

10^-9 error rate¹

Simple tee connection to cable; no directional coupler or transformer required

Multi-drop capability of up to 100 nodes on a single trunk cable

Modem synchronizes to first bit; no preamble required

Plug-in daughterboard configuration for OEM applications

Low cost, low maintenance

Figure 1
Model MCX-1 Modem

For two-way transmission on coaxial cable of asynchronous data from DC to 2 Megabits per second, up to 50,000 feet without repeaters. Point-to-point or multi-drop operation.

¹Error rate measured with an greater than 16 mV RMS, and a maximum in-band noise level of 1.6 mV.

DESCRIPTION

The MCX-1 Coaxial Modem transmits and receives phase- continuous FM signals on coaxial cable at rates from DC to 2 Megabits per second. The modem can transmit over distances up to 50,000 feet without repeaters on T4100J cable (see Table 1.)

Connection to the trunk cable is made with inexpensive tee connectors. The modem permits either point-to-point or multi-drop operation. Point-to-point operation can be achieved on a single cable in half-duplex mode, or on two cables in full duplex mode.

The modem requires no preamble. Once carrier is turned on, the detector circuit in the receiver synchronizes to the first bit of the message. The only control signal is the carrier gate which is turned on for the duration of the transmission.

The 30 dB dynamic range of the modem makes it possible to connect devices at any point on the cable without any gain adjustments and without concern about proximity to other modems.

A bandpass filter in the receiver blocks noise and improves rejection of common mode signals at power line frequencies. Additionally, the modem is AC coupled to the cable at both the center conductor and the shield to block DC ground potential differences and to permit multi-point grounding of the cable.

The MCX-1 modem is packaged on a 1.9" by 4.5" printed circuit board. The modem has 10 pins for power and signal connection, and maintains physical compatibility with the original MCX-1 modem. The modem's 0.60" total height including connecting pins permits its use in card cages with 0.75" centers.

SPECIFICATIONS

Transmitter

Data Input	TTL Compatible; any unipolar code with embedded clock
Gate Input	TTL Compatible; active low for duration of data
Output to cable	2 volts peak-to-peak minimum
Modulation	Phase-continuous FSK
Gate Setup Time	2 us minimum
Propagation Delay	150 nanoseconds maximum
Turn-off time	2 us maximum
Output Impedance (Gated off)	100K ohms minimum
Output Impedance (Gated on)	37.5 ohms nominal
TTL Data Input (Logic High)	VIH = 2 VDC minimum (IIH = 40 uA at VIH = 2.4 V)
TTL Data Input (Logic low)	VIL = 0.8 VDC maximum (IIL = 1.6 mA at VIL = 0.4 V)
Carrier Gate (Logic High)	VIH = 2 VDC minimum (IIH = 40 uA at VIH = 2.4 V)
Carrier Gate (Logic Low)	VIL = 0.8 VDC maximum (IIL = 1.6 mA at VIL = 0.4 V)

Receiver

Cable Input Impedance	50K ohms minimum
Dynamic Range	30 dB
Output Data	TTL compatible
Propagation Delay	2.5 us maximum
Output Jitter	80 nanoseconds maximum
Normal Mode Rejection	10 Volts at 60 Hz
Bit Error Rate	Less than 10^-9 at 20 dB S/N
TTL Data Output (Logic High)	VOH = 2.4 VDC minimum (IOH = 400 uA)
TTL Data Output (Logic low)	VOL = 0.4 VDC maximum (IOL = 4 mA)

Figure 2
MCX-1 Dimensions

Physical and Environmental

Operating Temperature	0º to 55ºC (32º to 131ºF)
Operating Humidity	5-90% RH, Non-condensing
Operating Voltages	4.90 to 5.10 VDC 11.75 to 12/25 VDC
Operating Current	+5V supply: 130 mA maximum +12V supply: 100 mA maximum
Size (LxWxH)	4.5" x 1.9" x 0.562"
Mating Socket	Concord No. 09-9034-1-03

Table 1
Maximum Cable lengths for an FM LAN

Data Rate (MBPS)	FM Carrier Frequency (MHz)	Distance (Feet)
Data Rate (MBPS)	FM Carrier Frequency (MHz)	RG-59	RG-11 (foam)	JT4750J	JT41000J
1.0	3.0	5,000	12,000	32,000	50,000
2.0	5.0	4,200	9,400	25,000	37,500

SYSTEM SUPPORT SERVICES
11046 State Road 52
Hudson, FL 34669
TEL: (727) 379-0484
FAX: (727) 379-0831
CELL: (727) 243-3656

ORDERING INFORMATION

Please use Model Number when ordering.

Model No.	Part No.	Description
MCX-1B	30-0278-2	1 MBPS, Half Duplex
MCX-1C	30-0278-3	2 MBPS, Half Duplex
MCX-1E	30-0278-5	1 MBPS, Full Duplex
MCX-1F	30-0278-6	2 MBPS, Full Duplex

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