Technical Manual
RELM/
BK RADIO
1
1. General Description
The SMX920 series employs state of the art design and construction methods to
deliver a range of high performance, very reliable radio base stations and repeaters.
They are ideally suited for use in VHF or UHF two-way voice communications radio
systems. Fractional synthesizers’ and the two-point modulation method give the added
advantage of linear frequency and phase response from DC to 3 kHz for accurate
reproduction of voice and low frequency digital signalling systems. The Receiver and
Exciter circuits are contained in single special aluminium housing together with the
associated audio processing and digital control on a single circuit board. The Power
Amplifier is also contained in its own extruded aluminium housing and can be easily
removed from the main chassis. The SMX920 also incorporates ‘Plug and Play’
technology and performs automatic self-calibration. A complete module changeover is
field replaceable in very short time.
The SMX920 employs some unique features in its design and much thought and
consultation has been used to provide a product that offers an extreme degree of
flexibility for the installer and service person. For example, all options may be easily
field retrofitted at a later date. A common chassis is used for both vertical and
horizontal version models. Batteries may be installed at two or both locations in the
chassis. Internal wiring has been simplified and cut by 90%. In addition, servicing is
simplified with one single main PCB having all components on one side of the PCB.
This permits the Technician to diagnose problems while either still connected in the
chassis or powered simply and independently on the test bench.
The flexibility of the SMX920 series allows it to be configured for a wide range of
applications without removing any covers.
Standard SMX920 applications include:
♦
Conventional 2-Way voice base station
♦
Full duplex or simplex base station
♦
Voice repeater
♦
Point to point link
♦
Fast 25 mS multi hopped repeater
♦
Local operation
The SMX920 incorporates special technical features, of which the key ones are listed
below:
♦
Extremely low conducted emissions
♦
Extremely low transmitter spurious
♦
Fast transmitter on time
♦
Transmitter frequency response down to DC
♦
Low group delay distortion
♦
Full sub band RF switching bandwidth
♦
No re-tune design for receiver and transmitter
♦
Fully software programmable
