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uLINK is a name for microHAM station network. It is an isolated, industrial standard RS-485 multi-master bus
which provides device control networking for the SMD system. All SMDs are connected to the uLINK bus
through uLINK HUB boxes and share control of multiple uLINK modules. These modules serve as network
interface devices to control antenna switches, stack switches, four square switches, rotator controllers, tuners,
power amplifiers, etc ...
NOTE: uLINK bus is completely different from, and independent of, a computer LAN network, never connect
them together.
Every uLINK device on the network is identified by its unique network address. uLINK supports up to 31 SMD
controllers (31 radio operating positions in any combination from 31 individual operating positions to 15 SO2R
operating positions). Each SMD can access up to 128 uLINK interface modules.
Hardware observations:
uLINK bus is strictly a linear bus; the physical connection must be a daisy chain, going from one device
(module) to another. Total length of the uLINK bus must not exceed 1.2km (4000 ft). Star topology is not
allowed.
uLINK, is a transmission line having specific impedance and must be properly terminated at both ends. uLINK is
designed to match the impedance of easy to obtain CAT5/6 cables which should be used as the network media.
The bus uses one pair of shielded cable for data, one, parallel connected, pair as a common relative reference
point and two pairs for power distribution. Details are described in the Connecting Hardware chapter.
IMPORTANT: If possible, put the control cable under ground if the control cable runs outside the shack into the
antenna field. The control cable can lay on the ground but avoid placing it near the end of radials, close
to transmitting elements or antenna feed points. Never allow the control cable to hang in open air where it
can pick up RF!
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uLINK BUS
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