User Manual

INSTALLATION AND MAINTENANCE MANUAL
LYNX.sc E1 FAMILY
SPREAD SPECTRUM RADIOS
OCTOBER 1998
SECTION 3: INSTALLATION & ADJUSTMENTS PAGE 3-35
For precision measurement of transmit output power, it is best
to connect an RF power meter to the antenna port. The PWR
port voltage may not provide enough precision. This is
especially important where EIRP limits apply to the installation.
In cases of no EIRP limits, the radio transmitter output power
can be adjusted to maximum for installation, except for very
short paths using very high gain antennas, where excessive
power may not be advised.
Don’t forget that the RF output port should be terminated at all
times when power is applied to the LYNX.sc radio. Therefore,
disconnect power to the radio before connecting a power meter
and reapply power once connected. Often, an RF power meter
may have a limit to the input power that it can measure without
damage. It is advised to place a calibrated fixed value RF
attenuator (typically 20 dB or more) between the LYNX.sc radio
and the power meter to assure proper operation and safety for
the RF power meter. The value of this fixed attenuation can then
be added to the value of the RF power meter reading to obtain
the actual LYNX.sc radio transmitter output power.
9. Connect a voltmeter across the GND and RSL front panel test points. This
voltage reading corresponds to the Received Signal Level (RSL) of the near-end radio. In
other words, RSL is the “amount” of signal the near-end radio is receiving from the far-
end radio. Since the antennas have not been finely aligned, it is not expected at this time
that the RSL will read very high. However, at this point it can be verified that some
communication is taking place between the two LYNX.sc terminals. Use the RSL voltage
reading to align the antennas. Align one antenna at a time in accordance with Section
3.10. Complete alignment of both ends of the radio link before going further.
The RSL voltage output on the radio's front panel will output a
voltage range over the full receiving capability of the radio
(approximately 10 VDC at 0 dBm to 0.0 VDC at threshold).
The LYNX.sc radio has a unique feature of allowing measurement of the far-end RSL from the
near-end radio. This is only possible if the LYNX.sc radios are communicating (the RSL is above
threshold). The far-end RSL can be used to verify that adjustments to local antenna alignment are
corresponding to the far-end radio reception. Far-end RSL is measured by pressing and holding
the DISPLAY FAR END front panel button. While this button is held, the RSL voltage indicates the
RSL of the far-end radio. RSL of both ends should be verified to be within approximately 2 dB of
predicted value (see Section 3.3.3). There are several factors that can contribute to low RSL:
- Incorrect antenna alignment (aligned on a lobe and not on the main signal)
- Improper polarization alignment of antennas (horizontal vs. vertical)
- Transmission line problems (loose connections, bent or damaged cables, lossy
adapters)
- Path obstructions (trees, buildings, hills, etc.)
- Path clearance (line-of-sight, earth curvature, Fresnel zone, diffraction and partial
obstruction)