Table of Contents
Advertisement
NOTE: always enable the power source first
and then the transceiver. If a generator or
alternator supports the dc source, always
turn off the transceiver before starting or
shutting off the dc source equipment. These
recharging devices often generate large
voltage spikes that can damage the
transceiver.
A WORD ABOUT GROUNDING
A good ground system is essential for
optimum operation of any HF transmitter.
The best solution is to connect all the station
equipment chassis together using a heavy
gauge of flat ground braid. Use a short
length of braid to connect to a ground rod. If
you are not using a linear amplifier, a less
ideal ground may suffice. A ground
connection to a copper cold water pipe was
often suitable, but that is now a violation of
the National Electrical Code. Be aware that
many modern water connections use plastic
pipe, and are not suitable ground
connections.
Antenna type and its proximity to the station
are also factors in choosing ground
methods. With good resonant antennas
located away from the station, the AC
ground in your house wiring might be
adequate.
HOW IS ORION DIFFERENT FROM
OTHER HIGH-PERFORMANCE HF
TRANSCEIVERS?
ORION is different from HF transceivers that
have come before it. The use of mode-
appropriate selectable crystal roofing filters
at the first I-F stage plus DSP bandwidth
filtering at the third I-F stage has never been
utilized in an amateur HF transceiver
previously.
The mode-appropriate roofing filters used in
ORION's main receiver are the centerpiece
of the radio's performance. It is common for
radio designers to be able to produce a
receiver that exhibits in excess of 100 dB of
available dynamic range. What is not
common is the ability to protect superior
receiver design from being compromised by
real-life on-band factors (i.e. loud closeby
signals).
565 manual
Part #74279
Printed in USA
Mode-appropriate roofing filters keep
closeby loud signals from having a negative
impact on receiver performance. A typical
high performance HF transceiver is
equipped with a 15 to 20 kHz wide roofing
filter at the first I-F stage. Any signal that
appears under the 15 to 20 kHz roofing filter,
even if you do not hear it in your receiver
passband, has the potential to compromise
receiver performance. Loss of dynamic
range, third-order intercept or the receiver
breaking into non-linearity (distortion) are
possible results.
When dynamic range and third-order
intercept are compromised, the ability to
copy weak signals is also compromised.
The typical 100 dB dynamic range high
performance HF radio, in the presence of
loud signals a few kHz above or a few kHz
below the targeted receiver frequency, could
lose a significant amount of the available
100 dB of range! Why? Because those
loud signals under the 15 to 20 kHz wide
roofing filter have had a negative impact on
the overall performance of the receiver.
If a mode-appropriate roofing filter is
substituted for the 15 or 20 kHz wide roofing
filter at the first I-F, the result is that closeby
loud signals do not compromise dynamic
range or third-order intercept point. A 2.4
kHz crystal filter will not allow loud signals
that are 3 or 5 kHz away from the target
frequency compromise the overall
performance of the receiver. This is where
every other HF transceiver that has come
before ORION is deficient. Imagine how
much worse the receiver performance of a
competitor's radio can be in the presence of
many loud signals across the band (like in a
major contest).
ORION is equipped with a total of seven
available crystal roofing filter slots. Four of
the seven crystal roofing filters are standard;
three are optional. The standard roofing
filters included are 20 kHz, 6 kHz, 2.4 kHz,
and 1 kHz. Optional filters are available at
1.8 kHz (model 218), 500 Hz (model 217)
and 250 Hz (model 219).
Note that the 20 kHz and 6 kHz roofing
filters are of limited utility for maintaining the
overall receiver performance level of a high
end HF transceiver like ORION. They were
September 2003
5
Advertisement
Table of Contents
