565 manual
September 2003
Part #74279
Printed in USA
46
signal) – ideally, you want to adjust this to
just before the clipping point for maximum
copy of the weak signal.
So, all that being said, how about a “set-it-
once-and-leave-it” value for programmable
AGC for weak signal DXing?
Set AGC hang at 0.00, decay at 40-60 dB/s,
and the threshold at .5 uV. This ought to
provide a good enough combination of
settings to allow just about anything that can
be audible to be detected by the radio (and
likely copied as well) and allow for plenty of
gain. If you need just a little more, you can
go in and change the AGC parameters for a
given situation as described above.
While you can have an optimal starting point
for programmable AGC – every signal and
every noise situation is unique!
This is
precisely what makes this system so
advantageous over traditional settings of
“fast” and “off”.
Consider the settings we have suggested for
single signal DXing: wider roofing filter, NR
(if desired) at a start value of “3” or higher,
use of programmable AGC, DSP bandpass
filter set at any value desired. Now
consider what we started with above:
conventional settings on a past transceiver
of 250 Hz crystal filter, AGC fast or off, DSP
NR on. Let’s say on Orion, you’ve put in
the 250 Hz roofing filter, put the DSP BW at
100 Hz, turned the AGC to fast or off, put
the DSP NR on “1”, and then went to copy a
single weak CW signal on the low bands.
Knowing what you now know, what is the
likely result? No chance that desired signal
is going to be as copyable (or copyable at
all!) as it would be with setting the
transceiver to take it to its full capabilities.
To summarize for weak signal, single-
signal DXing:
Use the programmable
AGC settings in the table above, adjusting if
needed for each situation to enhance weak
signal copy. Use the narrow roofing filters
only if a loud signal is close enough to
warrant it. Gain does not vary for DSP
bandpass filters – use any value down to
100 Hz you feel comfortable with. For weak
CW signals, either leave NR off or start NR
at a setting of “3” or “4” for quicker
adaptation. Make sure the narrow roofing
filters, if you choose to use them, are
centered using the C.F. controls in the
menu
. Make sure the signal you are
listening to is zero beat at the CW offset
you have selected.
Contest operation is a little different.
Generally, contesters are not going to want
to be fiddling with controls during the course
of the contest like DSP NR, AGC, etc.
unless it’s to quickly adjust some parameter
for a given situation. The needs of the
contester are somewhat different from the
single signal DXer. The contester needs the
radio to be set for a somewhat optimum set
of values to meet these criterion: 1) the
ability to copy both weak signals and loud
signals with AGC good enough to minimize
the output variability between the two. 2)
The minimization of loud nearby signals
having an effect on overall receiver
performance and 3) having an reasonably
optimum “start” setting that will keep the
operator from having to constantly adjust
controls on the radio.
Now, these goals are not common to single
signal DXing.
At first thought, it would
seem that what would be good for single
signal weak signal DXing would also hold
true for contesting
– and perhaps for
previous transceivers there was an element
of truth to that. Actually, though, what
would be good for copying a varying ratio of
signal strengths under crowded band
conditions is not at all the same as copying
one weak signal with a Beverage receive
antenna under quiet (non-contest)
conditions.
Recommended start settings for CW
contesting: In the filter menu, set
Xtal Filter
to AUTO. This will bring in the desired
mode-appropriate roofing filter automatically
as you adjust the DSP BW filter settings
across the value of the roofing filter. Likely
loud signals are going to be present nearby,
and minimizing them as a factor in overall
receiver performance is paramount. This is
where
every other radio fails
under contest
conditions. That S9+30 dB CQer 3 kHz up
the band from you? It’s
killing
the receiver
performance of other radios, even though
the operator doesn’t hear the signal through
the
bandwidth
filter. With the narrow
roofing filter, the
Orion has no negative
reaction to the same signal
– preserving
receiver performance down to the smallest
