Operating digital is something that most of us seem to learn more or
less on our own, with the (huge) help of the internet, with all of its
resources. One of the things that frequently surprises me are some of
the myths and misconceptions that are common among digital ops. Here
are a few.
1. Power does not matter for digital modes.
I have run into numerous ops who believe that since modes such as PSK
are "digital," the power level that they run does not matter. They
doggedly will stick to 10-20 watts even when characters are dropping out
and readability is 'way under 100%. While it is true that these modes
often do very well at low power levels (20-40 watts is common) it is
also true that in today's often poor band conditions, more power will
sometimes, even often, yield much better communications with fewer
characters missed. If you are in a QSO and copy is rough, it is OK to
raise power if you can! Going from 20 to 70 watts often will make a
tremendous difference on all of the digital modes. Yes, even Olivia.
Naturally, one must keep an eye on the rig's duty cycle, as most digital
modes are high duty duty cycle.
Some of this QRP habit derived from the fact that PSK emerged at a time
when the sunspot cycle was at its peak. Under such conditions, low
power produced much more consistent and reliable contacts. Under
today's conditions more power is often justified. CW is a digital
mode--the first. While some CW ops run QRP (nothing against QRP!)
plenty more run the legal maximum, and most run power at their rig's
usually 100 watt limit. PSK and other modes benefit from a bit of power
very bit as much as does the "first" digital mode.
2. Filtering is unnecessary for digital modes. Just plunk your rig in
the middle of the PSK (or other mode) band and change frequency with the
soundcard ("moving the flag.")
Narrow filters are a Godsend with most of the digital modes. The
digital portions of the band are not large, and are full of signals.
You want to have the station you are receiving at the center of your
rig's audio passband (typically either 1000hz or 1500hz). This means
that you tune with your radio, not the soundcard. This way, most rigs
will enable you to use the radio's narrow filters such that placing the
received signal in the center of the rig's passband creates a "wall"
that protects the signal from all but the closest adjacent interference.
Good digital programs like MixW and PSKDeluxe have functions for
centering a signal in the rig's passband--MixW's "ALIGN" command, and
the "Center" function in PSKDeluxe. This is why IF filtering is so
important--it prevents strong adjacent signals from desensitizing your
radio by pumping the AGC. When picking a rig for digital operations, in
my opinion the single most important factor is what kind of narrow
filtering the rig provides for digital mode operations. Good filtering
during a QSO will often make the difference between solid copy and no
copy. Often, when someone calls me, I can barely copy them until I kick
in the narrow filters. Then, because nearby interference is no longer
desensitizing my radio, the caller is Q5 copy.
Just some random thoughts. Hope this post is not too long or too
boring, grin.
de Roger W6VZV
