[160m] Bandplans and digital

[Tom W8JI]

Note:      The rule we have to follow is we can disagree all 
we like if we behave like mature adults, but name calling 
and/or personal attacks are not permitted by anyone for any 
reason. Anyone who cannot keep it in the road and disagree 
like an adult (without calling names) will be asked to 
change their tone or leave. This is the end of all reflector 
comments on behavior. This is the rule. Disagreements are 
fine, name calling or personal insults are NOT allowed at 
any time. This includes calling people old, dumb, slow, 
ignorant, and so on.

> Re the "Weak Signal" efforts--
> Stop and think--if the signals are weak enough, They wont 
> bother most 160
> users.
> Bill--W4BSG

Hi Bill,

 Let's think about how true that really is......

Between 1820 and 1835 or 1838 most evenings in winter, and 
1810-1835 most mornings in winter, hundreds of stations (I 
would guess 1/4 or 1/2 of the active 160 population) work 
signals that are very weak. The signals being worked or 
listened to are weaker here in the USA than a 1-2 watt 
transmitter that is stateside. The truth is any weak signal 
that is above noise can severely bother hundreds of people.

I can't speak for others, but I can easily solid copy the 
signal from a 13 dBm transmitter from 800 miles away. This 
is only 20 milliwatts, and it can be solid copy at that 
distance.  I'm sure many others can do the same.

There is are two facts that often escape consideration. Most 
digital modes run audio from soundcards into SSB mic inputs 
on transmitters. As such the transmitters produce carriers 
that are never perfectly suppressed, hum from audio lines 
that are never perfectly suppressed, noise and hiss, and 
even sometimes readable opposite sidebands. Transmitters 
also produce audio harmonic distortion of tones that do not 
show on "IM meters".

If we have a 100 watt transmitter with 40 dB carrier 
suppression, the carrier will be 10 milliwatts. This is true 
if the mic gain is set to run the rig at 10 watts, or set to 
run 100 watts. Hum and noise generally track transmitter mic 
settings **IF the gain is reduced only in the transmitter** 
and external line levels are normal, but harmonic distortion 
sometimes does not follow mic gain settings. While in many 
cases transmitters are clean, I hear a significant number of 
digital mode transmitters that are not clean at all. Mostly 
it is harmonic distortion and noise or hum. Often the stuff 
is outside the passband of the stations they are working, so 
no one notices it and reports it.

A second issue people forget or do not think about is 
bandwidth. The interference bandwidth is NOT the bandwidth 
of the transmitter alone. It is the bandwidth of the 
receiver plus the transmitter's bandwidth. When a CW 
operator is using 250 Hz bandwidth and a 10 Hz wide digi 
signal comes on 100 Hz away from channel center, he is 
INSIDE the channel occupied by the CW station.  The same 
applies to SSB, where the filter might be 2.7 kHz wide. The 
10 Hz wide signal has to stay well over 10 Hz outside the 
SSB channel to not cause problems.

It is not correct to view our interference bandwidth only as 
the bandwidth and frequency of our own transmitter. We have 
to, and as good operators we should, view our bandwidth as 
what we might typically expect for others sharing the same 
area of the band plus our own bandwidth.

This is why when I get on in heavily populated times on CW I 
consider my expected transmitter bandwidth of a few hundred 
Hz PLUS the receiver bandwidth of people near me as the safe 
frequency distance. When K9DX is on 1824 I would choose 1 
kHz away on CW as a safe frequency distance, because I know 
John has a good receiver. If I know the other guy does not 
have a good receiver, I try to stay further away. The 
closest people can get on CW, since the typical receiver 
filter is 250 Hz, should be at least 300-400 Hz if we are 
sure the transmitter is clean.

Because of this inherent incompatibility, and the safe 
spacing being limited by receiver as well as the transmitter 
necessary working bandwidth, we need to keep difference 
types and widths of modes grouped together. This is why 
bandplans and following bandplans is very important.

I personally think digital modes should have been grouped 
between 1835 and 1840, but the bandplan says they are 
1800-1810 in the USA. Placing a digital mode, not matter how 
wide or narrow, outside areas planned for similar digital 
modes is never going to be OK. It is always eventually going 
to cause problems. The same is true for placing SSB in CW 
bands, or CW in digital areas. When the band is empty, like 
during summer, there is especially no reason to operate 
outside bandplans. When the band overfills there is some 
reason to be flexible to make more room, but ever during 
light or normal times of activity.

It is inexcusable behavior to break a bandplan just because 
there is no direct law telling us not to do it. Good manners 
and common respect and common sense should be our 
guidelines, not what we can get away with. Shared resources 
like the highway, parking lots, and radio frequencies 
require a spirit of cooperation and are not the place to 
show out as "I can do what I like without regard for 
others".

73 Tom