Radio modes - pluses and minuses

[Bill Frantz]

I hear a lot about the various modes, so I guess I'll put my oar
in the pond. Before I start, I'll say that each mode has it's
advantages, and so I am glad to have QSOs from all the ones I
mention below in my log.

There are a number of measures of "goodness" for modes. They
include: Bandwidth, ease of tuning, complexity of equipment,
noise suppression, signal awareness, features, etc.

While some of these are obvious, others deserve some explanation.

Noise suppression measures how easy it is to understand a
message. FM is really good here.

Signal awareness is a measure of how easy it is to notice other
signals on your frequency. These signals can be your QSO partner
trying to get your attention, or other stations. Full break-in
CW is about as good as it gets while FT4/8 with its rigid time
slots is about as bad as it gets.

I think that bandwidth used is an important factor. When
operators complain that people using a mode with 50 or 100 Hz
bandwidth are using up "their" spectrum, I'm not very
sympathetic. In amateur radio, it's our spectrum. If we don't
use spectrum, it may become BigCommCorp's spectrum. (I AM in
favor of following well thought out band plans.)

There are the wide band modes: AM, FM, digital voice, SSB --
arbitrarily any thing over 250 Hz -- the width of my narrow
filter. AM is a classic mode, and goes well with your Collins or
Drake equipment. It is easy to tune and does a nice job of
producing the heterodynes or yore. With 6 or more KHz of
bandwidth it is quite wide.

FM is very popular on VHF and above, but is even more of a
spectrum hog than AM. It is easy to tune, and tends to have very
low noise. Receivers tend to lock on to the strongest signal on
the frequency, which can be an advantage or a disadvantage. The
FAA went to AM for airplane radios to be able to hear a weak
station as well as a strong one on the same frequency.
Particularly on 2M, we are running out of bandwidth. Converting
to a more bandwidth efficient mode would be an option, but
consider all those then useless Baofengs, Yaesus, iComs, etc.
The change over wouldn't be pretty.

SSB is our workhorse for HF voice. We can understand
communications in a 2 KHz bandwidth, although 2.7 KHz is easier
on the ears. It is noisy and hard to tune.

Digital voice - Doesn't yet have critical mass on HF. Might be
nice, but probably won't work well at ESP signal levels. Can be
slightly narrower bandwidth than SSB. Can have features like
automatic message forwarding, digital streams at the same time
as a voice stream etc. Just look at what the proprietary Yaesu
and iCom modes do on VHF/UHF. They are not simple to set up or
use, but they are loaded with features.

Amateur TV etc. are proof that amateur radio is a very big tent.


So now we have the narrow bandwidth modes. I'm only going to
mention a few of them -- there are so many.

CW is the classic. I'm glad people don't still use spark gap
transmitters to enjoy the full retro-experience. It has the
great advantage of needing very little in the way of equipment.
A Rockmite is a large complex radio compared with the minimum of
a simple transmitter with a regen receiver. It has the
disadvantage of requiring a lot of operator skill. Those
operators who have the skill are rightfully proud of their abilities.

When you apply modern technology to the problem you can get
something like a KX2 which can send/receive CW, tune your
antenna, and log your QSOs == all in a package which will fit in
a coat pocket.

Another advantage of CW, with a modern radio, is that you can
switch between receive and transmit quickly enough to determine
if someone is trying to transmit on your frequency while you are
still sending.

RTTY is the classic digital mode. It needs a computer or a
Teletype machine to decode and encode the signals. It is error
prone, so in a contest you frequently have to send calls twice
for redundancy. It is also quite wide for a narrow mode. You can
have some interesting fun with RTTY. It is possible to
interleave stations where the mark frequency of one station is
between the mark and space frequencies of another, which goes to
show that 170 Hz is wider than needed. Since transmissions
aren't synchronized, it is possible to notice someone else
transmitting on the same frequency as you, but noticing them is
nowhere as likely as with CW.

An amusing story: In a contest I heard 2 stations interleaving
RTTY CQs on 20M. They were on exactly the same frequency and
their mutual sync was perfect. I think they were in each other's
skip zone. I managed to work both of them.

The PSK modes were designed for rag chewing and require a
computer. That computer is built into some radios, e.g. K3, KX3,
KX2. PSK31 uses 31 Hz of bandwidth. Like the FT modes, they like
to have a number of users in a 2000 to 4000 Hz chunk of
spectrum. You might be able to cram 13 or so stations in a 1K
bandwidth. There are some error detecting PSK modes, but as far
as I can tell, no one uses them.

The FT4/8 modes are the most sophisticated modes in common use.
They require a computer, but are the only modes that can
successfully decode two overlapping signals. They work several
dB below the noise floor, so are attractive with low power, bad
antennas, or high local RF noise. The only way to discover if
you are trying to transmit through another strong signal is to
pause sending.

To slightly twist a famous quote attributed to Willie Sutton, I
go to FT8 'cause that's where the stations are. The nearly fully
automatic features were also very nice when I was physically
wiped out from my cancer treatments, but still wanted to get on
the air to improve my psychology.

73 Bill AE6JV

-----------------------------------------------------------------------
Bill Frantz        | Security is like Government  | Periwinkle
[phone]      | services. The market doesn't | 150
Rivermead Rd #235
www.pwpconsult.com | want to pay for them.        |
Peterborough, NH 03458

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