SSB Single Side Band
What is Single Side band?
First we must
Single side band is not!
This article is tailored and
written for the new ham.
is not a band! It is not a frequency! It is not a portion of a band!
It is not a rock group! It is not.......what you may have
Single sideband is more properly called a mode.
It is a very efficient method of superimposing your voice or
other information on a radio wave and the transmission of that radio
The method by
which audio, (information), is impressed on a radio signal is called
modulation. To modulate a radio wave is to add information to it
that can be received on a receiver for some useful purpose.
There are two
types of modulation that most people are familiar with, AM
(amplitude modulation), and FM, (frequency modulation), for which
the AM and FM broadcast bands were named. You have used FM
modulation on the 2 meter ham band and most likely used AM
modulation when you were a kid using toy walkie talkies. You may
also have used single sideband on other occasions also, but since
you are reading this, you want to know more.
When you are in
the AM mode, your voice modulates, (is superimposed), on a carrier
wave at a certain frequency in your transmitter and is transmitted
over the air waves.
The carrier wave
is used to "carry" the audio information to the AM receiver where it
is detected and transformed back to an audio signal that we can hear
representing the original information (voice) that was spoken into
In an AM modulated radio signal, the carrier, is continuously
transmitted. Due to the nature of the way AM is produced in the
transmitter, two identical
modulating signals are attached to the carrier wave, these are
called the sidebands. They are a mirror image of each other,
identical in every way.
Any audio that
you hear on an AM receiver is from the two sidebands. When the radio
transmitter you are tuned to is not transmitting any sound, you can
still hear from the speaker and see on your S meter that a signal is
present due to the background noise being quieter than either side
of that frequency. This is the carrier you are detecting being
detected by your receiver.
modulating (audio) sidebands are located on either side of the
carrier wave, one just above it and the other just below. As a
result, the sideband located just above the carrier frequency is
called the upper sideband and that which is located just below the
carrier frequency is called the lower sideband.
The audio sidebands that form an AM
broadcast signal are quite important. They contain the "information
or audio" intended for the receive station. Although AM signals were
transmitted almost exclusively for decades, it was discovered with
experimentation that the AM signal could be modified yielding much
were experimented with and ham radio operators often used both
sidebands without the carrier using special circuits in the
transmitter to eliminate the carrier wave while still leaving the
modulation to be transmitted.
This is known as
double sideband (DSB) without the carrier. DSB was typically used in
the earlier experiments because it was much easier to filter out
just the carrier than to filter out the carrier and one of the
sidebands. Soon the experimenters were able to filter out the
carrier and either of the sidebands to yield what we now know and
use as Single Sideband! So we are using a single side
band....meaning one side band.
circuits and filters, single sideband transmissions can consist of
either the lower sideband (LSB) or the upper sideband (USB). If you
listen to an SSB signal on an AM receiver, the voices are altered
and sound very muffled, garbled and distorted. Some people even say
"Donal Duck" sounding when tuned improperly in the sideband
Enter the SSB
receiver still needs the original carrier to “demodulate” or decode
the signal, you must have a special SSB receiver to listen to these
transmissions. This is accomplished in the SSB receiver by circuits
that re-insert a very low level carrier wave back with the lower or
upper sideband signal and magically, the audio that was transmitted
is restored in the receiver with almost identical reproduction of
the original voice. Tuning the SSB receiver is very touchy and
critical to make the voices sound natural. If you are tuned off of
the transmitter frequency, depending on which way you go, the voices
will be higher or lower pitched, resulting in that "Donald Duck"
sound. You will tune with ease with some practice.
MUST be in the same "mode" as the transmitted signal or the whole
process does not work!
It the transmitter of the other
station is in the USB mode, your receiver MUST be in the
USB mode and vice versa.
How do you know
which "mode" to use?
On HF and by agreements
worldwide, all stations transmitting SSB use LSB on 160 meters
through 75 meters, USB on 60 meters, back to LSB on 40 meters and
then all bands above 40 meters use USB. This agreement makes life
easy when switching bands. Every one knows which modes are used on
Here is a sample audio
file. At first you will hear a station in the USB mode on 20
meters properly tuned........then the receiver is switched to the AM
mode with a station transmitting in the SSB mode......then back
to SSB with tuning slightly off frequency and retuning to the
correct frequency by "ear". You will notice how the voice pitch changes as the tuning of the receiver
gets closer to the transmit frequency of the person
transmitting.....Click here for the audio. Mp3, 149KB, 1:16
seconds. (I did not get a chance to "ID" the stations
Since the fidelity of the SSB voice transmission has
been altered somewhat through various filters in the process of
producing the sideband that is not too wide, usually only the most
important portions or characteristics of the voice frequencies
needed to communicate are allowed through, and this causes the lack
of true AM or FM fidelity to the transmission, but the
communication, (understandable), portions of the voice
characteristics remain, which is all that is needed in the first
place. It is a "communications" mode, not wide
band HI FI commercial broadcast FM radio, CD quality mode!
The information contained in the
average human voice needed to understand
the voice is contained within about the first 3000hz of the human
hearing range. Frequencies of the human voice beyond this range are
not needed for communication purposes and are filtered out in the
modulation process. So the average bandwidth of a SSB signal is
about 3000hz wide with all of the voice characteristics needed
within that range to be understandable.
The Power Ratio factor
Back to AM
for a bit. When producing that AM signal we were talking about, the
end result is that it was discovered that approximately half of the transmitter power is
"wasted" on the carrier and the rest of the power is divided between
the two sidebands. As a result, the actual audio output from a 1000
watt AM transmitter (500 watts of carrier + 250 watts on each
sideband) would be the same as a 250 watt SSB transmitter in it’s
of SSB Transmitters
In the above, we
learned that it would take 1000 watts of AM to be as effective as
250 watts SSB. This is a 4 to 1 ratio. The reason for the efficiency
of SSB, is that all of that power that was used to produce both sidebands and the carrier are now used
in only one sideband at the transmitter,
and when you account for the receiver re-adding only a very,
very tiny portion of that power back into the equation, you are
increasing the efficiency about 16 times
better than the standard AM transmitter! It is one reason why long
distances can be covered effectively with SSB using much less power
SSB surprises for the new user!
tune around a ham band where single sideband is used, one thing may
startle you compared to listening to AM or FM. Two stations
occupying the same frequency can talk at the same time without those
terrible squeels and tones caused by two carriers beating together!
Since there are no carriers transmitted....no tones. If you are
familiar with the terms, "Pileups" or "Double"....you will
understand what this means.
So as not to get too technical,
those tones are caused by the differences in the two AM station
frequencies that fall within the audible range when added or
subtracted from each other creating the difference heard as an
Here is an
Station 1 transmits on 7.200000mhz exactly using
Station 2 transmits on 7.201000mhz exactly using
Station 3 is your receiver tuned to 7.200000 exactly on
When you subtract the difference between the two frequencies
of station 1 and station 2, you get 1000hz which is an audio tone
that you hear from the receiver. If one of the two stations adjusted
their frequency by a tiny amount, you would hear the difference
change in the frequency of the audio
When you are in either sideband mode and you're just
setting there listing to the background noise and all of a sudden
you hear a tone in the background, you are hearing the "carrier"
that is being re-inserted in your receiver beating against the
carrier of the other station and producing the difference frequency
if he is slightly off of the frequency you are tuned to. If you tune
your receiver on top and exactly on his transmit frequency...the
tone will simply vanish because the difference frequency between
your receiver and his transmit frequency are so close or exact that
you can not hear the low audio frequency. Most ham transceivers do
not reproduce audio frequencies below about 100hz or so, so
even if your ears could hear that frequency, the radio is simply
just not producing it.
One more thing that may surprise
you....When you key your mic and are in the SSB mode....look at your
watt meter......no output! Remember.....there is no carrier produced
in the transmitter when using the sideband mode.....so no carrier
will be registered on the meter. If you scratch your finger across
the face of the mic or speak into it, you will then see the meter
register the "modulation".
instant you "modulate" the transmitter with your voice, you will see
that the meter deflects showing you that now you have output....this
is normal so don't worry that your transmitter is not
operating....it is...and very effectively!
Now that you have
learned more about how SSB works just remember that the SSB mode of
transmission is the predominant mode of transmission used by most
hams to effectively and efficiently work the world!
Meet you on 10
You should learn more....try these
(Wikipedia online encyclopedia)
(Excellent information from DJ4BR)
(From the U.S. Navy)
Upgrade to General with the
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