Don Stoner is a pioneer when it comes to single sideband. He built his first ham SSB rig in 1955; his original CB call was 11W1507. An active "sidewinder" in the Seattle area, Don is one of the owners of SGC, Inc., prominent manufacturer of single
sideband equipment for the domestic marine and overseas market. "Mister
Sideband" will beconducting a monthly column on his favorite subject.

The majority of CBs made today
employ a circuit called a syn-
thesizer to create all the channels
with the least possible number of
crystals. It was only when this type of circuit was developed that 23-channel operation became a reality. Earlier sets used two crystals for each channel (one receive and one transmit). Thus, a 23 channel set would require at least 46 crystals for complete coverage. The present day AM CB sets use far fewer crystals to synthesize all channels, most using a
process known as heterodyning
or more simply, frequency mixing.
Whenever two frequencies are
combined in a mixer (a mixer can
be a transistor, tube. diode or
integrated circuit), two new
frequencies are created in ad-
dition to the original tWo. These
new frequencies are the
mathematical sum and difference
of the two original frequencies.
As an example, if ope mixes a 20-
MHz signal with a 7-MHz signal,
it will produce a sum of 27 MHz
and a difference of 13 MHz. A
simple filter can beused to ex-
tract the wanted 27-MHz energy
and discard the unwanted 13-
MHz signal. A typical AM unit uses 10 crystals to synthesize 23 transmit
channels by frequency mixing.
Usually, there is a group of four
"A" crystals .and six "B" crystals. Crystals one, two, three or four of the "A" group are mathematidally combined or mixed with one of the "B" group crystals to produce four chan-
nels. Crystals one, two, three or
four of the "A" group can also be
mixed with another of the "B"
crystals to produce a second
group of four channels and so on,
up to a total of 24 combinations.
One channel (27.235 MHz) is not
yet available for CB. This ac-
counts for the frequency gap
between Channels 22 and 23. The
radio is inhibited on this
frequency so the IQ crystals
actually produce only 23
channels, not 24. Most AM CB sets use 14 crystals altogether, four "A"
crystals and six "B" crystals for
generating transmitter carrier
frequencies, plus four''C"
crystals which, with the Six "B"
crystals, generate the second and
first plixer injection (local
oscillator) eignals, respectively, n a double-conversion super-
heterodyne receiver. Figure I is a block diagram for an AM transceiver (a Courier Classic III) crystal synthesizer
which illustrates the 10 crystal
concept for generating receiver
local oscillator frequencies. The
crystals form a 4 x 6 matrix to
create the 23 CB channels. Take
our old favorite. Channel 16
(27.155 MHz) as anexample of
the mathematics involved. In the
"B" group, the 23.440-MHz
crystal would be used, while the
,14.990-MHz crystal in the "A" group
would also be selected by 'the channel selector switch.

The mathematics of arriving at the
channel frequency can be ex-
pressed by the formula A +B MHz, which is 26.965 minus the
455 kHz I.F. Note that 26.510 is
divisible by 10 (2651). . In other words, the channel
frequency consists of the
. frequency of the sum of crystals
"A" and "B" ' romus 'the in-
termediate frequency (IF). Ad-
ding 23.440 and 14.990 equals the
local oscillator frequency of
38.430 MHz. This number minus
the IF of 11.275 MHz equals good
ole Channel 16 (27.155).
With an AM/SSB unit, .even
more crystals are required. Two
additional crystals are required
for the USE and LSB carrier
oscillator. Many Japanese units
use an intermediate frequency of
7800 kHz (7.8 MHz) and the
carrier oscillator crystals are
located 1.5 kHz above and below
this frequency (7801.5 kHz and
7798.5 kHz). The crystal filter has
& 3-kHz bandwidth and the
spacing between the carrier
oscillator crystals is also 3 kHz to
match the filter.
When you switch between USE
and LSB, you actually shift the
carrier oscillator and inter-
mediate frequency from one side
of the 7800 kHz crystal filter to
the other. However, the radio
must move the local oscillator
frequency by the same amount or
there will be a 3-kHz error in the
channel frequency. Remember
the channel frequency is the sum
of the carrier oscillator (which is
also the intermediate frequency)
and "the local oscillator
frequency. The fact that the local
oscillator must be shifted be-
tween upper and lower sideband
complicates the crystal synthe-
sizer considerably. As mentioned earlier, if requires 10 crystals to synthesize 23 AM channels for receiving. If these 10 crystals were used in an SSB rig for the upper sideband, one might assume it requires a second set of 10 (separated 3.0 kHz from the others) to synthesize
the lower sideband frequencies. In fact, however, only four additional crystals are required (total for SSB now 14 local oscillator plus two carrier Oscillator).
Remember the AM synthesizer
uses a group of four crystals and
a group of six crystals ("A" and
"B",in the example given earlier). If we add another group of four (call them "AA"), we can synthesize all theUSBand LSB frequencies required in an SSB transceiver. The "A" and "B"
crystals would be mixed to
produce the 23 USB channels and
the "AA" and "B" crystals would
be mixed to produce the 23 LSB

Figure 2 is the block diagram of
an AM/SSB transceiver illustrating this principle. I selected a Hy-Gain Model 674A for the example since it uses the same intermediate frequency
(11.275) as the Courier discussed
earlier. The synthesizer crystals are at approximately the same frequency also. Let's see how Channel 16 upper sideband is created in this unit. The same "formula" applies as for the
The 23.480-MHz crystal is mixed with the 14.950-MHz crystal to produce a local oscillator frequency of 38.430 MHz. This, minus the IF of 11.275 MHz equals 27.155 MHz and we are home. When you switch to the lower sideband, the IF increases to
11,278 kHz by 3 kHz. This is because the carrier oscillator is shifted to the other side of the crystal filter curve to create the opposite sideband, as mentioned earlier. Thus, the local oscillator must be decreased by the same amount if the channel frequency is to remain 27.155. It is done in the following manner. The USB/LSB switch is used to turn on a second set of four crystals. Now, the 23.480 MHz crystal is mixed with a 14.947- MHz crystal to create a local
oscillator frequency of 38.427 MHz. This, minus the LSB IF of 11.272 MHz brings us right back to 27.155 MHz.
If all this sounds pretty complicated, it is! Since crystals
cannot be produced to oscillate on the required frequency perfectly, each crystal must have a trimmer capacitor to "net" the crystal to the exact frequency.

Thus, if there are 16 crystals (14 + 2), there are also 16 netting trimmers. At the risk of digressing, don't Be tempted to "tweak" any of those intriguing little screws. Not
only is it illegal unless you have an FCC operator license, but you could foul up your rig so badly it would require a complete realignment with a frequency counter. It is difficult to know
which channels are affected by the adjustments you have "fiddled" with. Thus, the repairman will have to start from "scratch" and verify that all the oscillators are on frequency on all the
channels. If you think your SSB is off frequency, take it to a competent tech." He'll know which screws to turn, how far and in which direction to correct the
From the description of the crystal synthesizer, the reader can correctly assume the CBs gobble up crystals faster than kids eat cornflakes. Until
recently, the crystal shortage was unbelievable. According to Electronic News, the monthly output of CBs from
Japan is 1.35 million. One company alone, Cybernet, is producing more than a half million each month. The estimated total production for
1976 is between 12 and 15 million units. These radios consume more than 100 million crystals each year and these statistics are for Japan alone! The heavy usage of crystals has actually produced a worldwide shortage of quartz, cans, bases and even the tiny
springs which secure the crystal inside the can. Most crystal
companies refuse to accept any
more orders since their
production capacity is already
overioaded. None wish to expand
their facilities because of a new
developemnt called the digital
frequency (PLL) synthesizer.
When all CBs employ this type of
frequency synthesizer, the
crystal shortage may be over.
Frequency Counter - While
most people are familiar with the
CB channel numbers, very few
know what frequencies are
associated with each channel.
However, as channels are added
to the original 23, we SSB
operators should start thinking in
terms of kilohertz rather than
channel numbers. When someone
asks you to QSY down ten, doks
he mean to go down ten channels,
go to Channel 10 or (you guessed
it), move down 10 kilohertz.
A simple, low cost device to
display kilohertz (kHz) or, by
moving the decimal point,
megahertz (MHZ), is the HUFCO
Model TWS-6 frequency counter.
This device counts the number of
hertz (cycles) emitted by your
transmitter, decodes the impulses
and displays the frequency in
numerical fashion by light
emitting diodes. Incidentally, a
frequency counter and a
frequency display are not the
same. A counter does exactly
that. It measures your frequency
by counting the number of cycles
you transmit each second. A
display only lights up the ap-
propriate numbers (either
frequency or channel) and is
connected to the channel
The HUFCO TWS-six frequency
counter is only $69.95 in kit form
and I can 'confirm that it works
slicker than a greased bannister.
It took a total of four hours to
orient myself with the directions
and then assemble the kit. The
TWS-six worked perfectly upon
applying power except for the
fact I misplaced a decimal point.
However, I have the same
problem when I add up my check
The unit can be connected to
your rig very simply, without
making any interior connections.
Simply install a coaxial "T"
fitting to your antenna connector
on the rear of the radio. Connect

the coax lead which runs to the
antenna to one "leg" of the "T."
Connect the shielded input lead
from the counter to the other leg
of the "T," inseries with afive pF
capacitor. Noie, in order to read your
operating or suppressed carrier
frequency, it will be necessary to
switch to the AM mode. This
reinserts a carrier for counting
and measurement. For more information on the TWS-six and other models manufactured by HUFCO, write
to them at PO Box 357, ProVo,
Utah 84601. ®