©2003 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 10/2/07
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GENERAL DESCRIPTION.
The CC-( ) series VHF Receiving
Converter modules are designed to
amplify and convert the frequency of
vhf signals in specific bands to 28-30
MHz.
The input and output connectors
are BNC type when the unit is sup-
plied in a case and RCA type when
the unit is supplied without a case.
The Converter is used to convert
vhf frequencies in a block down to
28-30 MHz so they can be heard on
a 10 meter receiver.
CRYSTALS.
The converter uses crystals in
HC-50/u (wire lead) holders. They
are soldered to the board.
We can provide either standard or
special frequency crytals for the con-
verter. Crystals are cut for parallel
resonance with 32pf load capaci-
tance. The following table gives crys-
tal frequencies for standard models.
Model
Crystal Formula
CC50
22.0000
X = RF-IF
CC144
12.8889
X = (RF-IF)/9
CC145
13.0000
X = (RF-IF)/9
CC146
13.1111
X = (RF-IF)/9
CC222
21.5556
X = (RF-IF)/9
For purposes of determining cry-
stal, substitute the frequency of the
low end of the band of interest. I.e.,
the lowest frequency in the input
band is "RF" and the lowest output
frequency is "IF". For example, for
the CC144, 144 MHz is the bottom
end of the input band and this is
translated to 28 MHz in the output
band; so those frequencies are used
for the formula.
Hamtronics stocks crystals for the
popular frequency schemes (listed
above), and we will be glad to order
any special crystals.
MOUNTING AND
INTERCONNECTIONS.
If the unit was not ordered with
optional case, the pc board is easily
mounted to a chassis or panel with
4-40 screws and threaded standoffs
using the holes provided in the four
corners. A mounting kit is available
(see rear of catalog).
The i-f output should be con-
nected to the antenna input of the hf
receiver.
+13.6Vdc should be connected to
power pad E1.
INSTALLATION.
Installation depends on the type
of converter ordered. Connect J1 to
the vhf antenna and J2 to the input
of the receiver used for listening.
RCA plugs are used for boards with-
out a case. BNC plugs are used for
units supplied with a case.
Always use best quality low-loss
coax at uhf frequencies. We sell very
good rf-type RCA plugs, called by
part number A5. These are highly
recommended for best performance.
The power terminal on the pc
board or the feedthrough terminal on
the front of the case should be sol-
dered to a source of +12 to +14 Vdc,
preferably a regulated power supply.
Be sure that the same power
supply is not connected to any de-
vices which could produce damaging
voltage transients, for example, mo-
tors or relay coils. Reverse diodes
should be used across such devices
to limit transient pulses. The con-
verter draws about 25 mA.
ALIGNMENT AND TESTING.
The most difficult part of align-
ment is obtaining a stable test signal.
If you don't have access to a vhf sig-
nal generator, it is possible to use a
strong signal on the air.
➠
A tuning tool of the proper
type must be used to avoid cracking
the slugs in the coils. This is a .060"
square slot type tool. The slugs are
teflon coated; so they turn easily.
However, if a loosely fitting tool or a
tool only partially inserted in the slot
is allowed to slip in the slot, the
sideways force cracks the powdered
iron slug. Should this happen, the
slug must be drilled out and re-
placed. Variable capacitor C15 is ad-
justed with an insulated tool with a
small metal (slot type) bit in the end.
(See A2 and A28 Tuning Tools in
catalog.)
a. Connect a source of +12 to
+13.6Vdc to E1.
b. Connect signal source to J1,
and connect J2 to receiver used as
an i-f. Set both to the center of the
range you want to use. Note that
gain will be greatest at and near the
frequency used for alignment; so if
you want to emphasis one end of the
band, tune in the center of the range
you want to emphasize, for instance
for
144-145
operation,
use
144.5MHz for alignment.
c. Connect dc voltmeter to TP1,
which is a pad in the center of the
board.
d. Adjust oscillator coils L7 and
L8 alternately for a peak (about 1 to
2.5 Vdc). Note that indication may
be zero when tuning far off peak on
either side.
e. With a moderately strong sig-
nal applied to the converter, tune in
the signal on the receiver.
f. Alternately adjust multiplier
coils L9 and L10, rf coils L2, L3, and
L4, and IF coils L5 and L6 for maxi-
mum response.
Repeat adjustment to work out
any interactions between coils. Re-
duce input signal to a fairly low level
for final adjustment. There may be
some benefit to readjusting input coil
L2 slightly for best noise figure,
which you can do by ear by tuning
for best quieting on a weak signal.
g. After initial alignment, try de-
tuning L7 and L8 alternately to find
the combination resulting in the best
sensitivity. Sometimes, less drive to
Q4 results in better noise figure be-
cause the mixer injection is opti-
mized.
h. If a frequency counter is avail-
able, or if you have another way of
applying an accurate frequency at
the input, adjust variable capacitor
C15 to trim the oscillator exactly on
frequency.
The final sensitivity of the con-
verter should be about 0.1 to 0.2 uV
for 12 dB sinad after tuning, assum-
ing an i-f receiver of good sensitivity
is used with the converter.
OPERATION.
Operation is so simple, it is
hardly necessary to describe it.
However, some explanation of the
way broadband converters operate
may be helpful to you if you have not
used one before.
The converter operates by hetero-
dyning (mixing) an entire block of fre-
quencies down to a new band of
frequencies which your receiver is al-
ready capable of hearing. It does
this
by
mixing
an
oscilla-
tor/multiplier signal with the incom-
ing signals to produce the difference
of the two frequencies.
Thus, all the frequencies in the
incoming band are converted to new
frequencies a set value away from
HAMTRONICS® CC-(VHF) RECEIVING CONVERTERS
INSTALLATION & MAINTENANCE INSTRUCTIONS