©1998 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 4/2/03
- Page 3 -
installed on the board, you can merely
clip it out.
(Note: this jumper is always
used for the upper end of the amateur
repeater band, from 445.120 to
450.000.)
If the difference is greater than
2.560 MHz, turn on switch #1, and
subtract 2.560 from the difference
frequency to determine the remainder.
Otherwise, skip switch #1.
Do the same for each of the other
sections, from highest to lowest
weighting, in sequence. Each time
you consider the remainder, turn on
the switch section with the highest
weighting which will fit within the re-
mainder without exceeding it. Each
time it is found necessary to turn on a
switch section, subtract the value of
that section from the remainder to get
the new remainder.
As an example
, let us consider
how to set the Exciter for output on
449.150 MHz. The following discus-
sion is broken down into steps so you
can visualize the process easier.
a. 449.150 – 440.000 base freq. =
9.150 MHz remainder. Install jumper
from E6 to E7 to do the upper part of
the band, because the remainder is
greater than 5.12.
b. 9.150 – 5.120 = 4.030 MHz
remainder. Turn on switch #1, which
represents the largest increment to fit
remainder.
c. 4.030 – 2.560 value of switch
#1 = 1.470 MHz. Turn on #2, which
is 1.280 MHz, the largest increment to
fit the remainder.
d. 1.470 – 1.280 = 0.190 MHz
remainder. Turn on #5, which is
0.160 MHz, the largest increment to
fit the remainder.
e. 0.190 – 0.160 = 0.030 MHz
remainder. Turn on switch #8 and
switch #9, which have values of .020
and .010, respectively, which adds up
to the remainder of .030 MHz.
Note
that when the remainder gets down
into the double digit range, it is very
easy to visualize turning on multiple
switch sections to satisfy the entire re-
mainder, such as we just did.
When we finished, we had in-
stalled the jumper and turned on
switch sections 1, 2, 5, 8, and 9.
Note:
Dip switch information is
read by the synthesizer only when
power is first applied. If switch set-
tings are changed, turn the power off
and on again.
Shortcut ---
If you have access to the internet,
our website has a long table of num-
bers which gives the equivalent set-
tings for every possible frequency. We
couldn’t print it here because it takes
13 printed pages of space. Go to
http://www.hamtronics.com/dipswitch.htm
.
Look up the frequency, and it will give
you all the switch settings and tell you
if you need to connect the jumper.
The address is case sensitive, and you
must enter the address manually be-
cause there is no link on our web site
to click on for this.
Tricks ---
Although most users will set up
the Exciter on a single frequency and
perhaps never change it, there may be
applications where you want to
change between two or more nearby
frequencies. In such cases, it is help-
ful to note the switch settings for one
of the frequencies and simply which of
the lower value switch sections to
change to raise or lower the frequency
for the other channel. It is not neces-
sary to recalculate the whole range of
settings.
Another trick if you want to switch
between two or three frequencies used
regularly is to use a toggle switch or
rotary switch and a series of 1N4148
diodes to p5V to the micro-
controller inputs in place of the dip
switch. The diodes isolate the lines
from each other. This unit is not in-
tended to be used in place of a trans-
ceiver with its fancy frequency
programming, but for simple applica-
tions, several frequencies can be
switched this way. The microcontrol-
ler automatically sends data to the
synthesizer whenever the frequency
information at its input is changed; so
changing the rotary switch will clue
the micro to do the change.
ALIGNMENT.
A complete alignment is needed
whenever the frequency is changed by
more than about 1 MHz. Alignment
ensures that the frequency synthe-
sizer is optimized at the center of the
vco range and that all stages are
tuned to resonance.
Equipment needed for alignment is
a sensitive dc voltmeter, a stable and
accurate signal generator for the
channel frequency, and a regulated
13.6Vdc power supply with a 0-200
mA meter internally or externally con-
nected in the supply line.
The slug tuned coil should be ad-
justed with the proper .062" square
tuning tool to avoid cracking the pow-
dered iron slugs. Variable capacitors
should be adjusted with a plastic tool
having a small metal bit. (See A28
and A2 tools in catalog.)
All variable capacitors should be
preset to the center of their range un-
less the unit has been previously
aligned. (Do not preset the TCXO,
which is already set to frequency at
the factory.)
MID MAX MIN
Capacitor Adjustment
☞
☞
☞
☞
Note:
Meter indications used as
references are typical but may vary
widely due to many factors not related
to performance, such as type of meter
and circuit tolerances.
a. Set the SQUELCH pot fully
counterclockwise and the VOLUME
pot just a little clockwise.
b. Connect speaker and +13.6
Vdc. You should hear white noise.
c. Set dip switches for desired
frequency.
d. Connect voltmeter to TP1 (top
lead of R5). Adjust vco coil L1 for
+4Vdc. (Although the vco will operate
over a wide range of tuning voltages
from about 1V to 7V, operation is op-
timum if the vco is adjusted to 4V.)
e. Connect voltmeter to TP2 (top
lead of R23). Adjust doubler variable
capacitor C25 for a dip on the meter
(minimum voltage). The reading nor-
mally will be about +5Vdc, and you
will get a slight dip in the reading as
you tune through resonance.
f. Adjust buffer variable capacitor
Table 3. My Switch Settings
Frequency: MHz
Switch Sections Turned On: (circle)
1 2 3 4 5 6 7 8 9 10
❏
Jumper
Table 2. Frequency Settings
Device
Frequency
Weight
Jumper
E6-E7
5.120
MHz
Switch
#1
2.560
MHz
Switch
#2
1.280
MHz
Switch
#3
640
kHz
Switch
#4
320
kHz
Switch
#5
160
kHz
Switch
#6
80
kHz
Switch
#7
40
kHz
Switch
#8
20
kHz
Switch
#9
10
kHz
Switch #10
5 kHz