THE IDEA
It has been quite some time since I thought of building a
solid state 7 MHz SSB transceiver, especially
to work on 12 V battery. However, the project
took quite a few years to materialize due
to involvement in satellite work like building
special antenna systems, cavity type linear
power amplifiers etc. Finally since three
of my sons got their licenses, I thought
of building the equipment for them and sat
with the project seriously.
The following are the criteria, which I
considered as important in the proposed
circuit arrangement of a simple SSB transceiver.
1. To make use of Low priced components
available in Indian market.
2. To use simple and Low cost mechanical
devices for the Tuning system, dial etc.
3. Simple circuitry with acceptable performance.
4. Minimum controls on the front panel.
5. To work on 12 V battery and mains power
pack.
Keeping the above points in mind, I have
made the following circuit arrangement to
the best of my knowledge to suit my requirements.
THE EVOLUTION
I built this circuit for the first time in March 1995
using three PCB's (RM-95 version).
The first PCB consisted of complete Rx and
TX up to mixer and first amplifier stage.
The second PCB lodged the broad band linear
driver and the third contained the PA. Initially
I had used bipolar power amplifiers -
2N3632 and then 2N5070 both of
which could not give more than 5 watts
output. Later I switched over to the power
FET IRF830. In RM-95, I have used
BEL BCF 100/1, 9 MHz crystal filter. The
performance was reasonably good and reports
received on band were encouraging. Slowly
queries started coming in for my circuit
and PCB layout. Impressed with the performance
of RM-95 I thought of designing a new PCB,
which would incorporate all the circuitry
in one single board. My good friend FROM
Socky VU2N]S joined hands with me in bringing
about this modified second version. We sat
together and fabricated a single PCB and
Socky took up the artwork. The result is
the RH-96 Board.
All the discussions between VU2NJS and me
about the PCB layout were going on daily
on 7088 kHz. Having heard my signal on the
version (RM-95) quite a few amateurs who
heard us on the band discussing about RM-96
expressed their desire for the PCB for themselves.
Thus, we ended up making 37-numbers of the
PCB in the first batch itself and all of
them were whisked away from us.
THE CIRCUITRY
The circuit it self is very straightforward and quite simple.
A zip file with all relevant circuits is
downloadable by
clicking here.
Rx
On the receiver side, it starts with cascade RF amplifier
followed by a bipolar BF194/494 mixer feeding
into a crystal filter. It is followed by
a two stage IF amplifier and a product detector.
The audio amplifier is LM 380. Since we
have built a number of 2M VHF rigs where
LM 380s were used, I have special liking
for this IC as it requires minimum external
components and gives an output of 1 watt.
TX
On the Transmitter side is pA741 microphone amplifier, a
carrier oscillator plus buffer amplifier,
a simple two diode balanced modulator, a
BF194/494 TX mixer and a chain of linear
amplifiers ending with BD139 driver. The
PA is a power FET and you can choose from
IRF510 to IRF840 series. I have tried and
used successfully 510, 511, 530, 830, and
840 from the IRF series and VN66AFD with
appropriate supply voltage suitable for
that particular device.
VFO
The VFO is a Colpitts oscillator followed by a direct coupled
emitter follower. Since I used a 10 MHz
ladder filter in my RM-96, I had some trouble
with its harmonic 6 MHz, both on the receiving
and transmitting side (like the SWR/Power
meter showing a residual power, very critical
TX mixer tuning etc.). However, after introducing
a tuned circuit the output of the emitter
follower all evils have disappeared.
POWER SUPPLY
The power supply (Fig-2) is an economy type circuit with
18 to 20v center-tapped transformer rated
for about 3 Amps continuous duty cycle.
A bridge rectifier of 3 A rating is used.
Half voltage is taken from the center tap
and fed to a 7812 regulator IC giving 12V
supply for the Rx and TX exciter stages.
CHANGE OVER
The antenna cum Rx/TX change over (fig.4) is a 12v - 300
ohms DPTP type relay. In one set I have
used the garden variety (the type used is
voltage stabilizers) and in the other the
OEN sealed type relays.
AGC OPTION
You will observe in this circuit there is no AGC in the Rx.
It was purposely omitted to keep the circuit
simple. [ did not find any difficulty in
listening to strong signals as a RF gain
control is provided. However, on local signals
there is dome distortion. For those of you
who would like to have an AGC, here is a
circuit, which ]: have, used (Fig. 3).
THE PRINCIPLE
OF THIS CIRCUIT IS:
The AF voltage from top end of the volume control is fed
to a 741 operational amp and/ts output/s
rectified and fed to the base of a 2N2222A.
The collector voltage is taken and is fed
to the bases of the first ЈF amp and the
1st IF amp. The emitter voltage is fed to
an ' meter, which is a 250, uA meter with
an appropriate resistor.
THE CONSTRUCTION
It is presumed that the builder of this circuit is having
the required basic knowledge of SSB generation,
good soldering practice etc. with a little
bit of general construction abilities. However,
here are a few tips to keep in mind while
constructing this rig.
1. Use a l0-watt soldering iron.
2. A good quality 60/40 lead with a resin
core must be used.
3. All RF inter connection are made by RG
174 coax cable.
4. A two core shielded cable must be used
for volume control.
5. A good quality two core shielded cable
must be used for the microphone.
6. All chassis to ground connections may
be made with barbed wire.
7. Use shortest length of coaxial cable
possible to connect TX output to re/ay and
relay to antenna socket.
The PCB diagram (actual size) and the component
layout are given in the Fig.:[1 and Fig.12
respectively. This PCB consists of the entire
TRX circuit including the VFO, which is
on left side bottom corner of the board.
The VFO section is to be cut out from the
main board in old version but now in the
new version it is designed in a separate
small PCB. This is mounted on the 'L' bracket
behind the front panel.
After constructing the power supply first go about winding all
the coils and the RFC's according the data
given in table-l. Then solder all the components
on the PCB and make all inter connections
including the +12v continuous supply to
the VFO, IF amp, Carrier Oscillator and
the Audio amp. Do not connect the VR and
VT supplies until you are ready to align.
TUNING
MECHANISM
Since my aim was to make this stage mechanically simple and
easy to construct with readily available
parts (without having to use a reduction/
slow motion drive) a PVC 2x tuning condenser
was used with a plastic drum 2" or 2.5"
diameter and a nylon dial cord with metal
spindle, Both the VFO PCB and the PVC 2x-gang
condenser are mounted side by side on the
'L' bracket as shown in the Fig-5. I have
been using this setup for the past six months
and did not find any difficulty in tuning
and neither did I face any backlash problems
so far.
POWER FET STAGE
Since we are feeding nearly 50 watts DC input to the [RF
830 with 45 volts on the drain and drawing
about 1 amp current, a good 3.5" x 3.5"
x 1.0" heat sink must be used to mount the
power FET. What ever the FET you use (with
a TO 220 case) it is to be fitted on the
heat sink with a mica insulator in between,
coated with silicon compound on either side
with a nylon feed through bush etc., as
shown in the figure-6. A window of 1 inch
square is cut in the back panel of the cabinet
after positioning the FET (fitted with heat
sink) closest to the point on the PCB where
the leads are to be connected. The shortest
possible flexible wire leads must be used
for connecting the FET pins to the PCB.
DO NOT CONNECT TIlE FET TO TIlE CIRCUIT
INITIALLY UNTIL ALL THE STAGES ARE ALIGNED.
CAUTION
A ferrite bead is inserted on the gate lead to the FET to
suppress any spurious oscillations etc.
Since most of the ferrite beads available
in the market are a bit thick/n diameter
be careful when you d/de it on the gate
lead, as there is a strong likelihood of
a contact with the drain lead. Therefore
the high voltage supply of the drain will
be fed to the gate and the FET would go
(2ЈT. Hence, the fo/lowing precautions are
to be taken. (As shown/n Fig. 7)
-
Bend
the gate and the source leads away from
the drain and slightly forward.
-
Slide
short plastic or PVC sleeves on the
gate lead, one before and ne after the
ferrite bead preventing its free movement.
A DC current meter is mounted on the front
panel to indicate the idling current and
the voice peak current. This will enable
'o to observe any drift in the idling current
or an q, ease in the current on voice peaks.
Due to ,n number of unknown reasons like
mismatch . A 1.5 Amp fuse is introduced
into the .- supply circuit as a protection
for the pow( F i' and the power supply.
THE ALIGNMENT
Generally, most of the amateurs do not have access to test
equipments, which makes the alignment a
bit difficult. One should have lots of patience
and procee owly and carefully. It is easier
if two sets ar : It at a time since one
set will act as a signal source for the
other. In addition, look for local ham who
has a commercial transceiver with a digital
frequency read out.
Before proceeding with the alignment, check the PCB for any possible
short circuit in the tracks due to an over
flow of lead while soldering and for any
other snags and lapses in the construction.
ALIGNING THE
Rx
Start by aligning the receiver of the first
set. Connect the +12v DC supply to the Rx
stages only i.e. V connections, touch the
top terminal of the volume control, and
listen for a hum in the speaker. (]:t is
presumed that you have connected the loud
speaker. Hi! When you hear the hum it means
that the LM 380 stage is OK.
CARRIER OSCILLATOR
For LSB when you use a BEL 9 MHz crystal filter the
carrier, oscillator crystal's frequency
is 9001.5 kHz First check whether the stage
is oscillating or not. By using commercial
TRx (FT-757 GX etc.,) remove the antenna
of the commercial TRx and connect a piece
of wire about one meter long to its antenna
socket and bring the PCB near the set. Bring
the wire nearer to the 9001,5 kHz crystal,
You should be able to hear a strong carrier
anywhere between 8995 kHz to 9010 kHz, Having
heard it make sure that it is from your
oscillator only by disconnecting the +12v
supply to PCB, :If the tone stops then the
test is ok. Now bring the frequency of the
crystal oscillator to 900.5 kHz by varying
the 220 PF trimmer capacitor in series.
if 220 PF trimmers are not available use
a 22 PF Philips green trimmer along with
a fixed disc capacitor parallel to it, the
value of which as required to bring the
oscillator to the desired frequency.
Now the oscillator of the second PCB also is tuned in the same
way (remember it was suggested that two
of you start the project at the same time).
Bring the carrier frequency of the second oscillator to 9001.0
kHz and use this second set as a signal
source for the alignment of the IF stages
of the first set.
ALIGNMENT STAGES
Take a piece of hookup wire about one foot long and connect
it to the base of the Q-8 (product
detector). Keep the other ends of the hook
up wire closer to the oscillator of the
second set which is being used as a signal
source. Advance the volume control and you
will hear a tone in the speaker. By turning
the trimmer of the second set's carrier
oscillator, the pitch of the sound will
vary. This is because the carrier of one
oscillator is beating with the carrier of
the other and produces a beat note, which
is the tone you hear. After hearing the
tone remove the hookup wire from the base
of (-8 and connect it to the base of Q-7.
You may not hear the tone in the speaker.
Turn the slug of L7 up and down until you
hear the tone and then peak it for maximum
sound. Now shift the hookup wire to the
base of (-6 and peak the slug of L-6 the
same way for a maximum sound in the speaker.
Again shift the hookup wire to the base
of Q-5 and carefully listen for the tone
in the speaker and peak slug of L-5. Since
the signal is now passing through the SSB
filter, the tone heard will be weak. Now
in the same position again peak up the slugs
of L-6 and L-7 by varying them finely for
maximum sound. This completes the alignment
of the 9 MHz IF stages. Alternatively if
you have a signal generator with a 9 MHz
signal you simply connect it in place of
the hookup wire and align all the stages
step by step as explained above.
ADJUSTING
VFO
If you are using a 9 MHz BEL filter
for 7 Mhz band the VFO is to tune between
2000-1900 kHz. If you are using a 10 MHz
ladder filters then your VFO will have to
tune between 3000-2900 kHz. So depending
on the filter you use the frequency of the
VFO must be set. Adjusting the slug of L-!
and increasing or decreasing the value of
the series capacitor i.e. 25 PF can vary
the frequency of the VFO. These checks are
carried out with the help of the commercial
TRx's digital frequency read out.
ALIGNING THE FRONT END OF Rx
Connect the antenna to the base Q-5
and tune the VFO for some signal and keep
it there. Now shift the antenna to the base
q-3 and adjust the slug of L-4 for maximum
audio. Finally shift the antenna to the
antenna terminal at L-2 and peak the slugs
of L-2 and L-3 for maximum signal. Having
come up this far re-align all the stages
in the Rx again with the help'of a weak
signal. This completes the alignment of
Po<. Now peak the slug of L-14 for maximum
back ground noise and leave it at that for
the time being.
ALIGNMENT OF TX
First disconnect the V, supply and connect
the +12v supply to VT line and check
all the DC voltages present on the collector,
emitter and the bases of the transistors
and the pins of [C's in the transmitter
circuit. If all the voltages are ok only
then proceed as follows.
Disconnect the secondary line winding of
L-.2 going to the gate of Q-16. Then connect
a 6 volts 0.2 Amp dial lamp bulb between
the secondary end of L-:I. 2 and the ground.
For tuning the exciter upto, the driver
stage this bulb will serve as a dummy load
and a visual indicator for the power output.
Also for unwanted outputs like self-oscillations,
parasitic oscillations etc., keep the VFO
frequency at about 1950 kHz (the TX carrier
output frequency will be about 7050 kHz).
Tune the commercial TRx to about 7050 kHz
with only a one-meter hookup wire for an
antenna and bringing it closer to the BD139
stage until you hear the carrier. Make sure
that the carrier is from your TX only by
switching it off. Then peak the L-9 slug
for maximum carrier output either by the
help of the reading in the 'S' meter of
the commercial TRx or simply by the maximum
audio level heard in the speaker. Proceed
to peak the L-10 slug also the same way.
By now, the bulb in the output of BD139
should be glowing at least slightly. Now
peak both the slugs of L-9 and L-10 again
for maximum brilliance of the bulb. As you
do this take the piece of antenna wire on
the Rx farther away from the transmitter
or reduce the RF gain control of the Rx
so that it does not over load and misguide
you while adjusting the slug of L-9 and
L-10. Finally again go back and adjust the
L-8 slug for maximum brilliance of the bulb
BALANCING
THE CARRIER
This part needs a lot of patience. First, turn the i K ohm
balancing preset from one side to the other.
Some where around the center there should
be some reduction in the carrier level seen
as a reduction in the brilliance of the
glowing bulb or as heard in the receiver.
Keep the preset at the setting where carrier
level is minimum. Now take a 22 PF disc
capacitor and connect it first at point
A as shown in figure-9, on the bottom side
of the PCB and see if the glow in the bulb
has become dim or bright. Remove the 22
PF disc from point A, connect it at point
B, and observe the bulb.
The effect should be the opposite of point
Connect the 22 PF disc capacitor either
at A or B where ever the carrier level is
reduced. Then again adjust the L- 8 slug
and the 1K preset to balance and nullifies
the carrier completely. If the carrier persists
then try using a 10 PF or 33 PF disc capacitor
instead of the 22 PF used. By altering the
value of the capacitor and simultaneously
varying the L-8 slug and the I K preset
you can null the carrier. Now connect the
microphone and the 1 Meg preset in the lC
circuit for maximum gain first (i.e. maximum
clockwise). [f you talk into the microphone
you should be able to hear it in the receiver
and the bulb should glow and flicker. When
you stop talking then the bulb should not
glow. lf the bulb is glowing slightly all
the time that means there is a spurious
signal out put.
Leak the carrier a little by turning the
I K preset to one side and you can see the
bulb glowing slightly. Then adjust the L-14
slug at the VFO out put for maximum brilliance
of the bulb. Now again balance the carrier
by turning back the 1k preset to its original
position where the carrier disappears. Now
if you talk into the microphone the bulb
should glow, flicker, and stop glowing when
you stop talking. This completes the balanced
modulator stage alignment.
ALIGNING
THE P.A. STAGE:
Connect a perfectly matched
7 MHz antenna to the output of the P.A.
Set the !0K bias preset to minimum by tuning
it completely clockwise to give zero bias
to the gate of the FET. Now connect the
leads of the FET to the circuit board..Se
carefu/ wh//e $olderinq theўe /ead$. ]t
is adv/$ab/e tO d/ўCorln't the ўo/derinq
/rQn from the ma/ns while soldering the
FET to the circuit board. Now apply voltage
to the drain of the FET via a DC current
meter. The drain current meter should show
only a flick of the needle, which is due
to the charging of the electrolytic capacitor
in the de-coupling circuit, Then onwards
the device should not draw any current and
the meter should not show any reading. Now
very slowly and carefully turn the :[Ok
bias preset anti-clockwise (while pressing
the P'I-I' and with out talking into the
microphone) to give positive bias to the
gate. Until about +2.5, volts to the gate
there may not be any increase in the drain
current. When the bias is about +3.5 volts
the drain current will rise to about 20
to 30 ma, depending upon the device used
and the drain voltage, Anyhow adjust the
standing current / idling current to about
20-30 ma and leave it at that, This gives
the best linearity when these power FET's
are used as linear amplifiers.
Now remove the dummy load (bulb) and connect
the RF output from the BD139 i.e.
the secondary of L-!2 to the P.A. stage.
Now switch on the TX, there may be Only
a slight in the drain current to say about
40-50 mA depending on the residual carrier
or hum etc. Now if you can speak into the
microphone with single tone the drain current
should increase to about 0.8 to 1.0 Ampere
depending upon the device used etc. Do not
speak too long into the microphone at this
stage, as the P.A. tank is not tuned. Now
connect a SWR/Power meter between the output
of the P.A. and the antenna.
While whistling into the microphone, adjust
the 70 PF trimmer for maximum power output
i.e. for maximum forward reading in the
SWR meter. Also after a few minutes, check
the heat generated at the heat sink it should
be warm and not hot.
Finally listening on the commercial TRX
adjust the I Meg microphone gain control
while speaking into microphone for maximum
and good quality audio without any distortions.
Now make a call and you are on the air.
:It is up to you to make any other adjustments
or add any refinements to the circuit.
ABOUT CRYSTAL
LADDER FILTER (FIG. 10)
For those
of you who want to build filter, it is suggested
that crystals of 8 to 10 MHz ranges be used
for best results. According to the original
article of F6BQP, for a 4 crystal ladder
filter one has to select all the four crystals
having same frequency, within !00 Hz of
each other on series resonant frequency.
The termination impedance of 800 to 1000
ohms is chosen for SSB filter. The values
of the capacitors in the circuit given in
Fig. !0 are calculated by the formula.
C= 1/(2(r)
Where
'f' is the crystal frequency in Hz
'R' is the termination impedance in ohms
'c' is the capacitance in farads,
(c is latter converted to Pico farads by
multiplying farads by 1000000000000).
For a 4-crystal ladder filter the formula
is:
Co = Cx 0.4142
C = Cx '1.82
C2 = CX 2.828.
Make a small PCB for mounting the crystals. Use as little copper
foil as possible and cut away the remaining
part of the PCB after construction of the
filter. Make a small metal box and fit the
PCB in it, Ground the box with a short lead.
For 10 MHz
NOTE:
This circuit is basically made for use on
40M band. However for 20 M use every thing
is same, only point stated here is that
IRF830 is not very ladder filter the value
of the capacitors work out approximately
as given in the figure.
ACKNOWLEDGEMENTS
I would like
to thank the following Hams VU2DDX, VU2TVR,
VU2AD, VU3VKS VU2TSF VU2S3V, and many Hams
for supplying the literature, other materials
etc., and assisting in this project. effective
on 20-M band. During experiment, it is found
that IRF830 at 30-40 volts gives 5-6 watts
output only. Therefore on 14 MHz IRF510
T- MOS FET is used.
RM - 96
Coil and RFC Data for 7 Mhz.
|
Coil No.
|
Pri. turns
|
Sec. turns
|
SWG
|
Remarks
|
L1
|
80
|
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L2
|
2
|
32
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L3
|
32
|
5
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L4
|
32
|
5
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L5
|
25
|
4
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L6
|
25
|
7
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L7
|
25
|
7
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L8
|
25
|
10 at the center
on primary
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L9
|
20
|
5
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L10
|
20 (tap at
10 turns from ground end
|
5 (at center
of the primary)
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L11
|
30
|
4
|
28
|
On T - 05 HFA
|
L12
|
6
|
4
|
28
|
Looped through
an 1/2" TV balun core
|
L13
|
7
|
10
|
18-22
|
T - 10 HFA
|
RFC's 250 micro Henry
20 turns of 28 SWG wire on T-05 HFA toroid
cores.
Winding Coils:
Start winding the primary
first from the bottom to the top end of
the former beginning from the cold end (i.e.
DC supply or ground end). Then the secondary
is wound over the primary starting again
from the bottom with the cold end. The coils
are close wound without any gap in between.
RM - 96
Coil and RFC Data for 14 Mhz.
|
Coil No.
|
Primary.
turns
|
Condenser
|
Secondary
turns
|
SWG
|
Remarks
|
L1
|
38
|
100 pf
|
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L2
|
2
|
60 pf
|
32
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L3
|
17
|
60 pf
|
4
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L4
|
17
|
60 pf
|
4
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L5
|
25
|
100 pf
|
4
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L6
|
25
|
100 pf
|
7
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L7
|
25
|
100 pf
|
7
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L8
|
25
|
100 pf
|
10
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L9
|
16
|
100 pf
|
5
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L10
|
16 (tap at
8 turns from ground end
|
100 pf
|
5
|
36
|
On 5 mm coil
former with 10mm Sq. base &
5 pins, with ferrite slug &
can
|
L11
|
30
|
-
|
4
|
28
|
On T - 05 HFA
|
L12
|
6
|
|
4
|
28
|
Looped through
an 1/2" TV balun core
|
L13
|
7
|
|
10
|
18-22
|
T - 10 HFA
|
RFC's 250 micro Henry
20 turns of 28 SWG wire on T-05 HFA toroid
cores.
Supporting articles to
this projects are available from vu3upx
-
NOTES ON RM 96 FINAL PA TANK COIL
-
PUSH-PULL AMPLIFIER FOR 14 MHz
Sourcing
-
The above
cabinet (with the frequency counter
and S- Meter) is available from OM
Pratap
in Bangalore. He can also supply fully
assembled kits.
-
Good Quality
Glass Epoxy PCBs and Circuit diagram
for the project are available from Mr.
Rao himself . His QSL info is Mr. R.
M. Rao, 66-10-29 /4, South Auchutapuram,
Kakinada, ANDHRA PRADESH - 533004, INDIA.
-
Coil set
for the project is available from Mr.
P. Mohan Rao of Ruby Electronics. His
QSL info is Ruby Electronics, Wahaib
Road, Tenali, Guntoor District, Andhra
Pradesh, INDIA
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Torrid
for projects are available from Ferrita
Enterprises, C-4, Industrial Estate,
Udyambag, Belgaum - 590008.
Thanks to VU2UPX
URL:
www.qsl.net/vu2upx
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