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RM - 96 II - 14Mhz
Version
By: S. Rama Mohan Rao ,
VU2RM
RM 96
- 7 MHz transceiver was introduced to
the fellow Hams in year 1996. Ever since
listening on the band, many Hams have
built and are working satisfactorily, if
not excellent, keeping in view that the
aim was and is to keep the cost Low.
From
the year 2000, many builders are
swinging to build it for 14 MHz. Some
got the coil data, some do not have.
Therefore, in this article data is given
for 14 MHz. Constant experimentation, to
improve the performance of the set quite
a changes, have been made. It is that
during experimentation for higher output
of TX, compared to IRF830 etc,. I
found that the device IRF510 is best
suited by virtue of its Low CISS & COSS
value. With 30 volts, it is giving about
20 to 25 watts output. However, any
self-oscillator or over drive etc. it is
easy to burn it. 5o, get a proper
circuit to make the device withstand the
beating. I have now used IRF840. !t is
standing the beating and with 50 V on
drain, gives 20 to 22 watts output. A
measurement on spurious output was made
and it is found the spurious output is
27 dB below the peak power output.
I have
also experimented on the balanced
modulator. Many of my fellow Ham friends
asked me why I have not thought of
MC1496 or NE602 IC's etc. So, I have
wired up two circuits on general-purpose
boards using MC1496 and NE602. I have
simply replaced by giving external
connections and used for 3 days each PCB
in place of the two diodes balanced
modulator. None of them have reported
any change in the modulation quality
etc. So I have removed and restored back
the two diodes balanced modulator.
Then I
have used these boards in the TX mixer
circuit. Yes, there is a difference in
the quality of the signal. So, now I
wired one MC1496 circuit on the general
purpose PCB and removed all the
components that are used for BF194 TX
mixer. The new PCB size about 1"x1" is
standing up near the edge by the side of
L 9. If I make a new version, of RM 96
PCB. I intend incorporate ME 1496
circuit in Transmit mixer stage.
Therefore, that is all, for now.
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Data |
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COIL
AND TRANSFORMERS for 9
Mhz |
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9 Mhz |
Pri. |
Sec. |
SWG |
|
L 5 |
25 |
4 |
36 |
|
L 6 |
25 |
7 |
36 |
|
L7 |
25 |
7 |
36 |
|
L 8 |
25 |
10 |
36 |
|
L 1 |
75 |
|
36 |
|
L 14 |
45 |
|
36 |
|
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Data |
|
For 10
Mhz. Filter |
|
10 Mhz |
Pri. |
Sec. |
SWG |
|
L 5 |
20 |
4 |
36 |
|
L 6 |
20 |
7 |
36 |
|
L 7 |
20 |
7 |
36 |
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L 8 |
20 |
10 |
36 |
|
L 1 |
35 |
|
36 |
|
L 14 |
40 |
8 |
36 |
|
Wind
seconday at center for L
8 & L 10. The rest at,
bottom cold end. |
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Data |
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TOROIDS |
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|
Pri. |
Sec. |
SWG |
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L 11 |
16 |
4 |
O.5"
toroid 26 SWG |
|
L 12 |
6 |
4 |
1 cm
balun core 26 SWG |
|
L 13 |
4 (18
SWG) |
6
(Hookup wire single
strand) |
4 Nos
of 1/2" toroid |
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L 12
and L 13 are to be wound
similar way. |
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