| Basically, it is a revised
version of the MT-Pluto, a double conversion PSN all-band transmitter. The
block diagram/system is almost the same, but there are the following
differences: ① The balanced modulator for SSB generation has been changed from 100KHz to 270KHz. ② The IF frequency was changed from 11.5MHz to 10.7MHz, and the IF mixer IC was changed from AN614 to SL6440. ③ The power control (PCON) has been changed from a photocoupler element to an AD603, widening the variable range. ④ The ACN carrier detection circuit has been changed from a three-stage FET to a two-stage FET, and the adjustment algorithm has been revised to improve accuracy. ⑤ The display format has been changed from LED to LCD, and power/carrier level indication has been added using an analog meter. ⑥ The Q of the 2-TONE oscillator circuit has been increased, further improving purity. ⑦ Changed from a 4-element bandpass filter to a 3-element bandpass filter. Please refer to the items on the TOP page for each block of 2TONE/Limiting Amplification/AFPSN/Low Pass Filter/High Pass Filter/Balanced Modulator/Mixer/Final Stage Amplifier/Band Pass Filter. The signal of the final stage output is similar to that of MT-Pluto. |
| Front | Back |
 |
 |
Main-Board  SCF-LPF Mixer   DDS  |
display AFPSN  HPF  power supply  |
| ACN Operation |
In analog PSN generators, the carrier
point is completely designed as a passband region, so the carrier
suppression of the balamoji becomes the carrier suppression value as it
is. Therefore, depending on the frequency, the stability of the balamoji
is required, and the carrier suppression ratio changes with time after
turning on the power and due to temperature dependence. This is considered
to be the biggest drawback of analog PSN. This method operates immediately
after turning on the power, and the carrier suppression is
maintenance-free all year round, regardless of summer or winter, even if
the room temperature rises. In terms of operation, it is basically the
same as MT-Pluto, but the method has been slightly changed to achieve even
greater stability. This adjustment is only performed during reception, and
the adjustment result value is fixed during transmission, which means that
if you transmit continuously for a long time, such as 1 or 2 hours, no
adjustment operation will be performed during that time. However, if you
switch to reception even once, the automatic adjustment will be completed
in about 5 seconds, so I don't think there is any problem with actual use.
The detection signal for automatic adjustment is as shown in the left
figure (solid line) (TP4 terminal of RF board). The dotted line is the
ideal detection characteristic, but MT-Pluto has a characteristic close to
this. If the gain of the carrier amplifier is increased, it approaches a
V-shaped characteristic and the result value (answer) will be one, but as
the amount of noise increases, the detection becomes unstable and it
becomes difficult to stabilize the ACN operation. If the gain is lowered,
it becomes a U-shaped characteristic, and the lower it is, the wider the
U-shaped width becomes and the detection circuit becomes stable, but the
range of the result value becomes wider and the accuracy decreases. In
this unit, points A and B (the lower shoulder and the upper shoulder) are
extracted, the midpoint between A and B is calculated, and the adjustment
value is the result value. This operation is performed 8 times on the LSB
side and 8 times on the USB side. Therefore, regardless of the mode being
LSB/USB/ISB, the LSB side/USB side is always performed, so there is no
problem in switching the mode immediately and operating it. |
| Meter drive |
During reception, the display shows full
scale = 100 to indicate carrier suppression. During transmission, the
display shows the power of the final stage output, and it is designed to
output 250mW at PCON = MAX. The meter is a 100uA meter that costs 1000
yen, with a newly created sticker attached to it, showing the power in the
bulbs. |
| Each carrier output |
VFO  |
10.7M  |
270K  |
SCFclock  |
2T signal at final stage 500mW  |