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KPC-II.4
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1992-09-15
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KPC-II.4
You have a KPC-II, you like it and everything is ok until you want to do
HF with it, particulary with a receiver without digital readout.
Here is a design of mine for tuning the receiver more easily.
The RCV LED will light if the tuning is approximately on frequency, but is it
right on frequency ?
How many times have you seen this LED on with nothing happening on the screen.
This LED does not indicate if the mark and the space are exactly on the correct
frequency at the demodulator.
The circuit here is based on the alternating of the MARK and the SPACE tones.
When the RCV led goes on, it permits access to two new LEDS. The first one
shows when the MARK is on and the other shows when the SPACE is on. When both
leds light at the same level, you are right on frequency and you should now
see data on the screen.
As you can see on the following schematic, the only connections at the 7910 IC
of the KPC-II are pins 25, 26, 10, Vcc pin 2, and Ground.
┌───────────┐
U1 pin 26 │ │ + 5
>─┬────────────1───┤ ├──14───┘
│ │ 7 │
│ ┌────────2───┤ ├──13───
│ │ │ 4 │
│ └────────3───┤ ├──12───
│ │ 0 │
┌───┼────────────4───┤ ├──11──────────────────────┐
│ │ │ 4 │ │
│ └────────────5───┤ ├──10──────────────────────┼──┐
│ │ │ U1 pin 25 │ │
│ ┌─────────6───┤ ├──9──────────────< │ │
│ │ │ │ │ │
│ │ ┌──7───┤ ├──8───────────────────────┘ │
│ │ ■ └───────────┘ │
│ │ G │
│ │ │
│ │ │
│ │ ┌────────────┐ ┌──────┬┐ │
│ └───────┤ 470 Ohms ├────────┤ LED1 │├─────────┐ │
│ └────────────┘ └──────┴┘ │ │
│ ├───────┘
│ ┌─────────────┐ ┌──────┬┐ │
└──────────────┤ 470 Ohms ├───────┤ LED2 │├─────────┘
└─────────────┘ └──────┴┘
You should now be able to receive HF packets even with a KPC-II.
73 Claude VE2SR @ VE2GPQ.pq.can.na