Just to remind possible readers of this blog, much of what I write is also a store of ideas and information that I want to be able to find again.
Lately I have not been so active with the soldering. However, since the first test of a modulator I have built another one on a new PCB. This one is a version shown on the website of F6HCC .
My version is simplified, as the idea was to use it with one of my MP3 players for modulating a test signal. This could be voice or (WBFM) modulated morse code.
As far as I know there is a kit out there for the F6HCC modulator, but I built my version on an experimental PCB, as modifications are a lot easier than on such a board.
Compared to the original F6HCC I omitted the (microphone) audio amplifier stage, assuming that the MP3 player should have sufficient output for modulating the HB100.
The initial test, like the test of the first modulator, shows that the output of the IC-821 transceiver when using the CW side tone, works nicely, and can be adjusted to a voltage deviation of +/-100mV at 4.9VDC. This looks like a good start. Now, the MP3 players seem to have a too low output for the purpose, at least for the modified F6HCC modulator. Now I have two options:
1) Add the second audio amplifier stage, or
2) Build the "digital" morse generator. This could be:
- a keyed CMOS oscillator, like the F6HCC one, but with a simple keying circuit. I have ordered some CMOS 4001 (NOR gates) IC. Amazing that I did not have any in my stock of components, but they are on the way.
- a simple beep-beep generator as described in the F6HCC modulator, or
- the CMOS oscillator with a microprocessor generating a repeated CW keying signal. Somewhere I should have a program for that in a PICAXE. The other option is using the Arduino. I think I found a program for a "beacon keyer" with dual output, a simple CW key output and a (side) tone output. With a (hardware or software) modification a simple input for a CW keyer, even a straight key, is possible. The microprocessor road will require me to learn to set up programming of the processors, and I have to learn some programming, too. The PICAXE with the BASIC programming language that I have a decent grasp of, is probably the simplest way, and the smallest of the PICAXE processors is an 8-pin DIL package, so there is plenty of space on the PCB to have that as well as the keyed oscillator.
It looks like I will be building a third modulator PCB on a slightly larger PCB, because this time I want the full circuit on the PCB, with space to spare. The very first modulator used an external AF amplifier for modulation, but I want to avoid that for mechanical simplicity - and also avoid lots of wires between PCBs, switches etc.
The end result will have the microphone amplification, so it is likely to be usable for the MP3 player, too.
Later, I expect to make myself a "WBFM modulated CW beacon", that I can set up in the garden and test the range of the setup. That could be a simplified version using the microprocessor keyer/audio generator and the F6FCC modulator without the extra audio amplification.
The microprocessor should also be usable as a true CW beacon keyer.
Oh, yes, I do need to (re)learn some programming and get the things set up for PICAXE and/or Arduino programming. Everything takes time.
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