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Klaas Robers wrote:Harry, you should make the vertical scan somewhat larger, resistor lower or the potentiometer in the oscillator called "size". You might need to change the vertical position as well, that is the circuit going to -12 V. Then the circle becomes a real circle, which it should be. But I can imagine that you are happy because at least you can see things.
I also saw that the definition lines are fine and the gray blocks are all visible. Well done.
As you might know, there are two standards, a 50 Hz standard with line frequency 16 2/3 Hz (50 / 3) and an 60 Hz standard with a line frequency of 15 Hz (60/4). This is because som hum in the deflection is unavoidable. If you get SSTV from the other standard you have to readjust the scanning speeds. This is something you might want at the front panel. I coupled both, so this became a kind of "picture size" control. The oscillators should have a provision for that, which I designed in from the beginning.
Klaas Robers wrote:Harry, if you watch the testbeeld, then you see that the line sync is not always correct. This has to do with the setting of the potentiometer in the sync separator. May be also that it is wise to make the 1M resistor higher, 2M2 or even 4M7. That makes the hysteresis smaller. But the setting of the potentiometer is important and should be done carefully. It is one of the many controls that I have on my front panel and it is called "SYNC LEVEL". Sometimes it needs a small adjustment.
Klaas Robers wrote:Remarkable that these pictures are narrower than the testbeeld. However there are quite some strange standards out there.
What I mis Harry, is the sound. It is not uncommon to have an audio amplifier to the input signal, a set of computer speakers will do, so you can listen with the SSTV sound. Normally I could hear the differences in 16,6 Hz and 15 Hz signals. It is the repetition of the lines that you hear. In my Heathkit-like monitor I also built in a loudspeaker and a small amplifier.
Klaas Robers wrote:Yes, this is the kind of sound that I am used of for SSTV. You will see that you are soon familiarized with it.
Good luck with the extensions you are making.
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