Cathode modulation

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Cathode modulation

Postby Harry Dalek » Mon Feb 27, 2017 6:39 pm

I just remembered some where in control grid modulation its been swapped to cathode modulation well Klaas is a good negotiator.
So better make a new topic as the thing is built and almost read for testing .

I need Klass for you to have a look at the drawn schematic i think its pretty much what you mentioned in your last post well i hope i have got it right ! so i have drawn it up...my only worry is my general purpose BC549 BC558 transistor substitutes are good enough.
Also there were some resistor changes you mentioned for a 12 volt supply i was not sure if there will be a problem on the positive 12 side well we could give it a go and see as its together now .
BTW i did make as you see the 68k a higher wattage resistor also made the 33k one as i had it handy .
I will wait to hear back before hooking up the power supply in case i need to make changes .
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
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Re: Cathode modulation

Postby Klaas Robers » Mon Feb 27, 2017 8:32 pm

Yes Harry, however you may remove the 600 ohm at the input That is / was just to have the optimal loading resistor for the passive (coils and capacitors) filters. For the active filters that you built this resistor is of no use. Further you understood perfectly what I wrote.

A few remarks:
- The resistor in series with the trimming potentiometer of 1k should be 2k2 and not 22k.
- For the 12 volt supply you may also make it 4k7, but the original 2k2 also works.
- Don't forget to ground the blanking input pin. This input is for fly back suppression. We should see how you can get that signal from your deflection amplifiers or saw tooth generators.
- I have seen your circuit on the PCB. In the end you might want to have the potentiometers for contrast and brightness on the front of your monitor. But to begin with the trimming potentiometers are fine.

Harry, I don't understand why you don't use the test frame, the circle with the squares around and the grey blocks and line blocks inside, to test your monitor in construction. This gives all you want to see in one test frame. Should I send you a wav file?

Image

Edited: You may find a .wav-file in the now locked "Retro SSTV" thread on page 8. It is in 8 kHz 8 bits.
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Re: Cathode modulation

Postby Harry Dalek » Mon Feb 27, 2017 9:32 pm

Klaas Robers wrote:Yes Harry, however you may remove the 600 ohm at the input That is / was just to have the optimal loading resistor for the passive (coils and capacitors) filters. For the active filters that you built this resistor is of no use. Further you understood perfectly what I wrote.


Thanks Klaas OK no problems i will remove the 600ohm resistor .

A few remarks:
- The resistor in series with the trimming potentiometer of 1k should be 2k2 and not 22k.


Oh it was a 2.2 k thank goodness forgot to put the dot between the twos :roll:

- For the 12 volt supply you may also make it 4k7, but the original 2k2 also works.


OK i will see how it gos..

- Don't forget to ground the blanking input pin. This input is for fly back suppression. We should see how you can get that signal from your deflection amplifiers or saw tooth generators.


Yes since i have a different circuit that will be something to work out but yes i will ground the blanking input when i power up and test .

- I have seen your circuit on the PCB. In the end you might want to have the potentiometers for contrast and brightness on the front of your monitor. But to begin with the trimming potentiometers are fine.


OH i have the pots on the monitor case panel i have to wire the brightness control up ..now with your new circuit ...the focus is already wired up i forgot about the timmers might be a panel control yep i will use them for now and wire up a panel pot later on .

Harry, I don't understand why you don't use the test frame, the circle with the squares around and the grey blocks and line blocks inside, to test your monitor in construction. This gives all you want to see in one test frame. Should I send you a wav file?

Image

Edited: You may find a .wav-file in the now locked "Retro SSTV" thread on page 8. It is in 8 kHz 8 bits.
[/quote]

OH i forgot about that Klaas i remember there were test photos up there forgot about this test card i will look for it !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Cathode modulation

Postby Andrew Davie » Mon Feb 27, 2017 9:45 pm

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Re: Cathode modulation

Postby Klaas Robers » Mon Feb 27, 2017 9:58 pm

Sorry, my fault.

During the Retro SSTV thread I recalibrated my SSTV FM audio modulator. The first Testbeeld is off frequency. In page 10 of the same thread there is a .wav-file Testbeeld2, which is better and which Steve also aprooved.

Andrew, can you replace the direct link? Thank you very much.
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Re: Cathode modulation

Postby Andrew Davie » Mon Feb 27, 2017 10:25 pm

Klaas Robers wrote:Andrew, can you replace the direct link? Thank you very much.


Yup. I have changed it to point to the original post, so those interested can see the context and other files.
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