27-01-2019, 10:11 AM
(This post was last modified: 27-01-2019, 10:17 AM by ppppenguin.)
Jac has supplied this diagram of the 567 line waveform. Working from the figures on the diagram:
Line scan frequency: 14175Hz
Line scan period: 70.55us (approx)
Line sync pulse width: 5.64us
Back porch: 1.41us
Front porch: 0.71us
These are very narrow front and back porches!
Field sync is 3 each of pre-eq pulses, broad pulses and post-eq pulses. Total field blanking length is not clear. I would suggest 22 lines as a first attempt.
Sync amplitude is 25% of total (as against 30% in System A, I etc) though Jac has said that 30% would give better sync. He has also said that raising black level above blanking (as done in NTSC) would help with flyback blanking on his 567 line TVs.
Vision modualtion is negative. Sound is FM with 4.5MHz spacing. This gives a rather narrow vision bandwidth compared with system I or even system B/G. For vision BW equivalent to system B/G the sound spacing should be about 5MHz.
Aspect ratio is 4:3.
Carrier frequencies are:
Vision : 63.25 MHz
Sound: 67.75 MHz.
Jac also said there are drift problems with the receiver whch has fixed tuning. Hence a fine tune on the converter would be useful. In Jac's own words:
"So a "center" frequency of 67.750 (/ 63.250) MHz and a total range in steps of 30 kHz from 67.600 (/63.100) to 67.900 (63.400) would be nice. Or an extra 2 staps below and above that. That could take care of the fine tuning aspect."
Likely pixel clock frequency at output is 13.5MHz * 14175/15625 = 12.2472MHz (exact)
Line scan frequency: 14175Hz
Line scan period: 70.55us (approx)
Line sync pulse width: 5.64us
Back porch: 1.41us
Front porch: 0.71us
These are very narrow front and back porches!
Field sync is 3 each of pre-eq pulses, broad pulses and post-eq pulses. Total field blanking length is not clear. I would suggest 22 lines as a first attempt.
Sync amplitude is 25% of total (as against 30% in System A, I etc) though Jac has said that 30% would give better sync. He has also said that raising black level above blanking (as done in NTSC) would help with flyback blanking on his 567 line TVs.
Vision modualtion is negative. Sound is FM with 4.5MHz spacing. This gives a rather narrow vision bandwidth compared with system I or even system B/G. For vision BW equivalent to system B/G the sound spacing should be about 5MHz.
Aspect ratio is 4:3.
Carrier frequencies are:
Vision : 63.25 MHz
Sound: 67.75 MHz.
Jac also said there are drift problems with the receiver whch has fixed tuning. Hence a fine tune on the converter would be useful. In Jac's own words:
"So a "center" frequency of 67.750 (/ 63.250) MHz and a total range in steps of 30 kHz from 67.600 (/63.100) to 67.900 (63.400) would be nice. Or an extra 2 staps below and above that. That could take care of the fine tuning aspect."
Likely pixel clock frequency at output is 13.5MHz * 14175/15625 = 12.2472MHz (exact)
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
