NBTV transmissions

Forum for discussion of narrow-bandwidth mechanical television

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Postby Viewmaster » Mon Oct 15, 2012 6:30 pm

It would be both club CD's for testing and o/p from Gary's applications.
But please don't spend time on this.

I will need to recreate that missing frame pulse, but your circuit looks to be too complex for me. As your circuit was mentioned on the NIPTRIX post I thought I would have a look at it.

I also have Peter Smith's frame pulse inserter circuit in recent newsletter and also a one chip missing pulse inserter by Jeremy some time ago. ( newsletter 21/1) Neither as accurate as yours, no doubt.

Steve , I do hope that you will not be offended in my remarks. Many guys here seem to understand all about PIC and all the rest, but I can never get my head around much above ohms law. :)

added.....I always use the very old club sync seperator circuit which doesn't have the clamp line. So additionally if I built yours it would mean my going a new way and I have enough trouble at present with the NIPTRIX
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Postby gary » Mon Oct 15, 2012 7:21 pm

Just for interest's sake there is also Klaas's circuit for which there are PCB boards available from the club. It has both line and frame pulse extraction. Les Robotham sent me a couple of PCBs so I made one up - seems to work well - I only used the line syncs - but have noted the frame pulse being present.

I am pretty sure the information about it is under the "members only" section of the NBTVA web site.
Last edited by gary on Mon Oct 15, 2012 9:06 pm, edited 1 time in total.

Postby Steve Anderson » Mon Oct 15, 2012 9:05 pm

Albert, I'll pick this up in the original thread, "NBTV without any moving parts. THE NIPTRIX"
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Postby Klaas Robers » Sat Oct 27, 2012 1:35 am

The sync separator board, of which a PCB is available via Vic Brown, extracts indeed line pulses and a frame pulse. A description is in the NBTV Handbook, current version, but you may also find that on the web: www.nbtv.org in the clubshop section. However the frame pulse comes half way line 1 and not on the beginning of line 1. This is not always a problem.

If you want to have the frame pulse at a different place then you may canibalize the EPROM picture generator PCB. In the NBTV handbook and again on NBTV.org you may read how to do that. The trick is that the addressing of the EPROM is genlockable to the incoming sync, the syncs of the mentioned separator board. So you have to build that anyway. The EPROM addressing is free running on a cristal oscillator and you may program whatever you want in the EPROM.

So you may program a continuously running line pulse, on all lines, also on line 1, and a frame pulse with the duration and position that you want, and six pulses or patterns more as there are 8 bits to program. In this case you have not to build the Digital to analogue converter. But that is all documented!
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