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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 22nd Jul 2004, 1:29 pm   #1
tubesrule
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Default Specs and Feedback needed for converter

Hello all,
Much progress has been made on the PAL/SECAM version of the converter. All the electronic standards have been coded and verified. Which brings up the first request; does anyone have the original timing diagrams for the 441/25i, 240/25p or 180/25p standards? I have all the rest of them, and for now based the 441 standard off the 405, and the 240 and 180 off the RCA ones, but it would be nice to have the actual timing for them.
Also, for the 819, 441 and 405 standards I added a more modern equalization/serration vertical sync pulse rather then the simple broad pulses of the original standard. This will provide a much better and more stable interlace, and be compatible with all equipment. Which would most people rather see, this method or the original pulses? For myself, sometimes I like to go by the book, deficiencies and all, to experience what it would have actually been like, but sometimes it nice to just be able to fully enjoy the set.
Now it's on to the mechanical standards, which brings up the other request; what standards make the most sense for European use? I believe the Baird 30/12.5, TaKaDe 30/12.5, and NBTV 32/12.5 are all good choices. Beyond these I am not familiar with what other standards were in use in Europe, and I don't know what the possibilities are for using American sets in Europe. Most American sets used Mains synchronized motors, so assuming they would run at 50Hz, the frame rates would need to be so adjusted. This is what I would propose to do at this point for the other standards.

Thanks,
Darryl

PS I'll be gone for a few days and won't be able to respond until next week.
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Old 29th Jul 2004, 9:37 am   #2
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Default Re: Specs and Feedback needed for converter

Good morning Darryl

It is great that you made 819 too :.

Yes I think it is better to use equilizing pulses
at the V- sync.
Did you try the reduced level V- sync ?
(I discribed it in this forum)
Please tell me about your results!

I can not help you with the timings.
I watched in google and there are different
timings for one standard .
It seems in standard converters they calculate
down (or up 819) from the 625 standard 8).

Jeffrey is the expert for 405 .

But it is not so importand to have the exact standard
a 405 set works with 441 and vise versa .

Kind regards

Darius
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Old 29th Jul 2004, 12:47 pm   #3
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Default Re: Specs and Feedback needed for converter

Hi Darius,
I'm not sure about the v-sync level. Can you point me to a link in the forum where you discussed this?
Thank you for the feedback on the eq pulses. It appears that everyone also feels this is a good idea to modify the original specs to include these. I don't think there will be any incompatibilities with any equipment by doing this, and will it will greatly aid in interlacing the image.
I've have gotten some wonderful feedback on the timing for the standards, and believe I have everything now.

Thanks again for all you help,
Darryl
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Old 29th Jul 2004, 1:35 pm   #4
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Default Re: Specs and Feedback needed for converter

I think that Darius varied the amplitude of the V sync pulses (as compared to the H sync pulses) and found that it improved V sync.

I am not convinced that this is a good idea though it was something that Darius could do easily in his design. Since there are no counter chains in his design it is not easy to generate a complex V sync with equalising pulses.

I support the use of EQ pulses in a 405 line signal and believe that they should have been incorporated in the broadcast signal. Reading some early technical papers, possibly from as early as 1938, I think there was opposition to EQ pulses as being totally unnecessary and just taking up potentially active lines for no benefit.

The ideal would be to have a switch to turn the EQ pulses on or off. Then we can make our own judgement as to their effect.
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Old 29th Jul 2004, 2:24 pm   #5
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Default Re: Specs and Feedback needed for converter

Hi Jeff,
Thanks for the info on the v-sync level, and on the eq pulses. That is very interesting why the pulses were not added in the early days, but it sounds like it may have been the right choice at the time. I agree that a switch to enable or disable the eq pulses would be great, and that is how I was going to approach it, but I am running out of both fpga pins, and real estate on the board, so I don't think I can sneak another switch in anywhere. I think for now I will add them, and see how that goes.

Thanks,
Darryl
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Old 29th Jul 2004, 2:56 pm   #6
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Default Re: Specs and Feedback needed for converter

Hi Darryl
I moved it up in the forum for you.

" new V-sync for a better picture "

Maybe it makes sens to make this in the modulator.

I don't think it makes sense to make a switch
for the equalizing pulses.

@Jeffrey of course I have the equalization pulses
they are convertet as everything else in a line .

Kind regards

Darius

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Old 29th Jul 2004, 4:52 pm   #7
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Default Re: Specs and Feedback needed for converter

Hello all

I feel that the 405-line standard should be preserved as it existed throughout its service life.

The 405-line sync waveform was maintaned in its original form even when both
BBC and ITA switched to using standards converters to supply the service to the public.

There are small deviations from the original specs, some changes seem to have happened because of
the division down from a master clock, making pulses timed to the nearest clock edge and with the clock
frequencies used then, that ment a few 100's of ns here and there, the field blanking period also increased.

I had the same problem with my mere 10 MHz sampling clock, the BBC (PYE) analogue converter was only a bit higher at 11MHz.

But the BBC and ITA never fiddled with the sync to " improve the interlace " , it's true that some sets
did not interlace as well as others, but that would have been down to cost and design issues.

Set designers sometimes went to great lengths to get good interlace, with the addition of various
clipper and trigger circuits, maybe even adding an extra valve to the sync circuits.

The later large screen ( >12 inch) sets late 50's to 60's dont seem to do to badly on the original
sync waveform.

And remember it was the programmes you watched not the Test Card or the lines!,
it's ok to nit-pick about the lack of interlace or frame (oops I mean Field!) scan jitters, but the
standard should be maintained as it was, with nothing added, its bad anough that they (BBC etc..)
take away some lines of the pictue for the letterboxing of most programmes today, making our 405-line
pictures have even less lines.

It may be best to have it (the corruption of the 405 sync) switchable so a few people can say
" oh look at the quality of the interlace! "

And while I'm at it (whinging that is..) whats the sudden interest in all these other line standards,
441, 362.5, etc.. it's supposed to be " 405 Alive " cant we keep at least one thing British!
I know there was the Baird electronic system but with only about 4.5 sets in the world and most
of those are in America.

In my small way I have kept a few people (and one American export) and their 405-line sets happy,
orders for my Domino (Blatent advertising!!) converter have slowed to a dry riverbed, so I dont know
how many UK 405-line television collectors will go for the Aurora converter but I wish you well in your endeavours.

all the best
Malcolm

(now on only one Prozac a day!)

(please do not PM me, email is best..)
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Old 29th Jul 2004, 6:08 pm   #8
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Default Re: Specs and Feedback needed for converter

Hi all , hi Malcolm

In school they toled me:

On the transmitter side they do there very best they
can to bring a good quality picture on the screen
of the TV.
So the TV can be easy and cheep and you get a
good picture.

Now they make the transmitter cheep and the
customer must buy d-boxes and so on to get
a (good?) picture.
This is vise versa the vintage way.

So you follow an old tradition if you try to give your
TV the best signal you can .

If you convert actual programms the program contens is
not origin.
And you must suspress TXT etc.
So it does not matter if you make equalization pulses.

Original 405 you get only from a camera.
This is my oppinion.

I agree with Malcolm.
If I want to watch
a film like TV goes to London it must be in the
origin 405 standard.
I have a 405 VHS copy of this film
and I can see that it is converted.
I don't like this.

I am happy that Darryl made a multi standard coverter
because other standards have a chance to survieve too.

When I find a french 819 (in ebay)
I'll by Darryl's.

Sorry for my bad english,

kind regards

Darius

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Old 30th Jul 2004, 3:17 am   #9
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Default Re: Specs and Feedback needed for converter

Hello Malcolm,

I tend to be a purist at heart as well, and would rather see something represent the original as close as possible, shortcomings and all, but wanted to get feedback on which would be more appropriate.

I was looking for feedback on as many standards as there would be interest for, and thought there would be no better place than this forum to find out, and get myself educated as to what the different standards were about, but I could take this offline if it is inappropriate here. I know threads can meander in directions no one had anticipated. It's really more about the personal challenge and satisfaction of learning about, and implementing these standards, with the hope they will benefit someone someday.

I also wanted to make note that this converter is not associated with Aurora in any way. I work for them, and they just provided me a page to put the info up on, and since I am terrible at coming up with names for things, I just stuck that name up there. I have done the converter completely in my spare time (of which I seem to have less every year as I get older ). My original intent was to make a couple for myself and a few friends, but was asked by people on both sides of the pond if I could make a few more. Since I don't have the time available to make any real number of them by hand, I was looking to find out if there was enough interest to have a local assembler build them, and pass them on for the price they charge. I know if the interest is low, and the number they would make is low, the price would be much to high to be of interest.

Take care,
Darryl
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Old 30th Jul 2004, 8:01 am   #10
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Default Re: Specs and Feedback needed for converter

I understand Malcolm's feelings especially as he put an enormous amount of work into the Domino converter. I think I persuaded Malcolm to use a framestore based design. I saw it being developed, witnessed its birth and reviewed the first production unit for the BVWS Bulletin. Remember that Malcolm, unlike Darryl, is not a design professional. I guess (please tell me if I'm wrong) that although the design is done in his spare time, Darryl has access to the full suite of Xilinx design tools at work and the experience to use them effectively.

This makes the Domino a great achievement indeed and it still stands alone as the only 405 converter that you can buy right now. (I am overlooking the last few Pineapple units that were recently sold)

I think Malcolm is right in stating that he has now supplied the majority of the UK demand but if others want to enter the market they are free to do so. Unlike the recent resurrection of the Pineapple converter Darryl's design definitely has something new to offer. Notably its flexibility and reprogrammability. It may even be capable of doing 405 NTSC for that handful of people who have experimental receivers for that standard. See this thread for the rather technical discussion that we've had.

https://www.vintage-radio.net/forum/...read.php?t=956

I'm sure that there are a few people in the forum who will understand what we're talking about (certainly Evingar - any others out there?) If you get fed up with Darryl and I discussing this sort of thing (Xilinx, dual port RAM etc etc) in the open forum then we could do it privately.

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Old 30th Jul 2004, 1:45 pm   #11
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Default Re: Specs and Feedback needed for converter

Good points Jeff. While the converter may not be Aurora's, as you point out access to the knowledge and tools are, without which this wouldn't have been possible. In the end, this style design is more of a software effort than a hardware one anyway. Hat's off to people like Malcolm, Darius, and others who have, and continue to design and build converters making it possible to use these old sets, and get people interested in the hobby. We are still represented in such small numbers compared to the radio hobbiest's, making such a personal challenge all the more important.
And if Jeff and I do get to boring to readers here, or to far off topic, please let us know. Sometimes it's hard to know when you've wondered off.

Darryl
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Old 30th Jul 2004, 2:29 pm   #12
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Default Re: Specs and Feedback needed for converter

It is very kind of you Darryl
that you discuss with Jeffrey your converter here in the forum.
For me it is very interesting to learn something about
the digital way of standard conversation.
At the moment I really don't understand everything,
but be sure I will in the near future .

Hope the forum administrators will save this .

Please keep the discussion around converters
alive and don't go to personal mails.

Kind regards

Darius
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Old 2nd Aug 2004, 12:25 am   #13
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Default Re: Specs and Feedback needed for converter

Yes i think it should continue as well.
with all this brain power we soon will have the ultimate
sooper dooper converter.
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Old 2nd Aug 2004, 8:34 am   #14
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Default Re: Specs and Feedback needed for converter

Just a reminder that while Darryl's converter is undoubtedly a superb device which goes far beyond any previous design, we haven't actually seen it this side of the pond yet. I hope that I will be able to review it for the BVWS Bulletin as I have done with all previous converters that were commercially available.

One thing that's missing for the ordinary user is a modulator. I realise that it could be tricky to design a modulator to cover all the possible standards (Darryl, how about direct digital synthesis )

Those of you who are BATC members will be able to see a photo of Darryl, his converter and lots of other interesting stuff on pp26-30 of CQTV207.
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Old 2nd Aug 2004, 9:47 am   #15
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Default Re: Specs and Feedback needed for converter

Good morning

I am sure a multistandard modulator will be a compromise solution .

Look at 625.
The DF modulators used today make trouble in the
sound if you use a parallel sound set and vise versa .

If you want a perfect picture and sound you need
a special modulator for every standard .

So I think for those who only use 405 and want to
buy something compleatly finished,
Malcolm's " plug and play " is still the right choise .

For the others there are kit's avalible or they
can build there own modulator like me .

I can build a finished modulator for every standard
but it will be very expensive and good, of course.

Kind regards

Darius

Last edited by Station X; 30th Dec 2004 at 5:05 pm. Reason: Import
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Old 2nd Aug 2004, 2:03 pm   #16
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Default Re: Specs and Feedback needed for converter

Jeff/Darius,
I had thought of putting a PLL synthesized modulator right in to the converter, so that it would follow the standards selector switch, and modulate at an appropriate frequency, but it would be hard to get the RF connector in there, and I was worried that many times you might want different frequencies for the same standard, like channel 1 or 4 for 405. I was eventually going to make a stand alone modulator that just had a selector switch like the conveter, and you could choose from many different frequencies and modulation schemes. This way you would choose your standard, and then your modulator.

BTW, does anyone know where I could find a high quality image of Test Card C? I want to put up some images from the 405 output, but havne't been able to find a good quality version of this.

Thanks,
Darryl
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Old 2nd Aug 2004, 2:41 pm   #17
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Default Re: Specs and Feedback needed for converter

Gidday Darryl

Note that the output of the modulator is on a low
VHF frequency and you can catch noise from the
synthesizer. It is good to make it stand alone,
because the logic in your converter makes noise
too.
The synthesized oscillators have much phase noise
(every vco has this) so you will decrease the quality
of the converter.
The different TV systems have all their advantages
which can be pointed out in a special modulator
stage . With a universal modulator you can not do
this and it will allways be a compromise for everything .

I think for GB it is a good solution to have a modulator
that makes London and Birmingham at the same
time. Then you can connect all TV's on it and you don't
have to switch and connect around .

Kind regards

Darius
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Old 2nd Aug 2004, 5:08 pm   #18
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Default Re: Specs and Feedback needed for converter

Hi Darius,
I hadn't actually looked into the specifics much, so these are good things to keep in mind. Maybe just picking the most popular ones, and creating individual circuits, but packaging it in the same housing could work.

Cheers,
Darryl
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Old 2nd Aug 2004, 10:28 pm   #19
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Default Re: Specs and Feedback needed for converter

Quote:
BTW, does anyone know where I could find a high quality image of Test Card C? I want to put up some images from the 405 output, but havne't been able to find a good quality version of this.

Thanks,
Darryl
http://www.murphy-radio.co.uk/gallery/

It looks like Dave Grant would be a good person to contact.

Peter.

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Old 3rd Aug 2004, 12:38 pm   #20
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Default Re: Specs and Feedback needed for converter

Many thanks to all on the Test Card links. I now have a nice image it.

Darryl
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