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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 20th Oct 2022, 2:56 pm   #1
inaxeon
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Default My (mostly Philips) Analogue telly broadcast setup

Hey folks

Here's an update on the analogue television broadcast setup I'm building I mentioned previously in another thread.

When I say "broadcast" I really mean the largest and heaviest home A/V modulator probably ever built. Some of it is working now. Details if anyone's interested:

(Full sized picture)
https://xpander.mattmillman.com/file...p_first_go.jpg

Video source:
* PM5644 colour pattern generator (presently using it as an overpriced 1KHz tone generator)
* PM5631 colour generator - Generating the pattern seen on screen in the photo

Modulation:
* PM5680MS: Multistandard modulator. Technically this particular SKU is test equipment. The broadcast (non-test) PM5680 has at least 20 different SKUs. Not much chance I was going to find one of the appropriate configuration so had to compromise.
* PM5687: NICAM Encoder / Modulator (B/G standard)
* PM5686A: NICAM Modulator (I standard)

Channel converter:
* Eiden 4220C-006: A mystery bit of equipment (can't find a spec or manual) I took a punt on from eBay. I got lucky. It works perfectly.

Receiver (embarrassingly I don't actually own an analogue television):
* Arcam Delta 150: NICAM / terrestrial receiver
* And a makeshift LCD TV to cap it off

WORKING SO FAR:
* Video / Analogue audio transmitted over cable on UHF Channel 21 (as pictured).

THINGS LEFT TO FIGURE OUT:
* How to adjust modulation depth. There is a thread discussing this here: https://www.vintage-radio.net/forum/...d.php?t=194932 but I haven't been back to this topic yet. Too much going on at the moment.
* NICAM - Combine NICAM IF with Vision / audio IF, adjust levels etc. There's a bunch of bits involved in this. Adapters, attenuators, directional coupler blah blah. I think I have all of the components I need. Just need to crack on with it.
* Sort out a colour test card for the PM5644. Work in progress.
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Old 2nd Nov 2022, 12:51 pm   #2
inaxeon
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Another update. It's all working now:

https://xpander.mattmillman.com/file...ll_working.jpg

* NICAM is working
* Pattern generator sorted. Now have colour

The hideous rendition of the colours sent me on a bit of a wild goose chase. It turns out that's actually a fault inside of the Arcam Delta receiver. For some reason it is losing most of the chrominance signal. A second receiver I tried doesn't have the problem.

On a side note - I noticed there was a discussion about the legality of "TV senders" well actually I had one of those (purchased from a UK retailer) and I've attached a couple of spectrum analyser shots of its output versus this setup.

The TV sender transmitting a DSB for the video carrier, and also mirror image of the audio carrier occupying two UHF channels. That looks like a good enough reason to ban such devices to me.

The setup I show here outputs a beautiful 8 MHz VSB with no artefacts from 0 Hz to to 3 GHz. Very happy with that! Anyways. That's enough on this topic.
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Old 16th Nov 2022, 2:08 am   #3
Synchrodyne
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Most impressive!

I was thinking that a professional receiver would better complement the “transmission equipment”. On the other hand, if the objective is to see what representative domestic receiving equipment makes of a broadcast-quality transmission, then I guess that the Arcam Delta 150 is a good choice.

As far as I know the Delta used a fairly standard domestic TV SAWF and QSS IC set, with standard quasi-synchronous vision demodulation (no Nyquist slope cancellation, etc.), and also with quasi-synchronous type QSS. From what I have read (although not necessarily with in-depth understanding) on these aspects, PLL demodulation, and even then with phase correction feedback, is needed to match fully split sound in SNR terms.


Cheers,
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Old 17th Nov 2022, 11:29 am   #4
Tester.
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Impressive —and enviable— indeed.
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Old 5th Dec 2022, 4:31 pm   #5
inaxeon
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Back for more. This time I've added Zweikanalton to the setup using a Philips PM5588. The PM5680 technically does have the option of it however it is not fitted in this particular unit.

Full sized image:
https://xpander.mattmillman.com/file...th_zweiton.jpg

I spent hours and hours trying to make it work. My TV was point blank refusing to accept my stereo offering despite the amplitude and frequencies of the carriers being correct.

In the end after having re-read the Zweiton spec I noticed that the pilot tone was supposed to be on the second carrier, but I was seeing it on the first carrier? Long story short I discovered that some clever cloggs inserted the modulator modules into the unit swapped over. Easy fix. To be fair they do look identical.

Anyway I'll probably throw together some YouTube vids on this setup in the new year. Much more fun than looking at pictures.
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Old 5th Dec 2022, 8:50 pm   #6
inaxeon
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Quote:
Originally Posted by Synchrodyne View Post
As far as I know the Delta used a fairly standard domestic TV SAWF and QSS IC set
Sorry been a while since I visited these forums! Yes it has a QSS. You guessed correctly - the Delta 150 is made from bog standard consumer parts. Detailed picture of the inside up on my website:

https://techmattmillman.s3.dualstack...rcamlidoff.jpg

That having been said I'm not sure what a broadcast grade monitor/receiver would be built from. Philips did make them (PM5560/PM5696) but never seen inside one.
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Old 15th Dec 2022, 9:59 pm   #7
Synchrodyne
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Quote:
Originally Posted by inaxeon View Post
That having been said I'm not sure what a broadcast grade monitor/receiver would be built from. Philips did make them (PM5560/PM5696) but never seen inside one.
This block schematic of the BBC RC1-511 gives some idea of the structure, although I think that it may have been intended for broadcast monitoring rather than broadcast relay purposes. One may glean the impression that it used a larger number of simpler ICs than was the case in domestic receiver practice, where fewer, more complex ICs were typically used. (I have yet to see a full schematic for this unit.)

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I suspect that in performance terms, the emphasis in broadcast receivers would have been on producing low distortion video with flat frequency response right up to the transmitted maximum, and a flat (or otherwise appropriate) group delay curve. PLL fully synchronous demodulation might be used, or if quasi-synchronous, then with a relatively narrow bandwidth reference channel with Nyquist slope cancellation. On the sound side, either fully split or if QSS or intercarrier, with specific features to achieve SNR and signal-to-buzz ratios close to those achievable with split sound. Basic QSS comes out somewhere between regular intercarrier and split on that front.

To be fair, some late consumer TV receiver ICs addressed these issues. For example, Sanyo pursued Nyquist slope cancellation in the demodulator reference channel, some European IC makers used PLL demodulation (single or double reference) for QSS, to get it closer to split sound. With its mid-1990s MC44302 vision and sound IF/demodulator IC, which unusually used intercarrier for AM as well as FM sound, Motorola claimed that with the addition of a differential phase correction circuit, sound performance equalled that of a split sound receiver. So by then, it was probably possible to do close to professional broadcast quality with consumer type circuits.


Cheers,
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Old 16th Dec 2022, 11:28 am   #8
inaxeon
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Default Re: My (mostly Philips) Analogue telly broadcast setup

[QUOTE=Synchrodyne;1521654]
Quote:
Originally Posted by inaxeon View Post
Basic QSS comes out somewhere between regular intercarrier and split on that front.
Out of interest where is the line between QSS and split? The Arcam Delta 150 splits sound and vision with a special SAW with two outputs (output 1: vision, output 2: FM+NICAM) and demodulates them entirely separately using separate chips. Granted the actual chip is a QSS but does this qualify as true split sound?
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Old 16th Dec 2022, 10:39 pm   #9
Synchrodyne
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Default Re: My (mostly Philips) Analogue telly broadcast setup

True split sound is where the sound carrier was separated out, usually after the tuner, but sometimes, in earlier receivers with distributed IF selectivity, after a stage of common amplification, and then treated completely separately for amplification and demodulation, without further involvement of the vision carrier.

Split sound was used almost always for AM sound; in fact I know of only one IC that did it as intercarrier. It was used for FM sound in the early days, but fell away once the intercarrier technique took hold, thereafter being in the minority. There was something of a small renaissance in split sound FM in Japanese practice, for higher quality installations, in the later 1970s and 1980s.

Sometimes, more so with FM, but not unknown for AM, a second frequency conversion was used to obtain more favourable conditions for gain, selectivity and demodulation.

QSS is as you describe for the Arcam case. The sound IF channel, separate from the vision IF channel, took both the sound and vision carriers, and conditioned the latter for the optimum production of the intercarrier. The vision carrier conditioning included at least NO Nyquist slope, symmetrical narrow band filtering and limiting. Usually it also included quadrature phase shifting, and sometimes notching out of any residual sound carrier. Later, some implementations included a PLL for reference vision carrier regeneration.

In this sound processing was quite separate to vision processing all the way to baseband, even though intercarrier generation was involved. That I think is why it was named quasi-split, sometimes quasi-parallel.

Since QSS arrived there were developed some other approaches that may be described as hybrid. Where PLL demodulation was used in the vision channel, then sometimes a quadrature version of the vision reference carrier was used for intercarrier generation, in a sound IF channel where the sound had been separated after the tuner. This was sometimes referred to as single reference PLL QSS, as compared with the two reference kind where the QSS channel had its own PLL. The BBC “true intercarrier” system could be viewed as being a quasi-synchronous analogue of the single-reference QSS.

(Some more observations on this topic may be found here: https://www.radios-tv.co.uk/communit...carrier-sound/)

The BBC RC1-511 TV tuner mentioned in post #7 was of the “true intercarrier” type.

The Wireless World TV tuner mentioned here: https://www.vintage-radio.net/forum/...0&postcount=13 was of the true split sound type.


Cheers,
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Old 17th Dec 2022, 6:49 am   #10
inaxeon
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Quote:
Originally Posted by Synchrodyne View Post
There was something of a small renaissance in split sound FM in Japanese practice, for higher quality installations, in the later 1970s and 1980s.
Ah yes. Seen this?

https://www.youtube.com/watch?v=mR_wJkxKSXU

Looks like FM split sound to me (and it's Japanese).
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Old 18th Dec 2022, 9:27 pm   #11
Synchrodyne
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Default Re: My (mostly Philips) Analogue telly broadcast setup

Thanks – most interesting!

Australia chose the Zweiton system for TV stereo sound, so it is not so surprising that there was a Philips stereo generator amongst all the NEC equipment.

It was mentioned in the video that the oscillator frequency for upconversion from the IF to channel AUS7 was 221.15 MHz. Channel AUS7 vision was nominally 182.25 MHz, which implies an IF of 38.9 MHz, the European standard for system B. (Australian receiving practice used unique IFs, initially 36.0 and later 36.875 MHz for vision.)

I don’t know if split sound receivers were ever used for Zweiton stereo. In Japanese domestic practice, they were used for the Japanese single-carrier FM-FM stereo system. And there were exports to the USA where split sound was used initially for mono, and then for the BTSC single-carrier stereo system. But based upon just one or two datapoints, similar Japanese equipment (e.g. Sony Profeel) that went to Europe seemed to use QSS.

On the QSS vs. split issue, Philips did use the “split sound” descriptor for its TV front ends (tuner + IF strip) that used the Sanyo system. I suspect that this was to differentiate these from the regular QSS system also used for some front ends. The Sanyo system though was effectively a single reference QSS system, with a separate SIF amplifier but with conversion to intercarrier using a reference from the vision PLL. It was something of a hybrid, but ultimately it did fall into the intercarrier group, one might say getting there “the long way around”. I suppose that these various techniques lack hard formal definitions, although true split sound would be characterized primarily by the fact that at no stage was an intercarrier formed.


Cheers,
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