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Old 18th Nov 2017, 5:02 pm   #1
Pieter H
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Default Introduction PCC189 in Mullard tuners?

Hi all,

I've just uploaded the first part of my effort to trace back the history of Philips and Mullard TV tuners. It covers the VHF tuners till 1959.
http://www.maximus-randd.com/tv-tuner-history-pt1

For the next part I'm bumping into the next question:
Mullard was very late with the introduction of frame grid valves into their tuners; whereas all continental tuners introduced the PCC88 in 1956, Mullard only introduced the PCC89 in 1959/60. The likely reason, based on the discussion on this and other forums, is most likely the desire of Mullard to continue using remote cut-off concepts in the RF AGC, which meant they had to wait for the variable-mu PCC89, still in combination with the PCF80.

However, almost immediately the PCC189 (a differently pinned identical valve) and the PCF86 were introduced in 1960. So my question: what did Mullard do? Did they also switch to the PCC189-PCF86 valves like the rest of Philips, or did they stay with the PCC89 and switched to the PCF86 for the mixer-oscillator?

Who knows the Mullard tuners, their valves and the sets in which they were used?

Cheers, Pieter
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Old 19th Nov 2017, 4:38 pm   #2
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Default Re: Introduction PCC189 in Mullard tuners?

A very interesting website !

Steve
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Old 19th Nov 2017, 5:52 pm   #3
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Default Re: Introduction PCC189 in Mullard tuners?

Yes very interesting read.
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Old 19th Nov 2017, 6:01 pm   #4
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Default Re: Introduction PCC189 in Mullard tuners?

As far as I can make out the PCC189 first appeared in the Philips 19TG132A/01 series from 1963-64. It only appeared in the later models suffixed by /01 at the end of the model number. The early production models featured the PCC89. John.
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Old 20th Nov 2017, 8:49 pm   #5
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Default Re: Introduction PCC189 in Mullard tuners?

This is truly fascinating.

One question: why do you think there was no adoption of proper designed-for-VHF/UHF single-triodes like the EC93/EC94/6AM4 which had multiple cathode/grid/anode connections to minimise the degenerative inductance of the connecting leads?

And did any European VHF TV ever use a Nuvistor? I suspect not, since "DX" reception never seemed to be an issue in Europe [unlike in rural USA where the 'local' TV transmitter could be a couple of hundred miles away, giving rise to the "Yes we have television here! on tuesdays and thursdays if the wind's from the east and it's not raining!" effect].
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Old 20th Nov 2017, 9:32 pm   #6
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Default Re: Introduction PCC189 in Mullard tuners?

Some of the American valve makers did promote the use of such specialized triodes in VHF as well as in UHF TV tuners in the early-to-mid 1950s. For example, see post #20 in this thread: http://www.vintage-radio.net/forum/s...d.php?t=140359.

But there was little or no take-up by the tuner and TV set makers. I suspect that the cost-benefit analyses did not stack up. Also, the VHF TV tuner cascode valves, such as the 6BQ7 and 6BK7, had been developed specifically for this application, so one could say that they were also specialized valves keenly tailored to both the performance and economic needs.

The subsequent VHF TV RF amplifier developments included improved cascode valves, specialized triodes for use in “neutrode” circuits, guided-grid triodes, tetrodes and Nuvistor triodes. Whilst the Nuvistor was developed with a wide range of applications in mind, the other triodes were specialized TV valves, presumably developed with the performance/cost trade-off curve very much in mind.

The VHF TV triode-pentode oscillator-mixer valves were similarly purpose-designed. Although acknowledging the general superiority of the triode at VHF, the industry opted for the pentode mixer as a simple way (in a mass-production context) to avoid the regeneration problem that was consequent to the moving of Ifs right up to the bottom edge of Band I/low band.

TV tuners were of course a blend of cost-conscious mass-production and performance-conscious precision production techniques. It could be argued that in the 1950s, they were doing better at upper VHF and upper UHF frequencies than some commercial communications equipment – e.g. see post #26 here: http://www.vintage-radio.net/forum/s...=141387&page=2.


Cheers,

Last edited by Synchrodyne; 20th Nov 2017 at 9:37 pm.
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Old 21st Nov 2017, 10:06 am   #7
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Default Re: Introduction PCC189 in Mullard tuners?

The PC97 was employed as a RF amplifier [neutralized triode] particularly in Thorn's excellent tuners.

The RF stage tended to be very unstable on channel 1 probably as it was very close to the IF frequency and produced motor boating particularly with indoor room aerials. Thorn supplied 'loaded coils' [resistors across the tuning coils] to completely eliminate the problem.

In practice I used to fit the channel 2 coils and retune the oscillator slug to channel 1. Thorn frowned but all service engineers did it!

The cascode RF amplifier was very popular in UK tuners helped by the excellent valve designs from Ediswan Mazda at Brimsdown.

Philips tuners always performed with a slight cut above the rest with zero drift on Band 3. Other than the occasional contact cleaning I cannot remember ever repairing one as such.

Ekco tuners employed the Mazda valves and it is interesting to note that Pye, experts in tuner manufacture, continued to fit what appeared to be this rather large but electrically up to date tuner to their 1964 range after the take over of Ekco.

The last Philips valve tuner, PC900 and PCF801 was outstanding. Incredible gain and stability. This was bought it by many leading manufacturers. John.
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Old 21st Nov 2017, 10:19 am   #8
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Default Re: Introduction PCC189 in Mullard tuners?

A fault I had with Philips tuners circa middle 60’s was mechanical, the small plastic and metal fine tuning core tended to break off. A bit fiddly but once you got used to it replacement in the home was straightforward. The old one was screwed out, and new one screwed back in.
Apart from cleaning contacts and valve replacement the rest of the unit was very reliable.
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Old 21st Nov 2017, 6:31 pm   #9
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Default Re: Introduction PCC189 in Mullard tuners?

Yes the fine tuning 'wands'. I used to flatten the end of a 2 watt resistor then heat it up and press it into the bit that was still in the thread. When cool, as you say you could unscrew it out.

Four wands attached. Two Philips but can you identify the other two?

In desperation the long one could be repaired with a spring out of a Biro.

As I have said many times, it seems like yesterday! John.
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Old 21st Nov 2017, 7:01 pm   #10
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Default Re: Introduction PCC189 in Mullard tuners?

I'm not a vintage TV person, but I've seen Bush VHF tuners (both push button and rotary channel selection. the latter using a cam to operate the tuning wands) that had a pair of tuning wands like the long one in your picture.
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Old 23rd Nov 2017, 10:59 pm   #11
Pieter H
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Default Re: Introduction PCC189 in Mullard tuners?

Hi, thanks for all feedback and inputs.

To go back to the original question in post #5: in principle all Philips/Valvo/Mullard valves were optimized valves for the application. On my site on the early Philips TV development you can read all about the close co-operation between the set development and radio valve development labs. After the initial struggles with generic valves used in the tuners (UF42, EF42, EF80 and the ECC81 as a very first effort to RF optimization), from the PCC84 and PCF80 onwards all subsequent valves were designed primarily for their role in VHF cascode tuners with pentode mixer and triode oscillator. This architecture was used unchanged from 1954 to 1964, when the cascode was replaced by a single PC900 triode. Pure RF triodes like PC86 and PC88 were only used in UHF tuners, with one as pre-amp and ons as self-oscillating mixer. This architecture did not change until the introduction of transistors.

The result of the close co-operation between set/tuner development and valve development is illustrated by the extreme stability of the Philips tuner circuit. After two generations the circuit had almost completely stabilised, with minimal changes from then. New valves were what we call today "drop-in replaceable", requiring no changes to the application. The benefit of such stability in terms of minimal (re)-design effort and manufacturing streamlining should not be under-estimated, and has probably been one of the factors contributing to the dominant position of the Philips tuners over time. Jumping to completely different types of valves like the Nuvister, requiring serious concept changes, was then almost certainly considered too risky and not offering sufficient performance improvement to justify such a re-design.

In UHF the European approach of using a triode pre-amp was clearly superior to the American concept of a passive diode mixer with no pre-amp. Noise figure must have been pretty bad as any theoretical analysis of such a set-up will show. At the same time UHF remained a challenge for volume consumer modules, where probably the best solution was to use the minimal number of valves. The interconnect between the valves or valve sections probably gave more degradation than performance gain. Therefore just one triode as pre-amp instead of a cascode, and a single self-oscillating triode instead of separate oscillator and mixer. This approach didn't fundamentally change with the introduction of transistors, although a third transistor was used as oscillator.

All that in the next chapter of the tuner history!

Cheers, Pieter
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Old 23rd Nov 2017, 11:05 pm   #12
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Default Re: Introduction PCC189 in Mullard tuners?

I will be looking forward to the next chapter.
From memory, admittedly not that reliable after all this time but didn't the UHF transistor tuners just have RF amp and combined Mixer/osc whereas the VHF tuners had RF amp, Mixer and separate Osc?
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Old 24th Nov 2017, 7:56 am   #13
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Default Re: Introduction PCC189 in Mullard tuners?

Indeed Nuvistor is correct, the U.H.F. tuners employed just two AF186 transistors and gave a very good account of themselves, easy to align and having a far better noise figure than any valve tuner. I imagine the performance was not too far behind modern silicon tuners of to-day. The grounded base R.F. amp set the noise figure well above the mixer noise.
I refer to the Philips mechanical unit with a four section integral tuning capacitor in a silver plated frame and copper lined plastic top cover.
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Old 25th Nov 2017, 5:02 pm   #14
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Default Re: Introduction PCC189 in Mullard tuners?

Pieter,
thank you for this fascinating thread and the link to your very informative web page.
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Old 25th Nov 2017, 9:19 pm   #15
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Default Re: Introduction PCC189 in Mullard tuners?

Thanks guys!
And indeed, I typed too fast without checking properly. The UHF tuners had of course 2 transistors, the VHF 3. Working hard on that section.

Cheers, Pieter
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Old 27th Nov 2017, 12:31 am   #16
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Default Re: Introduction PCC189 in Mullard tuners?

Firstly, congratulations, Pieter, on producing a superb and most interesting website!

Secondly, an observation about Mullard TV tuners is that there seems to be very little accessible information about them before the mid-1960s. Did Mullard became more active as a third-party supplier of these units at about that time, perhaps coinciding with the start of the dual-standard era in the UK?

For example, Spreadbury (1), in 1962, provided much information and many illustrations of TV tuners from both the setmakers and third-party suppliers such as AB Metal, Cyldon, Ediswan and Plessey. One Philips printed circuit model was illustrated and described. But there was no mention of Mullard tuners.

Then King (2), in 1964, included a schematic for the Mullard AT6360/02 UHF tuner as a typical example, suggesting that Mullard was more active by then.

One may also find subsequent information about the AT6360 series of UHF tuners and AT7650 series of VHF tuners, the latter using the PC900 triode as RF amplifier.

I imagine that with their AT designations, these were basically Philips designs, perhaps with some adaptations for the UK market, such as non-sequential channel loading in the VHF case.

Mullard magazine articles, items and advertising pertinent to TV tuner valves before say 1964 appear to have been placed from the perspective of Mullard as a valve supplier, not as a TV tuner supplier.

The PCC89 was featured as the initial release in Mullard’s frame-grid series:

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The release of the PC97 was mentioned in a short Wireless World (WW) item, but this valve does not seem to have been heavily advertised by Mullard:

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After the PC97 was available, the PCC189 was advertised:

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In 1963 the PC900 was announced in a feature advertisement. It was billed as the direct successor to PC97, but the fact that it was compared with cascode RF amplifiers suggests that Mullard also viewed it as the successor to the PCC189.

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So, if the apparent “weighting” of the Mullard valve advertising is any guide, one might expect that Mullard would have moved to the PCC89, then to the PCC189, skipping the PC97, for its own VHF tuners, before changing to the PC900.



Cheers,



(1) E.A.W Spreadbury; Television Receiver Servicing; Volume 2 – receiver and Power Supply Circuits; Second Edition; Iliffe, 1962.

(2) Gordon J. King; Dual-Standard and 625-Line Television Receivers; Norman Price, 1964.
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Old 27th Nov 2017, 2:27 am   #17
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Default Re: Introduction PCC189 in Mullard tuners?

There’s also an interesting aspect in respect of valve development. As previously noted, the PCC84, whose triodes were of the sharp cutoff type, could be used – as a cascode amplifier - in either the sharp cutoff mode, with divider bias for the upper triode grid, or in the remote cutoff mode, with sliding bias for the upper triode grid. The PCC88, also with sharp cutoff triodes, was the frame-grid successor to the PCC84, but according to the Philips datasheet, was to be used only with divider bias, and therefore in the sharp cutoff mode. So, one may infer that at this juncture, Philips had decided that the sharp cutoff and remote cutoff requirements would be covered by two separate valves, and not by different circuit configurations for a single valve as had been the case in the PCC84 era. The PCC89 had remote cutoff triodes, and could be used with either divider or sliding bias, offering a range of grid bases that could be described as running the gamut from semi-remote to full remote cutoff.

In 1957-58, Mullard issued a couple of papers about its high-gain sync-cancelled AGC system. The first was: “A.G.C. Circuits for Positive Modulation Television Receivers”, published in Mullard Technical Communications No.27 of 1957 December. The second was: “Automatic Gain Control Circuits in Television Receivers for Negative Modulation Systems”, published as an IRE paper in 1958 May.

The positive modulation circuit was developed around a receiver that used a PCC84 RF amplifier, evidently in remote cutoff mode, PCF80 oscillator-mixer, EF85 1st IF stage, EF80 2nd IF stage, with AGC, and EF80 3rd IF stage, without AGC. Presumably this represented Mullard’s preferred valve line-up of the time. The paper also included the AGC divider network calculations for the case that an all-EF80 IF strip were used, but no mention was made of the alternative use of the PCC88 as RF amplifier. I’d guess that the EF85 1st IF amplifier covered the case where it handled both sound and vision, with sound takeoff after the that stage. The all-EF80 IF strip would have been applicable in the case where the sound takeoff was right after the tuner.

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The negative modulation circuit on the other hand was based upon a PCC88 RF amplifier and an all-EF80 IF strip. I’d guess that this was the kind of circuit that Mullard would recommend to the UK setmakers for their export receivers. And if it were supplying VHF tuners to any of these makers, they would have been fitted with the PCC88.

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This is, I think, indirect evidence that Mullard saw the PCC88 as being less suitable for positive/AM system receivers, although it was fine for negative/FM receivers. That was a view that was apparently not shared by Philips itself, though, as it used the PCC88 RF amplifier in VHF tuners for Belgian multi-system and French 819-line receivers. One may wonder if the PCC89 was developed mostly to keep Mullard happy, and if the bulk of PCC89 and PCC189 production was for the UK market.

Given that the (Mullard) PCC89 was announced in the second half of 1957, I’d say that Mullard did its AGC development work before then.


Cheers,
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Old 27th Nov 2017, 10:52 pm   #18
Pieter H
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Default Re: Introduction PCC189 in Mullard tuners?

Hi Synchrodyne,
thanks for the nice feedback!

As to the analysis of the Philips and Mullard approach, I think you are largely right. Up to the end of the 1950s the outward approach was very valve-centric. The successive generations of valves were always first introduced in the Philips tuners and/or TV sets, and then quickly afterwards announced on the market by the Electron Valves Division (HIG Elektronenbuizen), and its Valvo and Mullard brands. However, the fact that tuners received an official family product code (AT or NT followed by 4 numbers) next to their internal factory code, indicates they were avaialbe for external delivery. Reference designs of tuners were published to support the design-in of the valves, but it seems that actual third party sales of tuners was very limited. And if so it was mostly to companies affiliated with Philips, e.g. Kriesler in Australia from 1957 onwards and CBRT in Brugge, Belgium, which produced TV sets based on Philips reference designs for different brands. The only sale of a tuner to a "competitor" is in 1960 to Siemens, but as far as I can see only one set.

But around this time there has apparently been the decision to start offering complete tuners to the external market, which happened under the Philips, Valvo and Mullard brand names. At this time Valvo published a booklet promoting the AT7630 family of VHF tuners and AT6320 UHF tuners. Although this was more or less co-incidental with the introduction of UHF I doubt that was the reason. Personally I think it was more based on expansion ambitions, and/or the need to provide more load for the factories for higher cost efficiencies.

I think there is now sufficient evidence that Mullard stuck with the remote cut-off concept and the associated valves PCC84-->PCC89-->PCC189 for the positive modulation UK standard, while the continental tuners used the sharp cut-off PCC84-->PCC88 for the CCIR-B/G. But please note that the French and Belgium standards, although also based on positive video modulation like the British standard, employed the same sharp cut-off concepts as the standard continental tuners! With the PCC189 variable-mu triodes the continental tuners didn't move to remote cut-off (the gain control remained unchanged) but the valve improved the cross-modulation behaviour. From that moment onwards - around 1963 - all Philips tuners used the same valves again.

So yes, it seems the PCC89 was developed specifically for the UK tuners of Mullard, but that by itself was not exceptional. Nevertheless its use was only a fraction of the widely used PCC88 and 189's. I agree with you that Mullard developed its AGC concept before the PCC89, in fact it was largely introduced with the PCC84 from the beginning and continued with the improved PCC89.

Thanks for your inputs and analysis, it has definitely helped me to get the story clearer!

Cheers, Pieter
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Old 29th Nov 2017, 9:20 am   #19
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Default Re: Introduction PCC189 in Mullard tuners?

Hi Pieter, thanks for the additional background.

Something that particularly caught my attention in Part 1 was your discussion of the IF choices for the French 819-line system. It hadn’t occurred to me previously that any oscillator frequency that fell within Band III also had to fall on the vision or sound carrier for another channel. But now knowing that, the rest of the calculation falls into place. Of course, even if there were any apparent gaps in which local oscillators could fall safely, with the tęte-bęche channelling system, they would not align between the even and odd channels. Also, to achieve 13.15 MHz channel spacing for the tęte-bęche system as compared with the original 14 MHz, the outer guard bands – 0.1 MHz outside the sound carrier and 0.75 MHz outside the vision vestigial sideband – were discarded. Then the even channels were moved up 0.25 MHz relative to the odd channels (which were “hard left” against the 162 MHz lower limit of the band), I think for the best (and equal) disposition of the both the even and odd sound carriers relative to the vision sidebands. Thus, with the LO frequencies effectively determined by the channel plan, so in turn were the IFs. For an IF channel whose upper edge was just below 40 MHz, the vision IF had to be a multiple of 13.15 plus an offset determined by the relationship between the even and odd channels. For an IF channel with vision carrier at the low end, it was 28.05 MHz, as twice 13.15 MHz plus 1.75 MHz, the latter being the separation between the sound carriers of corresponding even and odd channels. And for the vision carrier at the high end, it was 35.7 MHz, as twice 13.15 MHz plus 9.4 MHz, the latter being the separation between the vision carriers of corresponding even and odd channels.

The decision to standardize on 28.05 MHz vision, 39.2 MHz sound, with oscillator high for the even channels and oscillator low for the odd channels effectively precluded the use of channel F3, for which one transmitter had been shown in the ITU Stockholm 1952 list. It would have required a local oscillator frequency of 28.1 MHz.

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With the oscillator frequency jumping from high side to low side channel-by-channel, it may have restricted the tune choice to the turret type. Possibly it could have been done with a switched incremental inductance tuner, but with a resultant awkward channel sequence.

The 36.15 MHz (vision) IF shown for the earliest 819-line receivers was, I imagine, worked out for the original channelling plan, of which only the first channel was ever used, and which survived as F8A.

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Cheers,
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Old 29th Nov 2017, 1:44 pm   #20
Pieter H
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Default Re: Introduction PCC189 in Mullard tuners?

Hi Synchrodyne,

Yes, it has taken me a while to figure out the French 819-line set-up. Interestingly there isn't a web site explaining it this way, so I had to discover it myself. But I indeed had an "aha-Erlebnis", as the Germans say, when I saw the LO-frequencies coincide with the opposing channel vision or sound, depending upon the IF concept used. And when you draw the frequency figures it all becomes clear. An additional complication was that there are many "wrong" sources on the internet, mixing up channel numbers and frequencies. This is undoubtedly partly due to confusion caused by the French authorities when they abandoned the original 14MHz channel scheme and switched to the 13,15MHz bandwidth and tęte-bęche scheme. In one of the early Philips tuner Service Manuals the frequencies were even wrong!

As to the effect on the drum tuners I haven't seen anything, as I would expect. By choosing the right coils the frequency-specific biscuits any filter or oscillator frequency could be selected. So assuming that a French tuner would step from channel F2 to F12 as most of them did, you would see on the biscuits a continuously reducing inductance for the input matching and bandpass filters, and an alternating large-small oscillator coil, linked to the oscillator switching for even and odd channels. As far as I can see there was no technical limitation whatsoever to realise this. (In this context it is interesting to see how this was managed in the non-drum type electronic transistor tuners of the end 60s to 70's, before there were digital memories. I'm almost there, finishing the last valve tuner story. Curious to see what the result will be.)

Cheers, Pieter
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