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[Sticky] Television Receiver Intermediate Frequencies

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Pieter H
(@pieter-h)
Posts: 18
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@synchrodyne 

Hi Steve,

interesting point you bring up there! I've done two quick checks on the "38,9 MHz emergence".

In the 1952 Philips Electronic Application Bulletin that introduced the intercarrier concept, the reference design is still based on the then standard 23,5MHz VIF as used by Philips. Which indicates that intercarrier introduction and 38,9MHz standardization were not linked. Although it effectively was within Philips: the 1953 TX1720 chassis introduced both these innovations.

Nevertheless, in my early Philips TV history I have made the link by stating:

In an inter-carrier receiver the video and sound remain combined throughout the entire IF chain up to and including the video detector. The output of that detector will now be the video baseband signal as usual but with the modulated sound on a sub-carrier at 5,5MHz, the picture-sound distance in the Gerber-norm. (In other standards the video-sound distance differs of course). The advantage is then that the remaining audio chain is much more low frequency up to the FM detector, avoiding more complex IF circuitry. The down side is that the combined video plus audio IF chain needs to be more wideband to pass both signals. Probably as a consequence of this the IF frequencies further moved upwards to a picture carrier of 38,9MHz and a sound carrier of 34,4MHz.

I then did a quick check on Radiomuseum.org on the VIF of German and Dutch (Philips) TV sets from 1951 to 1955. I will make a more detailed table one day for my site, but the summary is as follows:

1951: Philips 23,5, Metz 23,75, Schaub 25,7, Telefunken 25,75, Saba 26,2, Grundig 26,75, Greatz 27,75, Loewe 37,5

1952: Philips 23,5, Blaupunkt 25,5, Telefunken 25,75, Nordmende 26,0, Nora 26,5

1953: Blaupunkt Saba 25,5, Lorenz Schaub 25,7, Braun Telefunken 25,75, Grundig 27, Loewe 28,75, Graetz 29
         Siemens 35,35, Metz 38,5, Philips 38,9

1954: same as 1953

1955: Kreft, Metz, Loewe, Neckermann, Nora, Saba, Schaub, Tekade all switched to 38,9

This seems to mean, to my total surprise, since I have not seen any reference to this fact, that Philips introduced the 38,9MHz. At least when looking at Germany and the Netherlands, which were jointly the biggest CCIR-B market. Whether this was purely a "follow the leader" mechanism (Philips was establishing itself as a leading brand in Europe), or that Philips proposed this value to some (CCIR?) standardization body and the others followed, or that such a body had proposed the 38,9 and Philips was the first to adopt, is not clear yet and deserves some further research.

Other observations:

  • the Loewe 37,5MHz in 1951 seems to have been a one-off case, since on the next chassis they were back at 28.75MHz.
  • as in the UK chassis, Philips was originally on the lowest IF of all, but then in one go made the jump to the standard high value
  • it seems there was some industry consensus that higher IFs were better but not (yet) prescribed, see the values of Siemens and Metz in 1953. I would expect there is a conference or journal paper from around 1951/2 analysing this need, and driving this consensus. I haven't found that yet.

Interesting topic! I'll try to find more data on this.

Cheers, Pieter

 
Posted : 30/12/2021 4:41 pm
Synchrodyne
(@synchrodyne)
Posts: 519
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Topic starter
 

To recap on previously posted items:

The EBU TV IF survey of 1952-54, of which a précis was provided in Wireless World 1954 July, showed 38.9 MHz as the expected future VIF for Germany and the Netherlands.

The Fewings & Fife BIRE paper of 1955 included this in its bibliography:

W. Holm and W. Werner, "Choice of an intermediate frequency for television receivers to suit the C.C.I.R. standard," Funk und Ton, 8, pp. 129-138, 1954.

As far as I know, both authors were Philips employees, but Funk und Ton was a German publication. I imagine that the article included the calculations that pointed to the choice of 38.9 MHz as the VIF for the CCIR system (later system B). That may explain why it was labelled as being the “CCIR IF”. But whether it included any information about which organizations, if any, adopted it as a standard is hard to say. Whereas in the RTMA and BREMA cases, each trade organization commissioned the development work, in the 38.9 MHz case, it might have been a Philips initiative that then became a de facto standard, and possibly a de jure standard.

The CCIR started reporting TV IFs in 1959 Los Angeles meeting report. Whilst it noted the trend towards national standardization, in general it did not record who the standards issuing authority was in most cases, EIA (nee RTMA) being an exception. A reasonable inference is that the CCIR itself was simply reporting, and not promulgating standards or apparent standards.

Cheers,

Steve

 
Posted : 30/12/2021 10:11 pm
Synchrodyne
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Topic starter
 

In a posting last December, I said:

“Yes, I plan to compile a tabulation. In fact I have had several attempts at it so far, none with a satisfactory outcome. My thinking now is to have three tables. One would be a simple list in ascending VIF order, each entry with a comment to indicate with which system(s) it was used, where it was used if it was “geographical”, approximately over what period it was used, and whether or not it was an actual standard number.

“The second list would be ordered by system, using the CCIR letter designations, and would show standard and other IFs used for each system.

"The third would be a list of standard IFs and their direct and indirect derivatives.

"I’ll probably need to be selective about the inclusion of pre-standardization IFs, with just a representative sampling.”

I have now done the first draft of the first list mentioned therein, attached as a .png derived from an original spreadsheet.  (I think it is readable if one selects open image in new tab.)

I believe that I have captured all of the standard and quasi-standard IFs, along with (what appear to be) the more important combinations used for multistandard receivers.

tableDraft

As suggested above, the list of pre-standard IFs is not complete, and is intended to be representative only.

Cheers,

Steve

 
Posted : 06/08/2022 1:34 am
Sundog
(@sundog)
Posts: 173
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Hi Steve, is it possible to repost the table in a vector format such as pdf? The resolution of the png is insufficient for reading.

 
Posted : 06/08/2022 6:51 am
Synchrodyne
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Posts: 519
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Topic starter
 

I don’t think that the forum allows .pdf attachments. At least it won’t allow me to upload them.

Strange doings with the .png, though. My original is 138 kB, and quite readable if I enlarge it to give a convenient font size on-screen. When I download the posted version though, it comes in at 309 kB, but is not really readable when similarly enlarged – it gets very fuzzy.

I’ll have to find another way to do this.

Cheers,

Steve

 
Posted : 06/08/2022 7:22 am
crustytv
(@crustytv)
Posts: 11903
Vrat Founder Admin
 
Posted by: @synchrodyne

don’t think that the forum allows .pdf attachments. At least it won’t allow me to upload them.

That is partially correct, 11-years ago when the forum was founded a decision was made to only allow images as attachments to forum posts. I won't bore you with why, you can read here. Suffice to say it has served us well since VRAT formed.

That said, members can share PDF's via the private messaging system.

The files attached to a pm will only live for 24-hours, after that period the message and attachment, self-destruct. The recipient will receive a notification of a received message and has those 24-hours, to view and save the file. This is more than adequate time for them to do so.

Posted by: @synchrodyne

I’ll have to find another way to do this.

It's simple, why have such a behemoth of an image in the first place, all you had to do was simply snip it into three, so sundog and others could read. See below. Took me all of a couple of minutes to do. Perfectly readable, no need to go looking for a solution to a problem that is not really there.

Edit:
Attached demo images removed, as they have now been superseded (see 2nd post down) and we need to conserve disk space.

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

 
Posted : 07/08/2022 6:06 am
Sundog
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@crustytv Thank you Chris, It's perfectly readable now. And a big thank you to Steve.

Since you were able to split the file, I presume the uploaded file was preserved in reasonable definition; it's the serving of the file that limits the definition?

 
Posted : 07/08/2022 6:54 pm
Synchrodyne
(@synchrodyne)
Posts: 519
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Topic starter
 
Thanks much, Chris, for resolving my image issue.
 
Meanwhile, I have amended the list a little, attached below in four parts.  The changes include some additions, including the 32.7/43.85 MHz combination used for late French system E receivers.  Also, I have expanded some of the notes for clarity, particularly in respect of IFs that applied to multistandard receivers.
 
I’ll let this first list “settle” for a while before developing the previously proposed second and third variations.
 
TV IF Table 1 2nd 20220810 p.01
TV IF Table 1 2nd 20220810 p.02
TV IF Table 1 2nd 20220810 p.03
TV IF Table 1 2nd 20220810 p.04
 
Cheers,
 
Steve
 
Posted : 10/08/2022 2:14 am
Synchrodyne
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Topic starter
 
Mentioned upthread was the Murphy (UK) combination TV-FM receiver of the late 1950s, in which a second conversion was used on the sound side.  The 38.15 MHz initial SIF (the BREMA system A standard), used both for TV sound and FM, was downconverted to 6.31 MHz for final processing.
 
I have since found that Murphy wrote a BIRE paper on this matter, namely:
 
R.S. Hildersley
“The Combined Television-Radio Receiver and its Problems”
BIRE Paper #544, read 1959 July.
 
Therein were explained Murphy’s reasons for adopting double conversion.
 
At the time, two other techniques that were often used for UK TV-FM receivers were:
 
1. 38.15 MHz IF for both TV sound and FM.
 
2. Dual-frequency IF strip, 38.15 MHz for TV sound and 10.7 MHz for FM.
 
The first had two problems.  One was inadequate selectivity on FM, which required much better performance than was needed for TV sound, as shown in this chart:
 
Murphy Band II Selectivity
 
 
This problem could be solved by using more 38.15 MHz tuned circuits in the IF strip.  Murphy estimated that a total of 9 would be required, as compared with the 3 normally used.  However, this was considered uneconomic.  As well as a higher BOM cost, the alignment time required on the production line would have been increased.
 
The second problem was the difficulty of designing and producing a 38.15 MHz FM demodulator.  To quote from the paper:  “Ratio detectors operating at 38.15 Mc/s are usually found to be lacking in both a.m. rejection and sensitivity when compared with 10.7 Mc/s detectors. Optimum performance depends upon the balance of such small values of capacitance and inductance at 38.15 Mc/s that production specimens tend to vary considerably from a given standard, a.m. rejection suffering in particular.”
 
Thus that was essentially intractable with the technology of the time that was suitable for a consumer product.
 
The second approach, a dual-frequency IF strip, would have solved the FM selectivity issue.  But it was seen to reduce the available gain for TV sound at 38.15 MHz.  Also, there was some aversion to having a significant number of components (in this case the 10.7 MHz IF transformers, and the ratio detector components) that were used only for FM.  This may well have been a Murphy-specific position.  But there was another issue, namely obtaining adequate image rejection.  TV front ends were more broadly tuned than FM receiver front ends, and so had poorer image rejection with a 10.7 MHz IF, although that parameter was adequate with the 38.15 MHz IF.  Murphy noted that that would have been worse when a single coil set was used to tune the whole of Band II.  This chart shows the relatively broad front end selectivity provided even with the three FM coil sets that Murphy used:
 
Murphy Band II Front End Selectivity
 
 
Thus Murphy looked at the double conversion approach, on the basis that a 38.15 MHz 1st IF would provide adequate image rejection, whilst an adequately low 2nd IF would provide both adequate FM selectivity and for a stable ratio detector.  The economics of this approach were seen to be better if double conversion were used for TV sound as well as for FM.
 
Given that the desired selectivity was the same as FM receivers typically achieved at 10.7 MHz with five tuned circuits, a 2nd IF of that frequency or lower was indicated.  10.7 MHz itself was outruled by conflicts in conversion from 38.15 MHz.  Supradyne conversion required an oscillator frequency of 48.85  MHz, seen as being too close to the TV channel B2 sound carrier at 48.25 MHz.  And its fourth harmonic was close to the channel B9 vision carrier.  Infradyne conversion required an oscillator frequency of 27.45 MHz, whose second harmonic, 54.9 MHz, fell into the channel B3 passband.   (53 to 58 MHz, 53.25 MHz SC, 56.75 MHz VC)
 
It was thought that a 2nd IF in the vicinity of 6 MHz would be a good choice.  An oscillator frequency of 31.84 MHz was chosen, which gave a 2nd IF of 6.31 MHz.  Murphy provided a harmonic chart for that pair, and said that it was necessary to consider all harmonics up to the 6th in the oscillator case.
 
Murphy 2nd IF Harmonics
 
Of those harmonics, 63.68 MHz was fairly close to the channel B5 sound carrier at 63.25 MHz, and 191.04 MHz was quite close to the channel B9 sound carrier at 191.25 MHz.  This dictated the required 31.84 MHz oscillator stability at ±15 kHz, for a maximum 6th harmonic deviation of ±100 kHz.
 
The resultant receiver block schematic was:
 
Murphy Block Schematic
 
To minimize the level of level of the 31.84 MHz oscillator output finding its way back into the main IF strip, it was necessary to use a triode heptode as the 2nd frequency changer, even though  a triode pentode would have provided a higher conversion gain.
 
The resultant sound channel selectivity curve was:
 
Murphy Sound Channel Selectivity
 
This was a tradeoff between the FM and TV sound requirements, but was clearly a major improvement as compared with the 38.15 MHz case.
 
Murphy used an AFC system on FM, controlling the oscillator frequency in the front end.  Thus the second conversion was within the AFC loop.  The AFC system also worked for TV sound, but Murphy elected not to use it on the basis that it was less necessary in that case.  It is speculation on my part, but possibly there was also an element of leaving the receiver user free to offset the TV fine tuning if preferred for any reason.
 
In terms of the overall result, the author of the paper said:
 
“Combined receivers of this type perform satisfactorily as television receivers, whilst the Band II performance has been found to compare well with that of conventional Band II sound receivers.  Not only is the adjacent channel selectivity of a comparable order, but the usable sensitivity may be higher. This is because the performance of the r.f. unit fitted to a television receiver tends to be superior to the relatively simple and inexpensive circuits used in the majority of Band II radio receivers.  The low noise factor of a good television r.f. unit is especially valuable in a combined receiver in this respect.”
 
That low noise factor was largely attributable to the customary use of cascode high-gain, low-noise RF amplifiers in TV tuners, which minimized the effect of mixer noise.  On the other hand, UK FM radio receivers typically used a grounded grid triode RF amplifier, of relatively low gain.  Even FM hi-fi tuners did not always do a lot better; the cascode RF amplifier was rare in UK practice.
 
A curious comment in the paper was:
 
“When this project was begun, the design of a combined receiver having a double superhet sound i.f. system appeared most unlikely to achieve a successful conclusion. The double superheterodyne principle has been used before in conventional radio receivers, but even these have suffered from difficulties due to harmonics of one or the other oscillator.  It seemed unreasonably audacious to attempt to use the technique for a television receiver when, theoretically, beat-frequency patterns could occur on every television programme channel. In the event, however, the problems have appeared to be capable of solution.”
 
That creates the impression that the author was completely unaware of established practice with Belgian receivers of the time, which were designed to receive four different TV systems, namely B, with FM sound, and C, E and F, with AM sound.  Early practice was to use a second conversion in the sound channel, from the 27.75 and 33.4 MHz 1st SIFs down to 7.0 or 11.8 MHz for final processing.  Thus the basic interference issues surrounding the second sound conversion had already been addressed, albeit for a different set of frequencies, and without the FM selectivity issue.  If nothing else, the Belgian precedent would have established that the Murphy project was not in fact “unreasonably audacious”.
 
Although Murphy clearly had reservations about dual-frequency sound IF strips, in fact they became the norm in the UK dual-standard era, operating at 38.15 MHz for the system A, AM sound, and at 6.0 MHz for the system I, FM sound.  In that case, FM selectivity was not an issue, nor was image rejection, as the 6.0 MHz intercarrier frequency was effectively the result of a second conversion.  Evidently 38.15 MHz gain and stability issues were adequately addressed.  Also, before then, some Belgian receivers had adopted a similar approach, albeit with triple-frequency sound IF strips, 27.75 and 33.4 MHz AM, and 5.5 MHz intercarrier FM.
 
Nonetheless, as far as I know, Murphy was alone amongst the UK setmakers in adopting the double conversion sound channel approach for TV-FM receivers.  The modal choice seems to have been the dual-frequency (10.7 and 38.15 MHz) sound IF strips, perhaps doing what could reasonably done to address the difficulties and otherwise accepting the performance limitations.  In the very early days of TV-FM receivers in the UK, c.1955-56, Ekco also used the earlier 16.0 MHz VIF, 19.5 MHz SIF for one model, with the 19.5 MHz used as the FM IF.  Although the 16.0/19.5 MHz IF combination would have been less suitable for Band III TV reception, for FM, the 19.5 MHz IF may well have provided a tolerable tradeoff between image rejection, IF selectivity, and ratio detector stability.  In fact Bush used 19.5 MHz  the FM IF in an early FM-AM radio receiver.  Unusually, this had an aperiodic (wide band) FM front end.
 
The Murphy work is I think an example of how to go about finding a suitable IF when the standard/established numbers don’t work for what you want to do.  And whilst the “cause” of the exercise was the need to include FM radio reception in a TV receiver, in this case the outcome also affected the TV sound IF channel.
 
 
Cheers,
 
Steve
 
Posted : 04/09/2022 11:53 pm
Nuvistor reacted
Synchrodyne
(@synchrodyne)
Posts: 519
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Topic starter
 
Following the previous posting on the Murphy TV-FM receiver with a dual-conversion sound channel, it seems appropriate to include brief summaries on a couple of overlapping issues, namely:
 
- A list of known cases where there was dual conversion on the sound IF side (with normal single conversion on the vision side).
 
- TV-FM receiver approaches with specific reference to the effect, or not as the case may be, on TV IF choices.
 
TV Receivers with Dual-Conversion Sound IFs:
 
Belgian Four-System Receivers:
 
Early such receivers typically had dual-conversion sound IF strips.  The 33.4 MHz (systems B, C and F) and 27.75 MHz (system E) were converted to either a 7.0 or an 11.8 MHz 2nd SIF handling both AM and FM signals.  In part this was done to bring the SIF down to a frequency range where reliable FM demodulation, using consumer level circuitry, was easier to obtain.  It was also a way of dealing with two initial SIFs.
 
It appears that there was subsequent migration from this arrangement to triple-frequency SIF strips, handling 27.75 and 33.4 MHz AM carriers, and the 5.5 MHz FM intercarrier.  This evidently happened before the advent of UHF transmissions and system L caused further complications.
 
The 7.0 MHz 2nd IF case was addressed in a Philips Technical Review, 1955 December article, p.161ff, “A Television Receiver Suitable for Four Standards”, by H.L. Berkhout.
 
Both the 7.0 and 11.8 MHz 2nd SIF cases were covered in a WW 1956 November article, p.559ff, “Four Standards Television – Problems of Receiver Circuit Design in Belgium”, by H. de Laistre Banting.
 
Whilst the former article was specific to Philips TV receivers, the latter was general, so is presumed to have been pertinent to the majority of Belgian TV receivers of the early period.
 
In both cases, it was indicated that to minimize adverse frequency interactions, receiver used a buffer SIF stage (at 1st SIF) between the tuner output and the 2nd frequency changer, as shown here:
 
Belgian SIF 2nd Conversion
 
 
 
Murphy (UK) TV-FM Receivers:
 
As covered in the preceding post, Murphy alone used a second SIF in its TV (system A)-FM receivers of the later 1950s, and possibly into the 1960s.  The standard system A SIF of 38.15 MHz was also used for FM, and downconverted to 6.31 MHz for both TV sound and FM, the main driver here being obtaining satisfactory FM performance.)
 
Japanese TV Receivers with Stereo Sound:
 
When stereo TV sound arrived in Japan, using the EIAJ FM/FM system, higher quality receivers and tuners used split sound.  The by-then standard SIF of 54.25 MHz was down converted to 10.7 MHz, the international standard FM IF, for final processing.  One may assume that the latter was preferable for FM demodulation, and it also allowed the use of standard ICs developed for high-quality FM tuners and receivers.  Evidently the level of circuit subsection screening reasonably attainable with IC technology meant that no major problems were created by the use of the 10.7 MHz 2nd SIF, so there was no need to find an alternative.
 
This technique was briefly described in a couple of IEEE papers:
 
1979 December, “Present Status of Multichannel-Sound Television Broadcasting in Japan”, by Yasutaka Numaguchi, NHK.
 
1981 August, “Multichannel Sound System for Television Broadcasting”, by Yasutaka Numaguchi and Shunjiro Harada, NHK.
 
The same technique was also used in Japanese-origin, US market component TV tuners from 1981, in this case converting from the US 41.75 MHz standard SIF to 10.7 MHz.  Such tuners often also incorporated an intercarrier (4.5 MHz) SIF as well.  Although split sound was generally superior, apparently some US UHF translators and cable systems suffered from relatively severe incidental phase modulation, such that intercarrier, normally well inferior, gave better results.  I have not seen any evidence that this dual approach was either needed or used in the Japanese domestic market, but absence of evidence is not evidence of absence.
 
There is some evidence that the Japanese equipment makers migrated to the European quasi-split sound (QSS) system once it became available, so that the use of a second SIF conversion to 10.7 MHz may have died out.
 
Possibly there were other examples of SIF second conversions, but if so, they have yet to surface.
 
 
TV-FM Receivers:
 
US TV-FM Receivers:
 
Such receivers existed early in the post-WWII era, but soon faded away.  It would appear that the widespread introduction of the intercarrier sound technique, and the move to the “high” TV IF of 45.75 MHz VIF, 41.25 MHz SIF made combination receivers more difficult to implement, whereas it was the previous relative simplicity that probably encouraged some makers to offer them.
 
Thus American TV-FM receivers belonged to the era of the “low” IF and split sound.  The same 21.25 to 21.9 MHz SIF range as was standard for TV sound was also used for FM.  And apart from arranging for the front ends to tune through the FM band as well as the low and high TV bands, no additional circuitry was required, nor was any change needed in respect of IF practice.
 
The 21.25 to 21.9 MHz range was probably a reasonable choice for FM in those circumstances.  It would have provided reasonable image rejection given the likely lower front end selectivity as compared with FM radio receivers, but would not have been too high to make good IF selectivity prohibitive or for stable FM demodulation.
 
UK TV-FM Receivers:
 
Here there seem to have been five main approaches:
 
1. The early Ekco system, in which the pre-standard TV IF was used, 16.0 MHz VIF and 19.5 MHz SIF, the latter also used for FM.  So on the face of it, the addition of FM did not require any changes to the TV IFs.  It is possible that Ekco was simply standing back from implementing the new (1954) standard system A combination of 34.65 MHz VIF, 38.15 MHz SIF, but also possible is that in this case it chose the older, lower TV IF because it saw 19.5 MHz as being better suited to the FM requirements than 38.15 MHz.  If that obtained, then one could say that the IF choice was influenced by the addition of FM to a TV receiver.
 
2. Receivers in which the standard TV 38.15 MHz SIF was also used for FM, which clearly did not require any change in TV IF practice.
 
3. Receivers in which 38.15 MHz was used for TV sound only, with the 10.7 MHz standard IF being used for FM.  Although requiring a dual-frequency sound IF strip, this did not require any changes to TV practice.
 
4. The Murphy case, recently discussed, in which TV sound and FM shared a 38.15 MHz 1st IF (the standard TV number) and a non-standard 6.31 MHz 2nd IF.
 
5. Early dual-standard TV receivers, where the standard TV IFs were 34.65 MHz VIF, 38.15 MHz SIF for system A, and 39.5 MHz VIF, 33.5 MHz SIF, 6.0 MHz intercarrier for system I, and the FM IF was 6.0 MHz, thus enabling it to use the intercarrier sound sub-IF strip.  Thus the TV IF choices were unaffected by the addition of the FM facility.  This was probably the simplest of the UK systems, requiring just a VHF tuner that also covered Band II, and the requisite switching, but no additional IF circuitry.  One may wonder about the image rejection performance though.  Although there were examples of FM radio receivers with IFs in the vicinity of 6 MHz, they probably had better front end selectivity than was reasonably possible in the VHF TV tuner form.
 
The only example of this I have found is the Thorn 900 series chassis.
 
German TV-FM Receivers:
 
Here I have but one datapoint, contained in a WW 1955 October article, p.468ff, “German Radio Show”.  In the part discussing German FM receivers, on p.468, it was said:  “The standard i.f. of 10.7 Mc/s is used except in combined sound/television receivers, which have an i.f. of 5.5 Mc/s, the TV sound being produced by the difference-frequency principle to be mentioned later.”
 
From that one may infer that the TV practice was unaffected, and used the standard system B IFs or precursors thereto.  FM used the system B intercarrier frequency, 5.5 MHz, as its IF.  Thus it would have been similar in principle to the system later used by Thorn in its 900 series chassis.
 
Russian TV-FM Receivers:
 
Again I have just the one datapoint, in a WW 1961 August article, p.398ff, “Soviet Exhibition in London – Russian Radio, Television and Electronics on Show”.  On p.399, discussing TV receivers, it was said:  “…and some employ ingenious means for f.m. broadcast reception: for instance, the “Rubin 104” and the “Almaz 105” have a second frequency changer to convert the 8.4Mc/s f.m. i.f. to the 6.5Mc/s sound i.f. so that the set’s intercarrier circuits can be used.”
 
Thus the TV IF choice was unaffected.  The inference is that a separate FM front end was used, possibly of a standard radio receiver type, and that its 8.4 MHz IF output was then converted to 6.5 MHz to suit the TV intercarrier sub-IF system.  That also implies that 8.4 MHz was then the standard IF for the Russian FM band, 66 to 73 MHz.  I have not been able to verify that, although it appears to have been a reasonable number for the purpose.  Probably though Russian FM practice moved to 10.7 MHz for export models at least.
 
Other TV-FM Receivers:
 
I have not been able to ascertain to what extent TV-FM receivers were found elsewhere, let alone their IF configurations.  A WW 1959 October article, p.456ff, “Paris Radio Show – Impressions and Comparison”, included the following commentary about a French multistandard TV receiver that also included FM radio.
 
“In certain parts of France reception of television programmes from other countries is possible.  However, since these programmes have different characteristics, multi-standard sets have to be provided to receive them.  Among the numbers of such receivers on show we saw one, the Telemaster Super V5D FM, which could receive as many as five types of television transmissions-819 lines on French and Belgian standards, 625 lines on Belgian and European standards and even our own familiar 405 lines—not to mention f.m. sound broadcasts in Band II.”
 
How FM was handled in that case is anyone’s guess.  However, perhaps the TV IF choices can be deduced.  If we assume that a France-based receiver was required to receiver all French VHF channels, then the use of the standard French IF combination, 28.05 MHz VIF, 39.2 MHz SIF for system E seems to have been highly likely.  Then system B, assuming that Band I coverage was required, was likely accommodated in the same way was for some of the two-standard (E and F) border area receivers, with a 37.7 MHz VIF, placed so that the adjacent channel sound rejector fell at 39.2 MHz, the same as the system E SIF, and so a 32.2 MHz SIF.  The same combination would also have served for systems C and F.  System A would have required a direct IF channel to handle the Band I channels, so my best guess there is that it used 35.7 MHz VIF, 39.2 MHz SIF, i.e. the same SIF as for system E.  That would have required a sound IF strip that accommodated 32.2 and 39.2 MHz AM, and 5.5 MHz FM, assuming that intercarrier sound was used for system B.  If not intercarrier, then perhaps an early Belgian-style approach was used, with conversion of 32.2 and 39.2 MHz to a suitable 2nd IF of the AM/FM type.
 
In the intercarrier case, FM radio could have been accommodated by following the German precedent, using a 5.5 MHz IF.  In the non-intercarrier case, then perhaps the 2nd SIF could have been used as the only FM IF, or perhaps 32.2 or 39.2 MHz was used as a 1st IF, with the same subsequent down conversion as used for TV.  Of course, “none of the above” might have applied.  And the TV IFs I have used are but slightly educated guesses, 
 
And in the above-mentioned WW 1956 November article on Belgian TV receiver practice was included the following brief mention of FM radio reception:
 
“All channel selectors are fitted with coils for the C.C.I.R. Channels 2-11; in the 12th position is the French Channel 8A for Lille.  This is " rearranged" by changing the oscillator from the high to the low frequency side of the vision carrier.  This keeps the vision i.f. the same for all channels, but gives a second sound i.f. which is 5.65 Mc/s lower than that for the other channels.  The remaining position is normally left without coils and can be used for local f.m. broadcast reception if required.
 
Nothing further was said about FM.  If that FM facility was actually used, there were several ways in which it could have been done, but given that split sound was used, using the system B 1st SIF of 33.4 MHz as the FM 1st IF would have been logical, with the same 2nd conversion to 7.0 or 11.8 MHz, and thus making full use of the various SIF strip stages.
 
 
Cheers,
 
Steve
 
 
Posted : 05/09/2022 9:05 am
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Within the broad TV-FM receiver group also fall those TV sound tuners and receivers that also included FM.  In fact these pioneered the use of the 10.7 MHz standard FM IF for TV sound purposes, both as the only SIF, and also as the 2nd IF downconverted from the applicable standard TV SIF.  Not so much information on these is readily available, but one or two examples will serve as illustrations.
 
In the US in the mid-1950s, both Knight and Rauland offered AM-FM tuners that optionally included VHF TV (FM) sound.  Basically, they added a VHF TV front end modified to provide a 10.7 MHz sound IF output rather than the customary 41.25 MHz.  This was fed into the regular FM 10.7 MHz IF strip.  The normal FM front end was retained for FM reception.
 
The corresponding development in the UK was the Jason series of TV sound and FM tuners, starting in 1958.  These may be seen as an extension of UK TV-FM receiver practice.  They used TV-FM type front ends that provided a 10.7 MHz IF output on FM (as was the case with some TV-FM receivers), but which was modified to provide a 10.7 MHz TV sound (AM) IF output rather than the standard 38.15 MHz.  As with UK TV-FM receivers of the period, the IF strip was of the FM-AM type.  In some later models, the TV front end was further modified to provide for AFC.
 
Whether, during the 1960s, any US or UK maker offered TV sound tuners with coverage of the UHF TV channels I do not know, but I have not come across any evidence of such.  Here it might be assumed that the 10.7 MHz IF was too low, such that other solutions would have been necessary.
 
The visible next phase was in the UK, where in 1971 both Lowther and Motion Electronics offered solid-state TV sound tuners, the latter under the “TV Sound Monitor” moniker.  The Lowther model was UHF only, whereas the Motion Electronics model could be fitted with VHF and/or UHF tuners.  It was stated (in a Hi Fi News 1972 September test report) to have an IF in the vicinity of 35 MHz.   As far as I know it used standard Mullard varicap tuners of the time, which would have produced the 35 MHz IF without modification.  That number was between the standard 33.5 MHz  SIF of the system I UHF transmissions and the 38.15 MHz of the system A VHF transmissions.  The IF strip was of the FM-AM type with a ratio detector for FM.  Presumably in the relatively cool solid state environment and with modern passive components, reliable FM limiting and demodulation at 35 MHz was seen as less of a challenge than hitherto.  Here one could say that TV practice rather than FM practice had been followed in respect of the IF choice.
 
In the mid-1970s, Motion added another variant that covered UHF TV sound and FM stereo radio, the latter displacing the VHF TV sound option.  As far as I know, this continued to use the 35 MHz or thereabouts IF, so here, TV IF practice was applied to FM, rather like some earlier UK TV-FM receivers where the 38.15 MHz SIF was also used for FM.
 
The Motion Mk II TV Sound Monitor in the 1980s was actually a full TV tuner, providing video as well as audio, and as far as I know of the QSS type with standard IFs.  So it is nominally out-of-scope in this posting.
 
Information on the Lowther TV sound tuner is very scarce.  In the later 1970s, the concept was continued by Lowther’s apparent successor Chave Innovations, who also offered a UHF TV sound/FM stereo combination.  My guess is that as did Motion Electronics, Lowther used a “TV” IF.
 
There was also Japanese activity in the TV sound tuner filed during the 1970s, but information is scarce.  However, one Pioneer model, the TVX-9500, was offered in the US market in the later 1970s.  This covered the US VHF and UHF channels.  It used what appear to have been standard VHF and UHF TV front ends, providing the US standard 41.25 MHz VIF.  This was then downconverted to 10.7 MHz for processing in the usual way for FM radio.  The down conversion was supradyne, with a 51.85 MHz oscillator frequency.  (This was below the lowest US TV channel, A2, 54 to 60 MHz.)  There was a local AFC loop controlling this oscillator.
 
Pioneer TVX 9500 Block Schematic
 
 
This was the same basic pattern as was later used in Japanese split sound TV receivers and tuners.  Whether Pioneer was the first to use it is unknown.  But it does look as if the notion of converting from a standard SIF (41.25 MHz in the US, 54.25 MHz in Japan) down to 10.7 MHz had its origins in Japanese TV sound tuners of the 1970s.
 
Also unknown is whether there were any cases of conversion to 10.7 MHz from the European TV SIFs, such as 33.4 MHz.  There would have been more potential conflicts with the 2nd conversion oscillator frequency, although the good screening inter-compartment possible with IC-based circuits would have helped.
 
Another example was the US Realistic TV-100 TV stereo sound receiver of the mid-1980s.  This combined a TV sound tuner with a stereo amplifier.  In fact the tuner section was essentially a standard intercarrier TV receiver in respect of the front end and IF sections, the vision IF IC being used to generate the intercarrier and AGC and AFC biases, with the demodulated intercarrier feeding the stereo decoder.  Thus the IFs were all standard, 45.75 MHz VIF, 41.25 MHz SIF and 4.5 MHz intercarrier.  One may assume that Tandy/Realistic saw the use of standard TV circuits as the easiest and lowest cost pathway to the desired outcome.
 
In fact during the 1980s, the full TV tuner somewhat displaced the TV sound tuner.  If one looks at the Pioneer TVX-9500 TV sound tuner, it may be seen that the cost of segueing it into a full TV tuner was incremental.
 
The early consumer-type TV tuners associated with “component video”, such as the Sony VTX-1000R, were often quite complex machines, video switchers and sometimes audio control units as well as tuners.  But a simpler high-quality tuner-only species soon appeared, such as the Sony ST-7V in 1986.  Although a full TV tuner, this was also promoted as a TV stereo sound tuner providing a means of adding then-new stereo sound to an existing audio-video system.  Presumably Sony did not think it was worth offering a TV sound-only device.  By then I think that Sony was using QSS for this type of equipment, so that standard IFs would have been used.
 
Even so, for a while into the US stereo era at least, Pioneer did persist with handling the TV sound separately from the vision side.  Rather than a standalone TV sound tuner, it reverted to the 1950s idea of offering tuners that included TV sound as well as AM and FM radio reception.  The TX-V1160 was of c.1985 one such model.  Although no circuit details are available, my best guess is that it on the TV sound side, it followed the same double conversion pattern as the TVX-9500, except that the 10.7 MHz TV sound 2nd IF may have used the same IF strip as FM radio.  But probably different stereo decoder circuits would have been used.
 
As an aside industrial market TV tuners had existed for some time prior to the advent of component TV, as had consumer market tuner-timers for use with portable VCRs.  But these were “utility” devices, using standard intercarrier receiver circuitry and standard IFs, so add nothing to the “unusual IFs” story.
 
 
Cheers,
 
Steve
 
Posted : 09/09/2022 6:06 am
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Upthread, in taking about my thoughts on generating tables of standard and related TV IFs, I said:
 
"The third would be a list of standard IFs and their direct and indirect derivatives.”
 
I have since played around with various formats for the third list.  My thinking was that it should convey more information than was provided in the first table.  This developed into the idea of including, for each case, the salient points and references from the narrative story that is this thread.  In practical terms that meant that in my master spreadsheet, there would need to be a separate page for each IF that received this treatment.  But it does mean that the information is easier to retrieve.
 
To date I have drafted the sheets for System A, UK & Ireland, System I, UK & Ireland, and System E, France, attached.  Probably it will take some time to complete the whole set.
 
 
Cheers,
 
Steve
 
Table 3 System A   UK & Ireland
Table 3 System I   UK & Ireland
Table 3 Systen E France
 
Posted : 09/09/2022 6:19 am
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Lots of information to consider in the previous posts, thanks. 👍 

Frank

 
Posted : 09/09/2022 8:12 am
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Here are the Table 3 pages for systems B/G/H (except Italy and Australia) and system K1 (Francophone Africa).
 
Table 3 Systems B,G,H Worldwide except Italy & Australia
Table 3 System K1 Francophone Africa
  
There will be separate Table 3 pages for systems B/G Italy and system B Australia.
 
More to follow.
 
Cheers,
Steve
 
Posted : 12/09/2022 12:17 am
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Here are the Table 3 pages for system B, Australia, system L (France) and systems D and K (Eastern Europe).
 
More to follow.
 
Cheers,
Steve P.
Table 3 Systems D, K Eastern Europe
Table 3 System L France
Table 3 System B   Australia
 
Posted : 19/09/2022 2:40 am
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In the process of compiling the Table 3 page for system M, I was double checking the references, and as a consequence found some additional information about the development of the US standard IFs that is probably worthy of inclusion in the narrative ahead of the Table 3 entry.
 
The first of the newly found sources was a 1953 October IRE paper “Television Receiver Interference Industry Record to Date”, by Lewis M. Clement of Avco.
 
It is easiest to quote directly from the paper in respect of the standard IF:
 
“Industry standards for IF for radio, automotive radio and FM receivers have long been in effect and are universally used by all manufacturers.  Such standardization has resulted in simplification in the design, the testing and the manufacture of radio receivers. It, also, has helped to simplify the problem of interference to and from radio receivers.
 
“The problem of standardizing an IF for TV receivers was considered by the RMA Committee on Television Receivers, R4, for the same reasons.  After a thorough study, the Committee recommended, on October 31, 1945, that a narrow band 21.25 to 21.9 mc be established as the limits of a standard IF for TV receivers.  It should be remembered that at the time TV Channel 1 occupied the frequency band 44 to 50 mc.  On May 6, 1948, Channel 1 was eliminated by FCC action.
 
“Because of the interference problems of the 21.25 to 21.9 IF, the Committee on Television Receivers, R4, again reviewed the IF problem and on June 22, 1949 recommended the standardization of 41.25 mc as the IF for TV receivers.  At this time the only other service operating within the 21 to 26 mc IF band was low power state police transmitters.  The recommendations of the Committee were later embodied into the RMA Standard Intermediate Frequency REC 109.
 
The FCC made use of the information which was made available by the RMA, JTAC, and others.  The FCC Allocation Plan for Television, announced on April 14, 1952, was based on the RMA 41.25 mc standard IF.”
 
An interesting point is that the earlier “low” and later “high” TV IFs were both defined in terms of the SIF.
 
The RMA Committee R4 evidently worked fairly quickly on the low IF development, given that the FCC had only announced the revised VHF TV channel allocations on 1945 June 27 (as recorded in “Electronics” 1945 August, p.304).
 
Exactly when REC-109 inclusive of the TV low IF was promulgated is unknown, but it was reported as having been issued in “Electronics”, 1946 October, p.262.  Be that as it may, the 1945 October recommendation was probably taken as a cue by the industry, as would have the 1949 June recommendation in respect of the high IF.
 
As noted earlier in this series, the committee (now known to be R4) withdrew its low IF recommendation in 1948 April, as recorded in “Electronics” 1950 November, p.99.  It would appear though that REC-109 was left in place pending the approval of a replacement IF.
 
Again, as noted earlier in this series, the development process for the high IF was described in an article in “Electronics”, 1948 August, p.90ff, “Television Receiver Intermediate Frequencies”, by Paul F.G. Holst, of Crosley Division, Avco.  The outcome of the first phase of that process was that both 32.8 and 41.2 MHz (SIF) were suggested, with the latter preferred and by then available due to the FCC’s deletion of TV channel 1.
 
The second phase, in which the 41.25 MHz SIF was chosen, was described in a 1949 April IRE paper, “The Influence of UHF Allocations on Receiver Design”, by John D. Reid of Crosley Division, Avco.
 
To quote from the paper:
 
“Optimum IF for Combined VHF-UHF Usage
 
“The RMA R-4 Committee considered various if's between 21 and 42 Mc for vhf usage and chose 41.2 Mc as first choice for proposed standardization.  Re-examining the factors entering into a choice of 41.2, we find that the second harmonic of the sound if falls 850 kc below channel-6 picture.  41.65, as indicated by image requirements for the uhf band, would put this second harmonic within 50 cycles of channel-6 picture, and is therefore undesirable.  41.3, as indicated by uhf local oscillator radiation requirements, would put this second harmonic 650 below, channel-6 picture, which could probably be tolerated.  However, there is another consideration which should enter into the final choice of the exact if frequency.  It would be highly advantageous in respect to future developments where local oscillator frequencies might be obtained by multiplication and/or addition, that the local oscillator frequency be even integers.  With this requirement in mind, 41.25 Mc seems to be the best compromise in respect to all of the preceding factors, and in that it gives us a series of local oscillator frequencies starting with 522 Mc and increasing in 6-Mc steps, all of which are divisible by 6.”
 
(The 41.65 MHz and 41.3 MHz numbers, considered optimum respectively for UHF image rejection and oscillator radiation purposes, were derived in the paper.)
 
The choice of even integers, divisible by 6, for local oscillator frequencies was quite forward thinking.
 
In the UHF case, image rejection and oscillator radiation were major concerns.  There was an economic limit as to the extent that image response and oscillator radiation could be minimized in receivers.  Thus, the avoidance of major problems required careful choice of receiver IF, and careful assignment (by the FCC) of geographical channel allocations.
 
The high TV IF was included in RMA REC-109B of 1950 March.
 
Thus, we now have a good picture as to how the US high IF came about.
 
Derivation of the low IF remains obscure.  However, it is reasonable to assume that with the technology of the time, the desire was for a relatively low IF band.  Bearing in mind the prior use of 8.25 MHz (SIF), then in 1945 a number above 20 MHz may have been seen as a significant step upwards.
 
Cheers,
Steve
 
Posted : 24/09/2022 7:00 am
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Here is the Table 3 page for system M, USA and Worldwide except Japan.
 
Table 3 System M USA & Worldwide
More to follow.
 
Cheers,
Steve
 
Posted : 25/09/2022 12:18 am
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Previously I have said: “The origin of the 38.9 MHz VIF, 33.4 MHz SIF combination as a standard is thought to be this article:  Funk und Ton, 8, 1954, pp. 129-138, 1954, "Choice of an intermediate frequency for television receivers to suit the C.C.I.R. standard", by W. Holm and W. Werner.  This was given as the reference in the 1955 January BIRE paper:  “A Survey of Tuner Designs for Multi-channel Television Reception” by D. J. Fewings, and S. L. Fife.”
 
The Holm and Werner article itself remains elusive.  However, I have found an abstract that adds a little more information.  The abstract was in “Proceedings of the IRE, September 1954, p.1472, as follows:
 
“Choice of a Television-Receiver Intermediate Frequency to suit the C.C.I.R. Standard - W. Holm and W. Werner. (Funk u. Ton, vol. 8, pp. 129-138; March, 1954.)
 
“Considerations of interference by other services, various transmitter harmonics, etc., show that the optimum European television sound IF is 33.4 mc and vision IF 38.9 mc.  The use of these frequencies may require precautions against second-harmonic interference in channel 4 and sixth-harmonic interference in channel 8.  Sound in channel 7 may be interfered with by the fifth harmonic of the vision IF if the latter is mistuned by +50 kc.”
 
That creates the impression that the original article was quite thoroughgoing, so I’ll maintain the periodic searches. Allowing for publication lead time, it suggests that the development work was done in the latter part of 1953.
 
Cheers,
Steve
 
Posted : 25/09/2022 12:40 am
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Something of a surprise find recently was a 1955 IRE paper on early Australian TV planning, including a reference to intermediate frequencies.
 
The IRE paper, from 1955 April, was “Technical Requirements of the Australian Television System”, by A.J. McKenzie, of the Australian Broadcasting Control Board (ABCB).
 
It was a reprint of an Australian IRE paper of 1954 December, which itself was a print of a lecture delivered in 1953 November.
 
The IRE edition included an appendix, which it is assumed was part of the 1954 December paper, but not part of the 1953 November lecture.
 
ACBC made the decision to use a 625 line TV system in Australia in 1949.  Initially a 7 MHz channel was proposed, but in 1950 that was changed to 7.5 MHz.  That predated the adoption of a 7 MHz channel by the CCIR – the “Gerber compromise”.  Initially the latter did not affect the Australian planning, other than to change the sound channel parameters to align with the CCIR numbers.
 
The Australian 625 line system had a vision bandwidth of 5.5 MHz, a vestigial sideband (VSB) of 0.75 MHz, and an intercarrier spacing of 6.0 MHz.  It was actually very close to the later system I, the latter having a VSB of 1.25 MHz (although in the late I1 variant, that was reduced to 0.75 MHz.)
 
A set of 7.5 MHz VHF channels was allocated, and a standard IF derived.  Apparently receiver maker views on this differed, but investigations favoured an IF channel in the 30 to 40 MHz band, and the chosen numbers were 37.25 MHz VIF, 31.25 MHz SIF.
 
After the 1953 November lecture, and one supposes during the course of 1954, the ABCB had a change of viewpoint, and decided to adopt the CCIR standard.  Accordingly, a set of 7 MHz VHF channels was allocated, different to the European channels.  And to suit those channels, an amended standard IF was developed, namely 36.0 MHz VIF, 30.5 MHz SIF, as recorded earlier in this series.  This information was included in the Appendix to the paper.
 
A salient point is that standard IF was developed a spart of the overall planning process, and not separately and/or on a post facto basis.  Australia may have been unusual in that the same authority chose the TV system, assigned the channel frequencies and recommended the IF.  In many other territories, the IF work was left to industry organizations, although taken account of by the frequency allocation authorities.  By way of examples, in the USA, the FCC based its UHF allocations on an IF channel developed for the purpose by the RTMA, having stated in advance that it would do so.  The European UHF allocations developed by the ITU at ST61 were based upon the IF channels, howsoever developed, advised by the various country delegations.
 
What was written about the initial Australian 625 line proposal, with its 7.5 MHz channel, was interesting beyond the IF issue, and certainly adds a modicum of clarity to the generally murky early 625 line history but I’ll avoid digressing in this series.
 
Cheers,
Steve
 
Posted : 25/09/2022 11:56 pm
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Here is the Table 3 page for system M, Japan.
 
Table 3 System M Japan
More to follow.
 
Cheers,
Steve
 
Posted : 26/09/2022 12:18 am
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