UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 22nd Nov 2017, 1:54 pm   #1
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,252
Default Mazda 30F27 RF tetrode for TV tuners.

The Mazda 30F27 RF tetrode is another valve that was never employed by TV tuner manufactures.
Perhaps it's the same for the American 6CY5 which is also a tetrode specifically designed for VHF TV tuners. https://www.radiomuseum.org/tubes/tube_6cy5.html
More likely it was decided beam shield triodes such as the PC95/6ER5 and PC97 were better than the RF tetrodes particularly in terms of noise performance.
From the 1960/61 R & T servicing book: Developments in Television Receivers, page 23. A new frame grid triode (PC97)
The presence of this beam shield provides a new way of neutralising the valve which has the advantage that one side of the neutralising capacitor can be connected to chassis, the other side going to the beam plate: see Fig 3. This technique is used in some recent tuners.

DFWB.
Attached Thumbnails
Click image for larger version

Name:	Mazda30F27.jpg
Views:	124
Size:	60.3 KB
ID:	152698   Click image for larger version

Name:	Mazda30F27info.jpg
Views:	70
Size:	129.0 KB
ID:	152699   Click image for larger version

Name:	MazdaPC95.jpg
Views:	98
Size:	32.4 KB
ID:	152701  
FERNSEH is offline  
Old 23rd Nov 2017, 3:43 am   #2
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

The 6CY5 VHF tetrode dates back to c.1956-57 and I think it was from Sylvania. It was of the sharp cutoff type whereas the Mazda 30F27 was remote cutoff. Quite possibly Mazda was inspired by 6CY5.

The 6CY5 might have slightly post-dated the 6BN4, which was the first of the new generation of TV tuner VHF triodes. Both developments were aimed at reducing the cost and complexity of VHF TV tuners without losing too much performance. The 6BN4 was in fact half of a 6BZ7 double triode, this having been one of the early American cascode valves, along with 6BK7 and 6BQ7. Attention was paid to lead-out resistance and capacitance, and pin layout in order make the 6BN4 relatively easy to use.

I imagine the argument in favour of the 6BN4 was that although it required neutralization, that was not as complicated as it was in the “old days” when the 6J6 was sometimes employed as an RF amplifier, and it was as quiet as a cascode stage. It had less gain, but that was easily made-up with recent and improved triode-pentode oscillator-mixers and improved pentode IF amplifiers. In favour of the 6CY5 was that it was easy to use as a pentode, no neutralizing required – and before the cascode valve arrived, most makers were more comfortable with using a 6AG5 (or similar) than a 6J6 - and it had more gain than a triode.

The 6BN4 had a “featured” application in the new Standard Coil “Neutrode” turret tuner. I am not sure if the 6CY5 had such a prominent debut. It was used though, including in at least one RCA VHF tuner, the KRK71D/E.

The RCA Nuvistor development program plan included both a VHF triode similar to the 6BN4, and a VHF tetrode similar to the 6CY5.

The next step prominent step with American VHF TV triode-based tuners was the Standard Coil Guided Grid turret, later 1959 I think. This used either a 6ER5 (EC95) or a 6ES5 (might have been from Sylvania). By that time Amperex was making inroads into the US TV set market with Philips valve designs such as the EC95. Both the 6ER5 and 6ES5 were described as semi-remote cutoff. The 6FY5 (EC97) was described as being remote cutoff. These triodes were easier to use in the neutralization department and being of the frame-grid type, had higher gain.

In 1960 RCA claimed that its new VHF tuner using a 6CW4 Nuvistor triode was about 1.5 dB better in noise factor than could be obtained with frame-grid triodes such as the 6ER5 or conventional triodes such as the 6FH5. I am not sure that a consumer-oriented Nuvistor tetrode was ever realized, although there were industrial tetrodes. Perhaps this putative gap between intent and reality reflected the fact that the triode was essentially the valve of choice for non-cascode VHF TV RF amplifiers, and that interest in the tetrode had faded.

By way of a sidebar item, the descriptor “semi-remote cutoff” appears to have been an American term, not much used in respect of European valves. It was used to describe valves, mostly those developed for TV applications, that had grid bases wider than was typical for sharp cutoff valves, but distinctly shorter than those of remote cutoff valves developed for radio receiver use, such as the 6BA6. Early examples were the 6BZ6 pentode and 6BC8 cascode double triode. The adoption of such valves was one solution vector in addressing the cross-modulation and AGC difficulties that were occurring with existing sharp cutoff valves and the scatter in the curves when operating biased well back. Another approach was the issue of sharp cutoff valves with more tightly controlled curves, examples being the 6CF6 (a selected 6CB6, as I understand it) and the 6DE6 pentodes. There was a good article on this topic in RCA Engineer 1955 October-November, page 18ff. This is accessible at: http://www.americanradiohistory.com/..._Issue_Key.htm.

Returning to the Mazda 30F27, evidently it was released in the UK at about the same time as the Mullard PC97:

Click image for larger version

Name:	WW 196107 p.366 Mullard PC97; Mazda 30F27, 30C17.jpg
Views:	32
Size:	107.9 KB
ID:	152735Click image for larger version

Name:	RadCom 196108 p.65 Mullard PC97, Mazda 30F27.jpg
Views:	44
Size:	91.5 KB
ID:	152736

Given this timing and the recent events in the USA, I’d say that there was little chance that Mazda would succeed with its new tetrode. Perhaps its view was that it had to innovate in directions other than Philips/Mullard was going. Hence the 30C13 (printed circuit compatibility) and the 30C17 (remote cutoff mixer pentode).


Cheers,
Synchrodyne is offline  
Old 28th Nov 2017, 6:16 am   #3
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Curiosity got the better of me, and I did a quick search to obtain some idea of the extent to which the 6CY5 tetrode was used in American VHF TV practice. I found a couple of examples.

It was used in the Sarkes Tarzian Hot Rod VHF turret tuner of the late 1950s. That the latter had a tetrode RF amplifier is confirmed by Tarzian advertising, and that the tetrode was the 6CY5 was confirmed by a mention in respect of its use in a Hoffman TV receiver:

Click image for larger version

Name:	Electronics 1959 p.149 Tarzian Hot Rod Tuner with Tetrode RF.jpg
Views:	57
Size:	74.8 KB
ID:	152983Click image for larger version

Name:	PF Reporter 195909 p.02 Hoffman TV Rx with Hor Rod Tuner with 6CY5.jpg
Views:	62
Size:	67.3 KB
ID:	152984

The 6CY5 was also used by RCA in its KRK71D/E VHF tuner:

Click image for larger version

Name:	R&TVN 195904 p.79 RCA KRK71D-E with 6CY5 Tetrode.jpg
Views:	27
Size:	73.5 KB
ID:	152985


Cheers,
Synchrodyne is offline  
Old 29th Nov 2017, 10:07 am   #4
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

It also occurred to me that the Mazda 30F27 would have been suitable for use as an RF amplifier in FM tuners and receivers. Whether Mazda ever promoted this end-use I don’t know.

At the time, triodes, pentodes and cascodes were used as FM RF amplifiers. The triode was probably dominant, mostly as half of an ECC85 or similar in a single-valve front-end, but not universal. Although pentodes were noisier than triodes, evidently the typical in situ difference at Band II frequencies was not enough to preclude the pentode from use in higher performance units. The 30F27 would have offered pentode performance and simplicity, with a lower noise level that was probably not too far above that of a triode.

A 1961 Tarzian advertisement shows that by then, it was also offering an FM front end as well as two types of TV tuner:

Click image for larger version

Name:	Electronics 19610512 Tarzian.jpg
Views:	19
Size:	68.9 KB
ID:	153092

Possibly the FM tuner also used the 6CY5 as RF amplifier, the same as the Hot Rod TV tuner. Whilst a proprietary FM front end was not in and of itself unusual, a two-valve type – as a separate unit - might have been. On the other hand, the single-valve type, originally developed I think in Germany, was legion amongst the third-party makers. It reached the USA in the later 1950s via imported radio receivers from the likes of Telefunken and Grundig, and by 1959-60 had been taken up by General Instrument and Standard Coil, both major TV tuner makers.

Looking at UK practice, the single-valve FM front end, from both in-house and third-party sources, was widely used. Where more elaborate FM front ends were required, these seem to have been designed and built as an integral part of the chassis rather than as bolt-on units. The only exception that I have noticed (from web pictures) are the Dynatron T10A and T11 models, which appear to have a “bolt-on” two-valve unit, the original T10 having used a single-valve unit.

The 6CY5 and 30F27 were not alone; there were other small-signal RF tetrodes of that era.

Sylvania offered the 6C9 dual tetrode (on a decar base) for use in FM front ends, one tetrode as an RF amplifier and the other as a self-oscillating mixer. I’d say it was intended to provide a tetrode option for single-valve front ends.

But the “triode lobby”, as it were, was not standing still. The 6EZ8 was a triple triode, intended for use as a combined FM RF amplifier, self-oscillating mixer and AFC valve. Or it could be used as an RF amplifier and mixer with separate oscillator, or as a mixer, separate oscillator and AFC valve. And the 6JK8 had one frame-grid triode, for use as an FM RF amplifier, and one conventional triode, for use as a self-oscillating mixer.

There were a couple of triode tetrode VHF oscillator-mixers intended for V use, namely the 6CL8 and 6CQ8. And another couple of VHF amplifier tetrodes, the 6EV5 and 6FV5. So, it does seem as if the VHF tetrode garnered some attention in the American market.


Cheers,
Synchrodyne is offline  
Old 29th Nov 2017, 12:01 pm   #5
ukcol
Dekatron
 
ukcol's Avatar
 
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,851
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Quote:
Originally Posted by Synchrodyne View Post
.....The 30F27 would have offered pentode performance and simplicity, with a lower noise level that was probably not too far above that of a triode.....
The extra noise generated by a pentode over a triode (as I understand it at least) comes from the noise generated when the electron stream from the cathode splits to the screen and anode. This is also true of the tetrode.

Is the better noise performance of the 30F27 over a pentode true generally of tetrodes and if so why?
__________________
Best Regards,
Colin McLaughlin
BVWS Member
ukcol is offline  
Old 29th Nov 2017, 7:32 pm   #6
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

No. The VHF valves at interest were special tetrodes, designed to minimize partition noise. This was done by aligning the grids so that the screen grid was shadowed by the control grid. This minimized screen current. In the case of the 30F27, the normal screen current was just 10% of anode current. For comparison, the EF183, a frame-grid remote cutoff VHF pentode of the same era had a normal screen current that was 35% of anode current. The smaller proportion of the cathode current that is going to the screen, the less effect fluctuations in that current have on anode current.

The designers of those VHF tetrodes would have had as an objective getting the partition noise as low as they reasonably could, well below that of pentodes and not too far above that of triodes. Otherwise they would not have had much of a case against the emerging crop of triodes, which were getting easier to neutralize.

That said, if one stands back it could be said that in the realm of receiving valves at the time, none of the tetrodes were what might be called conventional. The audio, video, field and line output tetrodes were all of the beam tetrode type, with aligned grids and kink-minimizing geometry. Aligned grids were sometimes use with output pentodes, an example being the PL84/UL84/EL86 group, where it might have been a necessity to keep the cathode current within a manageable limit.

I suppose that a VHF pentode might have been designed like these VHF tetrodes with, aligned grids and low screen current. But presumably the designers felt that their tetrodes were adequately kink-free such that there was little benefit to adding a suppressor grid. And whilst cascode performance was a reference point, the tetrode would have to be competitive in first cost with the new triodes, which of course had but one grid.


Cheers,
Attached Thumbnails
Click image for larger version

Name:	WW 196107 p.366 Mazda 30F27.jpg
Views:	21
Size:	108.1 KB
ID:	153121  
Synchrodyne is offline  
Old 29th Nov 2017, 9:07 pm   #7
ukcol
Dekatron
 
ukcol's Avatar
 
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,851
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Thank you Synchrodyne.
__________________
Best Regards,
Colin McLaughlin
BVWS Member
ukcol is offline  
Old 30th Nov 2017, 2:40 am   #8
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

No problem!

These attachments provide additional background and some comparative noise factor figures:

Click image for larger version

Name:	R&TVERB 4th p.15-6 Tetrode RF Amplifier.jpg
Views:	27
Size:	54.6 KB
ID:	153128Click image for larger version

Name:	R&TVERB 4th p.15-11 TV Tuner Noise Performance.jpg
Views:	27
Size:	58.4 KB
ID:	153129

This goes into more detail about the tetrode circuit details:

Click image for larger version

Name:	Hawker TVEPB 4th p.30,31 Tetrode RF Amplifiers.jpg
Views:	22
Size:	119.6 KB
ID:	153130

And this older reference provides noise figures for some of the VHF pentodes:

Click image for larger version

Name:	Fisher p.34.jpg
Views:	26
Size:	63.2 KB
ID:	153131



Cheers,
Synchrodyne is offline  
Old 30th Nov 2017, 10:44 am   #9
ukcol
Dekatron
 
ukcol's Avatar
 
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,851
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Thanks again Synchrodyne.

Are the higher noise figures associated with the PC86 & PC88 because the noise distribution is frequency dependant (higher frequency, higher energy)? I imagine there is not a simple answer to that question.
__________________
Best Regards,
Colin McLaughlin
BVWS Member
ukcol is offline  
Old 30th Nov 2017, 1:48 pm   #10
ukcol
Dekatron
 
ukcol's Avatar
 
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,851
Default Re: Mazda 30F27 RF tetrode for TV tuners.

I may have gone some way to answering my own question.

The formula for shot noise below from Reyner & Reyner, Radio Communication (1972) suggests that shot noise increases with bandwidth rather than absolute frequency.

This would, in part at least, explain why the PC86 and PC88 are noisier than triodes operating at VHF.
Attached Files
File Type: pdf Shot noise.pdf (236.4 KB, 22 views)
__________________
Best Regards,
Colin McLaughlin
BVWS Member

Last edited by ukcol; 30th Nov 2017 at 2:00 pm.
ukcol is offline  
Old 1st Dec 2017, 1:09 am   #11
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

To add to that, this chart shows increasing noise factor with frequency for several American UHF triodes:

Click image for larger version

Name:	from Fink p.16-20 UHF RF Amplifiers.jpg
Views:	28
Size:	68.5 KB
ID:	153191

I’d guess, and it’s only a guess, that the PC88 curve would be proximate to that of the 6BA4. I doubt that its gain as an RF amplifier would be sufficient that PC86 mixer contribution to the overall noise factor could be neglected, so on its own it would need to be somewhat better than 10 dB at 500 MHz and similarly better than 15 dB at 900 MHz.

The 10 to 15 dB range previously shown for the PC88, PC86-based UHF tuner probably means 10 dB at the bottom of Band IV and 15 dB at the top of Band V.

The frequency effect is also observable for the VHF tuners, in that the Band III noise factors are higher than those for Band I.


Cheers,
Synchrodyne is offline  
Old 1st Dec 2017, 10:18 am   #12
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,986
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Quote:
Originally Posted by Synchrodyne View Post

The 10 to 15 dB range previously shown for the PC88, PC86-based UHF tuner probably means 10 dB at the bottom of Band IV and 15 dB at the top of Band V.
That would make sense, the Winter Hill transmitter used the high channels and required minimum 1mv to clear the noise, the Philips tuners faired a little better but still not good.
Being close to Winter Hill we could usually get 2-3mv with a decent 10 element aerial but we still had areas in shadow.
WH started transmission in 1965, transistor tuners came out soon after 1966, perhaps late 65 and the difference was enormous to those shadow areas.
__________________
Frank
Nuvistor is offline  
Old 2nd Dec 2017, 4:22 am   #13
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Here are the comparative noise figures for the Mullard AT6360-02 (valves) and AT6380/02 (transistors) UHF tuners:

Click image for larger version

Name:	Mullard AT6360-02.jpg
Views:	25
Size:	38.0 KB
ID:	153236 Click image for larger version

Name:	Mullard AT6380-02.jpg
Views:	23
Size:	38.8 KB
ID:	153237

At the top end of Band V there was quite a difference - <14 dB for the valve tuner and <11.5 dB, typically 10 dB for the transistor tuner.

I’d expect though that the transistor tuner had a lower signal handling capability than its valve counterpart, perhaps not too much of an issue when getting enough signal was the bigger problem in many locations.

D.C. Read (of the BBC, I think) commented about the narrow signal range window in respect of the later ELC1043 UHF tuner:

Click image for larger version

Name:	WW 197601 p.56.jpg
Views:	34
Size:	97.4 KB
ID:	153238


Cheers,
Synchrodyne is offline  
Old 2nd Dec 2017, 5:31 pm   #14
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,986
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Overload was not something I saw on UHF with any tuner, certainly saw cross mod on VHF tuners though.

The noise figures for the Mullard valve tuner I think are better than the ones used by Ekco/Pye, they seemed particularly deaf.
__________________
Frank
Nuvistor is offline  
Old 6th Dec 2017, 8:34 am   #15
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

The American 6CY5 VHF tetrode was used as an FM RF amplifier as well as in the VHF TV RF amplifier role. An example was the Heathkit AJ-10 AM-FM tuner of 1960. At least from the schematic one gains the impression that the front end was a separate unit, whether of in-house or proprietary origin being unknown. The AJ-10 had a three-gang front end with a 6CY5 RF amplifier and a 6EZ8 triple triode as mixer, oscillator and AFC reactance valve. The same front end was carried over to the AJ-11 successor in 1961.

The AJ-10 was an “economy” model. The corresponding “deluxe” model was the AJ-30, which had a 6BS8 cascode FM RF amplifier and was generally more elaborate.


Cheers,
Synchrodyne is offline  
Old 20th Dec 2017, 11:04 pm   #16
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Heathkit also used the Sylvania 6C9 double tetrode in some of its tuners, for example in the AJ-12 FM-only model. This was essentially a 6CY5 pair in a single envelope with a Decar 10-pin base, intended for use as a combined RF amplifier and autodyne mixer in a single-valve front end, presumably with some performance advantages over a double-triode single-valve front end. This was effectively an FM valve, less suitable for use in VHF TV tuners where autodyne mixers did not really fit. As an aside, when FM multiplex stereo was on the horizon in the USA, it spurred the development of new FM receiver-oriented valves, both for improved front end performance and for multiplex decoding functions. GE Compactrons and Sylvania decar-based types featured amongst these new FM valve releases.

Returning to VHF TV RF amplifiers, as well as tetrodes and specialized triodes, another approach was the “shadow-grid” type, apparently introduced by GE in 1960 as the 6FG5. This was basically a beam tetrode with an additional grid between the control grid and the screen grid. This was the shadow-grid, which was aligned with the screen grid and connected to the cathode. It directed the electron flow into sheet beams that largely avoided contact with the screen grid, with resultant low current for the latter. The mechanism is shown here:

Click image for larger version

Name:	RE 196008 p.96 GE 6FG5 Shadow-Grid.jpg
Views:	21
Size:	78.5 KB
ID:	154305


The 6FG5 anode curves showed some kinking, but so did those for the 6CY5 tetrode:

Click image for larger version

Name:	6FG5 GE 196001 p.02.jpg
Views:	14
Size:	62.0 KB
ID:	154302 Click image for larger version

Name:	6CY5 RCA p.03.jpg
Views:	14
Size:	151.6 KB
ID:	154303


The later 6FS5, with screen current down to less than 2% of anode current, had only marginal kinking:

Click image for larger version

Name:	6FS5 GE 196112 p.02.jpg
Views:	14
Size:	60.7 KB
ID:	154304


The 6FS5 was used at least by Tarzian in its “Silver-Sealed” switch-type TV tuner.


Cheers,
Synchrodyne is offline  
Old 20th Dec 2017, 11:07 pm   #17
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

GE described its 6FG5 and 6FS5 as being of the “shadow-grid beam pentode” type:

Click image for larger version

Name:	6FG5 GE 196001 p.01.jpg
Views:	15
Size:	75.5 KB
ID:	154306


These valves did not have a suppressor grid; what was shown as a fourth grid on the pinout diagram was actually the set of beam confining plates.


GE’s nomenclature seems reasonable in the context that it used the term “beam pentode” for valves such as the 6AQ5 which were more conventionally know as beam tetrodes. So, the term “shadow-grid beam pentode” referred to a beam pentode to which a shadow-grid had been added.

On the other hand, RCA referred to its 6GU5 as being a “beam hexode”:

Click image for larger version

Name:	6GU5 RCA 196512 p.01.jpg
Views:	14
Size:	64.7 KB
ID:	154307


It typically used the term “beam power amplifier” for beam tetrodes, but then showed these as having a grid #3, even though they had beam-confining plates rather than a suppressor grid. Whether the 6GU5 had, for grid #4, an actual suppressor grid or beam-confining plates is not unequivocally deduced from the available evidence.


Cheers,
Synchrodyne is offline  
Old 20th Dec 2017, 11:17 pm   #18
turretslug
Nonode
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 2,478
Default Re: Mazda 30F27 RF tetrode for TV tuners.

At risk of being both off-topic and in the wrong forum section, the above brings to mind the pre-war EF8 hexode, another attempt at enhancing performance with addition of grids and juggling of function. There were evidently some decades of off-the-beaten-track research going on in valve- makers labs with varying degrees of success;

http://www.r-type.org/exhib/aai0175.htm

http://www.r-type.org/exhib/aaa0469.htm

https://frank.pocnet.net/sheets/046/e/EF8.pdf
turretslug is offline  
Old 21st Dec 2017, 2:06 am   #19
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Mazda 30F27 RF tetrode for TV tuners.

Quite relevant I think. I'd say that the EF8 was an early version of the shadow-grid principle, which GE then dusted off and re-used in 1960.


Cheers,
Synchrodyne is offline  
Old 21st Dec 2017, 10:50 am   #20
turretslug
Nonode
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 2,478
Default Re: Mazda 30F27 RF tetrode for TV tuners.

I think (but it's all a bit wooly) that the EF8 may have been used as an RF stage in early CH receivers- this would have been slightly before the EF50/45MHz IF strip saga, and also where high HF/low VHF application really focussed attention on shortcomings of established valve types, both electronically and physically. Perhaps Philips simply sidelined the EF8 in favour of the EF50 and developments and, as the transistor started to establish itself as a genuinely useful device, the shadow-grid principle was an expired patent but proven idea that could be usefully, inexpensively and relatively easily developed with two decades of experience of miniaturised and highly precise valve construction.

A rough analogy could be drawn with M-OV's relinquishing of commercial development of the beam tetrode, and RCA's subsequent running with the ball to considerable advantage, though the keen technical and commercial incentive meant a much more rapid progression of events.
turretslug is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:23 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.