Talk:Pentagrid converter

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I have extensively rewritten this article. I have included the Hexode, and Octode into the story as there is not really enought to justify a separate article. I have endeavoured to keep the content that some contributors felt was valuable enough to put in the article. Sadly some, I couldn't really work in without disturbing the flow - If you can work it back in without upsetting the flow, then feel free.

I particular, I have removed the lists of valve (tube) types that were used in the All American Five. These are better documented in that article, and it seemed rather pointless to duplicate the information.

There is also a fetish for adding links to valve or tube numbers. There really is no point unless you supply the linked to article as well, otherwise there remains rafts of broken links.

I know that Cmacd123 is awaiting this rewrite. I should be interested to hear your observations. I took the liberty of removing your discussion points as they do not relate to the new article (and some had bee addressed anyway).

This week I am: 86.133.15.213 16:46, 2 July 2006 (UTC)

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I don't want to start an edit war. What reference do you have that the Pentagrid converter was in any way invented outside north america? The Mullard design you quote was NOT a pentagrid.

BTW I am NOT american

cmacd 13:04, 16 May 2006 (UTC)

I have cleaned the garmmar a bit, and added an link to the Octode. If you have some data on the Octode, PLEASE write an article there, and feel free to compair and contrast.

Again, If you know of any British or other "pentagrids" please list them with their dates.

Finaly, The Information on the BVA has been moved to a separate article by that name! It is naturaly incomplete, please add what ever information you have that is relivant to THAT article.

I really want to see the section on Vaccuum tubes reflect the worlds knowledge on the subject.

cmacd 16:50, 16 May 2006 (UTC)

Maybe I've got you wrong. I find it quite surprising how difficult it is to find even fundamental information on electronics in the valve era. The internet in general seems to concentrate on the more modern stuff and even information on technology that is considered 'old hat' but still in use is hard to find even in modern encylopeadias. Wikipedia is slowly developing reference to these old technologies as people contribute. It is nice to see articles on old valve (tube) technology, because this was the era I was brought up in - my electronic apprenticeship was almost all valve with a hint of the then very new transistor. The problem is that much relies on expert knowledge rather than any attributable sources. I can recall going through the BVA era on the development of wireless (as it was then known). I can also recall that the wireless manufacturers were attempting to develop any technique that they could to reduce the valve holder count because not only did they have to pay £1 to the BVA for each valveholder, but the Marconi company wanted 12/6d (62½ pence) per valveholder as well. I also recall that the self oscillating mixer in the form of the pentagrid was one such development. This was either the late 1920's or possibly the beginning of the 1930's.

Not dug up any references yet, but I have found one reference to the MOV company enforcing the BVA cartel rules against one German company (identity lost) who was attempting to import into the UK, radio sets using triode-hexodes as the mixer. Ths enforcement occured in 1932 which predates the date you cited in the article for the US patent - and shows that pentagrids must have been in use even before this date. The MOV company were to repeat the enforcement 2 years later against another company German Company (Lissen). Interestingly, it would also appear that the pentagrid developed in the US was not quite the same as the one developed in Europe. I am on the case further - developments will appear.

I strikes me that reducing a single triode and a single hexode into a single valve (saving £1 12s 6d) was quite an incentive to develop the pentagrid. Whereas there was somewhat less incentive in America where combining a triode and a hexode into a single envelope would not provide a significant cost saving over a pentagrid (though I am aware that the designers of the All American 5 would save a couple of hundredths of cent if they could, but the pentagrid predated that design). Indeed the UK manufacturers dropped the pentagrid (and the octode) just as soon as they were able build triode/hexodes wihout incuring the wrath of the BVA.

The Mullard design you refer to was not contributed by myself. And indeed it has not got 5 grids, being an octode (though the 'K' designation would have been used for a pentagrid whereas 'H' was for a hexode or a heptode that operated like a hexode). Having said that, the octode is a development of the pentagrid and were designed as self oscillating mixers.

I can now only hope that my old text books surface at my loft clear out in the next couple of months and that I can amend the article as necessary.

In case anyone reading this is confused. A hexode is a frequency changer requiring both a signal and an oscilator input. The remaining 2 grids are screen grids. The Heptode added a suppressor grid. The pentagrid, although having 7 electrodes was not regarded as a true heptode as two grids was used as the oscillator, one for the incoming signal and the remaining 2 were screen grids. The octode added the suppressor grid to this design. Thus heptodes are sometimes refered to as 'heptodes of the hexode type' or 'heptodes of the octode type'. The difference being the design parameters and to a lesser extent the way the internal electrodes are sometimes connected together. Since writing this paragraph, it seems that US Pentagrids may differ from UK ones.

Contents 1 ============= 2 PENTA is Latin for 5 3 Lot scomes out when you look hard. 4 Refactoring

[edit] =============

Hi there 86.113 ....

I must admit that I have not really heard of any British Pentagrids before I started looking for references. When I first asked amoung the folks who are on the international tube collectors list, They had not heard of any either. After Ludwell Sibley - President of tube collectors and the follow who stores the archives of two american tube plants at his house for the antique Wireles association, came up with the Feranti one. (I guess Feranti counts as local to me, did'ent Mitel buy them, or was that Plessy....

I am slowly collating information. It looks like it is going to be muliple sourced. 20.133.0.14 13:26, 22 May 2006 (UTC)

Anyway, I do know that the european method was the separate triode section, often coded with a european Number Starting with ECH or xCH depending on the filament. I have an old Hi-fi with a 6AJ8/Ech81 in it. American designed TV sets used a dual triode for the converter, often a 6BQ7. Of course almost all AM radios in North america were based on the AA5 so they had a 12SA7 or 12BE6

I really don't know WHY they prefered that method. I will guess that Philips had some patents to do it that way, and so it because the style in Europe, (and Mullard although suposidly a british company was like Rogers-Majestic after the 1950's a Philips company.

Mullard was owned by Philips long before 1950. In fact it dates from as long ago as the 1920's. The ECH81 is a triode/heptode (of the hexode type). This is a hexode but with the addition of a suppressor grid to combat secondary emission. 20.133.0.14 13:26, 22 May 2006 (UTC)

I would not want to try to tell you what to do, but My sugestions.

1) The BVA was an interesting group, Here I know very little about them, they seem to have fulfilled the same function as "canadian Radio patents" but were a much stonger cartel, which would likly have faced Anti-Trust proceedings if they were on this side of the pond. I have exactly one New in box BRIMAR tube, and the side of the carton FORBIDS a dealer to sell it for less than Full list Price. That would not stand up in North america for more than 5 minutes.

I did take the former parts about the BVA and START an article about them. In a month I hape to have some new pictures of some tube boxes and I will try to upload that Blurb from the Brimar Box I have.

In the UK we used to have something called 'Retail Price Maintenance' This meant that a retailer could only sell something for the price dictated by the manufacturer. In the case of valves (tubes) this right was ceded to the BVA. The BVA was a price fixing cartel that would be illegal under current European law.20.133.0.14 13:26, 22 May 2006 (UTC)

2) the triode hexode (ech series) are not explained, and the history is lacking. Perhaps you could find some good references on that side of the pond to write the article for those.

I could also add articles on the Hexode, Heptode and Octode, but until someone starts an edit I am not able to add articles. I am unable to register because of observations on another article where there are security implications. Maybe you could start the edit bu just stating that they are 6 (7,8) electrode tubes or something.20.133.0.14 13:26, 22 May 2006 (UTC)

On second thoughts, I am not sure that there's enough to fill out an article on each of the types - it might tend to look like a stub. I'm giving serious thought to combining the whole lot under this article as, from whay I'm gathering, it would be a nice history on the development of self oscillating mixers. If I don't like it or it looks wrong, it can always be separated out afterwards without too much difficulty.

3) I will be looking for the Book Lud referenced, but you may be able to find it quicker on that side of teh atlantic. It looks like it would fill out articles on several of teh radio related topics.

Will have a look20.133.0.14 13:26, 22 May 2006 (UTC)

My plan when I get a time to play with this agaian is ot fill out teh technical explantion of how the 12SA7 family works.

I have dug up some info on this type of tube - watch this space.20.133.0.14 13:26, 22 May 2006 (UTC)

ALso offtopic, I just got a "OSRAM EMPIRE" 2B7 from a colector in Australia, it was made here in canada. - it is a dual diode triode of the same era as the 2A7/6A7.

Hmm. ITYWF that it is in fact an indirectly heated Double Diode *Pentode* also manufactured by RCA, Sylvania and a few others. Equivalent to a 6B7 (though the later had a 6.3 volt heater instead of a 2.5 volt heater). The pentode is suitable as either an RF amplifier or an AF amplifier. It was made (AFAICT) from the early 30's until after the war.20.133.0.14 13:26, 22 May 2006 (UTC)

By the way if you use 4 Tilde charachers, it will sign you posts in talk,

Let's see.20.133.0.14 13:26, 22 May 2006 (UTC)

cmacd 02:49, 22 May 2006 (UTC)

[edit] PENTA is Latin for 5

I can understand that the idea is that perhaps a full article on Superhetrodine conversion is what one was tring to do, but A pentagrid converter IS a tube with 5 GRIDS used for superhertodine conversion.

It was CLARLY Ivented by a dude working for RCA in the States. (I wish it was some Canadian) I had the actuall patent number there,

I'm not saying RCA didn't invent it. What it appears, is that it was independently invented here as well, and patented. As I said, the UK version was implemented differently. You are right in one respect: I inadvertantly dropped the patent number - I shall put it back. Rember that Alexander G Bell is credited with invention of the telephone, but someone completely independantly invented it and turned up at the patent office just a few hours after Bell (and firmly believd that Bell stole it). It happens. It happens a lot!86.133.15.213 17:53, 5 July 2006 (UTC)

I really don't want to revert and take all your effort out but...

The stuff about the OTHER converters belongs somewhere else...

There really isn't enough to justify articles in their own right. I think a better solution would be to make the pentagrid article more general on frequency changers (which was my intent (except I don't know how to change the title and adjust all the links, so a bit of help here would be useful)).86.133.15.213 17:53, 5 July 2006 (UTC)

cmacd 01:55, 3 July 2006 (UTC)

[edit] Lot scomes out when you look hard.

I have been looking at how best to clarify this article..

1) The pentagrid certianly belongs by itself, owing to the great numbers of radios in North america that used this tehcnology between 1930 and 1970. (40 year Span)

I'm not so sure. I think it should be a more general article on mixers. The pentagrid has a section to itself. A fair number of the other types are pentagrid type devices in that they operate in a similar way, even if the electrode count isn't exactly 5. North America isn't the only place on the planet.86.133.8.129 16:33, 5 August 2006 (UTC)

'frequncy conversion' does require a article... Much of the material that has been added on other types and methods of conversion should be moved into that article. The existing material on "power conversion" should be redirected to the existing articles on the subject. That would also be the place to discuss various methods used in solid state devices to change frequencies of signals.

The Pentagrid is a separate item of technology, notable because of the masive deployment in millions of radio receivers around the world. cmacd 14:32, 9 August 2006 (UTC)

There does appear to be a consensus in this direction. I will naturally bow to the majority. You suggest further down that you are already advanced on a rehash. Is this the case? If so I will wait and see what you come up with.86.132.201.65 19:12, 17 August 2006 (UTC)

2) The US designs - acording to the "radiotron designers handbook - written in australia were actually two different designs, over the years. The decription in the article really does not quite corespond to eitehr type. The grids in some are actually just the support wires with no actual grid windings, they extract signal for the osc, without affecting the electron beam in any major way.

What are we talking about here? 86.133.8.129 16:33, 5 August 2006 (UTC)

Someone has tried to include geo-politics and attempted to separate the uses different tipes of pentagrids as being from differnt geogrphical areas. The elctrons don't know where the tube was made or is operating.cmacd 14:32, 9 August 2006 (UTC)

I quite agree.

3) The 6K8 while shown as two separate sections actually has them coaxialy mounted. The European types that are simalar like the ECH81 are probaly the same.

The only photographs that I have of a (Sylvania) 6K8 show a metal enveloped tube, and it is not possible to see the interior. The photos of the RCA 6K8G, and the Raytheon 6K8GT show what at first glance, appears to be a single (but large) electrode structure. But yes the triode must be in there somewhere. Are you saying that the triode is actually inside the hexode?

86.133.8.129 16:33, 5 August 2006 (UTC)

I am refering to the diagrams the the "radiotron designers handbook" third and fourth edition which show the constuction of many types of tubes used in frequency conversion. The 6K8G and GT both have a large built in shield which would make examining the stucture rather difficult.cmacd 14:32, 9 August 2006 (UTC)

I don't have acces to a copy of that.

The European devices (and certainly the ECH81) use two distinctly visible structures mounted side by side. I can see the advantage of a coaxial arrangement if only to reduce the inductance of the coupling between the devices and hence improve the frequency response.

86.133.8.129 16:33, 5 August 2006 (UTC)

The ECH81 also has a large perforated shield, at least on the german and hungraian examples in my collection.cmacd 14:32, 9 August 2006 (UTC)

Indeed, but on the early Mullard/Philips examples, the shield is semi see through and the two structures are visible.

Have a look at http://www.r-type.org/exhib/aaa0036.htm . The lower illustration shows the structure. In this particular example, the triode section is located above the heptode section on the common cathode.

4) looking at "freqency converter", it curently talks about conversion fo power frequencies, while that would be the logical title for the discusion of hetrodyne conversion in general, and as well as the less common variants. The information that is curently there would have to move to a better place, or be a sub-article.

I had the idea that the link for 'frequency converter' could link to this article since power frequency conversion is irrelevant. I don't know how to carry out such mammoth changes. 86.133.8.129 16:33, 5 August 2006 (UTC)

If you look at the talk page on that article, you will see there is a consensus to make the changes. seeTalk:Frequency_converter I would sugest that Rotary converter and Motor-generator might also need some refactoring. but that is outside my area of primary interest. I only got into this because I saw someone saying that the Pentagrid converter was a british invention taht never caught on because of british politics, while I was looking for other inacuracies in teh various artiles in the vaccuum tube catagory.cmacd 14:32, 9 August 2006 (UTC)

The pentagrid did catch on in Britain - at least for a while. The triode-hexode supplanted it, but it remained popular in battery designs where the extra drain of a separate oscillator was undesireable, though this was more often an octode (but the pentagrid principle was preserved.

5) I discovered that Sylvania actually published tech buletin on AutoDyne converters using 12AU6 tubes in the late 50's.. I am waiting to obtain a copy of the article.

The Autodyne Converter predated the pentagrid converter. For example: Airzone Ltd produced a number of radio designs in the early to mid 1930's. Their models 500, 505 and 515 used an autodyne mixer section (and yes: I did forget this important development from the article). Their design notes refer to problems with early versions in that the oscillator was a little reluctant to oscillate. This was solved by decreasing the inductance of the first IF transformer and increasing the capacitance. The sets used a pentode mixer (57) followed by pentode IF amplifier (58), then a pentode (anode bend) detector (57) and a tetrode output stage (2A5). A double diode rectifier (80) completed the line up. The volume control was achieved by altering the detector's biasing. The reason I settled on this example is that the 500 model had an upgrade to a 500P at some point changing the mixer to a 2A7 pentagrid converter. Airzone refer to this as being "... much more reliable ..."86.133.8.129 16:33, 5 August 2006 (UTC)

Acording to Sylvania, the conflict was that AVC would throw off the operation of the occilator, and thus it was not posible to use avc on an early triode autodyne. The P5 could take AVC without problem because of the separate occilator grids. (hence explaining your example) Later a method was developed to allow AVC by using a separate diode, but of course that would have been generaly more expensive unless their was a half a 6H6 unused. Later, using a 12AU6 pentode as an autodyne was posible for receivers to be sold in urban areas, as AVC was not a serious problem when listening to local stations and the higher gain from effectily having the same tube amplify the signal twice, once as RF and once at IF allowed a 4 tube receiver by cutting out an IF stage.cmacd 14:32, 9 August 2006 (UTC)

Indeed. Airzone couldn't work out how to include AVC, so they didn't bother. The lack of AVC survived into the 500P model.

6) The need for a converter for superhetrodyne receivers only began after Armstrong invented the superhet.

You don't say. They were around before hand though for other purposes. 86.133.8.129 16:33, 5 August 2006 (UTC)

7) The superhet article nees to be checked as acording to RDHandbook converters running at the lower frequency were popular for shortwave applications.

8) It is still clear in my mind that the device was invented by a dude from RCA.

As I said, he may indeed have independently invented it. It is clear that a pentagrid existed in the Ferranti design department before he filed his patent. This technically would be enough to render the patent invalid if it were to be challenged - similarly the UK patent would have been equally invalid because of the RCA device. The UK patent office would have refused to issue the patent had the US patent been known of. The US patent office, on the other hand, have always been notorious for granting almost any patent application and letting the claimants argue it out in the courts. 86.133.8.129 16:33, 5 August 2006 (UTC)

cmacd 17:43, 24 July 2006 (UTC)

I am no fan of the USPTO, I only know what radios I grew up with, and they generaly had a 12SA7 or 12BE6, except for my first clock radio at age 10, with the mysterious 12AU6, which I now have an explantion of how its works.cmacd 14:32, 9 August 2006 (UTC)

What was mysterious about the 6AU6 (12AU6) apart from it's unavailability in Europe. It is a miniature RF high slope pentode. Probably not too different from our EF91, of which I have 3 examples in service here.

The 6AU6/ef94 and 12AU6/hf94 are sharp cutoff pentodes often found as Limiters in FM and TV sound, preamps, as well as in autodyne converter circuts. They can be overdriven to remove the AM component from an FM signal before a 6BN6 (ef80?) fm detector. (another good one for an article just because of the effort made to sidestep RCA patents - it looks like a pentode but really is not) The ef91/6AM6 is fairly rare in Canada, I think the only examples I have are UK brands, I have not seen a radio that uses it.cmacd 13:34, 18 August 2006 (UTC)

All the literature that I can find describes the 6AU6 is simply a 'pentode', nothing more. The only data sheet that I have is in French (EF94), and does not describe it as any special type of pentode, but generally most non variable-mu signal pentodes tend to be high slope types. The 6BN6 is not an equivalent for an EF80. They are not even the same type of valve. The EF80 is a regular high slope RF pentode. The 6NB6 is a strange device known as a 'gated beam' tube, having deflector plates and two anodes. The 6JH8 is a more complex example, but described as 'sheet beam' tube.

It was not designed to circumvent the pentode patent, but was designed to be a demodulator for synchronous and quadrature signals. It found use for a number of tasks in radar work but in particular, in colour demodulator circuits in US TV sets. It also turned up in early Ampex video recorders. Its main advantage was that the gain of the device to the two anodes remained fixed (being largely determined by the common cathode and grid geometry). If two separate valves were employed, the gain between the two would not be constant, due to uneven wear. They were not uncountered in Europe in TV applications. The construction is interesting as the electrode structure is not concentric. Some manufacturers seem to have published data sheets where the pin out in the data sheeet does not match the actual valve having included a diagram of a regular pentode with only one anode (presumably an error as the 6BN6 most definitely has two anodes - clearly visible through the glass). However, the only data sheets that I have to hand are from Tung-Sol and General Electric - both containing the error.

The web site at http://www.r-type.org/static/museum.htm acts as an index to most of the valve colections in the UK. The entry for the 6NB6 at http://www.r-type.org/exhib/aaa0277.htm gives some limited information on this valve including a photo. It is interesting that in light of the comments by the above contributor, they too mention the disparity between the published literature and the valve in their possession. 86.132.201.65 20:19, 22 August 2006 (UTC)

[edit] Refactoring

The plan is to move a decription of the various types of converter tubes out if the pentagrid article, and explain all of them in Frequency converter. That will leave the Pentagrid article talking about that device in relation to its importance as the major way that radios were built many places from the 1930 to 1975 era. I started several weeks ago just to corect a few minor errors in the article as it existed then... It has been a lot of work...

OK.

I will document the material on the Autodyne in the other page, one item I have to find is the use of autodyne circuts in Solid state receivers. I have seen some references of the "in passing" kind that indicate that they are very common in xister sets.

Indeed they were. Most broadcast receivers used them, but some did run to a separate oscillator. A quick shufty at some circuit diagrams (schematics to you) makes this abundantly clear.

Then i have to clean up All American Five, where someone said it was "all costs removed" they have not seen some of the 4 tube specials over the years, in comparison a AA5 is a delux product. cmacd 19:28, 11 August 2006 (UTC)

Actually, I used the term 'every expense spared' which was its design goal and therefore an apposite description. But, as you note, that didn't get in the way of someone sparing even more expense.