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 5th Oct 2017, 9:25 pm   #1
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,984
Default Vintage Television Technology.

Split from this thread:-

https://www.vintage-radio.net/forum/...d.php?t=140224



It’s fascinating to me to have first hand information about the radios and TV used in the USA. Many components used were introduced either at similar times or perhaps a little earlier in the USA such as silicon power rectifiers. Many circuit designs such as the totem pole power with the sound output valve, voltage doublers in the PSU did not get used in the UK, perhaps voltage doublers but rarely.

With electronics like other disciplines, there is more than one way to do a job, some due to contraints such as 117v power or just convention.

Thanks usradcoll for the info
__________________
Frank
Nuvistor is online now  
Old 6th Oct 2017, 8:25 am   #2
Argus25
Octode
 
Argus25's Avatar
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 1,656
Default Re: Vintage Television Technology.

Quote:
Originally Posted by Nuvistor View Post
Its fascinating to me to have first hand information about the radios and TV used in the USA.
From down here in the Antipodes, I have had the opportunity to look objectively at very early TV sets from both the USA & the UK. Since television here started in the late 1950's here, the sets we have here that are older than that were imported.

As a general rule many early UK TV sets were AC/DC or transformer-less designs. While nearly every American set had a power transformer. Plus, in American sets there is a paucity of aluminium. They used it for IF transformer shields but that is about it. In UK sets often the entire chassis was aluminium like the Bush TV22.

VDR's (voltage dependent resistors like NTC's, and Metrosils) were common in UK sets and hardly ever used in American sets.

American sets pioneered the use of Turret tuners earlier than the UK sets. And even though the efficiency diode concept was worked out by Blumlein, pre war, the Americans (RCA) were first to commercialize it.

What we now know as the "standard monochrome television design, complete with efficiency diode & inter-carrier FM sound" appeared from RCA in 1946 as the RCA 621TS model.

All American post war TV sets, regardless of brand or model, followed this 621TS format, while the UK sets lagged behind before they caught up in the mid 1950's. The 621TS was designed during the war, but the war delayed its release. Here is a restoration of a 621TS:

http://worldphaco.com/uploads/621TSARTICLE.pdf

It is worth mentioning that the power transformers in many American sets are not well suited to 50Hz operation. The primary currents are high with magnetic saturation on this frequency and they have very large radiated magnetic fields and very high off load primary currents. They simply run too hot on 50Hz.

In two American TV sets I have, the 621TS and a Meissner 1939 pre-war set, both the power transformers required replacing for this reason (we are 50Hz here in Australia). Fortunately there are modern power transformers made by Hammond which solve the problem.
Argus25 is offline  
Old 6th Oct 2017, 11:30 am   #3
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,984
Default Re: Vintage Television Technology.

I think the lack of multichannel tuners in the UK was simply due to, using pre war designs to get started in 1946, only one station, keep the sets simple and as affordable as possible. Money for expansion of the service was very tight so area coverage was slow to increase, Sutton Coldfield 1949 and then Holme Moss 1951.
By that time set makers were starting to make sets that would tune all Band 1 channels but no Band 3.
__________________
Frank
Nuvistor is online now  
Old 6th Oct 2017, 8:11 pm   #4
rambo1152
Heptode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 828
Default Re: Vintage Television Technology.

So there would have been no simple TRF designs in America, as there were in the UK.
__________________
--
Graham.
G3ZVT
rambo1152 is offline  
Old 6th Oct 2017, 8:28 pm   #5
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 6,369
Default Re: Vintage Television Technology.

In the UK immediately-post-WWII for most people there was only one TV 'channel' up until the late-1950s [and then there were only two... unless you were lucky enough to live in one of the North Midlands areas where you had the luxury of getting both ATV and Granada!] so when TV returned after the War a fixed-tuned TRF was likely to be the cheapest/easiest option for manufacturers wanting to return to the market.

The US preference for transformer-based power supplies is no doubt predicated on their ubiquitous 110/120V AC utility supply: if you want to provide line/frame drive to a decent-sized CRT [by which I mean 17-inches or greater] you need higher voltages than you'd get from simply half-wave-rectifying the 117V supply.

Did any US TVs use half-wave voltage-doubler/tripler HT supplies? I recall that this approach was sometimes used on more-upmarket "All American Five" broadcast-receivers who wanted more audio-output than was achievable with half-wave-rectified 117V for the audio output-stage's anode supply.
G6Tanuki is online now  
Old 6th Oct 2017, 8:44 pm   #6
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,984
Default Re: Vintage Television Technology.

Yes they did use voltage doublers see post 5
https://www.vintage-radio.net/forum/...d.php?t=140224

There is a link on that post to Radio-Electronics mag.
__________________
Frank
Nuvistor is online now  
Old 7th Oct 2017, 2:03 am   #7
dtvmcdonald
Pentode
 
Join Date: Mar 2016
Location: Champaign, Illinois, USA.
Posts: 149
Default Re: Vintage Television Technology.

Quote:
Originally Posted by rambo1152 View Post
So there would have been no simple TRF designs in America, as there were in the UK.
The 1932 RCA 120 line test set was TRF.

All other fully electronic (i.e. no mechanical transmitter) sets were superhet.

Typical early IFs were in the 8-12 MHz range and were very complicated.
My TRK12 is 8MHZ audio, 12 video, uses discrete component bandpass filters
rather than transformers, and has a rock solid super great response curve,
fully capable of 1954 color TV. Its split AM sound. The TT5 is similar
but fewer IF stages. Note that prewar US TV was 441 lines; all sets work fine
at 525 an FM sound by slope detection.

What most WON'T work is nonstandard frequencies ... the fine tuning is
usually barely enough to tune in the audio. There were originally 5 channels which changed
TWICE to get to our current 5 "Band I" ones by 1947. The channel width and relative carrier positions
never changed from 1939 just the overall frequency.

Many prewar superhet tuners were horrendously bad designs which had vastly too-big
diameter round switches. This required things like 3/8 inch wide strap "inductors"
to get low enough inductance. This all at only about 96 MHz. But they are STABLE.

Last edited by dtvmcdonald; 7th Oct 2017 at 2:17 am.
dtvmcdonald is offline  
Old 7th Oct 2017, 6:52 am   #8
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,984
Default Re: Vintage Television Technology.

Yes I had read about the change in frequencies and the lost channel 1 to accommodate the 40 odd MHz IF whereas Europe went for 30 odd MHz and kept the Ch 1 freq.

UK UHF valve (tube) tuners were not very sensitive circa 1964/65 when UHF TV started in the UK, quickly changed to transistor which were much better.

USA started with UHF in the early to middle 50s, how good was the UHF performance of those early tuners?
__________________
Frank
Nuvistor is online now  
Old 7th Oct 2017, 4:13 pm   #9
usradcoll1
Pentode
 
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 203
Default Re: Vintage Television Technology.

Quote:
Originally Posted by Nuvistor View Post
It’s fascinating to me to have first hand information about the radios and TV used in the USA. Many components used were introduced either at similar times or perhaps a little earlier in the USA such as silicon power rectifiers. Many circuit designs such as the totem pole power with the sound output valve, voltage doublers in the PSU did not get used in the UK, perhaps voltage doublers but rarely.

With electronics like other disciplines, there is more than one way to do a job, some due to contraints such as 117v power or just convention.

Thanks usradcoll for the info
Thanks for your kind thoughts!
I'll try to provide any information I can about US products.
usradcoll1 is offline  
Old 7th Oct 2017, 6:19 pm   #10
kan_turk
Pentode
 
kan_turk's Avatar
 
Join Date: Mar 2014
Location: Dublin, Ireland
Posts: 205
Default Re: Vintage Television Technology.

Quote:
Originally Posted by Nuvistor View Post
Yes I had read about the change in frequencies and the lost channel 1 to accommodate the 40 odd MHz IF whereas Europe went for 30 odd MHz and kept the Ch 1 freq.

UK UHF valve (tube) tuners were not very sensitive circa 1964/65 when UHF TV started in the UK, quickly changed to transistor which were much better.

USA started with UHF in the early to middle 50s, how good was the UHF performance of those early tuners?
Early US UHF tuners were very very insensitive - typically employing no RF amplifier at all - simply an oscillator and mixer feeding into the VHF tuner - this was no great problem, however, as UHF was used in the US, and in most other countries to provide additional, local services, with VHF (with its vastly superior propagation characteristics) continuing to be used for nationwide services. It was only in France and GB, where VHF channels were already occupied by legacy systems ie 819 and 405 line respectively, that UHF only had to be employed for nationwide coverage
kan_turk is online now  
Old 8th Oct 2017, 4:09 am   #11
dtvmcdonald
Pentode
 
Join Date: Mar 2016
Location: Champaign, Illinois, USA.
Posts: 149
Default Re: Vintage Television Technology.

"as UHF was used in the US, and in most other countries to provide additional, local services, with VHF (with its vastly superior propagation characteristics) continuing to be used for nationwide services"

That's simply not true in the US. Many cities right from the start had no VHF station,
and almost all had insufficient VHF for the usual original three networks plus one
local. When PBS ("public") became the 4th network it got worse. Most of the US has never had much use for "gap filler" transmitters, except Utah. Only the maybe the 10
biggest ... and islolated ... cities had an excess of VHF channels (e.g. New York
and Los Angeles, and even New York had one officially across the river.) The east coast
has cities too close for VHF.

Also note that we had coverage of even modest size cities with one or two stations
long before coaxial cable and microwave networks. They had to do network
programs on 16 mm film.

Note that in the US external UHF preamps were readily available and worked
well enough.
dtvmcdonald is offline  
Old 8th Oct 2017, 12:44 pm   #12
kan_turk
Pentode
 
kan_turk's Avatar
 
Join Date: Mar 2014
Location: Dublin, Ireland
Posts: 205
Default Re: Vintage Television Technology.

Perfectly correct of course - I was alluding only to the initial introduction of UHF and should have made that clear - as mentioned extensive use of external preamps which gave both gain and in some cases added selectivity - very much providing the RF amp which was, almost invariably, integral to UHF tuners from the start in Europe

Last edited by kan_turk; 8th Oct 2017 at 12:46 pm. Reason: Words omitted
kan_turk is online now  
Old 8th Oct 2017, 4:28 pm   #13
rambo1152
Heptode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 828
Default Re: Vintage Television Technology.

For anyone who has not already see it, there is a fascinating film on Youtube about the early days of UHF in the US called "Fog over Portland".

It's marketing, thinly vailed as a documentary, and as well as addressing the suspicion the public and the trade had about UHF, the film's sponsor, Zenith, attempts to extol the virtues of its combined VHF/UHF turret tuner that would need an engineer to fit a module for any additional channel, or change of channel should the customer move to a different area, whilst rubbishing other manufactures that used a simple continuous UHF tuner that covered the entire UHF band.
__________________
--
Graham.
G3ZVT

Last edited by rambo1152; 8th Oct 2017 at 4:44 pm.
rambo1152 is offline  
Old 8th Oct 2017, 10:53 pm   #14
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,984
Default Re: Vintage Television Technology.

Thanks for that info Graham, just watched it, pity they didn’t actually show some off screen photos of the performance at the distances claimed, power of the transmitter and receiving aerial installations used.
Still well worth watching.
__________________
Frank
Nuvistor is online now  
Old 12th Nov 2017, 3:27 am   #15
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Vintage Television Technology.

Re the issue of RF amplifiers (or not) for UHF TV tuners during the valve era, was there much net advantage for the European approach as compared with the standard American approach?

The standard American approach was predicated on the use of a bandpass tuned input circuit followed by a passive diode mixer followed by a low-noise IF amplifier, the last-mentioned usually being the RF amplifier of the VHF tuner, and so equipped with (delayed) AGC.

The European (German) approach was based upon the use of a triode self-oscillating mixer. Since this would have been a lot noisier than a diode mixer, it would have needed to have been preceded by a low-noise grounded-grid RF amplifier just to match performance of the American configuration. Whether it was any better in terms of noise factor I dont know. But presumably it was better in terms of blocking the oscillator signal from getting back to the aerial input.

With a noisy mixer, there was no point in feeding the UHF IF into the (low-noise) VHF RF amplifier, so instead it went into the VHF mixer which then operated as an IF amplifier. And the overall gain at UHF provided by the RF amplifier and active mixer meant that the additional gain that would have been provided by the VHF RF stage was less needed. Perhaps though the deletion of an AGCd stage was the reason for the introduction (in Europe) of triode-pentode VHF mixers with remote cutoff pentodes that could be connected to the RF AGC line.

I think that German practice was to use a broadband aerial input (presumably for lowest noise) to the RF amplifier, with a bandpass interstage. For UK application, an additional tuned RF stage was necessary, so that a single-tuned rather than aperiodic input to the RF amplifier was used. This was evidently necessitated by the BREMA decision to move the IF upwards from 38.9 to 39.5 MHz, whilst retaining the same European channel matrix as previously agreed at the ITU Stockholm 1961 meeting, including the co-siting of channels n and (n+10) transmitters. Thus, the required image rejection became 53 dB, whereas it would have been 29 dB with the standard 38.9 MHz IF (which was quite suitable for System I, and for example was used in South Africa).

The American standard valved UHF tuner might not have been a product of necessity, though. Quite early on the US tubemakers had developed a range of valves that could be used for the various UHF tuner functions, and were designed with the consumer application in mind, rather than being industrial products pressed into consumer service. By mid-1952 GE was offering the 6AJ4 as a grounded grid RF amplifier, the 6AM4 as a grounded-grid mixer, and the 6AF4 as an oscillator. (I think that the 6AF4 was originally developed by RCA, from the 6F4 acorn valve.) And by the end of 1952 Sylvania was offering the 6AN4 for use as an RF amplifier and as a mixer, and the 6T4 for use as a local oscillator. RCA added the 6BC4 RF amplifier by mid-1954. So, one might infer that it was the tuner makers and setmakers who opted for the simpler form of UHF tuner, used in tandem with VHF tuners. Evidently the benefits that accrued from using RF amplifiers and/or active mixers did not justify the extra costs. The 6AF4, later succeeded by the 6AF4A, became the most common American UHF oscillator valve, but the others did not achieve any prominence.

The 6AJ4 became the EC84 in Europe, and I understand that from this was developed the EC86/PC86 for European UHF tuner use. Originally the EC86/PC86 was intended to cover both the RF amplifier and mixer applications, but the EC88/PC88 was then developed for better RF amplifier performance. The European choice of self-oscillating UHF mixer does not seem to have had an American precedent. It might have been done for cost reasons, to avoid the need for a third UHF valve; in general, self-oscillating mixers were seen as being not as good as the externally excited type.

The simple American UHF tuner design was evidently viewed as being satisfactory, as it was retained until the early 1970s. In the mid-1960s, transistor oscillators replaced the UHF triode oscillators, but the nature of the UHF signal path remained basically the same. (In the USA, the move to solid-state VHF tuners was slowish until suitable dual-gate mosfets became available, given that circuits based upon bipolar devices had rather poor cross-modulation performance.)

It would appear that the advent of varactor tuning in the early 1970s was the driver of changes in US UHF tuner design. The early varactors were lossy as compared with their variable capacitor predecessors, and the use of low-noise RF amplifiers became desirable to offset these losses. Typically, a grounded base amplifier, with single-tuned input and agc was added ahead of the bandpass interstage and crystal diode mixer. The extra tuned circuit might have been desirable to offset the possibly lower Q of early varactors. From circa 1975 suitable UHF-capable dual-gate mosfet RF amplifiers became available, and these offered a step improvement in cross-modulation performance.

At the same time, the advent of varactor tuning in VHF tuners made it less convenient to route the UHF IF signal via the RF amplifier. Rather it would go direct to the VHF mixer transistor, bypassing the VHF varactor circuitry. This change required extra gain in the UHF signal path, typically achieved with a grounded base stage following the UHF mixer and included in the UHF tuner, although sometimes I think within the VHF tuner (which then allowed said VHF tuner to be used with a conventional UHF tuner if desired). An alternative approach, used by Sylvania at least, was to use an active (transistor) mixer, still fed by a separate transistor mixer. That the agcd VHF RF amplifier was no longer in the UHF signal path was probably the reason why the new UHF RF amplifiers were agcd, in order to retain the full agc range.

Early European solid-state UHF tuners appeared to follow the same basic pattern as their valved predecessors, although sometimes with the addition of agc for the RF amplifier. So, they had grounded base RF amplifiers followed by grounded base self-oscillating mixers. In the UK case, there were some variations in the distribution of the RF selectivity, for example an aperiodic input with the fourth gang used for a tuned image rejector, and as another example, an aperiodic input with a triple-bandpass interstage.


Cheers,
Synchrodyne is offline  
Old 12th Nov 2017, 10:03 am   #16
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 5,984
Default Re: Vintage Television Technology.

Excellent post Synchrodyne.

Reading the USA magazines the 6AF4 tended to have a short life, the 6AF4A was developed to make the valve more reliable. It appears that the valve had to work at it max potential for the tuner to work.
The European PC86/88 were not that great on reliability or performance but in the USA case and European, circuits had to be designed on what components were available.

Thank you for taking the time to write it all up.
__________________
Frank
Nuvistor is online now  
Old 12th Nov 2017, 3:50 pm   #17
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 5,252
Default Re: Vintage Television Technology.

An example of an American mid-sixties UHF tuner. Diode mixer and transistor local oscillator.
RCA KRK120.

DFWB
Attached Thumbnails
Click image for larger version

Name:	RCA_KRK120.jpg
Views:	126
Size:	71.4 KB
ID:	152144  
FERNSEH is online now  
Old 12th Nov 2017, 9:33 pm   #18
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Vintage Television Technology.

And here is the RCA KRK-226 UHF tuner of 1975:

Click image for larger version

Name:	RCA KRK-226.PNG
Views:	94
Size:	45.4 KB
ID:	152158

It was RCAs first, and I think the first UHF tuner anywhere to use a dual-gate mosfet RF amplifier, foe which a 10 to 20 dB reduction in cross-modulation was claimed.

There was a preceding UHF varactor tuner that used a grounded base bipolar RF amplifier. The grounded base IF preamplifier in the KRK-226 was a carryover from this previous model, so one may infer that the use of a mosfet in this position was not justified.

The KRK-226 was intended to work with the KRK-228 VHF tuner, also of 1975, with the UHF IF going to the mixer, not the RF amplifier:

Click image for larger version

Name:	RCA KRK-228.PNG
Views:	62
Size:	43.2 KB
ID:	152159

This was RCAs first VHF tuner to use a dual-gate mosfet in the mixer position, for which it claimed a 10 to 20 dB reduction in channel 6 colour beat. RCA wasnt though the first to use dual-gate mosfets in both the RF amplifier and mixer positions. Others, I think including Zenith and Magnavox, got there first.

The preceding VHF varactor tuner would have used a cascode bipolar mixer. The latter goes back at least to the KRK-142 of 1968. This was a switch tuned unit that was the first anywhere to use a dual-gate mosfet as RF amplifier:

Click image for larger version

Name:	RCA KRK-142.jpg
Views:	47
Size:	54.7 KB
ID:	152160

The cascode bipolar mixer may have had earlier use, Im not sure. As far as I know, preceding the KRK-142 was a top-end VHF tuner that had a nuvistor RF amplifier and a bipolar mixer; the latter may well have been of the cascode type.

The KRK-132 UHF IF input was to the RF amplifier, and it was designed to work with the KRK-132 UHF tuner, which was probably similar to the KRK-120.


Cheers,
Synchrodyne is offline  
Old 12th Nov 2017, 9:46 pm   #19
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Vintage Television Technology.

This is the Sylvania UHF varactor tuner that had an active (bipolar) mixer. As best I can work out, it arrived for the 1971 model year range:

Click image for larger version

Name:	Sylvania UHF Tuner.jpg
Views:	66
Size:	54.7 KB
ID:	152161

And here was its companion VHF varactor tuner:

Click image for larger version

Name:	Sylvania VHF Tuner.jpg
Views:	47
Size:	48.5 KB
ID:	152162

That had a dual-gate mosfet RF amplifier and a cascode bipolar mixer. UHF IF input was to the VHF mixer.

I think that the dual-gate mosfet RF amplifier plus cascode bipolar mixer combination was also used by Heathkit for its early 1970s VHF tuners.


Cheers,
Synchrodyne is offline  
Old 12th Nov 2017, 10:12 pm   #20
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,089
Default Re: Vintage Television Technology.

Returning to the valve era and in particular UHF valves, these advertisements give a picture as to what the American valve makers were doing in the first half of that decade.

Firstly, a couple from GE:

Click image for larger version

Name:	Electronics 195204 p.39.jpg
Views:	57
Size:	75.4 KB
ID:	152163Click image for larger version

Name:	Electronics 195205 p.95.jpg
Views:	75
Size:	78.2 KB
ID:	152164

Clearly, it was pushing the use of the 6AJ4 as a UHF RF amplifier.

And it was also promoting the use of its UHF valves in combined VHF-UHF tuners. That a pair of 6AJ4 are shown might have indicated that at VHF, the two were used in a cascode circuit.

Next, one from Sylvania:

Click image for larger version

Name:	Electronics 195307 p.293.jpg
Views:	63
Size:	73.2 KB
ID:	152165

It was also suggesting combined VHF-UHF tuners. In this case the 6AN4 was used as a grounded grid RF amplifier at both VHF and UHF, and as a grounded grid mixer on both bands. A grounded cathode triode mixer would preferably have neutralization for the VHF low band lower channels when used with a 40 MHz IF. The latter was more-or-less mandatory at UHF, as the FCC UHF channel allocations had assumed its use. Such triodes (usually half a 6J6 or 12AT7) were used as VHF mixers with the high IF, but pentodes were much preferred because they dispensed with the need for neutralization. But a grounded grid triode mixer would presumably have more protection against regeneration.

And finally, an RCA advertisement featuring the 6BC4:

Click image for larger version

Name:	Electronics 195406 rco.jpg
Views:	68
Size:	62.7 KB
ID:	152166

All quite interesting, but as previously said, only the 6AF4 had any material use in domestic TV receivers.


Cheers,
Synchrodyne is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 8:48 pm.


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.