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GL Mk. I radar

GL Mk. I radar (edit | talk | history | links | watch | logs)

• Featured article candidates/GL Mk. I radar/archive1

Nominator(s): Maury Markowitz (talk) 19:55, 10 December 2024 (UTC)

This article is about a British radar system that aided the Army's anti-aircraft gunners. I think it's interesting because it was so low-tech that it helped convince the Germans that British radars were not very good (along with the similar MRU, an article I'll get to) and the amusing bit about it causing a nationwide shortage of chicken wire.

The article went through A-class some time ago, and it looks like I'll have some time to work it over the holidays, so here goes... Maury Markowitz (talk) 19:55, 10 December 2024 (UTC)

Image review

• Suggest adding alt text

• Don't use fixed px size

• Why are there two of File:GL_Mk._II_radar_transmitter.jpg?

• File:GL_Mk._II_radar_transmitter.jpg: source link is dead

• File:GL_Mk_IIIc_radar_Accurate_Position_Finder.jpg needs a US tag. Nikkimaria (talk) 05:47, 11 December 2024 (UTC)

@Nikkimaria: Queries: (1) what should I use instead of fixed px sizes? (2) should I use an archive URL for the dead link, or find another page with the same image? (3) There are two copies of the one image simply because we needed one to be in the lede for the DYK - I'm trolling the web looking for one to replace it at the bottom. (4) Canadian pic, what do I need in this case, a second tag for the US as well? Maury Markowitz (talk) 16:56, 11 December 2024 (UTC)

(1) |upright=. (2) Either, as long as the latter would verify the information provided on the description page. (3) If no other image can be found, the duplicate should be removed, DYK or no. (4) Commons requires images to be free in both the US and their country of origin. Nikkimaria (talk) 00:26, 12 December 2024 (UTC)

Ok all fixed. Maury Markowitz (talk) 00:37, 13 December 2024 (UTC)

It doesn't look like the dead source link has changed? Where and when was File:GL_Mk_IIIc_radar_Accurate_Position_Finder.jpg first published? Nikkimaria (talk) 04:38, 13 December 2024 (UTC)

Ok, it seems to have saved the new URL this time, not sure what I did. The second was first published in 1942/3. Maury Markowitz (talk) 16:24, 13 December 2024 (UTC)

Where? Nikkimaria (talk) 04:32, 14 December 2024 (UTC)

NRC lab reports, Ottawa. They would have been available in the UK and US at the same time, and likely other Commonwhelth nations but I can't confirm that. The original image is now in the archives in Waterloo. Maury Markowitz (talk) 14:56, 14 December 2024 (UTC)

Sorry, to clarify, which part of that cannot be confirmed, and what do you mean by "available"? Nikkimaria (talk) 15:41, 14 December 2024 (UTC)

Comments from Graham Beards

• "Plans to introduce the Mk. II with accurate bearing and elevation were underway from the start" From the start of what?
• "1,679 Mk. IIs were ultimately produced." Can we avoid starting this sentence with numerals?
• "The GL effort was started very early during CH development, and like CH of that era, used relatively long wavelengths as these could be generated and detected easily using existing electronics from commercial shortwave radio systems". The lay reader might wonder how long wavelengths can be obtained with shortwave radios.
• "The antenna was only marginally directional, with the signal being sent out in a wide fan about 60 degrees on either side." There is a fused participle here. How about "and the signal was sent out in a wide fan about 60 degrees on either side." Or just drop the "with"?
• "A more serious limitation was the displays themselves" I think "themselves" is redundant.
• "As Mk. I arrived in the field, a number of improvements in the basic electronics were introduced." Perhaps "several improvements"?
• "To better study the AA problem" Are you happy with the split infinitive?
• "The separate range and bearing receiver units could operate on a number of frequency bands" Several ?
• "A common oscillator was used by both receivers, which was sent into the four-tube radio frequency (RF) section" Perhaps provide a link to Electronic oscillator?

That's it from me for now. Graham Beards (talk) 17:00, 14 December 2024 (UTC)

Comments from Mike Christie

I've copyedited a bit; revert anything you disagree with.

• "which provided both mobile early-warning service, as well as relocatable service in case a main CH station was knocked out". You don't need both "both" and "as well as"; either "both mobile early-warning service and relocatable service" or "mobile early-warning service, as well as relocatable service" would work. But it took me a second to understand the point of "relocatable". How about "which provided mobile early-warning service, and could also be relocated to replace a main CH station if one was knocked out"?
• I don't think any change is needed, but I'm curious as to how accuracy was measured. If the radar was accurate to 25 yds for an aircraft several miles away, how was this determined? Even at slow speeds an aircraft would cover that distance in less than a second, so any form of human-triggered measurement seems unlikely to be precise enough. Could tests be done against objects on the ground?
• "and produce a null on the display": what is a null? I understand the concept, but does this just mean that the display would be blank? And I see the word is used later in the article; it appears the display is not blank so I am unclear what is meant.
• I see there's an article on GL Mk. III radar, but not on GL Mk. II radar. If the Mk. II is covered in this article, shouldn't the title reflect that?
• "by sliding a copper ring along post on the core": presumably this should read "along a post"?
• I don't think we need the wikilink to ladder, unless you intended that to go to some technical article with a similar name.
• "Images exist that show both antennas combined on a single cabin": why is this worth mentioning? Surely images exist of many of these devices and their installations.
• For note c I think you need a source for the suggested explanations. Without one I think it would be best to cut the note.

I don't know enough about electronics to provide any subject matter feedback on the description section, and I struggled to understand some of it, but that's the nature of technical articles. I think the article does what it can reasonably do towards explaining the material as simply as possible. Mike Christie (talk - contribs - library) 19:58, 15 December 2024 (UTC)

RoySmith

I'm reading through this now. So far, looks pretty good. Note that I'm not into milhist; I approaching this from the engineering standpoint.

• The first mention of radar in the UK was ... Do we really have a solid source for there being no earlier mentions? See User:RoySmith/essays/First is worst.

• The GL effort was started very early during CH development, and like CH of that era, used relatively long wavelengths as these could be generated and detected easily using existing electronics from commercial shortwave radio systems I stumbled when reading this, because I remembered reading earlier about 600 MHz being used and didn't think there was any 600 MHz gear in commercial use back then. When I went back I saw that the 600 MHz was a different unit, but you might eliminate this confusion by saying up front something like "Despite Butement's earlier experiments with 50 cm technology, the CL used relatively long 50 meter wavelengths as these could be generated ..."
• antennas on the order of 25 m perhaps link to half-wave dipole here.
• Clearly, this was not practical is that you doing the editorializing ("clearly"), or does the source say that?
• produce a smoothly varying voltage, does the source say "smooth"? I assume "linear" would be a better word, or more likely Sawtooth wave.
• sent into the CRT's other channel, typically the Y-axis It took me a little bit to understand what you're getting at here, mostly because my familiarity with modern radar sets had me assuming it would be using a Plan position indicator, which these early radar sets didn't. It might be useful to mention that this is known as an A-scope display, and perhaps use the illustration at Radar display#A-Scope.
• For this role, the system used two receiver antennas mounted about one wavelength apart I'm having trouble visualizing this. One wavelength apart in what direction? Normal to the azimuth? Vertical? Horizontal? Drawing a diagram would help here.
• The transmitter, which had a power of about 20 kW is that 20 kW average continuous power, or peak power? I suspect the latter, but the source should say.
• Three antennas were mounted in a line down one of the long sides of the framework again, a diagram would be really helpful here.
• Behind the two bearing antennas were reflectors mounted about a wavelength away, which had the effect of narrowing their reception angle that sounds like you're describing a yagi. If so, link to that.
• it provided very accurate range measurements on the order of 50 yards does the source characterize it as "very accurate"?
• You've described a few different crew positions; people watching each of two different scopes, and "the range readers", which I suppose are the same people. It would be useful to give an exact rundown of how many people were in the crew and what each person did.
• could be attained with these lobe switching systems. a reader who is familiar with antenna design will understand what you mean by "lobe", but most readers won't, so a short explanation (and, again, a diagram) would be useful here.
• It was found that in certain orientations of the transmitter and receiver, the small antenna used to trigger the time base would see too small a signal to work I'm confused. I think what's going on here is that the time base sync is sent from the transmitter shack to the receiver shack by radio, but that's not clear. Again (and I know I'm getting repetitious here) a diagram would help.
• By late 1939 became clear "IT became clear"?
• well into an effort to build an S-band GL radar system I know that S-band means a certain wavelength (although I had to go look up the exact number), but most readers won't have a clue what you're talking about. It's especially confusing since if you click on S-band you get to an article that's talking about frequencies, and most of this article has been talking about wavelengths. They're just two different ways to say the same thing, but most readers won't understand that. So a short explanation here would be useful.
• it combined scanning and tracking into a single unit with an internal generator set that touches on something I've been wondering about; where did the Mk I and II units get their power? I assume in addition to the receiver and transmitter shacks, there was a separate generator shack that came along with it? How many total vehicles did it take to move and set up one of these units?

At this point, I'm done with Development. I'll pick up again with the rest another day.