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March 31[edit]

Television antennae[edit]

What kind of metal(s) are television antennae typically made of? I was unable to find details in the article. Thanks. Martinevans123 (talk) 13:12, 31 March 2022 (UTC)[reply]

Almost always aluminum. 97.82.165.112 (talk) 13:37, 31 March 2022 (UTC)[reply]

Or copper? Searching for this just gets me lots of non-authoritative forum discussions. Card Zero (talk) 13:43, 31 March 2022 (UTC)[reply]

Every television antenna for sale at our Home Depot, Lowes, and WalMart is aluminum. They have copper wires to connect the antenna, but the antenna itself is aluminum. Copper quickly corrodes, restricting the ability to pick up a good signal. If, theoretically, you had a copper antenna in an enclosed inert environment, that would work fine. That isn't normal. 97.82.165.112 (talk) 19:12, 31 March 2022 (UTC)[reply]

Copper costs more than aluminium. Martin of Sheffield (talk) 20:22, 31 March 2022 (UTC)[reply]

I think a little patina wouldn't matina. Here's an actual source, of a kind, asking "Why are Antenna’s Made of Aluminum?" It's annoying how hard it can be to find a source for the obvious, sometimes. Ideally I'd like one from a well-established publication, without a grocer's apostrophe in the title. I know TV antennae are always aluminum, but I'm not a reliable source. Lots of instructions for home-made (indoor) antennae say to use copper, and at least one person's outdoor antenna was copper, but that seemed to belong to a radio ham (before it blew down in the wind). Card Zero (talk) 20:48, 31 March 2022 (UTC)[reply]

An antenna is a kind of electrical conductor. The same science and engineering applies to them as does to conductors used for carrying "power". Of course, in your typical receiving antenna, the power involved is small, so no concern about things like electrical fires. As that article describes, the materials for your everyday conductors are copper and aluminum. Aluminum has the advantages of lower cost and greater resistance to the environment, both of which motivate its use in antennas as well as long-distance electrical wiring. Copper has a higher conductivity, but also costs more and reacts with "the elements", which means copper conductors are usually insulated. --47.147.118.55 (talk) 03:52, 1 April 2022 (UTC)[reply]

It reacts to form a coating of verdigris. So then you have a green antenna, which still works. Card Zero (talk) 07:13, 1 April 2022 (UTC)[reply]

It should also be noted that Aluminum also forms a coating, though because it doesn't have such a striking difference in color, this goes unnoticed. Pure aluminum is almost white; while most aluminum you see has a darker grey oxidation coating on it. Aluminum is a very reactive metal, the paradox of aluminum is that it is a very reactive metal (only slightly less reactive than the alkali metals and alkaline earth metals), see Reactivity series to see aluminums relatively high positioning (especially compared to copper, which is much lower on the series), which is highly corrosion-resistant. However, the layer of aluminum oxide that forms is a) very thin b) adheres strongly to the surface of aluminum and c) is basically impervious, preventing further corrosion. See here: [1]. What makes copper corrosion so much more noticeable is that copper compounds are generally blue or blue-green in color; making a striking difference between the metal and the corrosion. Aluminum basically just turns a slightly darker shade of grey, so it doesn't really stand out. --Jayron 32 15:59, 1 April 2022 (UTC)[reply]

Aluminium has another advantage over copper. Copper has a low melting point, so if stolen is easily to melt down with minimal facilities; aluminium on the other hand requires much more elaborate equipment, which an individual or a dishonest small-scale scrap-metal dealer (at least in the UK) is unlikely to have. If home TV aerials were typically made of copper, they would be stolen frequently: thefts of copper and bronze memorials, artworks and statues already occur.

This is a live issue with mobile phone (cellphone) infrastructure in the UK, where typically in the summer months several more isolated sites per week (out of the ca. 100,000 in the country) have much of their copper cables stolen (a typical mast might have several hundred metres of cable). One of the measures used to discourage this is/was to replace them with aluminium cables (actually slightly more expensive, presumably for manufacturing reasons) and to place prominent notices at the site saying this has been done. (There are of course other measures – I'm not going to say what they are.)

The effectiveness of this has been diminishing, however. After the UK's laws controlling scrap-metal dealers were tightened a few years ago, locally based thefts diminished, but there was a rise in the activity of pan-European gangs, who instead of taking their stolen cables to UK dealers ship it by the container-load to Eastern Europe, where large facilities with aluminium-handling equipment process it with impugnity.

[Disclosure: my last job involved handling job reporting and client billing for a company carrying out emergency repairs on mobile phone aerial sites, some of which was necessitated by such thefts.] {The poster formerly known as 87.81.230.195} 90.209.233.48 (talk) 23:12, 1 April 2022 (UTC)[reply]

Entomological cabinet[edit]

I recently read in a book where a medical doctor of 1840 wished to dispose of his entomological cabinet comprising about two thousand species and nearly a thousand duplicates and it was offered for four hundred dollars. Trying to figure out what an "entomological cabinet" is and apparently it has something to do with insects. Would these be live insects? --Doug Coldwell (talk) 21:00, 31 March 2022 (UTC)[reply]

No, they would be neatly arranged in trays, impaled on pins. Here's another example big enough to see the pins and labels. Card Zero (talk) 21:07, 31 March 2022 (UTC)[reply]

@Card Zero: OOOOOh -> now I get it. Thanks for clearing that up and showing me examples.--Doug Coldwell (talk) 21:13, 31 March 2022 (UTC)[reply]

See no weevil, grok no weevil. Card Zero (talk) 21:17, 31 March 2022 (UTC)[reply]

Imagine the trouble you'd have maintaining your collection if it included live (briefly) examples of Doliana mayflies. Clarityfiend (talk) 03:49, 1 April 2022 (UTC)[reply]

Are these Greek mayflies dancing the συρτάκι and therefore hard to pin down, or did you mean Dolania? --Lambiam 10:20, 1 April 2022 (UTC)[reply]

Aka D'ohlania. Clarityfiend (talk) 10:39, 2 April 2022 (UTC)[reply]