Talk:Hot-wire barretter

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Completely wrong

The section "Description and construction" describes an Electrolytic Detector. It has nothing to do with a Hot Wire Detector.

And the link to "Electrolytic detector, a development of the barretter detector" is completely wrong.

The two have nothing to do with each other. They use completely different principles.

In fact there is almost nothing in the article which is correct!!!

Definitely not the first Detector

It claims that "it was invented in 1902 by Reginald Fessenden" and "was the first device used to demodulate audio signals".

(and leaving aside that they weren't used to Demodulate "Audio Signals" at all, but used to demodulate Amplitude Modulated Radio signals)

Clearly the "Point Contact" and "Carbon" Detectors developed by David Hughes around 1880 could also Demodulate AM transmissions,

even today we use "Crystal Detectors" in our simple AM radios.

The article seems to confuse the action of Coherers (which could not demodulate speech) with other types of Detector (which could).

While Fessenden did develop one of the first low-distortion AM transmitters, Amplitude Modulated signals had been used since the earliest days of radio.

When his first AM signals appeared on the Air, his transmissions could be heard by countless thousands of existing receivers.

Other uses

Im sure Ive heard of barretters being used as early forms of surge arrestor. Has anyone else? (I could have dreamt it tho'!)--Light current 02:20, 30 April 2006 (UTC)[reply]

No Im pretty sure now that they are!. See ballast (electrical)--Light current 03:23, 7 June 2006 (UTC)[reply]

Yes, the generic Barretter is a universal device which existed long before Radio was invented.

Barretter photo

Image:Bareters 085b55 12.jpg is not a hot wire barretter - demodulating detector. This is barretter for electric current stabilization, but not radio frequency demodulation! --ScAvenger lv 19:48, 8 November 2007 (UTC)[reply]

Yes, most definitely.

Iron hydrogen barretter

I might be wrong but ISTR iron wire hydrogen filled barretters being used as constant current devices to stabilise power feed. Tabby (talk) 10:51, 9 June 2008 (UTC)[reply]

Yes. And a Barretter does not need to use Iron (in Hydrogen) as the Filament. These days a Tungsten filament is often used to stabilise current (eg in a simple battery charger).

Disambiguation page needed

This page only represents details of Fessenden's original "barretter" patented in 1902 and this is confusing for many people searching for "barretter".

The barretter of Fessenden has little physical resemblance to the popularly known "barretter", mass-produced by GEC, Sylvania and others. Fessenden's Barretter is designed for detecting AM radio signals and the latter "barretter" for stabilizing current. Each device operates in a different mode:

The former: miniaturized geometry, sensitive to the influence of external energy, resulting in a current variation The latter: large geometry, insensitive to external energy, resulting in a stabilised current

Examples of the latter "barretter":

--"Sylvania 4A1 Barretter" http://www.andycowley.com/valves/var/barr/index.html

--Victoria Museum, Stock No. ST 029230 http://museumvictoria.com.au/collections/items/412007/electronic-valve-amperite-regulator-type-4a1-1930-1949

I propose a disambiguation page as so:

Barretter could mean:

Barretter = Hot wire Barretter of Fessenden patented 1902 > Barretter

barretter = popular name often used to describe a current-regulation device > Iron-hydrogen resistor

There is some more work that needs to be done with the etymology of the word " barretter " . I suspect more people know the popular " barretter " than they know of Fessenden's "Barretter". Akin to the former trademark name " Aspirin " has become 'generic' " aspirin ".--86.8.82.197 (talk) 18:26, 30 April 2012 (UTC)[reply]

Would you care to write it up and add it either here or at Iron-hydrogen resistor, which latter article could possibly be merged here as one of the types of baretters? I don't think there's enough text to need two articles and a disambiguation page at Barretter, it could all be here. --Wtshymanski (talk) 19:00, 30 April 2012 (UTC)[reply]

To sum up the above, it seems most people start out looking for "barretter" (the current regulator) and find Fessenden's Barretter which is completely different to their expectations.

Before I write up anything, I am not sure enough of the etymology of the word 'barretter'. Was Fessenden's "Barretter" the first use of this word, and then some years afterwards the term: 'barretter' became a popular short-name for "Iron-hydrogen current stabilisation tube" , then Fessenden's Barretter forgotten? I only suspect this and more work would need doing.

In the meantime I still think a disambig page (or perhaps as you say, include both 'Barretter' and 'barretter' within the same article) is the way to go.

Though having said that, after looking more at each type of 'barretter', apart from some similarities it seems that they are so different to each other that merging these two 'types' within one article may be messy and difficult to follow, especially if they have shared references and external links sections. So I'm going to revert back to my original suggestion of suggesting the Disambig page, or at the least some way of separating these two concepts from eachother enough.-- 86.8.82.197 (talk) 19:44, 30 April 2012 (UTC)[reply]

Well, both types rely on a wire changing resistance when heated, so taht part is similar. Flipping thorugh the electronic bookshelf, I find tne Newnes dictionary of electronics says "ballast resistor" while the McGraw Hill says "detector". Google Books turns up mostly "detector" use of barretter, mostly in a microwave context, as does the IEEE standards dictionary. Ballast resistor would seem to be obsolete, but detector seems to have survived the vacuum-tube era. I don't think it will be insurmountably messy, let's merge them and see what results. --Wtshymanski (talk) 19:36, 1 May 2012 (UTC)[reply]

Or, better yet, how does Barretter look now? Three uses so far. --Wtshymanski (talk) 20:04, 1 May 2012 (UTC)[reply]

My understanding is that the general term "Barretter" (meaning a Globe with a Positive Temperature Coefficient Filament) long preceded the Radio Detector usage.

In fact to anyone conversant with the art, the Radio Detector was an obvious application of the universal Barretter. And likewise a Radio Detector could equally use a Negative Temperature Coefficient device. All that is needed to "Detect" is non-linearity.

runaway

This article should explain a little more about how the device worked. It sounds like the device is placed in parallel with a base power source and a signal source (the antenna), and increases in signal current cause a resistance drop which permits a much greater (and hence more directly observable) increase in base current. But why doesn't this extra base current in turn cause a further resistance drop, in an exponential run-away (or at least swap to a second equilibrium mode at which the antenna signal gets swamped)?

Is the trick that the signal provides a small perturbative component on a otherwise-constant applied voltage, and that the current (as always) equilibriates according to a function of the total applied voltage, but by exploiting nonlinearity in that function (in this case departing from ohmic linearity due to exagerated thermal effects but remaining monotonic -- or more relevantly its inverse remains monotonic -- on the domain in order to avoid stable bimodality) so the small voltage perturbation can produce a very large purturbation in output current?

Still, I think it is a failing of the article to overemphasise the process that involves the wire becoming hotter, without explaining the complementary process that involves the wire becoming cooler. Cesiumfrog (talk) 02:52, 13 June 2012 (UTC)[reply]

Sorry, but No:

You can get "runaway" with a Negative Temperature Coefficient device (it's then called a "Relaxation Oscillator"), but not with Positive Temp Coefficient, as it's inherently self regulating.

However the non-linearity of the Tungsten filament is key to it's operation. As the Amplitude of the incoming signal varies, it modulates the resistance of the filament. And because a DC bias current is superimposed, an audio signal is developed in response to the modulation.

However trying to correct anything on Wickipedia is pointless as the "expert" Mods will just revert your contribution.

Late edit: That is exactly what happened. Oshwar came along and deleted it!

It's helpful to sign your posts. The Wikipedia convention is to use two dashes and four tildes ( -- ~~~~ ), which the software will automatically convert to your signature.

There's only a "runaway" effect if the negatively-changing resistance was the largest component of the circuit's total resistance. As long as the external resistance is significant, all that happens is that the circuit's "operating point" move up and down the "load line".

It's not clear to me that Fessenden's hot-wire detector was ever commercially used for voice, though it seems to have allowed identification of different arc transmitters by their sound, according to Sarkar. It's probably much more important because it led to the discovery of the electrolytic detector, which was commercially useful. Fessenden himself in his "improved" patent admits that a micrometer size scrap of wire is easily damaged by stray surges and rough handling. --Wtshymanski (talk) 16:37, 2 November 2017 (UTC)[reply]

You completely missed my point: I didn't claim that ALL Negative Temperature devices will Oscillate, but that you cannot get Oscillations using a POSITIVE Temp Coefficient device.

And how does it matter whether or not a device was commercially used? When did that become relevant?

Fessendon was one of the the first to develop a clean Sinewave (using his high-speed Alternator) and was the first to Voice modulate it, so he gets the credit for the first practical AM TX.

However many had Voice modulated a Carrier (AM) before, eg using a Negative Impedance Arc to generate a Sinewave, or even the noisy spark itself.

The claim that the Hot-Wire Detector can identify arc transmitters is utterly spurious, simply because ALL Square Law detectors can do this. It is only the Coherer which is different (and then only when it is used to ring a bell). P.S. Sarkar is one of the worst references. Has been many times discredited. You seem to be aware that even today Experimenters and Historians are building and testing these devices.

While both the Hot-Wire Detector and the Electrolytic Detector were developed by Fessenden, it is spurious to claim that the development of one led to the development of the other. The two clearly rely on completely different principles. And what possible relevance does the reference to the fragile filament have? Almost all of the early Detectors were fragile/delicate and were superseded by later developments.