Talk:Autodyne

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[edit] description

The description of an autodyne mixer is too precise to the extent that it would include configurations that are not, in fact, autodyne mixers. The Pentagrid converter, for example is a mixer where the mixing and oscillation take place in the same active device. But it is not an autodyne mixer. In fact the Pentagrid works by turning a single active device into effectively two active devices by using different parts of the same device to perform the oscillation and mixing.

An autodyne mixer strictly uses the same active device as the oscillator and the mixer. 20.133.0.14 14:39, 22 August 2007 (UTC)

The Superhetrodyne articles have been a problem. The Pentagrid converter article became a bit of an edit war with a fellow who was upset that the americans claim the invention, while the Brits used something along the same lines. The discusion then got to be about BVA rules, and far off topic. I set aside the material I had found as it would have been a lot of work to clear things up. I even found the reference in "radiotron designers handbook" showing the two types of Pentagrid and the Heptode all in one mixers. That is even a neutral source being published in australia.

Best explanation I came up with was an Old Slyvania Technical note, which stated that the autodyne was fairly early, and worked OK but was unable to co-exist with AGC. The 2A7/6A7 came out which COULD live with AGC, and the american industry switched over. The european industry seeming to prefer the two unit converters. (triode-hexode) Later after the War, The americans came back to the autodyne, using (typicaly) a 12AU6 as the conversion gain was higher, and for sets in urban areas, the set could do without AGC on the converter. Transitor radios tened to have more gain stages and so could also avoid the need for AGC on the converter, and thus use an autodyne.

Talking about stable in relation to transistors is a bit NPV as they typicaly came in to the set maker from the transitor maker with a wider range of values, even though they did not change characheristics as much, the circuits had to be designed to compensate for the variablity in what was supplied. Tubes tended to be closer to the specifications when new, and gradualy lost some performance over many years. Tube equipment thus did not need to have as much compensation for device characheristics. As time went on and silicon repleced Germanium, the gain did get better on run of the mill transistors.cmacd 16:25, 22 August 2007 (UTC)