Differential Capacitor (reaction/regen)

[ms660]

Ref the link below, does anyone know of a commercially produced domestic receiver that used the idea in that patent?

From what I can understand it's a method of equalizing (or trying to equalize) the high end audio response to the users ears when tuning from strong to weak signals or t'other way round eg: strong signal = less regen thus wider pass band, weak signal = more regen thus narrower pass band.

http://www.google.com/patents/US2031034

Lawrence.

[G6Tanuki]

My understanding of the *original* use of a differential capacitor for regeneration is to prevent 'pulling' of the tuned-circuit by the varying anode-to-earth capacitance that would be presented with the traditional regeneration circuit.

Of course this effect would have been predominantly an issue with the high anode-grid-capacitance of triodes.

My suspicion regarding this patent is that it represents an attempt of the patentee to 'explain' an already well-established circuit design as having a peripheral and incidental function other than the usually-accepted one, and so be able to patent it!

[ms660]

It's the switch contacts on the differential capacitor that caught my attention (Fig. 2 in the patent diagram) and I wondered if that system was used in any model of receiver.

Lawrence.

[julie_m]

Just because something was patented, doesn't mean it was ever used in practice. Even when the patent expired and the invention was freed, other factors might have rendered it obsolete in the meantime. The arrival on the scene of the tetrode would have obviated the need to be so careful about grid-anode capacitance .....

For example, there was no shortage of patents taken out for efficiency improvements to steam engines -- but some of them cost more in royalties than they actually saved in coal, and were quietly forgotten when they became unshackled.

[G8HQP Dave]

Just because something was patented in the US doesn't mean it was original, or would work. It seems quite common there to patent something which is well known to everyone in a particular field, but nobody has bothered to patent it. As the patent office there only seems to search previous patents rather than other literature it is easy to patent other people's ideas. Challenging a patent is very expensive.

[ms660]

The filing date was 1933, sought of on the edge of the superhet boom, still, I'd be interested to know if that system as described within was ever used.

Lawrence.