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Author Topic: 6SQ7 cathode bypass  (Read 2767 times)
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VK7ZL
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« on: July 20, 2010, 05:43:17 AM »

When a 6SQ7 is used as a 2nd detector/AVC/1st audio stage some circuits have the cathode grounded and some use cathode bypass.
An example is the Halli SX24 which has cathode bypass and the SX25, essentially the same receiver, has the cathode grounded.

Can someone explain why different configurations are used.

Bob,  VK7ZL
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w3jn
Johnny Novice
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« Reply #1 on: July 20, 2010, 06:36:25 AM »

The 100 ohm cathode resistor in the SX-24 is very very low in comparison with the high impedance of the AVC circuit, which is the DC completion of the diode section of the 6SQ7.  It was probably done to give a slight bit of negative bias on the 6SQ7 grid and/or AVC delay.
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