[ARC5] 10 meter BC-454 - yet more

[Bill Fuqua]

  Just looked at GE's data sheet on the 6BA6 and guess what.
They show an optional 33k screen resistor instead of fixed voltage to 
extend the cut-off voltage even more negative.
It is a remote cut off already, this suggest that this technique may be 
used for later stages to
reduce clipping and allow larger plate voltage swing.
73
Bill wa4lav


At 09:49 AM 2/5/2013 -0500, Geoff wrote:
>There is a difference between remote cutoff and extended cutoff that some 
>manufacturers referred to as semi remote. In a simple radio without 
>multiple AGC loops it was prone to easily overload.
>
>The 6AC7 had an almost zero use as a gain controlled RF amp in any 
>commercial products that I am aware of and was often used as an AVC, S 
>Meter, panadaptor IF amp, or similar application.
>
>Another problem as an RF amp is that the grid circuit loaded the input 
>coils, broadened the bandpass, and reduced image rejection in low IF sets. 
>Not a problem on the high IF ARC-5's with images.
>
>
>
>
>----- Original Message ----- From: "Ian Wilson" <ianmwilson73 at gmail.com>
>To: "ARC-5 List" <arc5 at mailman.qth.net>
>Sent: Tuesday, February 05, 2013 1:41 AM
>Subject: Re: [ARC5] 10 meter BC-454 - yet more
>
>
>>The 6AC7, according to the data sheet, is either sharp cutoff or remote
>>cutoff depending on how you control the screen grid:
>>
>>*When a fixed screen voltage is used, as shown in condition 1, a
>>sharp-cutoff*
>>*characteristic is obtained.*
>>*
>>*
>>*When a screen resistor is used, as shown in condition 2, an extended cutoff
>>*
>>*characteristic is obtained which may be utilized in applications where the*
>>*gain is controlled by variation of the grid bias.*
>>
>>(GE data sheet).
>>Condition 1: 150v fixed screen voltage.
>>Condition 2: 60k screen resistor to +300v.
>>
>>73, ian K3IMW
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