[R-390] IF Subchassis

[Stephen M. Murphy]

Yes, Y-501 is absolutely, positively, and without any doubt "SOLELY used 
as a crystal filter".  It's a high-Q resonant circuit in a can; nothing 
more, nothing less.  It's simply shunted in various degrees to establish 
the 0.1 and 1.0 bandwidths, and is essentially bypassed when the 
mechanical filters are in the signal path.

There's nothing particularly fancy or unusual about this circuit, I'm 
having a hard time understanding why it's become so controversial.

-Steve N8NM

On 02/27/2011 01:52 PM, rbethman wrote:
> In spite of all assertions that Y-501 is SOLELY used as a crystal
> filter,  It would perhaps be of value to *carefully* look a t TM 11-856,
> Figure 106.
>
> Looking at the schematic, It is very obvious that Y-501 is ALWAYS tied
> to the control grid of V501 without regard to the position of the S-501
> wafer of the bandwidth switch.
>
> The other end of Y501 is tied from its other side to ALL the positions
> of the S501 wafer for all filter positions from 2, 4, 8, and 16 positions.
>
> I can indeed read the cited paragraphs!  I've done so.  They do NOT,
> however "change" the circuitry and the feeding of the internals of Z501
> to V501 whatsoever.
>
> Exactly "how" two positions of S501 result in .1Kc and 1KC filtering, I
> do not know.  I won't dispute the "written" function in the cited
> paragraphs.
>
> However, it CANNOT be dismissed NOR ignored that Y501 is in "play" and
> feeds V501 ALL the time.
>
> Bob - N0DGN
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>