[AMRadio] WB4AM product detector answer

[Bill Cotter]

Charlie,

The attached may be the source of the PD circuit for SX-101. Looks 
like it was March 1965 issue of 73 or CQ. Just happened to Snip it 
one day and used it in my SP-600JX14.

The 6BE6 PD is a more common circuit. I use the N6PL version in the 
R390A as a PD. Don't know about the SX-100.

73 Bill N4LG


At 09:35 PM 5/31/2025, CL in NC via AMRadio wrote:
>Well, there is a lot of info on the web on the science and reasons 
>for product detectors, some including more math than you want to 
>deal with.  I believe the plus side to the PD is that with an 
>AM/CW basic design receiver and a simple diode detector,  you will 
>notice that a strong SSB of CW signal may not demodulate properly 
>since you don't have enough BFO signal for the level of the 
>incoming RF.  Most times, the AVC in an AM receiver has to be 
>turned off and the gain controlled by the RF gain pot in order to 
>maintain a balance between the BFO sig and the incoming SSB RF, 
>the same for CW.  The SX101 uses a multigrid  6BY6 as a PD, an in 
>this SX100, the builder used a 6BE6.  The circuits are similar, 
>but the components are greatly different.  Pretty sure he copied 
>the SX101 set up, and tie in points.  Where he came up with this 
>exact circuit is unknown, and his changes to the 6BJ7 circuit in 
>order to tie it all in without the use of an extra wafer on the 
>function switch was pr
>  etty ingenious.  It did make it fun to trace out all the wiring 
> to figure out what the builder did though.
>
>Charlie, W4MEC in NC
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