[Milsurplus] BC-348-R BFO problem

[John Hutchins]

Jim -

Speaking of BC-348-R -
Per QST article November 1947 on ANL fix, the author, Wayne Parcel, 
noticed that the Cathode, VT-98, 6B8, pin 8  would modulate the IF grid 
under large signal conditions thus the root of the ANL poor performance 
problems.   "In fact", or in my opinion, the ANL circuits are basically 
the same as published in the Surplus Conversion Manual volume 1 1947.  
The cure was to add a lager capacitance between Pin 8 Cathode and ground.

Now with this simple mod, how is the over all SSB reception with the AVC 
and MVC mode, is the reception improved? Per the author Wayne Parcel, 
November 1947 QST.

Presently, observations on my BC-348R are that when receiving strong 
signals I need to detune the receiver antenna to get intelligible SSB 
reception.

This may be a good fix to cure more that one problem.

Hutch


On 1/28/2013 3:15 PM, Laura and Jim wrote:
> The bypass cap (#11-2, .01uF/500V paper) in mine failed and smoked the associated resistor (#62, 68k, 1/2W). This resistor appears to drop the B+ for VT-70 (6F7). I don't have a direct sub, but close (60k and 80K).
>
> My question: which way would be better for BFO operation? I think use the 60k for higher B+?
>
> I hope to have it and the BC-375-E on the air for the coming AM CX.
>
> 73 ALL DE JIM K6FWT
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