[Elecraft] A couple of questions re: toroids

[Tom Hammond NØSS]

GM Kevin:

>1. In the SSB Carrier Null Notes by AB7MY there is an additional note from 
>N6KR at the bottom which states (in part):
>
>There's some signal leakage *around* the BFO attenuator, which puts a 
>lower-limit on how far down you can go. This leakage can be reduced by 
>about 10 dB by changing the BFO inductor  (L33) to a toroid (45 turns of 
>#28 on a T44-8/90 , which can be purchased from our parts department, 
>support@elecraft.com ). This will improve carrier suppression on sideband. 
>The toroid should be mounted securely underneath the PCB, and you'll have 
>to re-run CAL FIL. (Write down your present BFO frequencies before making 
>the change.)
>
>Is this a note related to older K2's using a solenoidal inductor for L33 
>compared to the toroids that were used later on?

You are correct. This note applies to the older K2s which used a solenoidal 
choke at L33.

>2. One of the mod notes says suggests RFC11 should be replaced with a 
>FT37-43 toroid. The closest I can get to that is either an FT37-61 or 
>FT50-43. Would I need to adjust the number of turns used if I used the 
>FT37-61? Having moved recently, my ARRL Handbook is in storage so I can't 
>check the toroid information and formula re: changes in turns from one 
>core material to another.

The '37'-sized core was specified, I believe, due to its smaller physical 
size, and since it mounts on the bottom of the RF Board.

IF the size FT50-43 core will fit physically, I'm pretty sure it'd work as 
well.

73,

Tom Hammond   N0SS