[Elecraft] sidetone mod now works

[Sverre Holm]

> My L1 82 mH inductor has a DC resistance of 62 ohms. This is quite
different 
> from the 180 ohm version used in the mod. Would a series resistor be
desired 
> as Fred indicates in the message below? I have 100 ohm, 120 ohm, and 150
ohm 
> resistors on hand. Where is this resistor installed between U10 pin 7 and
the 
> inductor or between the inductor and C33?

> What type of capacitor would be best suited for this mod? My junk box only
has 
> 1 uF 100 V 5% metallized polyester or 2.2 uF 16 V 10% dipped tantalum 
> capacitors. The polyester caps are rather large. A couple of the 2.2s in 
> series would be 1.1 uF. 


Darrell,

I did the TF3MA sidetone mod some months ago on my K2 serial #2198 and I am
very pleased with it. See my comments on 
http://www.ac6rm.net/mailarchive/html/elecraft-list/2006-12/msg01043.html
where I wrote that "This mod really works wonders with the sidetone quality
of the K2". I had done the sidetone upgrade to the 3000+ model previously,
but this latest change still was very worthwhile doing.

You should add series resistance to the inductor. If I understand your
question right, the order, L+R or R+L, doesn't make any difference. I would
try the 120 ohm resistor giving you a total of 120+62 = 182 ohms. Maybe the
size

I would probably have tried with the series combination of two 2.2 uF
tantalum capacitors in order to avoid putting the large 1 uF capacitor in
there.



73

Sverre
LA3ZA

Unofficial Guide to K2 Modifications
http://www.qslnet.de/member/la3za/K2/mod.html

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