[Elecraft] K3 AF Upgrade Kit (for speaker amplifier and LINE OUTs)

[Bob Tellefsen]

Wayne
Can you tell us the serial number at which
these changes were incorporated?
We need to know who needs to order them
and who does not.
Thanks and 73
Bob N6WG

----- Original Message ----- 
From: "wayne burdick" <n6kr at elecraft.com>
To: "Elecraft Reflector" <elecraft at mailman.qth.net>
Sent: Thursday, November 13, 2008 10:40 AM
Subject: [Elecraft] K3 AF Upgrade Kit (for speaker amplifier and LINE OUTs)


> With minor circuit changes, both the K3's speaker amplifier and line 
> outputs can provide lower IMD (intermodulation distortion) at higher 
> signal levels. We've been testing these changes for a couple of months, 
> and have already phased them into production.
> 
> These changes can easily be made to existing K3s. A kit of parts is 
> available (K3AFMDKT). All parts are leaded (not surface mount), and 
> full instructions are provided. See:
> 
>    http://www.elecraft.com/order_form_parts.htm#K3%20Parts
> 
> Details
> -------
> 
> SPEAKER AMP:  The mod kit includes a very low-resistance RF choke for 
> use at RFC47 on the RF board. This improves speaker amplifier IMD by as 
> much as 25 dB at moderate to high AF GAIN settings by reducing the 
> voltage drop across RFC47 during signal peaks.
> 
> LINE OUT:  The kit also includes smaller resistor values for R19 and 
> R20 on the KIO3 module. At present R19 and R20 are about 600 ohms, 
> while the replacements drop the resistance to around 50 ohms. The 
> smaller resistors increase the available voltage swing at the output of 
> the LINE OUT transformers, which improves IMD at higher signal levels.
> 
> These two changes are independent. For example, if you never use LINE 
> OUTs, you might want to do only the speaker amp modification.
> 
> 73,
> Wayne
> N6KR
> 
> ---
> 
> http://www.elecraft.com
> 
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