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

[Igor Sokolov]

I would also like to know that please.
73, Igor UA9CDC

> 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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