[Elecraft] [KX3] Re: [elecraft] KX3 VFO tuning noise reduced or eliminated

[Wayne Burdick]

TJ Campie wrote:

> How come this works? What was the function of those pins that caused the problem?  

The three pins removed in the KXFL3 modification provide control signals for accessing a small EEPROM on the module. This memory device was intended to store DSP gain/phase parameters for opposite-sideband nulling. However, it turns out that gain/phase parameters are also dependent on hardware on the RF board. So we have never used the EEPROM, and it will be eliminated from future production runs.

The noise heard when tuning the VFO is due to RF radiation from the digital control lines into adjacent circuitry including the synthesizer. When the three pins are cut or removed, the bus is no longer loaded by the EEPROM on the KXFL3, and the signal path is shortened. 

73,
Wayne
N6KR