[Elecraft] VFO IND in the KX3?

[Wayne Burdick]

Hi Dave,

To resurrect a technical description about LF-band receive I posted earlier this year:

* * *

The KX3 does not have filtering specifically for the lower portion of the AM radio band. It is intended primarily as a ham-band transceiver, and covers nearly the entire SWL range. But to completely eliminate low AM-band 3rd-overtone LO images such as the one you're hearing would require at least two and possibly three more filters (more on that below). Complicating this is the high-pass filter in the T/R switch, which is intended to protect the PIN diodes from very strong signals below 1 MHz or so. This attenuates low-AM-band signals. (To quote the KX3 product brochure on our web site: "...also covers 0.31 - 1.5 MHz with reduced sensitivity….)

The KXAT3 ATU provides some additional filtering for the lower AM range when correctly configured. But at 500 kHz, the LO still isn't filtered enough to eliminate strong signals.

* * *

The IC706mkIIG probably uses a keying relay rather than PIN diodes in the main T/R path.

73,
Wayne
N6KR


On Oct 27, 2014, at 1:47 AM, Dave <elecraft at g4fre.com> wrote:

> I found similar at GW0FRE. The kx3 HAD to have an external BPF but was still
> outperformed on the band by my IC706mkIIG which didn't need one. I now use
> the KX3 with a 30m IF Xverter which works fine
> 
> Dave
> 
> WW2R