[Elecraft] KX3 Receive Performance Below 1500 kHz

[Mike Morrow]

A discussion of KX3 MF lack of sensitivity recently took place
on the KX3 list.  The KX3 should not be considered really
usable below about 1500 kHz, as Wayne explsined:

---- Original Message (from KX3 list)

> I thought there was some advantage to AM BCB reception
> to be had with the KXAT3.

If a KXAT3 is installed, harmonic images are attenuated,
but this has little effect on signal strength.
 
> Why wouldn't the T/R PIN diodes be as well protected by
> high pass filtering that rolled off below 400 kHz rather
> than 1500 kHz

The carrier lifetime of the diodes is roughly 1.5 microseconds.
This means that strong signals at the low end of the broadcast band could cause IMD (IP2) if not attenuated. The HPF provides
about  20-30 dB of rolloff by this frequency, ensuring that
this isn't a problem. The KX3 is optimized for ham-band use
so this is entirely appropriate. 

Wayne