[Elecraft] "K3 test w/o & w I7SWX 2T FSA3157 H-Mode Mixer”

[Wayne Burdick]

Hi Sergio,

Thanks for reporting these interesting results.

A few K3 users in extremely high-signal environments might benefit  
from a few extra dB of dynamic range, at the cost of a mixer add-on  
module like you described.

However, I'd be concerned about the possibility of additional mixer  
spurs. Switching mixers put out a large number of VHF/UHF spurs that  
can mix with harmonics of other signal sources (primarily the VFO) to  
produce HF-6 meter spurs. This is an inherent issue with high-level  
superhet receiver designs.

Our first mixer design trades about 1 dB of dynamic range and  
conversion loss for excellent rejection of mixer products above 60 MHz  
by integrating a balanced low-pass filter into the commutating path.  
Without this, there would be a "picket fence" of additional VHF/UHF  
products and thus many more spurs.

Please let me know if you do a comparison test of the two mixers in  
this regard. The best way to do it is to slowly sweep through each ham  
band in CW mode using a narrow crystal filter.

73,
Wayne
N6KR


On Sep 20, 2011, at 9:16 AM, ik8tng wrote:

> The *Elecraft K3 *is one of the best performance commercial  
> transceivers
> available to amateur radio operators.
> While discussing with some friends it's receiver performances we  
> decided to
> see if there were chances to improve it.  When a receiver has a  
> dynamic
> range over 90dB it is not so easy to pull-out additional dBs.
> One easier mod to experiment was the replacement of the 1st mixer....