[Elecraft] u-Tune equivalent for the K3?

[Bill Tippett]

N7RR:

 >he praises the optional u-Tune units, which "are hi-Q motorized 
preselector circuits designed to enhance weak signal operating." (p.70)

         He states "As shown in Table 1, use of the u-Tune units 
makes a noticeable improvement in third order intercept in many 
cases."  For direct comparison, I converted ARRL's results with 
u-Tune to IMD (for which we have data with K3):

dB IMDDR3, 2 kHz spacing, 500 Hz filter

2000            K3

71 (69)         94

(69 for stock...71 for u-Tune

u-Tune only makes 2 dB difference in IMD...not "noticeable" in my 
book.  To achieve this on 160-30, you'll buy 3 u-Tune units at ~$500 
each (if my memory is correct).

 >I'm wondering whether the optional KAT3, as an impedance-matching 
device, will serve in practice as a practical substitute for a high-Q 
preselector.  If not, perhaps a similar auto-tracking external 
preselector might be a popular K3 accessory.

         To be perfectly candid, the 2000 has *terrible* performance 
for both IMD and BDR at close spacings in the presence of strong 
signals.  Perhaps Yaesu recognized this and added u-Tune in an 
attempt to improve things, but the bottom line is that it remains 
terrible.  IMD: ~70 dB versus ~95 for the K3.  BDR: ~87 dB (with or 
without u-Tune) versus ~140 for the K3.  (Both at 2 kHz spacings 
although Elecraft has not published final BDR results).

         Bottom line, the K3 simply does not need a pre-selector to 
achieve outstanding performance...and the 2000 is still terrible even 
with ~$1500 worth of pre-selectors.

                                 73,  Bill  W4ZV