[Elecraft] [K3] Difference in sensitivity on 50 MHz between K3 and KRX3

[Joe Barger]

Hi All,



I have the KRX3 installed in my K3.  Using identical setup (PRE, ATT, filter, filter widths, mode, etc.), the S-meter levels between the main RX and the KRX3 are pretty close on all bands except 50 MHz, where the KRX3 sensitivity seems to be about 15 db or so lower and the MDS is definitely lower on the KRX3 (exactly how much I don't know since I don't have the instruments to accurately measure the MDS).  Turning on/off the ATT and PRE on the KRX3 on 50 MHz makes about the same relative difference as seen on the main RX, so they seem to be working as expected.  The only circuits in the KRX3 that are used only on 50 MHz appear to be the input filters, so I tried peaking them up on the KRX3 with no improvement.  I then used a Minicircuits splitter to feed the antenna into the main antenna input as well as the AUX input and switched the KRX3 between Main and AUX.  When on AUX, the signal levels seemed to increase about 7 or 8 db (resulting in the KRX3 sensitivity being about 7 or 8 db below the K3).  The AUX input appears to feed directly into the KXR3, so is the increased loss due to the K3 signal splitter to the KRX3?  There is the 3 db loss from the K3 splitter when using the Main input, but that still doesn't explain the entire difference.  As for the other 7 or 8 db loss, I haven't been able to figure out where that's coming from.  



Do other users of the KRX3 on 50 MHz notice the same difference in sensitivity between the KRX3 and K3 on 50 MHz when using the Main input?  Or is something wrong with my K3/KRX3 on 50 MHz?



Thanks



Joe N6KK