G4AON asked about the K3's price class vs. 6 m sensitivity.
The K3 was designed from the ground up to exceed the dynamic range of every ham transceiver available. That it does (see Sherwood, the QST review, or our own K3 page).
In order to achieve this, we had to use a down-conversion design to a low I.F. This requires narrow band-pass filters on each ham band, plus supplemental image-rejection filtering on the highest bands. Other rigs make different tradeoffs -- usually sacrificing dynamic range.
The narrow BPFs result in a loss ahead of the existing preamp and switching mixer that is nearly ideal for the HF bands, in terms of maximizing dynamic range in challenging operating situations. That was our primary goal. (We were also trying to keep the basic transceiver affordable, and achieve a form-factor consistent with DXpeditions and portable operation in general. There are many more things we wanted to add that were outside budgetary constraints, but we adding the needed "hooks" in the I/O.)
For some applications on 6 m you might want a lower NF, and we took this into account by providing a path into which you could patch an external preamp, if necessary. Thus the RX IN and RX OUT jacks on the KXV3. We also provided a way to power it (12VDC OUT) and turn it off/on (DIGOUT1). We also included through-mode jacks on the PR6 itself so it can be bypassed while still allowing the connection of RX antennas or filters for other bands.
The resulting MDS with the PR6 inserted is better than nearly every HF transceiver that also covers 6 m. Of course many 6-m stations doing weak-signal work already have external preamps either in the shack or mounted at the antenna, and they likely will not need the PR6.
73, Wayne N6KR
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