[Elecraft] K1 or KX1?

[Mike Morrow]

Jim wrote:

>Have been thinking about getting my feet wet with building either
>a K1 or KX1.  ... I can work with either one but would prefer the
>one with best performance. 

As far as RF performance only goes, the K1 is clearly superior.

(1)  The K1 uses an LC VFO that is cleaner than the direct digital synthesis frequency generation scheme of the KX1.  This reduces transmitter spurious output, and improves receiver performance because fewer spur frequencies are part of the local oscillator signal fed to the front-end mixer.  In fact, according to reported measurements, the K1 has better transmitter spurious output specs than even the K2.

(2)  The K1 can be placed on any of the HF bands, though Elecraft currently sells parts for 80m through 15m only.  The KX1 DDS chip is clocked at its maximum rate of 50 MHz, which limits KX1 frequency coverage to around 20m and lower.  The 15m band is one of the best QRP bands when open.

(3)  The K1 IF uses a four-pole crystal filter, while the KX1 IF uses only three.

(4)  The K1's optional auto antenna tuner tunes a wider range of impedances than that of the KX1.

(5)  Most find the continuous LC VFO tuning of the K1 to be more natural than the step-wise tuning of the DDS in the KX1.

(6)  The K1 has a noise blanker option, while the KX1 does not.

(7)  The K1 transmitter can produce up to seven watts of output power.  The KX1 is about half that.

(8)  The K1 case contains a speaker, the KX1 does not.  (The K1 has plenty of audio to drive it too.)

(9)  Personal preference...I like the front mounted controls of the K1 more than the top mounted controls of the KX1.

OTOH, the KX1 is clearly superior in terms of VFO stability...a DDS is about as stable as a crystal oscillator.  It is superior in its span of frequency coverage within the limits of the DDS.  It can switch between USB and LSB due to the frequency agility of the DDS as the local oscillator.  It has neat features like audio feedback to controls.  It is definitely smaller and lighter.

IMHO, the KX1 has many positive features that the K1 doesn't have, but none of them except VFO stability actually are improvements over K1 RF performance in the ham CW bands.  In overall RF performance, the K1 has the clear lead.

But...if the K1 were not available, the KX1 would be my very next choice for a QRP rig.

73,
Mike / KK5F