Chris wrote:
>Am I the only person on earth who wishes that there was a
>21 MHz option for the KX1? I emailed Elecraft some months
>ago and was told that there are no plans to make the KX1
>anything other than 20M-80M...
There are good fundamental technical reasons why the KX1 doesn't cover 17m and 15m.
The DDS frequency generating chip in the KX1 is the AD9834. When the KX1 was introduced several years ago, the AD9834 had a maximum rated clock frequency of 50 MHz, which is used in the KX1. The maximum usable clean frequency generated by any DDS is one-third the DDS clock. Thus, the highest usable frequency from the KX1 DDS is 16.67 MHz. That doesn't support operation on 17m, much less 15m. The highest frequency required for the receiver local oscillator to support both USB and LSB reception is the operating frequency plus the IF frequency (4.915 MHz). For 21.45 MHz operation, a DDS output of 21.45 plus 4.915 MHz (26.365 MHz) is required.
Late versions of the AD9834 are rated for a 75 MHz clock, but even that doesn't support generation of DDS output frequencies higher than 25 MHz.
A non-trivial re-work of KX1 hardware to change the clock and the DDS type would be necessary to support operation on the 15m and 17m bands, in addition to various firmware and RF circuit revisions and additions. A new little RF circuit board similar to a KB3080 that could be added to existing KX1 units wouldn't be sufficient.
Availability of 15m operation is one of the several reasons the good old K1 is my favorite QRP rig of all time.
Mike / KK5F
PS: My apologies for this OT posting on the K3 list.
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