[Elecraft] How to put an Elecraft K2 on 60 meters

[Wayne Burdick]

Our K60XV option (60 m + transverter I/O) isn't available yet, and neither is
the 60-meter U.S. ham band. But K2 owners in the U.K., who already have limited
privileges on this band, want 60 meters yesterday. MARS operation is also
possible in this band, and WWV can be received at 5.000 MHz. So we thought we'd
provide some instructions for those who want to experiment.

1. The 40 meter band-pass filter must be resonated on 60 meters:

Install a DPDT switch on the rear panel, close to the 40-m band-pass filter. The
two switch commons should be wired to either side of C6, the top coupling cap in
this filter. In the 60 m switch position, a 4.7 pF capacitor should be placed in
parallel with C6. From either side of this capacitor to ground, you'll need a 50
pF trimmer and a 47 pF fixed cap, in parallel. The filter will be peaked later.

2. Two memories can be set up for easy 60m/40m access:

Turn on the K2 and switch to 40 meters. Select the 1-kHz-per-step VFO tuning
rate and tune the VFO down from 40 m to the center of the 60 meter band (~5.3
MHz). Hit A=B to set both VFOs to this frequency, then STORE the setup in a
frequency memory (I used #5 since this is 5 MHz). Then tune back up to 40
meters, hit A=B, and STORE this in another memory (#7 makes sense: 7 MHz). Now
you can jump to either 60 or 40 meters using RCL.

3. The VCO requires additional capacitance:

Use RCL #5 to get back to 60 meters. The PLL will be out of lock because the
40-meter VCO capacitance is too small to allow the VCO to tune down to 5.3 + 4.9
= 10.2 MHz. To get the PLL to lock, you'll have to parallel some 30-70 pF of
extra capacitance across C71. Connect a voltmeter to R30, and find a value of C
that results in a VCO voltage of 1.5-7.5 V over the desired 60 m segment. Then
install a tiny SPST switch on the board which, when thrown to the 60 m position,
puts this cap into the circuit. Use very short leads, and if desired, cut an
access hole in the bottom cover. (Note: the K60XV will be supplied with two
MV209 varactor diodes, D19 and D20, that will work in combination with the K2's
new "D19" menu entry to change the VCO tuning range so that it covers both 40
and 60 meters with new VCO relay combinations. You don't need new firmware to
use the fixed capacitance method described here. But if you have it, leave "D19"
set to "N".)

4. With both the VCO and BPF switches in the 60 m position, align the BPF
trimmers on 60 meters.

5. The K2's original 40-m low-pass filter and push-pull PA does a decent job of
suppressing the 2nd harmonic on 60 meters, but if you want some extra margin,
use the new 40m/60m elliptic low-pass filter components shown in the Revision D
K2 manual. This filter is already present in K2s s/n 3000 and up.

You're now ready to use the K2 barefoot on 60 meters (up to 15 W). The KAT2 and
KAT100 automatic antenna tuners will both work on this band, although the KAT2
f/w has to be at revision 1.06 or higher. Use the ATU menu entry to check the
revision. 

We don't recommend using the KPA100 (100-watt final stage) on 60 meters at this
point. Since the KPA100 uses a 40/30 meter low-pass filter, the 2nd harmonic
attenuation on 60 meters would be determined solely by the balance of the PA
strip. Of course if you have a spectrum analyzer, you can try it and see whether
the attenuation is adequate. (Note: The K60XV option will include parts for the
KPA100 that will allow its 80 meter LPF to be used on 80 and 60 meters. The K2
will detect the presence of the K60XV and will send the appropriate band-select
commands to the KPA100.)

That's all there is to it. 

73,
Wayne
N6KR