Hi Paul,
If you've already built your KFL1-4, then the easiest way is to
remove the following components:
X1, X2, C9 (Premix / Bandpass Filter)
CJ (RF Band-Pass filter)
C21, C22, C23, C24, C25, C26, C27, L1, L2, L3 (Low-Pass Filter)
Then install the following components in the Premix / bandbass area:
X2 - 11.5 MHz crystal
C9 - 33pf (might be 68pf)
Add two more capacitors, going from either side of C9 to ground, both
are 68pf in value
Add two more capacitors, in parallel with C3 and C4, both are 120pf
in value
Install in the RF band-bass area:
CJ - 33pf (might be 68pf)
Add two more capacitors, going from either side of CJ to ground, both
are 100pf in value
Add two more capacitor in parallel with CC and CD which are between
680 and 820pf in value (you may need to experiment)
Install in the Low Pass area:
Here, I'd just use the same lowpass filter as in the KFL1-2 / 80M
option. Just have a look at the schematics & component values for
that. Or, check out the schematics for the K2's 80M low-pass
filter. Either way, there's two ready-made choices for low-pass
filter component values.
This would give you band 1 = 40M, band2 = 30M, band 3 = 80M, band4
not used.
For alignment, the 30 & 40 meter sections would work up just like in
the manual. For 80M, you have to tweak all eight remaining variable
capacitors in order to fully tune it. For simplicity though, I'd
just set C1, C2, CA and CB at a fixed position, either halfway or
maximum, then work with the other four in order to finish alignment.
These values are from my notes, which may not be up to date, I know I
was doing more experimenting with the values of CJ and C9 to increase
the bandwidth. I'll double-check against what is actually in my K1
later today to be sure, but I can say I have got as much as 5 watts
out on 80M in the 4-band board, and have got the bandwidth up to
about 200 kHz. There's some drop off at the far ends, down to about
3 watts.
For what it's worth, before I decided to go for the K2, I had built
my 4-band board for 80-40-20-15 with the intention of making a little
external 80M low-pass filter that I could just add in between the
radio and the antenna when needed.
As always, your mileage may vary & experiment at your own risk.
73 de Stephanie
va3uxb
K2 # 5311 / K1 # 2132
On 21-Jan-2006, at 13.08.32, hip0 wrote:
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