[Elecraft] Upgrading to KFL1-4? buider tip...

[Rod N0RC]

Folks,

RECOMMENDATIONS

If you're adding the KFL1-4 band module to an existing K1; ensure that
R11 on the K1's RF board is the original 82 ohm part, before aligning
the KFL1-4


BACKGROUND:

To optimize performance of KFL1-2 R11 may be lowered to as little as
33 ohms**. I lowered RF-R11 to 51 ohms on my K1 to maximize the KFL1-2
performance on 40 & 20m.

Lowering RF-11 increases the gain of the Buffer Amp (U9) for the
Transmitter Mixer stage (U8). With the KFK1-4 installed the this extra
gain can overdrive the XMTR driver stage (Q6). The buffer amp is
routed though the Bandpass Filter on KFL1-4, then to the TX Driver.
The BPF on the KFL1-4 is a different design than the KFL1-2, and in my
case at least, allowed more signal to pass into the TX driver,
over-driving it.


** Detailed in an email to the Elecraft Reflector by Gary Surrency,
dated Monday, July 16, 2001.


CONCLUSION/OBSERVATIONS

When it came time to align my KFL1-4, adjustment was difficult. Most
notable were erratic power readings and sharp tuning peaks especially
on 30 meters. After a little midnight-oil head-scratching, I realized
my RF-R11 change of long ago. So I changed RF-R11 back to the original
82 ohms. Problem solved, the KFL1-4 tuned right up, smooth and easy.
I've since lowered RF-R11 to 68 ohms to maximize Pout on all four
bands (40, 30. 20 & 15m), the change increased Pout on 20 & 15 by a
few tenths of a watt. I ended up with 5+ watts on each band from 12.8
Vdc supply and 6+ watts on all bands with a 13.8 Vdc supply.

The addition of the KFL1-4 to my K1 has made a nice little field rig
even better. Can't wait to try 15m in the next TTF or ARS event.

On to the KBT1.... ;-)


73, Rod N0RC
Ft Collins, CO