[Elecraft] Question on K1 build - internal or external tuner?

[Mike Morrow]

Stan/AE7UT wrote:

> ...trying to convince myself I can build a K1.

Excellent choice!  For twelve years K1 #175 has been my favorite QRP
rig.  But PLEASE...seriously consider buying your kit with the 
K1BKLTKT LCD backlight option BEFORE you begin building a K1. It was
not available when I bought my K1 in 2000, and after I installed it
three years ago I can not describe how much of an improvement in
low-light utility it has made.  But it is rather painful to back fit
into a K1 after the front panel board has been assembled.  Painful!!!
When installed as part of the original front panel build, it's child's
play.

> So when I build the K1 should I get the internal tuner or just get a T1?

The KAT1 has 10 relays that switch its four inductors and five capacitors
to produce an inductance range from 0 to 4.9 uH and a capacitance range
from 0 to 300 pF in 2^10 (1024) various combinations, of which 1020 are
unique.

The T1 has 15 relays that switch its seven inductors and seven capacitors
to produce an inductance range from 0 to 7.5 uH and a capacitance range
from 0 to 1300 pF in 2^15 (32768) various combinations, of which 32764 are
unique.

Thus, the T1 has a significantly greater likelihood of establishing a
match for a broader range of load than does the KAT1.  There's no contest
here.

However, if one is interested in a small integrated station with all
the key devices inside one box and operated from one panel, the KAT1
is terribly tempting.  Especially for backpack and camping operation.
The KAT1 also gives the K1 a good indication of output power and VSWR.

I use my K1 in backpack and campsite locations, and I almost always use
a resonant dipole antenna system.  The KAT1 is the ideal device for my
use, which requires typically little tuner reactance insertion, and thus
results in little tuner loss for a match.  (Tuner loss is seldom discussed
in Elecraft Auto-Tuner World.  But with respect to loss, a small tuner
with thin wire inductances is not a friend, even at QRP power.)

So you'll need to consider what types of antennas you will be using.  If
all your QRP operation is at home or in the field using more or less
resonant coax-fed antennas, the K1 with KAT1 will be entirely satisfactory.

If you will be using your K1 with antennas and feed lines that have less
well-behaved impedance vs. frequency characteristics, the T1 will better
serve.

Finally, as you mention, the T1 may be utilized with QRP rigs other than
the K1.  (I found that once I built the K1, I seldom ever use anything
else, except once in a blue moon one of my SWL DSW-20/30/40 units, just
for fun.)

73,
Mike / KK5F