Elecraft Tuner comparison

[Craig Smith]

I'm presently using a K2 with the internal ATU unit.  I'm quite pleased with
both.

I will be getting another Elecraft for portable use this summer, either a K1
or a KX1.  One consideration is the autotuner performance.  Can someone who
has experience with them provide some practical comparison between the
internal autotuners in these rigs?  Mainly interested in the range of loads
that can be matched.  I will be operating 40 thru 15, depending on the rig I
get.  Using the typical portable antennas such as fishing pole vertical,
non-resonant dipole, and end fed wire.  Another possibility is to forgo the
internal tuner and use an external T1.  So ideally what I'm after is a
comparison between the matching range of the K1 internal tuner, KX-1
internal tuner and the T1.  If you can relate this to the performance of the
K2 internal tuner I'm familiar with, that would be great.  Would also be
interested in any other factors I should be considering in my decision.

Thanks and 73
                       ... Craig   AC0DS




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[Dave, G4AON]

Craig

I have a K1 and K2, both with the auto tuner options. The K2 will almost
tune "anything", well at least anything that looks remotely like an
antenna. It compares well with an MFJ-993 auto ATU that I also have.
While the KAT1 is adequate for end fed wire antennas on the lower bands
and doublets on the higher bands, it struggles with the often quite
reactive loads presented by open wire fed doublet antennas on 40m and
especially 80m. My home antenna is usually a 100 foot centre fed doublet
with twenty odd foot of 450 Ohm slotted ribbon and 4:1 balun. The K2
will tune this on all bands from 80 to 10, the KAT1 struggles on 80, 40
and 30. I have done a small reversible modification to the K1's ATU to
add fixed capacitors and selectable links (details at:
http://www.astromag.co.uk/k2/g4aon_kat1_mods.pdf). From the circuit, it
appears the KX1 ATU has less tuning range than a K1 ATU, so will need a
carefully chosen antenna.


73 Dave, G4AON
K1 #1154, K2 #1892
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[Don Wilhelm-3]

If I may offer something else to extend the range of any tuner - add a
capacitor or an inductor to the output of the tuner (or at the output of a
balun) for those bands the tuner has trouble matching.  The idea is to
cancel (or reduce) the reactive component of the feedline impedance and it
may bring the feedpoint impedance into a range that the tuner can match.

How much capacitance (or inductance) - well I have no single answer for that
other than 'it all depends' on your particular tuner and antenna - a bit of
experimentation is in order.  If you use capacitor values in 100 pf
increments and inductors in 10 uH increments, I am certain you will find
something that works.  You may have to use different value capacitors or
inductors for each band (do not use both an inductor and capacitor together,
they will cancel each other's reactance out).

One caveat: a halfwave long wire (half antenna flattop plus the feeder
length) has a high resistive component, and will be difficult to match with
the L-network autotuners in any case.

73,
Don W3FPR

> -----Original Message-----
>
> I have a K1 and K2, both with the auto tuner options. The K2 will almost
> tune "anything", well at least anything that looks remotely like an
> antenna. It compares well with an MFJ-993 auto ATU that I also have.
> While the KAT1 is adequate for end fed wire antennas on the lower bands
> and doublets on the higher bands, it struggles with the often quite
> reactive loads presented by open wire fed doublet antennas on 40m and
> especially 80m. My home antenna is usually a 100 foot centre fed doublet
> with twenty odd foot of 450 Ohm slotted ribbon and 4:1 balun. The K2
> will tune this on all bands from 80 to 10, the KAT1 struggles on 80, 40
> and 30. I have done a small reversible modification to the K1's ATU to
> add fixed capacitors and selectable links (details at:
> http://www.astromag.co.uk/k2/g4aon_kat1_mods.pdf). From the circuit, it
> appears the KX1 ATU has less tuning range than a K1 ATU, so will need a
> carefully chosen antenna.
>
>

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