Hi Daniel and all,
I have all four Elecraft rigs, including internal ATU's. The ATU in the KX1
is the least effective of all of them. While my K2 and K3 ATU's can tune my
R7, which is optomized for around 7130 khz on 40 meters, to nearly "flat"
on each end of the band (the R7 has fairly sharp tuning on 40 meters), the
KX1 ATU struggles at each end of the band. I've borrowed a 2nd KX1, and
gotten much the same result, so I don't think it is just my particular ATU.
In such a small package, it's not hard to understand why the KX1 ATU might
not be nearly as versatile. The ATU in the K3 is the best of any internal
ATU I've ever had. The K2 ATU is also quite good. The ATU in my K1 does a
"fair" job, but I've always been somewhat suspect that I might have a small
problem with that ATU. Occasionally it acts like it doesn't want to
activate.
Since my R7 on 40 meters seems to be a good application for an ATU when
doing wide excursions on the band, maybe it would be interesting to see (and
plot) how each rig's ATU performs across the band. It's also interesting
(to me at least) that my K3 ATU will tune the R7 on 80 meters. The K2 might
do that, but I haven't tried it. Obviously the R7 is very inefficient on
75/80, but at least the radio seems happy.
The bottom line for me is that the KX1 ATU is useful, but not very wide
ranging. It may work better on some other types of antennas. I'm glad I
have it, but some situations probably require an outboard unit that is more
versatile. Since I use balanced feedline type antennas a lot when I am
portable, I usually have an outboard tuner for that reason. I really like
"Z" match tuners for QRP use. The NorCal BLT is a good one too.
Dave W7AQK
----- Original Message -----
From: "Daniel Paul Perez" <daniel.pe...@fshsociety.org>
To: <elecraft@mailman.qth.net>
Sent: Friday, January 15, 2010 10:02 PM
Subject: Re: [Elecraft] [OT] High SWR on 20 and 40
Dave,
Thanks for posting this.
I'm going through the exact same exercise with my KX-1 KXAT1 and
Icom703+. Glad to know I'm not alone. The Icom is able to tune just
fine and when I switch the KX1 does not tune all bands – not on 40M.
The KX1 tuner is optimized for shorter lengths of wire. I too wanted to
use one antenna for both radios. I wonder if the K2 is optimized for a
shorter wire? I find the more coax I insert between the 4:1 balun and
radio the better the Icom tunes and performs and the opposite for the
Elecraft -- it then loses 80, 40, 30 and barely tunes 20. It’s really
odd. I get perfect SWR with a dummy load and KX1.
I'll try a few things over the next few days per Elecraft. But
will be very interested in what you find. Is the window ladder line 450
ohm?
Does Elecraft give guidance on how the tuners are optimized?
Eighth to quarter wavelength?
I want to be sure as you do that the max power goes out.
Best,
Daniel ad1p
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