After spending some time modeling my antenna in EZNEC and then running
some calculations in TWL, I added 30 ft to the feedline. That brings
the total feedline length up to 90 ft. So far, the KAT2 seems to be
able to tune all bands very quickly with the BL2 set to the 1:1
position. Thanks for
Geoff, GM4ESD, makes some excellent observations about using other types of
multi-wire line to maintain low resistive losses and to provide a
lower-impedance line when needed.
Jack Bindle took me to task, quite appropriately, about one statement in my
first comments in this thread in a private
Fellow Elecrafters,
I am putting up a 135 ft flat-top at my QTH. I'll be feeding it with
about 60 ft. of 450 ohm ladder line, connecting the feedline to the BL2,
and tuning it with the KAT2.
I was wondering if anyone on the list has tried this arrangement and
could comment on whether the
I have a 135' OCF (Off Center Fed) dipole which is coax fed with a 6:1
balun at the feedpoint, and it works on all bands from 80-10 except 15
with my K2/KAT2. Performance seems very good an all bands except 30m,
where it's just OK.
Larry N8LP
Karl Larsen wrote:
Zac Brown wrote:
Fellow
Zac:
I'm guessing that the configuration that you propose could run you
into all sorts of trouble on 80 M. The problem is that the 135 ft
flat top would have low impedance, about 50 Ohms. The transmission
line is disturbingly close to a quarter wavelength. A 450 Ohm line
with an exact
Steve,
The feedline is actually 65 ft long. It happened to be the perfect
length from the antenna to my radio, but I could add some more line in
the middle if needed. I'd just have to make the feedline take a less
direct path through the attic. What would you suggest as a good
feedline
Perhaps Elecraft might like to consider adding an 'old fashioned' type of
balanced antenna tuner to their product range, with a balun at the
transmitter connection, to make it easier to match some types of antenna
system to the transmitter? One that could be used outside and be remotely
So what's the best way to add some more line to the middle of my
feedline? Is there a technique for joining two pieces of 450 ohm ladder
line that doesn't create an imbalance in the line? Can I just leave one
leg straight and then wrap the corresponding leg (on the other
piece) other around
I'm sorry but I need to add this before Zac Brown does something
real stupid. When using 450 ohm feed line you must use this EXACT
length. The exact length is that which goes from the antenna to the
balun in your shack.
Any talk about matching the 450 ohms is not correct. The feed line
If you want to splice balanced line, you can do a simple splice with two
wire nuts of both the same size.
That theoretically, would affect each side of the line the same and preserve
balance. Your tuner takes care of that and any other bumps'' even the
mixing of 300 ohm and 450 ohm line to
Zac,
Why guess?
You can find the antenna feedpoint impedance for various bands on L B
Cebik's website (at least it used to be there) www.cebik.com .
Armed with that information along with the known length of your feedline,
use TLW which you can download from the ARRL website
Doc,
I was thinking of the link coupled parallel or series tuned type of coupler
which was at one time known as an Antenna Matching Unit before the name
Antenna Tuner became the norm. The Johnson Matchbox was an example, and such
'tuners' can convert a considerable range of impedances as
Jack makes excellent points. I would like to elaborate on one comment he
made:
...open-wire feed. There we don't care about the mismatch since
the feedline loss is microscopic. The RF currents balance themselves
out so that the feedline doesn't radiate. But we then need a decent
tuner to
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