>Jim WB8ZBD Wrote:
>
>I use balanced feedlines exclusively with balanced tuners. Is it possible
>to use an unbalanced tuner (LDG "group buy" QRP tuner) with a balanced
>feedline?
---------------------------
Although I may catch some "techno-flack" for what I'm about to say, I
just have to share my success feeding balanced feeders with an
unbalanced antenna.
Several years ago in the QRP Quarterly John Collins KN1H had an article
called "Is a Balun Eating Your Lunch", which dealt with balun losses,
balanced feeders with unbalanced tuners, etc. After reading it I tried
feeding 300 ohm (narrow type) ladder line to various dipole antennas
directly with a Tee tuner using no balun at all. Worked well except I
got more RFI into my shack than normal at the 100 W output level.
I did some experimenting over the years with both commercial and
homebrew 4:1 and 1:1 baluns with tee tuners and found less RFI (better
balance?) with a balun regardless of impedance transformation ratio. I
tried comparing 4:1 vs 1:1 baluns on the air and no one could see a
distinct loss with either.
But... I did find that with really low Z antennas like a 100 foot end
fed wire on 160 meters, the 1:1 balun allowed me to always tune to a 1:1
SWR (probably because the 4:1 balun was making a low impedance so low it
was impossible to match.)
Then one day I smoked my Spiro 1:1 Balun at 100 watts on 160 meters! I
cut that dude open with a hacksaw to see what happened, as I couldn't
ruin it any worse, and I found the company had slipped 4 ferrite cores
each 1/2 inch long over some unusual gray-colored coax inside the balun
container. Unfortunately, they folded up the coax inside the little PVC
tube they use for the balun cases. The center conductor had drifted
over during the heat I was generating and shorted to the braid leving me
with a pile of smoky smelling junk. I saved the 4 cores and decided to
put them on whatever diameter of coax fit them and use them
open-air-style for experimentation.
I found that they fit perfectly over RG-59 TV coax. So I wound some
black pvc tape round and round the coax to make a stopper where the
cores can't slip down the coax. I have the RG-59 coax (about 18 inches
long) soldered directly to some 300 ohm ladder line that goes a few more
inches to my knife switches for selecting feeders to my antennas. Also
I decided to put some clamp-on ferrites onto the RG-58 link to my
wattmeter just to kill any more RFI or unbalance in the system, or
whatever it is.
I know this lash-up is very unorthodox but the results I am getting are
very
encouraging. I get far better sig reports from my systems that I feel I
deserve using QRP.
My low band antenna: An inverted ELL wire (27 feet vertical + 100 feet
horizontal) which is fed with narrow ladder line at a point 9 feet above
ground on the vertical leg. I run the feeder through a Radio Shack
"wall-thru" tube to my unorthodox 1:1 choke balun and then to the Murch
KW tuner currently in use. Attached to the ground rod at the bottom of
the vertical leg are about 10 radials 35 feet long each buried about 3
inches deep. I use a big tuner because of the rotary inductor for more
precise matches. I am able to make lots of QRP QSO's all over the U.S.
on 160/80/40 with this antenna, and inspite of the very short vertical
leg, using 100 watts on 160 meters I have worked JA, KL7, VK6, and KH6.
If this is a lossy system it's news to me.
My high band antenna: a HB roof-mounted 20 meter aluminum tubing quarter
wave vertical GP with 4 wire radials and 300 ohm ladder line feeder.
This is a great DX getter and works very well on 40 through 10 meters.
Yes, that is correct; 40 meters is just fine on this antenna due to the
low loss feeder and the ability to match nearly anything with my tuner.
So there you have it. Don't spend time worrying about all the hocus
pocus of antenna lore, just be sure that you include the low loss
attributes of ladder line or open wire feeders on at least one of your
antennas. You'll be bragging here on the list about your DX feats soo
after.
72 and have a QRPerfect day,
Jerry L. Bartachek KD0CA <><
Washington, IA
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