IsoLoopTM 10-30 HF Antenna
LC-2 Loop Controller
Operating Manual
Advanced
Electronic Applications, Inc.
CONTENTS
Helpful Hints
Features
Theory of Operation
Specifications
Unpacking Instructions
Mounting the Isoloop
Hook-up
For Your Health and Safety
LC-2 Calibration
Operation
Troubleshooting and Service
Packing List
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1
4
5
5
5
6
9
10
11
12
13
14
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LC-2 Schematic Diagram
LC-2 Parts Pictorial
Warranty
16
17
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HELPFUL HINTS
1. HELPFUL HINTS
The following was sent in by John Pollock, KA7MCX, regarding some of his
experiences with the IsoLoop 14-30 antenna. You may want to read this section
now, as it might provide you with some insight as you set up and operate the antenna for the first time. We also recommend re-reading this section after you complete the installation and have operated the IsoLoop a few times, as some of the
terms and ideas used will be more familiar at that time.
Why was I one of the first to buy the original IsoLoop? Many times
the first few days thereafter I seriously pondered that question. The
durn thing wasn't working, the instructions were less than clear, and
I was hearing lots of "told you so's" from friends. I was on the verge
of returning my IsoLoop for something more conventional, but
decided instead to call the folks at AEA who had had the gall to put
this weird product on the market.
difference.
A phone call to AEA's Customer Service made a
From then on, the more I used my 'Loop, the better it seemed to play.
Some of the mistakes I had been making were due to my inability to
understand the instructions, others were due to plain old operator
incompetence. All were, in retrospect, dumb! But as most of them
could still apply to the new (and greatly improved) 10-30 IsoLoop, I'll
list a few hard learned experiences that just may help someone else.
big
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Coax.
and connected it to an unused piece of RG-8. Results were disap-
pointing: finally bought some new, lighter coax and things suddenly
got much better. Heavy coax does not appear to be essential and
fresh coax is well worth the small investment.
Tuners.
rig has the optional internal automatic tuner, it was in this position
when I connected the coax. Not knowing whether to fist tune the
'Loop or the 440, I tried both methods — with horrible results. After
one of the phone calls, I set the AT-TUNE switch to OFF, and the
difference was dramatic! And it certainly made things more simple
when I later used the 'Loop with a TS-680S - meant I didn't have the
cost and bother of an external tuner.
Frequency Modulation.
programmed into memory channels, as it can be interesting to hear
FM signals from the other side of the country, or even across the
Pacific. The first time I tried to use the 'Loop on the of these, it
wouldn't tune - until I switched the mode from FM to USB. Once
tuned, I switched back to FM and worked repeaters on several
frequencies. Moral: tune in SSB, CW or AM modes, not FM. [White
noise will not "peak" in
QSO's.
an interesting QSO in progress, then to tune the 'Loop on the received
signal(s). I soon learned that this was a tough way to do it because
After I assembled my original 'Loop, I climbed to the roof
I first used my 'Loop with a Kenwood TS-440S. As this
I have a few of the ten meter repeaters
FM mode!]
It seemed natural to tune across the bands until
heard
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HELPFUL HINTS
SSB signals cause the "S" meter to bounce so much that it is almost
impossible to identify the "hot spot" while tuning across it. Much
better to find a nearby frequency and tune on the "white noise"; even
better to find an RTIY signal or a heterodyne where the "S" meter
will have little or no fluctuations.
position to you can see the
[Also, turn the AGC switch to "FAST"
fast peak on the "S" meter while tuning.]
Audio.
The IsoLoop is something the engineers call a "high Q"
design. I now understand that means it is very efficient, but only
within a very narrow frequency range. The motor driven capacitor
lets you move that one spot over several bands; learning to find that
"hot spot" quickly is the key to really enjoying a 'Loop. My technique
when changing bands is to first turn up the transceiver's audio much
higher than normal, then run the motor switch at full speed in one
direction. The higher the gain, the easier it is to hear that very quick
burst of noise the first time the 'Loop tunes through it. Then change
to the slowest speed and run the motor in the opposite direction,
while carefully watching the "S" meter. Now turn the gain down to a
comfortable level. Tweak the motor a click or two at the slowest speed
as you tune up or down a band. It should not be necessary to adjust
the audio level if you pay attention to that "S" meter.
Direction.
the CQWW; I wondered if it might be possible to work DXCC
Soon after learning how to use it, I used the 'Loop in
during
the contest weekend. (Turned out it was - 116 countries in less than
24 hours operating time!) Each time I changed bands, I would
carefully note which direction the motor switch was working as I
would "hunt & pounce" up a given band. When I later returned to
the previous band, I would tweak the switch the same direction as I
tuned up that band. Sometimes it would work, sometimes it
wouldn't. Finally figured out that each time that giant capacitor
inside the 'Loop makes one complete revolution, it tunes through any
given frequency twice; once in each direction.
[This is important
to understand. If you hold down one direction button
on the LC-2, the IsoLoop's tuned or resonant frequency will go up to
the end of the range and then back down, or vice versa. It will not go
up to 30 MHz and then start over again at 10 MHz.]
I soon learned to listed carefully the first time I moved the VFO after
tuning the 'Loop - to nudge the motor just a bit in each direction
until I was sure "which way was up".
Bandwidth.
During that contest, I learned that on ten meters I
could often move as much as forty to fifty kHz before retuning the
IsoLoop. When ten [the
night and I moved to twenty [the 20 meter
10
meter
band; 28 to 29.7 MHz]
band; 14.0 to 14.35 MHz],
shut for the
I
was not doing as well. Eventually I figured out that the lower the
frequency, the narrower the "hot spot" and the more frequently it
was necessary to retune. I now tend to tune every 30-40 kHz on ten
meters but every 10 kHz when on twenty meters. I also discovered
the fun to be had on the twelve and seventeen meter bands - I tune
the 'Loop near the center of either the CW or SSB portion. and seldom
find it necessary to retune as I listen across these narrow bands. And
2
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HELPFUL HINTS
the 'Loop compares favorably with many of the stations on these
bands, not nearly so many giant monobanders and legal limit amps
to compete against.
Mobile.
to have convenient low band capabilities on my TS-680S when the
six meter band went dead while I was miles from nowhere during
some VHF contest. I had in mind some quick and simple mounting
system that would not get in the way of my VHF/UHF beams.
Discovered that a small roof tripod could be easily snapped on and
of my vehicle's luggage rack, and that the 'Loop seemed to work well
with only a five-foot mast. I finished a few test QSO's from my
driveway, and the tripod looked solid, so I left it in place while taking
the YL on a grocery run. Six bags later, I had worked three continents
from the parking lot, and it would be nearly three months before I
removed the tripod! I ran a
set of mobile whips; soon I learned that the IsoLoop was hearing and
being heard much better. Horizontal polarization may have had
something to do with that, but the difference was dramatic while
driving among the city's skyscrapers. A "freeway flutter" essentially
disappeared, perhaps due to less flexible antenna configuration.
Hint: That less-than-flexible configuration can be unforgiving on
tree-lined side streets and country lanes. Drive verrrrrry(!) slowly
under such circumstances.
Listening.
configuration) the IsoLoop can be a superb listening antenna, on the
Short Wave bands as well as amateur bands. But tuning quickly
across several bands requires patience and skill. I sometimes use a
random wire with an A/B switch to "check the band" or to look for
interesting signals between the bands. As soon as I find action on
an interesting band, I switch to the 'Loop and tune for maximum
signal strength. I've also learned that my six-meter antenna can
sometimes work for spotting, finding interesting signals to work with
the IsoLoop.
My primary objective when purchasing the IsoLoop was
A/B comparisons with my previous
few
Because it is omni-directional (when in a horizontal
•
If you have
that may help others enjoy it more, please write to us! In the case of the IsoLoop,
there are so many different configurations and ways it can be used, we can't possibly try them all here. So, let us know what you're doing with
hints or suggestions about the IsoLoop (or any of our products)
'Loop!
your
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FEATURES
2. FEATURES
The IsoLoop is a tuned loop antenna and consists of a band of aluminum (act-
ing as a radiating inductor) with a stepping-motor-driven tuning capacitor
mounted in series with the band. The LC combination is made to resonate at the
chosen operating frequency. The loop has very high Q and the bandwidth is
quite narrow, resulting in attenuation
ter, or strong local signals from
Tuning is accomplished by controlling the stepping motor from a small remote
control box called the LC-2 Loop Controller. It allows forward/reverse direction
and speed control of the motor. An audio level indicator consisting of an array of
4 LEDs coupled with a sensitivity control pot allows easy visual tuning of the loop
at resonance. A frequency indicator helps speed tuning by showing the current
resonant frequency
The IsoLoop is small in size, and is excellent in limited-space applications
such as apartments or attics. It may be easily carried to remote locations.
Figure 1 shows that the IsoLoop may be mounted in either the horizontal (lb
and c) or vertical (1a) plane. Vertical mounting allows the antenna pattern to be
rotated with a rotator to "null" interfering signals. When mounted in the horizontal
plane, the pattern is omni-directional. Ground radials are not necessary and the
impedance is approximately 50 ohms when tuned to a chosen frequency — an
additional antenna tuner is not necessary.
of any harmonics from the user's transmit-
any adjacent transmitter.
The IsoLoop design results in the loop antenna being
from the feedline so the feedline does not become part of the radiating structure
and distort the pattern. (This is the source of the "IsoLoop" name.) Another
benefit is that the operator does not have RF in his operating environment — his
(and the neighbor's) equipment is less likely to be interfered with.
isolated
or decoupled
4
Fig. I a
Fig. 1 b
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