February 2003 81
THIS COLUMN follows up and expands
on the “chokes” topic from the September
2002 column, offers two product notes, and
suggests ways for inquiring readers to help
me help you.
The September column offered some
information about the nature and use of
chokes in E-Radio Control (RC). That
discussion referenced the April 1995 column
which covered the topic in greater detail.
Both references included photo information
about “choke insertion units” (CIUs):
simple, low-cost assemblies you can make to
aid in tracking down and even curing some
common electrical “noise” problems
associated with E-power. (Article reprints
are available from AMA Headquarters.)
Shortly after that September column
came out (in July), readers began reporting
success in using chokes with some noise
problems they were encountering—some for
a very long time. No one reported failures.
This is consistent with my long-term
experience: chokes nearly always solve such
problems.
At the NEAT (Northeast Electric Aircraft
Technology) meet in mid-September, I was
approached by a modeler describing a
“funny” with his power system. He showed
me that as he advanced the throttle, he soon
reached a point where the motor became
“sputtery” and would not run up any further,
even though this happened well below full
throttle.
I invited him to try a CIU (which I
always carry with my flying stuff). He
installed this in the Electronic Speed Control
(ESC)-to-receiver lead, and presto! He had
full-range solid throttle control! The CIU
allowed him to fly that airplane the next two
meet days.
We left the meet without “reconnecting,”
so he took the CIU with him. Days later it
arrived in the mail along with a thank-you
note. I’ve since learned that he subsequently
ordered three dozen chokes for himself and
his friends! (Each CIU needs three chokes—
one in each wire of the ESC-to-receiver
cable.)
Not long after this experience I was on
my own flightline, and a local modeler was
out with a new hand-launch E-aerobatic
model. Ground-range checkout looked good,
and motor and control-surface operation was
fine. It was time to extend the transmitter
antenna and launch, but the motor would not
come on and the control surfaces were
inoperative.
After some trial and error, we learned
that the control functions were fine with the
transmitter antenna collapsed but not when
extended near the airplane. All was well if
someone launched the airplane from several
feet away, but it was impossible for one
person to hold the transmitter and launch the
model. There was clearly some kind of
signal overload or related effect. But what,
and why?
On a long shot I offered my well-traveled
CIU and, once again, presto! The problem
(whatever it was) was solved! This had
nothing to do with classic noise trouble, so it
appears that chokes may have more to offer
than previously known. As I write this, Sam
has had my CIU in use for several days,
flying his new airplane and waiting for the
dozen chokes he ordered to arrive.
This recent experience brought to mind a
similar personal experience of years ago. It
was also with a hand-launch craft, but in this
case the motor came on by itself when I held
the model and the transmitter. This similar
“non-noise” problem was also solved with a
CIU.
I don’t know exactly what’s going on in
these examples, but I can speculate on two
possibilities; one is that the power-system
stuff, connected to the receiver via the
ESC/receiver cable, disrupted the normal
receiver/antenna operation. In effect, the
receiver has much more “antenna” than it
normally does, so nearby transmitter output
Bob Kopski, 25 West End Dr., Lansdale PA 19446
RADIO CONTROL ELECTRICS
Harry Stewart’s (Nevada City CA) 44-inch Electric Flash on Flash
Floats has MGK motor/gears/propeller on six 2/3AAA NiMH.
Weldon Smith’s (Cary IL) 60-inch hand-launch P-38F has two
Aveox 27/39, each with sensorless controllers on 10-cell packs.
02sig3.QXD 11.21.02 1:50 pm Page 81
can more easily overload the receiver. The
other possibility I see is the same thing but
the other way around.
When the ESC is connected to the
onboard radio stuff, it is also fair to picture
the ESC as having an extensive conductor
attached; i.e., there is the ESC with all the
radio stuff “dangling” on it. All this
conductive stuff can act as a huge “pickup”
wherein nearby strong radio frequency (RF)
fields can travel into the ESC electronics and
effect malfunction—possibly including that
of the BEC (Battery Eliminator Circuit),
which normally powers the radio. There are
other situations in everyday life where
transmitted RF signals can adversely affect
the operation of electronic apparatus.
As I see it, a CIU inserted into the
ESC/receiver cable effectively “breaks up”
the combination with respect to high
frequency effects. Essentially the receiver
and ESC are “disconnected” RF-wise,
allowing normal operation. Although I
continue to be unsure of the exact
explanations of the problem and the cure, I
am sure that the chokes worked in these
cases.
I realize that there are many hand-launch
E-airplanes in use everywhere, seemingly
with no such problems. On the other hand, if
there’s one or two such troubled craft, there
are likely others out there somewhere.
Perhaps the symptoms are not as severe as
herein, but the chokes idea is worth a try.
Thus if you have a model with control
functions that don’t seem quite right (i.e., if
you have control “funnies” that defy
explanation), chokes are worth a try.
I have one more application example for
your consideration. It is common for RCers
(including wet-power fliers) to experience a
glitch at the same place in the air on almost
every flight. It’s as though there are
repeatable locations where it seems that the
airplane always gets “hit”—to use a common
(though inappropriate) expression. These
spots can be quite close by, so range is
usually not a factor.
This experience is often more
pronounced during slower flight. At the
same time, other fliers may not have the
same experience at that same location. If the
plagued pilot simply moves a few steps from
his “normal” flying position, or perhaps
reorients his transmitter antenna or changes
to a different channel, the problem goes
away. Or maybe the problem relocates and
Dan Rossman’s (Roswell GA) 71⁄2-pound Hobby Hangar OV-10 conversion has two Astro
05s, MA 3.5:1 gearboxes, 12-inch propellers, a Griffin 40 ESC, and 11 cells.
Big is Better and Safer too!
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82 MODEL AVIATION
02sig3.QXD 11.21.02 1:50 pm Page 82
occurs elsewhere in the sky. “Nulls” may
be the explanation.
Radio-signal nulls are normal and
common. One may experience short
duration fades of an auto FM radio as a car
moves along a road. It’s as though there are
periodic locations of “lost signal”—even in
open spaces. Signal nulls are the result of
many factors coming into play, including
the particular signal frequency and local
propagation considerations.
When this happens, the receiver
automatic gain control circuitry raises the
gain of the receiver; it allows the receiver to
become more sensitive as it looks for that
lost signal. But this, in turn, makes the
receiver more susceptible to electrical noise
in the environment. In the case of E-RC, the
onboard power system is a good nearby
source of interfering noise.
Thus as a model may fly through
regions of null signal, some onboard Enoise
gets right in the open door of the
raised-gain receiver, and surfaces may
twitch or, more likely, the motor may
sputter momentarily. Skilled pilots can
actually make this happen (or not) by
knowing where to fly (or not). This
situation can be quite annoying with speed
controls that shut down upon loss of proper
signal then require full “off” throttle
command to restart.
Chokes can also be a great help here. As
described in the 9/02 column, chokes act to
impede the flow of high-frequency “stuff”
between the ESC and the receiver while
permitting normal function of the
interconnect. Thus power-system-related
electrical noise of the right frequency
makeup has a much harder time getting into
the receiver when chokes are present in the
cable, signal null or not.
If you have system behaviors like any of
the preceding, you owe it to yourself to
give chokes a try. Chances are good that
they will be helpful. Please do check out
the RC Electrics column in the September
issue for detailed parts/procurement info,
and invest the few dollars and the little time
it takes to make one (or more) CIUs. As I
wrote in that column, you could even
become a hero on your own flightline by
helping someone with a choke assembly to
try!
Anderson Power Poles are the connectors
of choice for most E-modelers I’ve met.
John Sermos—a now departed friend—
popularized them in this hobby with his
Sermos Connectors. These were Anderson
Power Poles with heavier contact plating
than the standard ones, although the latter
work quite well as is.
I recently stumbled upon an excellent
suppler of Power Poles at good prices. West
Mountain Radio (see the October 2002
column) lists quantities of 25 pair for
$19.95 on its www.westmountainradio.com
Web site. Larger quantities are available at
even lower prices, so check it out for your
group or club.
As I write this, early discussion is
underway and there is a possibility that the
ever-popular Universal Slow Charger
(published in the September, October, and
November 2000 issues), or USC, will
become a manufactured product by an
established electronics company. If/when
this materializes, I’ll let you know.
Many readers have built the USC, and
many more wish they could but feel as
though they lack the resources or skills.
Soon maybe everyone who wants can have
a USC!
E-beginners and their questions don’t
seem to change much with time. Even
though Electrics is in its third decade (give
or take some), the same sort of newcomer
questions appear in reader mail. I always
reply to inquiries accompanied with a selfaddressed,
stamped envelope (SASE), and I
always do my best to help. I may not
always have a good answer, and I’ll say so
and/or suggest other sources of information.
Reader questions often focus on a
problem with some specific product(s).
Whether the writer realizes it or not,
beginning questions usually involve
Electric fundamentals, and these don’t
change much with product or with time.
That is fortunate because there is an
enormous amount of Electric product
available, and surely no one can be familiar
with it all. I recently read a review of some
Electric design software that included a
database for hundreds of motors. (I can’t
help but wonder how many wet engines
there have been throughout all time!)
Even if I’m not familiar with the
particular product(s) you have (I can’t buy
and try everything!), I’m quite familiar with
what makes Electric tick and can likely be
of at least some help.
To help me help you, include all the
relevant info you can. Tell me what
products are involved and everything else
you can think of, such as finished-airplane
details (size, weight, etc.), battery details
(cell type, capacity, etc.), or
charger/charging specifics—all depending
on your particular question. All too often I
have to respond with requests for more
info, then try to address the problem.
For the fun of it, consider this innocent
beginner letter: “I had three packs charged
according to instructions but none of them
flew good.”
What eventually surfaced as missing
was that the packs were charged more than
two months prior! Get the idea? So be
generous with the detail. I’ll sort out what
seems relevant, then do my best to help
with your inquiry.
So ends another column. Please do include
an SASE with any inquiry for which you’d
like a reply. Everyone so doing does get one.
Many happy and safe E-landings,
everyone! MA
