INSTRUCTION MANUAL
FOR THE
ISOTRON 20, 11 OR 10
MANUFACTURED BY
BILAL COMPANY
FLORISSANT, CO. 80816
PH: 719/687-0650


TABLE OF CONTENTS
ASSEMBLY INSTRUCTIONS 2
WARRANTY 3
FINDING THE RESONANT POINT 5
COMPENSATION FOR VARIATIONS IN LOCATION 8
SIDE TOWER MOUNTING 10
GROUNDING 10
USE OF A TUNER 12
POWER RATING 13
SINGLE FEEDLINE OPERATION 14
PERFORMANCE 15


PAGE 2.
INSTRUCTIONS FOR THE ISOTRON 20, 11 OR 10
(Isotron 10 and 11 are completely assembled)
1. Mount the aluminum plate (1) on the end of
the coil as in fig. 1, pg. 4. (Applies to
Isotron 20 only.) Remove the second nut, then
replace it to secure the plate. Mount the Ubolt
assembly as illustrated on pg.11.
2. For best performance the antenna should be
mounted as much in the clear as possible and
as high as possible. A coaxial feedline of 50-
75 ohms should be connected to the coaxial
connector (3). The coax should be taped or
secured with stand-offs down the metal mast.
A neat run should go to your radio.
Grounding the bottom of the metal mast is
important for outdoor installation. Ground
wires should never be run up the mast or to the
antenna itself. Indoor installations need not
be grounded. See page 8 for more information.
PLEASE NOTE: Lengths of coax that are an exact
1/4 wavelength should be avoided. This length
would have the velocity factor considered for
your type of coax. This is only for the first
1/4 wavelength. Adding a few feet of coax to
avoid this length is fine.
3. Note the jumper (4) in fig 2. This jumper
grounds the counterpoise (2). Start with the
counterpoise (2) about 1 inch below parallel
to the coil. The jumper will be explained
later.


4. There is only one frequency adjustment for
this antenna. If a higher resonant point
frequency (point of lowest SWR) is desired,
then rotate the counterpoise (2) away from the
coil a few degrees at a time. For a lower
resonant point frequency move the counterpoise
closer to the coil or plate (1). Be sure the
plate (1) and counterpoise (2) do not touch.
See Pg. 5 titled FINDING THE RESONANT POINT if
you need more help.
PAGE 3.
5. (4) in fig. 2 (pg. 4) is for impedance
matching of the antenna. Normally with it
connected gives the proper match needed and a
1:1 SWR will occur at your resonant point. If
the SWR is too high at the resonant point then
the jumper may be removed to raise the
impedance value of the antenna. If this
situation occurs it is easiest to do the
adjustment with a Noise Bridge or equivalent
to avoid guessing if your impedance is low or
high. A capacitor of 100 pf or less may be
jumpered in if a point between the two values
is desired. (capacitor not supplied) This
complication of impedance value is the
exception rather than the rule. A determination
of your resonant point should be known before
attempting to adjust your impedance value.
NOTE: A tuner or matching device should never
be in the line during the tune-up. However a
Tuning Device is highly recommended for the
solid state radios during normal operation.
WARRANTY
Bilal Company warrants this equipment against
defects in material and workmanship for a
period of one year from the date of purchase.
This warranty is limited to replacing or
repairing the defective parts and is not valid
if the equipment has been tampered with,
misused or damaged.
NOTE: Do not ship to the factory without prior
authorization. First write or describe the
difficulty. Many times we can diagnose and
correct problems by mail.
PAGE 5.
FINDING THE RESONANT POINT
1.Locating the resonant point or the frequency
that the SWR is lowest is the major part of the
tune up. The following steps is a reliable
technique for locating the resonant point.
2. IF YOUR SWR IS OVER 3:1, IT IS A RESONANT
POINT ADJUSTMENT THAT NEEDS TO BE MADE.
3.You will need a SWR meter. You will also need
to hear the receiver from the antenna location.
4. Connect the antenna to your transceiver by
means of a suitable length of coax. NEAT RUNS
AND INSTALLATIONS ARE VERY IMPORTANT.
5. Tune your receiver near a frequency desired.
6. Listen to a Signal at this frequency.
7. Bring your hand toward the top plate of the
antenna.
8. Carefully listen. If the signal increases
at some point while your hand is approaching
the Top Plate, then the resonant point is
higher than the frequency you are set at.
9.You will need to make the necessary
adjustments to lower the resonant point of the
antenna. (Rotating or adding hardware.)
10. If the Signal decreases only while bringing
your hand toward the Top Plate, then the
antenna is resonant at a lower frequency than
the receiver is tuned.
PAGE 6.
11. If the antenna resonant point is low, it
is best to start at the lowest frequency
available to you. Check it again with your hand
. This technique for determining the resonance
is very reliable. It is not necessary to spend
a lot of time guessing where the antenna is
resonant. Continue this procedure through the
following steps as a reliable resonant point
check.
12. If the test shows the antenna is resonant
lower than you desire or below the band, then
tune your receiver to the lowest frequency
available to you. Check the SWR as in the next
step.
13. SWR should be check at the lowest power
that the meter will read. The sensitivity
control should be all the way up and the meter
calibrated by the gain on the exciter.
14. Note the SWR at the lowest frequency. Then
move up 25 khz and check the SWR again.
Continue to do this until you can see a
pattern.
15. If the SWR increases as you move up
frequency, then the resonant point is below
the band or minimum frequency. Adjusting the
counterpoise (2) away from the end plate (1)
will raise it.
16. The object is to locate a minimum SWR by
graphing as described in step 15.
PAGE 7.
17. If you have a general coverage receiver
you can listen at a lower frequency and check
the antenna with your hand as described.
18. Once your resonant point is located in your
operating area, your SWR will make a noticeable
dip (below 3:1). Unless your environment
interaction is very strong, this normally
produces a low and acceptable SWR.
19. If you are using a Noise Bridge, it should
be located near the antenna for tune up.
20. Impedance may be adjusted if necessary
after completion with the resonant point. If
your SWR is under 3:1, but is not under 2:1 or
better then the impedance value of the antenna
can be adjusted. This is described on page 8.
PAGE 8.
COMPENSATION FOR VARIATION IN LOCATION
The antenna-to-ground capacitance of your
ISOTRON antenna depends on its location with
respect to other objects and to the ground
itself, and how and where it is mounted.
Antenna-to-ground capacitance affects resonant
frequency and feed-point impedance of your
antenna.
For example, if the ISOTRON is mounted on a
tower, somewhere near the middle, its resonant
frequency and impedance value will be lower
than if the antenna is mounted in the clear.
By insulating the antenna from the tower, you
can increase its feedpoint impedance and raise
its resonant frequency. Different locations on
the tower will produce different values, and
it may be necessary to compensate differences
by tuning your ISOTRON.
If the feedpoint impedance and resonant
frequency become higher than desired, then it
is possible to decrease them by connecting a
capacitor of about 100pf or less between the
antenna and the tower (see pg. 11). Another
words the lowest impedance would be directly
grounding the antenna to the mast. A point in
between can be obtained by the use of a
capacitor as described. This technique will
apply on most mountings where the feedline is
longer than 1/8 wavelength. If the feedline is
shorter, then the impedance value is determined
by the ground of the radio and cannot be
varied.
It is important to know what the value of the
impedance will be at resonance, and what the
resonant frequency of the antenna is. An
impedance bridge (Noise Bridge) is a very good
way to make these measurements, and can be a
valuable investment for the radio operator.
PAGE 9.
If a Bridge is not available, then a little
guess work will tell the story. Once you
located the resonant point and put it where
you want, your SWR should be no higher than
3:1 at a low power reading. The antenna should
be grounded when determining resonant point.
Release the grounding wire (12). Check the SWR.
The resonant point may move up a little and
will have to be relocated.
Attic and top-of-building mounting where your
ISOTRON cannot be easily grounded, could
produce a feedpoint impedance of as much as
200 ohms. It is desireable to ground your
antenna to a good earth ground, but if this is
not possible, then the next best thing is to
use the ground in your electrical system. This
is attached to your outlets where the third
prong would insert on some appliances. The
ground wire should be attached to the bottom
of the mast only where the antennas are
mounted.
Please note that the shield of the coax is not
considered to be the same ground as the
grounded components of the antenna, such as
mast or bottom plate.
One factor to consider is the environment
interaction when transmitting at various power
levels. The instructions call for tuning at a
minimum power level. Tight or highly conductive
surroundings (metal sidings, machinery, etc.)
will show an increase in SWR from the low power
to the high power setting. This can be
compensated for by relocating the antenna. If
this is not practical a tuner can clean this
up. (See the page on USE OF A TUNER)
PAGE 10.
SIDE TOWER MOUNTING
The antennas should be offset from the tower.
This can easily be done with a 5 or 10 foot
mast mounted across the legs of the tower. The
Isotrons can be mounted horizontally on the
mast. A light nylon cord could be attached to
the mast an back to the tower at a 30 to 45
degree angle to keep the mast from drooping.
GROUNDING
There is much confusion about grounding
antennas. The Isotrons do not use a ground for
performance. Grounding offers a change in
impedance value as well as protection against
static discharge. All outdoor installations
should be grounded.
The ONLY way to ground the Isotrons is by
connecting the ground wire to the bottom of
the mast the antenna is mounted on.
NEVER run a ground wire up to the antenna. The
wire will interact with the feedline and
drastically change the tuning. Avoid running
ground wires parallel to the feedline if
possible.
Do not use plumbing as a ground.
If the antennas are indoors and grounding is
not available close by, then it may be best to
leave the antenna ungrounded.
With indoor installations ground wires to the
radio should be avoided. Most radios are
grounded through the power supply.



PAGE 12.
THE USE OF A TUNER
The instructions provided basically discourage
the use of a Tuner. This is for the purpose of
initially tuning up the antenna only. However
there are times when a tuner has its place.
With the increasing popularity of solid state
transmitters a tuner is almost a must. Back in
the days when tube finals were used the
manufactures automatically provided the tuner.
Since the solid state circuits have become
popular, they have left the tuners out. This
makes it a must for an antenna system to be
very critically tuned so the exciter will not
cut back its power. In many cases this is very
impractical and the use of a tuner can be a
good asset to your set up.
In tight locations or locations not favorable
for an antenna installation, the impedance of
the antenna may not adjust to the 50 ohms
needed. An installation indoors with a very
short feedline may keep the impedance lower
than 50 ohms. The recommended adjustments may
have little affect due to the short feedline.
At the lowest the antenna will exhibit a 20
ohm impedance, giving a SWR of around 3:1.
Please keep in mind that if your SWR is over
3:1 the problem is your resonant point, not
impedance value. This can be corrected by
following the instructions on resonant point.
If you find isolating the antenna from ground
does little to raise the impedance due to your
location, then the tuner can be used to match
the exciter to the antenna. This will not
sacrifice performance if done correctly.
Expanding bandwidth is another asset of the
tuner. To avoid retuning the antenna for
different parts of the band a tuner can be used
to flatten the line and make it acceptable to
the exciter.
PAGE 13.
In conclusion, tuners can be used if not abused
in your installation. Under a conventional
installation the Isotron will tune up directly,
but many operators have to operate in less than
ideal circumstances. The Isotron was intended
for this challenge and we will be willing to
help you with it.
POWER RATING
The power rating defined in the catalogue is
OUTPUT POWER.
The Isotrons are intended to handle outdoors
1,000 watts PEP or 500 watts CW into the
antenna. Indoors the rating is 500 watts PEP
or 250 watts CW into the antenna.
YOU SHOULD MONITOR YOUR SWR AT ALL TIMES WHEN
USING HIGH POWER.
IF THE SWR IS UNSTABLE OR SLOWLY INCREASES
WHILE TRANSMITTING, CUT BACK YOUR POWER
IMMEDIATELY UNTIL IT STABILIZES!
PAGE 14.
SINGLE FEEDLINE OPERATION
The Isotrons have been designed so they can be
mounted back to back. As many as three can be
mounted this way around a mast at the same
height.
Electrically the antennas can be fed with one
feedline by simply connecting them in parallel.
Three antennas of any band you desire work well
on one feedline. There is no limit to how many
you can put on a single coax. However, the more
you connect over three the more complicated the
match becomes. An electrical diagram is shown
below.
With antennas mounted back to back, a coaxial
"T" is connected to the antenna of the highest
band. This is done by either the male side of
the "T" or by a short jumper from the female
side. The remaining connection will jumper over
to the next highest frequency antenna. If there
is a third antenna, then the procedure is
repeated again.
Tune up is the same for the resonant point as
in the individual antennas.
Impedance value becomes the average of all of
them. Therefore if you isolate one antenna from
ground, you must isolate all of them. What you
do with one antenna for impedance you do with
all of them. You can see if you have over three
it can get quite complex and the aid of a Noise
Bridge will be a big help.



PAGE 15.
PERFORMANCE
What makes the Isotron Antennas perform?
Starting from the exciter, RF need to arrive
at the antenna. This is done through your
feedline. Next it needs to enter through the
antenna. This is accomplished by ending the
feedline with a radiating resonant circuit,
the antenna. Contrary to popular opinion the
impedance match has very little affect on
performance of the antenna. A mismatch of up
to 6:1 SWR will still provide performance that
compares to a 1:1 SWR.
This is not to be confused with the exciter
protection circuit that reduces power output,
in some cases at a 1.5:1 SWR and higher. This
can be overcome with the use of a tuner for
those solid state exciters.
In most cases a 1:1 SWR can be achieved with
the Isotrons. However, many are operating in
very tight locations which may make it
difficult to achieve the ideal match from the
antenna. The antennas radiation will still be
optimum as long as you adjust the resonant
point. The resonant point can be adjusted in
any location regardless of how tight the
installation is. The radiation performance can
easily be checked by a simple Field Strength
test, either using a Field Strength meter or
another local station close by.
From this point radiation is at the mercy of
the environment which will determine how well
your signal is received by other stations.
Height enhances your performance best. So do
not sacrifice height if you have a choice. The
Isotrons are designed to mount high with a
light mast so you can take advantage of this
feature.


INSTRUCTION MANUAL
FOR THE
ISOTRON 20, 11 OR 10
MANUFACTURED BY
BILAL COMPANY
FLORISSANT, CO. 80816
PH: 719/687-0650

TABLE OF CONTENTS
ASSEMBLY INSTRUCTIONS 2
WARRANTY 3
FINDING THE RESONANT POINT 5
COMPENSATION FOR VARIATIONS IN LOCATION 8
SIDE TOWER MOUNTING 10
GROUNDING 10
USE OF A TUNER 12
POWER RATING 13
SINGLE FEEDLINE OPERATION 14
PERFORMANCE 15