INSTRUCTION MANUAL
FOR THE
ISOTRON 160C
MANUFACTURED BY
BILAL COMPANY
137 MANCHESTER DR.
FLORISSANT, CO. 80816
PH: 719/687-0650

TABLE OF CONTENTS
ASSEMBLY INSTRUCTIONS 2
TUNING 4 - 5
ASSEMBLY DIAGRAM 6 - 11
FINDING THE RESONANT POINT 12 - 13
TRIMMING THE COIL 14
COMPENSATION FOR LOCATION 15 - 16
SIDE TOWER MOUNTING 17
GROUNDING 17
THE USE OF A TUNER 18
POWER RATING 19
SINGLE FEEDLINE OPERATION 20
PERFORMANCE 21
WARRANTY 22


PAGE 2.
INTRODUCTION
The Isotron 160C will be assembled on the mast from the
top down. You will need a metal mast to support the
antenna during assembly. A temporary mast can be used if
you are going to relocate the antenna.
The Assembly instructions will refer to diagrams 1 - 5.
PARTS LIST (See Fig. 1-5 for identification)
1. TOP PLATE #11
2. BOTTOM PLATE #1
3. BOTTOM SUPPORT #2 (4 HOLES, 7/8" OD,
NON-METALLIC).
4. MIDDLE SUPPORT #6 (3 HOLES " " ).
5. TOP SUPPORT #13 (4 HOLES " " ).
6. COIL #4 WITH 1/4" CROSSBAR.
7. BOTTOM COIL SUPPORT ROD #3, 8 1/2" X 1/4"
SOLID ROD.
8. TOP COIL SUPPORT ROD #5, 60Z' X 1/4 " SOLID
ROD.
9. TUNING ROD #14, 36" X 1/4" SOLID ROD, NO
THREADS.
10. GROUNDING WIRE #15.
11. TUNING ROD BRACKETS (TWO) #9 AND #12.
ASSEMBLY
1. Attach BOTTOM SUPPORT #2 to BOTTOM PLATE #1.
Use one 14" x 1 12" bolt with a GROUNDING WIRE #15
and nut. Use the holes that are closest to the mast, do not
tighten at this time. See FIG. 1. NOTE: PLATE #1 has the
SO-239 Connector mounted on it.
2. Attach COIL #4 to BOTTOM COIL ROD #3. Each end
of #3 should have a nut threaded to the end of the
threads. The end with the shorter threads is screwed into
the COIL #4 bottom. The nut is tightened to the coil to
secure it. See Fig. 1 & 2.
3. Mount the COIL #4 to the BOTTOM PLATE #1 by
inserting BOTTOM COIL ROD #3 into the hole farthest
from the mast through #2 and #1. Use a second nut to
secure. Now you can snug up both nuts on the BOTTOM
SUPPORT #2. See Fig. 1.
4. Put a stop nut on each end of the COIL CROSS BAR.
Insert the COIL CROSS BAR into the side holes and secure
with a second nut. See Fig. 2. NOTE: There may be some
downward tension on the bar.
PAGE 3.
5. Attach the wire pigtail from the SO-239 Connector and
the wire pigtail from the bottom of COIL #4 to the 8/32
stud at the bottom of the coil. Remove one nut, put the
solder lugs on and replace the nut and secure. See Fig. 1
and 5.
6. Put one nut on one end of the TOP COIL ROD #5. Put
this
threaded end through the wire eye at the top of the COIL.
Attach a second nut, then screw the TOP COIL ROD #5
into the COIL. With the threads most of the way into the
coil, tighten the nut against the coil, then tight the nut
above the wire eye. See Fig. 1 and 3.
7. Slide the MIDDLE SUPPORT #6 on to the TOP COIL
ROD #5. Use the single hole at the end of the support.
This support will be at 1" above the adjacent nut on the
COIL.
8. At the opposite end of the 30" rod that is screwed into
the coil, screw a 1/4" nut about 1/2 way down on the
threads. Next screw the 1/4" x 7/8" coupling nut so it is
against the standard nut. Snug these 2 nuts together. Set
this section aside and go to the top section for assembly.
9. Slide TUNING ROD BRACKET #9 onto the second TOP
COIL ROD #5, leave it loose. Set this aside. See Fig. 3.
10. Attach the TOP PLATE #11 to TOP SUPPORT #13.
Use a 1/4" x 1 1/2" Bolt with a nut in the hole closest to
the mast, but do not secure. See Fig. 3.
11. Slide the second TOP COIL ROD #5 through the
U-JOINT #10. If needed you can loosen the set screw, but
re-tighten once everything is in place. See Fig. 3
12. Slide the second TUNING ROD BRACKET #12 on to
the TOP COIL ROD #5. See Fig. 3.
13. Thread a 1/4" nut all the way down on the top of
second TOP COIL SUPPORT #5. Then add a flat washer
from the hardware packet, then slide into the hole
attaching the TOP SUPPORT #13 and TOP PLATE #11.
Secure with a second nut, but leave it loose. Secure the 1
1/2 " Bolt previously installed in step #11. See. Fig. 3.
PAGE 4.
14. Mount a U-bolt at the top of the mast where the
antenna is to be. See Fig. #6.
15. Mount the TOP SUPPORT #13 (with Top Plate, 30"
Rod and Tuning rod brackets) on to the top U-BOLT. Put
a second set of nuts from the U-BOLT Packet and leave
them a little loose against the outside of #13. See Fig. #6.
Use an open end wrench to tighten securely the nuts next
to the mast and metal strap of the U-bolts. Tighten so the
strap forms to the mast. Then secure the second set of
nuts against the #13 Top Support.
16. 76 inches down from the top U-Bolt mount the bottom
U-Bolt in the same manner.
17. 20 1/2" up from the bottom U-Bolt mount the center
U-Bolt in same manner.
18. Mount SUPPORTS #2 and #6 on the U-bolt. Be sure
they are
parallel, then secure with a second nut from the U-BOLT
package and tighten as described in step 15.
19. The two 30" Coil Support Rods #5 should meet. Screw
a 1/4" regular nut onto the top rod. Then Screw the rod #5
onto the 1/4" x 7/8" Coupling nut until it stops. Then
secure it by tightening the 1/4" regular nut against it.
20. Tighten the 1/4" nut at the top where #5 attaches to
the Top Plate #11
21. Slide the TUNING ROD #14 through the two TUNING
ROD BRACKETS #9 and #12. #12 will always be
positioned at the top of rod #5. #9 will always move with
the bottom of the TUNING ROD #14. When tuning is
complete, secure the 8/32 nuts on the brackets.
TUNING
1. The Isotron 160C should be mounted as high and in the
clear as possible on a metal mast. See Fig. 6 on page 10 for
the proper installation of the U-BOLT Assemblies.
2. 50 ohm coax should be connected to the SO-239
Connector on the antenna. The coax should either be
secured to the mast with tape or stand-offs. A neat run
with no excess should go to the radio.
PAGE 5.
3. 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.
4. No tuning devices should be in the line for the initial
tune up. These can be used later if desired.
5. Maximum resonant frequency will be with the TUNING
ROD #14 in the lowest position or removed.
6. To decrease the resonant frequency, raise the TUNING
ROD #14 according to what you want. Secure the Brackets
#9 and #12
keeping them positioned properly. Refer to step 17.
7. Start at low power and graph your SWR across the 160M
band.
Locate the minimum SWR. This is your resonant point.
Please read over the section on "FINDING THE
RESONANT POINT".
8. For frequencies higher than 2.0 Mhz see the section on
"TRIMMING THE COIL".
9. If the minimum SWR is not low enough, then refer to
the topic "COMPENSATION FOR VARIATION IN
LOCATION" for the minor
adjustment.

PAGES 6-11























PAGE 12.
FINDING THE RESONANT POINT
1.Locating the resonant point 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 to the frequency desired.
6. Listen to the Noise/Signal at this frequency.
7. Bring your hand toward the top plate of the antenna.
8. Carefully listen. If the Noise 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 Noise decreases only while bringing your hand
toward the Top Plate, then the antenna is resonant at a
lower frequency than the receiver is tuned.
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.
PAGE 13.
12. If the resonant point is low, it will be necessary to
remove all tuning hardware to bring the resonant point to
maximum. It is possible for your environment to make the
antenna resonate below the designed band.
13. 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.
14. 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.
15. 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.
16. If the SWR increases as you move up frequency, then
the
resonant point is below the band or minimum frequency.
Trimming the coil may be necessary.(See page 11 for 160
- 40.)
17. The object is to locate a minimum SWR by graphing as
described in step 15.
18. If you have a general coverage receiver you can listen
at a lower frequency and check the antenna with your hand
as
described.
19. 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.
20. If you are using a Noise Bridge, it should be located
near
the antenna for tune up.
21. Impedance may be adjusted if necessary after
completion with the resonant point. This is described on
pages 14 through 15.
PAGE 14.
TRIMMING THE COIL
For specific frequencies such as for MARS, CAP, FAA and
so on where frequencies near, but not in the amateur band
are required, coil trimming may be done to reach those
frequencies. In cases of extreme environment interaction,
trimming may be necessary for proper resonant point.
Before trimming the coil, the antenna must either be
properly operating at some point on the band being used,
or you have confirmed the resonant point is lower than
where your operating. DO NOT TRIM THE COIL PRIOR
TO THIS.
Remove all the tuning hardware and take note of where
the resonant point is. Trimming will be from this point,
therefore the tuning hardware could be used for lowering
the resonant point to where desired.
1. Remove the Top Coil Support.
2. Tape the coil securely so the windings will unravel.
3. Clip the eye on the top lead of the coil.
4. Slide the wire back through the two holes in the coil
form.
5. REMOVE 1/2 TURN AT A TIME! Slip the wire back
through the two holes from the opposite direction. Looking
through the hole as the wire comes to you will help line it
up.
6. Reconnect the wire to its original position and trim the
excess.
7. Check your resonant point. If needed repeat the
procedure as many times as necessary in 1/2 turn
increments.
PAGE 15.
COMPENSATION FOR 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. 10, fig. 6). 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. A Noise Bridge
is quite inexpensive, and enables you to make the
measurement quickly, simply and accurately.
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.
PAGE 16.
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.
The diagram on page 14 shows how to insulate your
antenna from
ground if necessary and how to connect the mica or ceramic
capacitor for values in between.
One factor to consider is the environment interaction when
transmitting at various power levels. The instructions on
page 7 call for tuning at a minimum power level. In some
very tight or highly conductive surroundings (metal sidings,
machinery, etc.) will show up as 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 sheet on USE
OF A TUNER)
PAGE 17.
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.
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.
PAGE 18.
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. 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 re-tuning the antenna for different parts of the band
a tuner can be used to flatten the line and make it
acceptable to the exciter.
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.
PAGE 19.
POWER RATING
The power rating defined in the catalogue is INPUT
POWER. This is how many exciters are rated. However,
some exciters or amplifiers are rated in 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 20.
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 21.
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 an
outboard tunerfor 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.
PAGE.22
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
correspondence.

TABLE OF CONTENTS
ASSEMBLY INSTRUCTIONS 2
TUNING 4 - 5
ASSEMBLY DIAGRAM 6 - 11
FINDING THE RESONANT POINT 12 - 13
TRIMMING THE COIL 14
COMPENSATION FOR LOCATION 15 - 16
SIDE TOWER MOUNTING 17
GROUNDING 17
THE USE OF A TUNER 18
POWER RATING 19
SINGLE FEEDLINE OPERATION 20
PERFORMANCE 21
WARRANTY 22

INSTRUCTION MANUAL
FOR THE
ISOTRON 160C
MANUFACTURED BY
BILAL COMPANY
137 MANCHESTER DR.
FLORISSANT, CO. 80816
PH: 719/687-0650