INSTRUCTION MANUAL FOR THE ISOTRON 15, 17 OR 12
MANUFACTURED BY
BILAL COMPANY
137 MANCHESTER DR.
FLORISSANT, CO. 80816
PH: 719/687-0650


TABLE OF CONTENTS
INSTRUCTIONS 2
DIAGRAM 3
WARRANTY 5
FINDING THE RESONANT POINT 6
COMPENSATION FOR VARIATIONIN LOCATION 9
SIDE TOWER MOUNTING 11
GROUNDING 11
USE OF A TUNER 13
POWER RATING 14
SINGLE FEEDLINE OPERATION 15
PERFORMANCE 16








PAGE 2.
INSTRUCTIONS FOR THE ISOTRON 15, 17 OR 12
1. The Isotron 15, 17 or 12 comes completely assembled and ready for mounting
on a standard METAL mast, 1 1/2" or smaller. Use the U-Bolt assembly provided
in conjunction with the holes provided at one end of the antenna, see pg. 12.
Counterpoise (2) is mounted just below the connector (3), see pg. 3.
2. The metal mast should be grounded at the base on all outdoor installations.
Do not run grounding wires directly to the antenna. It is not necessary to
search
for a ground on indoor installations.
3. For the 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 to the mast
securely and neatly run to your radio. Stand-offs can be used also. Extra coax
coiled up or left loose should be avoided.
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.
4. The jumper (4) grounds the counterpoise (2) to the metal mast, see pg. 3.
Depending on where you have the antenna mounted will determine whether the
jumper
should be removed or not. Most installations require it to be on. This will be
explained later.
5. There are two frequency adjustments for this model. Your fine adjustment (1)
and your crude for larger movements in resonant point (2).

Page 3

Page 4.
6. Start with (2) parallel to the coil and (1) as in the diagram on pg. 3.
Rotate
(1) for either an increase or decrease of your resonant point to the desired
portion of the band. This will be indicated by the lowest SWR at this point. Be
sure you are operating at the lowest power level that your SWR meter will read.
7. If a higher resonant point is desired and can not be achieved with (1), then
rotate the counterpoise (2) away from the coil a few degrees at a time.
8. (4) shown on pg. 3 is for impedance matching of the antenna. Normally with
it attached 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 of the antenna. If this situation occurs it
is easiest to do the adjustment with a Noise Bridge to avoid guessing if your
impedance is high or low. A capacitor of 100 pf or less may be jumpered in if
a point between the high and low values are desired (capacitor not included).
This complication of impedance is the exception rather than the rule and a
determination of your resonant point should be known before attempting to adjust
your impedance value.
8. See page 6 for more help on adjusting the resonant point.
8. See page 9 for more help on adjusting impedance for various locations.
NOTE: A TUNER OR MATCHING DEVICE SHOULD NOT BE IN THE LINE DURING THE TUNE UP
PROCEDURE. HOWEVER A TUNING DEVICE IS HIGHLY RECOMMENDED FOR THE SOLID STATE
RADIOS DURING NORMAL OPERATION.
Page 5. 
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 6
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 a Signal near this frequency.
7. Bring your hand toward the end (1) plate of the antenna.
8. Carefully listen. If the Noise increases at some point while your hand is
approaching the End 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.
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.
Page 7.
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. Adjust the antenna accordingly.
16. The object is to locate a minimum SWR by graphing as described in step 14.
Page 8.
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. This is described on page 9.
Page 9.
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. 12).
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.
Page 10.
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 (4). 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 on page 7 call for tuning at a minimum
power level. In some very tight or highly conductive surroundings (metal
sidings,
machinery, etc.) SWR 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 11.
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.
Never use plumbing for a ground.
The third wire on an electrical ground can be used. However on indoor
installations if the distance is too long to an outlet it is best to not have
a ground wire.
On indoor installations the radio should not have a ground wire. It should be
grounded through the power supply only.

Page 12


Page 13.
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 ante.
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 antennafor different parts of the band a tuner can be used to flatten the line and makeit acceptable to
the exciter. 14.In conclusion, tuners can be used if not abused in your installation. Under aconventional installation the
Isotron will tune up directly, but many operatorshave to operate in less than ideal circumstances. The Isotron was
intended forthis challenge and we will be willing to help you with it.
Page 14
POWER RATING
The power rating defined in the catalogue is INPUT POWER. This is how manyexciters are rated. However, some
exciters or amplifiers are rated in OUTPUTPOWER.The Isotrons are intended to handle outdoors 1,000 watts PEP or
500 watts CW intothe antenna. Indoors the rating is 500 watts PEP or 250 watts CW into theantenna.YOU SHOULD
MONITOR YOUR SWR AT ALL TIMES WHEN USING HIGH POWER.IF THE SWR IS UNSTABLE OR
SLOWLY INCREASES WHILE TRANSMITTING, CUT BACK YOURPOWER IMMEDIATELY UNTIL IT
STABILIZES!


SINGLE FEEDLINE OPERATION SEE PAGE 15 BELOW


Page 16.
.PERFORMANCE
What makes the Isotron Antennas perform?Starting from the exciter, RF need to arrive at the antenna. This is done
throughyour feedline. Next it needs to enter through the antenna. This is accomplishedby ending the feedline with a
radiating resonant circuit - the antenna. Contraryto popular opinion the impedance match has very little affect on
performance ofthe antenna. A mismatch of up to 6:1 SWR will still provide performance thatcompares to a 1:1
SWR.This is not to be confused with the exciter protection circuit that reduces poweroutput, in some cases at a 1.5:1
SWR and higher. This can be overcome with theuse of an outboard tuner for those solid state exciters.In most cases a
1:1 SWR can be achieved with the Isotrons. However, many areoperating in very tight locations which may make it
difficult to achieve theideal match from the antenna. The antennas radiation will still be optimum aslong as you adjust
the resonant point. The resonant point can be adjusted in anylocation regardless of how tight the installation is. The
radiation performancecan easily be checked by a simple Field Strength test, either using a FieldStrength meter or
another local station close by.From this point radiation is at the mercy of the environment which will determinehow
well your signal is received by other stations. Height enhances yourperformance best. So do not sacrifice height if you
have a choice. The Isotronsare designed to mount high with a light mast so you can take advantage of thisfeature.




TABLE OF CONTENTS
INSTRUCTIONS 2
DIAGRAM 3
WARRANTY 5
FINDING THE RESONANT POINT 6
COMPENSATION FOR VARIATIONIN LOCATION 9
SIDE TOWER MOUNTING 11
GROUNDING 11
USE OF A TUNER 13
POWER RATING 14
SINGLE FEEDLINE OPERATION 15
PERFORMANCE 16


INSTRUCTION MANUAL FOR THE ISOTRON 15, 17 OR 12
MANUFACTURED BY
BILAL COMPANY
137 MANCHESTER DR.
FLORISSANT, CO. 80816
PH: 719/687-0650