305 BROADCAST AKG/7N User manual

305 Broadcast AKG/7
N, M, F
User Manual
Circular Polarization
FM Antenna
This manual provides important guidelines for installing. Review this
information carefully for proper installation. Both unit specifications
and manual contents are subject to change without notice.

FM Antenna User Manual
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MOUNTING INSTRUCTIONS
POWER ANTENNA ANTENNAS DB WEIGHTBAYS
n.rs
1 1
1
1
1
1
-1.5
1.5
4.5
6
7.5
-1.4
1.4
3
4
6
1,8 mt.s
4,3 mt.s
9,3 mt.s
14,3 mt.s
19,3 mt.s
9
18
36
54
72
2
4
6
8
Bays Gain Gain Aperture kgs.
These wide band FM antennas, made of Stainless Steel are particularly
recommended for medium Output Power Transmitters.

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SUGGESTED MAST SECTION
Is suggested install this Antenna over poles or guyed mast because the section
higher than 110mm.
DISTANCE ESTIMATION BETWEEN FM
ANTENNA BAYS
Wave Length = λ = 300 : f(MHz)
Distance between antenna bays (any antenna types) = d
d (suggested) =
λ x 0.85
88MHz
λ = 300 : 88 = 3.41 mt d = 3.41 x 0.85 = 2.9 mt
98MHz = 300 : 98 = 3.06 mt d = 3.06 x 0.85 = 2.6 mt
108MHz = 300 : 108 = 2.78 mt d = 2.78 x 0.85 = 2.36 mt
Distance dsuggested 2.5 - 2.6mt even if working frequency is 88MHz or
108MHz
FM Antenna User Manual
λ
λ
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.
.
.
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FM Antenna User Manual
MOUNTING INSTRUCTIONS
AKG/7
The antenna must be assembled with the central insulator down.
The elements without the hole must be mounted looking to the high while the
elements with the hole must be mounting looking down.
The elements with the hole have different length and for this reason have
been marked with different letters , pay attention to follow the A- B - C - D
letters.
After inserting the elements lock nuts lightly.
Insert the central link and lock it to the inner brass conductor coming out
from the central insulator.
Lock strongly all the nuts.
Lock the antenna to the mast at the distance indicated from the lines.
Protect the connector with appropriate tape.
Using an array of 2 or more dipoles it’s necessary to calculate the spacing between
the elements ; we give you the formula to do this in function of the frequency used :
“300.000 : F ( Mhz ) x 0.8 = Distance in mm“.
845mm
50mm
Circular Polariz.
W.B. Antenna
730mm
730mm
840mm
920mm
6mm

Complaints about High Reflected Power, High VSWR, or Poor Match all mean
the same thing. The antenna does not appear to be absorbing as much power
from the transmitter as it should. It must be determined whether the
installation or the product is the cause. Answers to the following technical
questions can help determine if the product qualifies as defective per the
manufacturer's warranty. Our statement will be found on the current Celwave
Price List (we presume all connections are clean, dry, and tight. We also
assume all test equipment to be in good, calibrated condition.):
Some Criteria For Evaluating Antennas
Check to see if it is a higher number than the Celwave catalog value for this
product. Most of our antennas have a match of 1.5:1 or 1.6:1 across a
specified bandwidth. Performance at a Voltage Standing Wave Ratio greater
than 2.0:1 may be unsatisfactory. Some technicians will refer to match as
"Return Loss" in which case rates of 14 dB or 12 dB apply. Performance at a
R.L. of less than 9 dB may be unsatisfactory.
1. What is the VSWR you have measured?
Check to see that it has been properly calibrated and that any connector
adaptors are of good quality. A poorly matched adaptor will invalidate the
results.
2. What test equipment did you use?
(These devices are inexpensive and therefore more common but can be
inaccurate, particularly if more than one RF carrier is present.
Technicians who use them will eagerly tell you how many Watts of power
is reflected back to the transmitter but often do not know the actual
mismatch. The forward power measurement is required to calculate the
VSWR or Return Loss number. This can be tricky because some
transmitters have an output stage protection circuit which reduces power
under highly reflection conditions).
a. Wattmeter/Power Meter?
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Some Criteria For Evaluating Antennas
The technician may have chosen not to perform this test because it requires
climbing the tower. This procedure should be done to eliminate jumper cable or
down-lead cable factors. These cables could be either defective and cause the
problem or be fine and absorbing the reflection which masks the problem.
3. Did you perform the measurement directly at the
antenna’s connect or?
Check to see if the antenna was ordered for the correct frequency. The
manufacturer may have mis-marked the antenna or carton. Several methods
can be used to determine an antenna’s frequency. If the technician has swept
the response of the antenna he will know the frequency of best match. That
should be its designed frequency. The technician may also measure the
physical length so that we may compare it to a cut chart.
This is a crude method. If the antenna is of relatively new and the model
number is known, the factory may still have the production test data sheet
which will identify its frequency by Serial Number.
4. What is your operational frequency?
(These devices do not rely upon the site’s transmitter as a signal source.
They can produce more accurate and meaningful results but do not
subject the antenna to full power where arcing or flashover would occur).
b. Network Analyzer/Spectrum Analyzer with Tracking
Generator?
(Occasionally, a technician will use a “TDR”. This is not an industry
recognized instrument for antenna testing, and many manufacturers will
not respond to these measurements because the equipment uses
pulses rather than RF and does not measure beyond band limiting
devices. See Nov/Dec 1996 Microwaves & RF Magazine Article entitled
“Identifying Transmission Line Faults” on page 40 forexplanation of TDR
misapplication).
c . Time Domain Reflectometer?
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Some Criteria For Evaluating Antennas
Side mounting too close to the tower can detune an antenna. The required
spacing distance between the antenna and any other metal object decreases
as the operational frequency increases. Some good numbers per our factory
test procedure for omnidirectional antennas are from 100 ft. at 30 Mhz to 5 ft.
at 900 Mhz.
5. Did you measure the antenna erect , free and clear of
metal objects?
Some antennas have direct ground lightning protection. These normally
measure as a DC short between the connector’s inner and outer conductor but
will be the proper 50 Ohm impedance at RF. See lightning notes in the catalog
specs to determine if this antenna model should measure as an open or a
short.
6. What is t he DC continuity measurement using an
ohmmeter?
If the second antenna measures OK under the same mounting conditions, the
technician’s first antenna is probably defective. If the second one yields the
same bad result, the problem is unlikely to be the antenna. Perhaps the
transmitter is not operating on the expected frequency. Substitution of a
dummy load is an option if a second antenna is not available but the test is
less meaningful because it is actually testing only the cable.
7. Did you have the opportunity to substitute an identical
antenna?
It could either be new and defective or had performed nominally for some time
before failing. It is a good practice for technicians to test products on receipt
before transporting them to the job site. Manufacturer's warranties cover only
manufacturing defects, not damage from an improper installation. An example
would be mounting a standard antenna upside-down. This would put the drain
hole at the top where it could collect water and cause the product to fail over
time. Factory options given to an inverted antenna include reconfiguring both
the drain hole location and any electrical beam tilt.
8. When was the antenna installed?
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FM Antenna User Manual

Some Criteria For Evaluating Antennas
They are placed at the bottom of the antenna for draining internal moisture.
Periodic inspection of these openings is the responsibility of the owner. They
must remain clear of debris to preclude corrosion from internal condensation.
Such damage can drastically affect performance and is not covered by
warranty.
9. Are the antenna drain holes open?
It is a good idea to shake the antenna during the above tests to ensure there
are no mechanical intermittence. Poor connections may lead to RF
intermodulation products. Water entering the antenna may lead to electrical
intermittence which subside when the antenna dries out.
10. Is the antenna intermittent ?
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Some Criteria For Evaluating Antennas
Match is only one indicator of antenna quality. VSWR tells us how well the
product’s impedance matches to (absorbs) a transmitters signal, and is easy to
measure in the field. Unfortunately, VSWR does not reveal an antenna’s
efficiency (how well it radiates the signal). This measurement (an antenna’s
radiation pattern) is more difficult to perform in the field. We may presume that
match bandwidth and pattern bandwidth are equal, but this may not always be
true. For example, operating an end-fed antenna below its design frequency
will result in an electrically down-tilted vertical pattern. Usually, substitution
with an identical unit of known quality is the method of choice when a
defective product is suspected.
The typical VSWR for a good antenna is 1.5:1. Although some site engineers
may specify a minimum acceptable value of 1.3:1 there is only a minuscule
improvement. For example at 1.5:1 ratio, 4.0% of the power is reflected back,
creating a 0.18 dB loss.
At a1.3:1 ratio, 1.7% is reflected resulting in 0.07 dB loss. The performance
improvement is only 0.11 dB. It is a good idea to document performance upon
installation. This is usually done by choosing a remote site and measuring the
signal level received from the transmitter. Periodic measurements at that same
location will reveal the amount of any degradation so corrective action may be
taken.
Notes
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FM Antenna User Manual