Acom LS 108 Programming manual

ASSEMBLING MANUAL
LS 108
HF Log – Periodic Antenna
14 – 30 MHz

1mm=39.37mil 1cm=10mm=0.3937” 1m=100cm=3.281ft 1kg=2.205lbs 1m2=10.764sq.ft
1km/h=0.62137mph
ACOM LS108
HF Log-periodic Antenna
ASSEMBLING MANUAL
1. GENERAL INFORMATION
ACOM manufactures a range of antennas designed and produced to give top performance and reliable long-
lasting service. They are completely manufactured of non-corrosive materials. The antennas come partly
factory-assembled in order to facilitate and expedite your labor.
1.1. Introduction and Description
This manual explains the assembling of the ACOM LS108 HF Log-Periodic Antenna. The LS108 is a
directional wideband antenna that covers the HF spectrum between 14 and 30 MHz continuously. It can be
used with the full legal power of 1500W continuously or 3000W PEP.
1.2. Owner Assistance
If assistance or service is needed, your local dealer should be contacted first. In the unlikely event you need
further information, you may get in touch with ACOM by facsimile, telephone, email, or standard mail. Fax:
([phone]; telephone: [phone]; e-mail: [email protected]; standard mail: ACOM,
Blvd. N. Mushanov 151, 1330 Sofia, Bulgaria.
1.3. Specifications
Number of elements 10
Frequency coverage 14-30 МHz continuously
Gain (average) 9.5 dBi
Front-to-Back Ratio 20 dB
Nominal Input Impedance 50 Ohm
SWR (typ) 1.5 : 1
Maximum Input Power 1500 W continuously
3000 W PEP
Boom Length 8 m (26.25 ft)
Boom Diameter 50 mm (1.97”)
Mast Diameter 50 mm (1.97”)
Longest Element 11 m (36.1 ft)
Turning Radius 6.8 m (22.3 ft)
Wind-load Area 1.5 m2 (16,15 sq.ft)
Wind Survival (no ice) 145 km/h (90.0 mph)
Weight Operating 30 kg (67 lbs)
Shipping 36 kg (80 lbs)
Connectors: antenna / coaxial feed line SO239A / PL259
1.4. SAFETY FIRST!
Get acquaint with and observe strictly the requirements and instructions of your local legislation. Direct
grounding of the antenna and the tower structure is essential as protection from lightning strikes and static
electricity. The entire earth-connection system must meet your local standard requirements.
Do not install the antenna close to power lines and cables, as their proximity, arc-over or contact with them
during assembly, installation, and exploitation is hazardous and can be lethal.
Do not work alone! You must have at least one assistant always when you work on the antenna. If you have
any doubt concerning the safety, please consult your dealer or engage a professional company.
WARNING!
Exposing to strong electromagnetic radiation can result in dangerous maladies or death. Do not
allow people or animals around the antenna during operation and exploitation.

ACOM LS108 HF Log-periodic Antenna
1.5. Location
The antenna should be mounted on a support tower structure at a height between 10 and 15 meters (33-50
ft) above the ground level. It must be located in the clear, away from trees, power installations, buildings,
other antennas etc. Such objects can be dangerous and they can reduce the antenna efficiency or cause
interference. If metal guy wires are used for the tower, they should be broken electrically with strain
insulators, at 2 meters (6 ft) apart or less.
1.6. Your first steps
The first step to installation is to fully read this manual. Then, carefully inspect the shipping cartons for any
physical damage. ACOM ships antennas in highly protected containers, but it cannot assure that
mistreatment by shippers will not occur. If there is any such damage, notify your ACOM dealer immediately.
Failure to do so may invalidate your warranty.
Select a large and clear area (10 x 11 m or 33 x 36 ft minimum) to assemble the antenna. Provide some
supports for holding the boom at a suitable working height.
The ACOM production uses metric (European) system of measurement units. The antenna elements (two
halves) and the phase-line straps are placed in separate polyethylene sleeves, marked respectively. The
hardware is bagged by size (there are some spares). A set of required tools to do the job is enclosed, too.
2. ASSEMBLING
The antenna comprises the following main components: boom, mast, ten elements, balun transformer, and
phase line (called also distribution feeder). The set includes also guys, installation elements, hardware, as
well as required tools.
An overall view of the antenna is shown in Fig. 1 LS108 - Appearance. All the ten elements are isolated-
mounted on the boom by ten supporting insulator blocks and each element is driven by the phase line.
2.1. Boom Assembly
The boom is composed of four pieces (sections), which are to be assembled together. The section ends to
be joined together are marked by letters A-A, B-B and C-C directly on the tubes. Sections have the element-
supporting insulators, mast bracket, balun transformer, and the boom guys readily installed in the factory.
You will find the required hardware situated along the boom sections.
Locate the four boom sections. Put them in order and orient letter markings so that “A” faces “A”, “B” faces
“B” and “C” faces “C” as shown in Fig. 2 Boom Assembly.
Join together the sections marked A-A. Align the mount-hole pairs. Insert 2 bolts M6x60 mm through the
holes. Place a lock washer on each free bolt end. Screw in a nut on each bolt and tighten properly but
without losing the tubes shape.
Fit the other boom joints (B-B and C-C) together similarly. This completes the boom assembly.
2.2. Element Assembly
Each antenna element has two symmetrical halves, called half-elements hereafter. They consist of sections,
which are partly assembled in the factory to the longest suitable transportation length. The customer should
do the final assembly as described below.
For transportation, the element sections are bundled up in pairs and packed each element in a separate
polyethylene sleeve. The polyethylene sleeves are marked as follows: ELEMENT 1, ELEMENT 2, etc to
ELEMENT 10.
Note: The shortest half-elements (number 10) are fully assembled in the factory.
Locate all polyethylene sleeves and identify them before to start assembling. Do not take out sections of
more than one sleeve at a time to avoid mixing up of sizes and lengths.
Begin with ELEMENT 1. Put all sections in the size order. Insert the smallest-size section into the next one at
a distance of about 100 mm (4”) - see Fig. 3 Element Riveting.
1mm=39.37mil 1cm=10mm=0.3937” 1m=100cm=3.281ft 1kg=2.205lbs 1m =10.764sq.ft
1km/h=0.62137mph 2
2

ACOM LS108 HF Log-periodic Antenna
Align the three riveting holes and insert a rivet in each hole, without riveting. Arrange the whole half-element
in this manner for a test only, without riveting for now. Check the total half-element length per Table 1 - Half-
Element Lengths. If you find any discrepancy, correct the mistake prior to continuing. This check will ensure
possible mistakes are avoided that could necessitate un-riveting multiple sections at any later stage.
Table 1 - Half-Element Lengths.
Element Nо. 12345678910
Half-length, m: 5,51 4,98 4,45 3,99 3,57 3,20 2,86 2,56 2,29 2,05
(ft): 18,1 16,3 14,6 13,1 11,7 10,5 9,4 8,4 7,5 6,7
After passing the arrangement test, disassemble the half-element. Lightly smear the contact surface of the
smaller-size section with conductive paste (supplied with antenna). This will ensure corrosion-free electrical
contact between the element sections. Insert the smaller-size section into the next one at a distance of about
100 mm (4”) and align the three riveting holes again. Insert a rivet (4 x 8 mm) in each hole. Begin riveting
them one-by-one, without removing the others out of their places. Support the free rivets in order to keep
them in place during riveting. This is important since the tubes could come out of position otherwise.
Use the "Hand Blind Riveter" tool, which is supplied with antenna, together with the needed number of rivets
(there is a reasonable reserve). Operation instructions about this tool appear on its original packaging.
Proceed similarly to assemble the remaining eighth half-element pairs.
2.3. Mounting the Elements to Boom
All element-supporting insulator blocks are factory mounted on the boom sections. They isolate between
half-elements as well as from each half-element to the boom.
The large ends of the completed half-elements are to be mounted on the supporting insulators at the same
time. All the required hardware and mounting tools are bagged in polyethylene envelopes.
Please look at Fig. 4 Elements mounting. Start with the longest element (ELEMENT 1). The left half-
element is marked with “1L” and the right one - with “1R”. The insulator has two channels for element
installation. They have the same marking “1L” and “1R”. Lay the two half-elements in the corresponding
channels.
Select two bolts M5x60 mm and place a plain (flat) washer on each bolt. Align the mount holes of the half-
elements and the insulator. Push the two bolts upside-down through insulator and half-elements. Use the
holes located next to the boom. Please note that the bolts heads are underside of insulator as shown in Fig.
4 Elements mounting. Smear a small amount of conductive paste on the tubes as pointed in the figure.
Push an M5x45 mm bolt with a plain washer through the next holes that are more distanced from boom.
Secure with lock washers and nuts on top of the tubes. Tighten the joint well but without deforming the tubes.
Mount the next elements – ELEMENT 2 tоELEMENT 4 on their insulators in the same way.
The rest antenna elements (ELEMENT 5 to ELEMENT 10) should be installed in the same way but you
should use shorter bolts in the holes next to the boom - M5x55 mm. Refer to Fig. 4 Elements mounting.
2.4. Attachment of Phase-line Straps
The distribution (phase) line feeds each antenna element in the center. It comprises nine pairs of straps
(called phase-line straps hereafter) that cross-connect in pairs between adjacent elements. Each phase-line
strap has a mount hole drilled at each end.
Locate phase-line straps and arrange them in pairs according to length. Now look at Fig. 5 Phase-line
straps mounting. Start mounting the longest strap pair between the longest antenna elements (ELEMENT 1
and ELEMENT 2). Place four plain washers on the four bolts of ELEMENT 1 and ELEMENT 2 that are closer
to the boom. Smear these bolts and the strap ends (on the two surfaces) with conductive paste. Attach one
end of the straps on the smeared bolts of ELEMENT 1. Cross the straps above the boom so that their free
ends reach the smeared bolts of the opposite ELEMENT 2. Place a plain washer, lock washer, and a nut on
ELEMENT 1 bolts only. Do not fully tighten at this time.
The second-length straps should be installed between the inner bolts of ELEMENT 2 and ELEMENT 3 in a
similar way. Remember to smear the straps with conductive paste on the two surfaces. Now place a plain
washer, lock washer, and a nut on the bolts of ELEMENT 2. Do not tighten the nuts yet.
1mm=39.37mil 1cm=10mm=0.3937” 1m=100cm=3.281ft 1kg=2.205lbs 1m =10.764sq.ft
1km/h=0.62137mph 3
2

ACOM LS108 HF Log-periodic Antenna
Continue in the same manner until you install all the nine strap pairs crossing between the antenna elements
(straps actually zigzag). At the last element (number 10), place a plain washer on the bolts closest to the
boom. Smear some conductive paste on the two surfaces of the cable ring terminals (lugs) of the balun-
transformer. Connect the terminals to the bolts using M5 lock washers and nuts but do not tighten for now -
see Fig. 6 Balun Connection.
At this stage of the installation check, whether all the nuts holding the phase line are screwed in but still
loose.
CAUTION!
The nuts holding the phase line should be tightened when you have reinforced the boom against the sag
(refer to section 2.7 Boom Support Assembly).
Now insert a strap-insulating spacer at each crossing point of the straps as shown in Fig. 5 Phase-line
Straps Mounting. Orient the strap spacer between the two straps as shown in the figure. Slide it along the
arrow shown in the figure until the straps engage the top and middle spacer slots.
2.5. Attachment of Coaxial Feed Line
Use coaxial cable with 50-Ohm characteristic impedance. Check whether your cable will withstand the power
you intend to use at the highest frequency (30 MHz). To make use of the maximum permissible power of
LS108, cable type RG213 or better is required.
Stripe one end of the cable and install a type PL259 plug connector (male UHF) according to the connector-
producer instructions for the appropriate cable type. Couple it to the balun-transformer SO239A jack
connector - see Fig. 6 Balun Connection.
Protect the coaxial connection against moisture leak in the connectors as well as in the cable.
Leave some cable drip-loop (see Fig. 1 LS108 - Appearance) to eliminate any undue mechanical strain on
balun transformer. Fasten the cable along underside of boom using ties delivered with antenna. First lay two
ties at the nearest strap-insulating spacer (located between ELEMENT 10 and ELEMENT 9). Together with
the cable, fasten also the legs (skirts) on the two strap-spacer sides (see Fig. 5 Phase-line straps
mounting). Continue fastening the cable with two ties at each spacer until you reach the mast.
Now fasten also the strap-insulating spacers in the other part of the boom (although there is no cable there).
2.6. Boom to Mast Assembly
The mast bracket (boom to mast holding assembly) consists of a pair of metal brackets and four U-shaped
bolts. It is factory mounted on the boom. Project the way you will mount the mast on the tower structure so
that the antenna is installed at a distance of no more than 30cm (1 ft) above the support. The mast must
protrude at least 80 cm (2.6 ft) above the antenna. Mark the draft position for the bracket on the mast.
Install firmly the mast in a vertical position so that it can bear the weight of the whole antenna.
Please look at Fig. 7 Boom to Mast Assembly. Unscrew the nuts from the two unengaged U-shaped bolts
and remove the bolts. Bring the boom near the mast at the height marked for the bracket. Re-install the two
U-shaped bolts so that they embrace the mast as shown in the figure.Place the removed four lock washers
and nuts and fully tighten all 16 nuts of the holding bracket.
Fasten the coaxial feed line to the mast using two ties.
If you will use a rotator, leave a large enough loop of cable around the mast in order to allow at least 360
degrees free rotation of the antenna.
2.7. Boom Support Assembly
To reinforce the boom against sag, it is tied up to the mast top via guys. They consist of two legs of
stainless-steel cable with a turnbuckle each as shown in Fig. 8 Boom Support Assembly. On the mast top
is installed a drawing bracket which serves for guys support.
After the boom has been assembled to the mast, uncoil the two guys (factory mounted to the boom). Adjust
the two turnbuckles so they extend to their maximum length. Loosen the two U-shaped bolts and slide the
1mm=39.37mil 1cm=10mm=0.3937” 1m=100cm=3.281ft 1kg=2.205lbs 1m =10.764sq.ft
1km/h=0.62137mph 4
2

ACOM LS108 HF Log-periodic Antenna
bracket downwards along the mast in order to hook the guys. Unlock the shackle-locking pin. Align the
drawing bracket, shackle holes, and re-insert the locking pin. Tighten properly.
Now move the drawing bracket upwards again and stretch the guys until the boom is essentially
straightened. Tighten the two U-shaped bolts securely. When the guys are properly installed, the bracket-to-
boom distance should be at least 70 cm (2.3 ft).
With guys attached to the drawing bracket, adjust the two turnbuckles in order to get the boom accurately
horizontal. If needed, either guy length could be adjusted via loosing its wire-rope clip - see Fig. 8 Boom
Support Assembly.
Check up whether all antenna elements are horizontal. If alignment is needed, loosen the two U-shaped
bolts of the respective element-holding insulator and get the element horizontal.
Now tighten properly all the nuts that hold the phase line (remember the caution note in S.2.4 Attachment of
Phase-line Straps). Do not over tight!
Check all antenna dimensions per Table 1 - Half-Element Lengths and Fig. 9 LS108 Dimensional
Drawing before to start lifting the antenna on your permanent tower structure.
Check the quality of all mechanical and electrical joints.
Do not miss checking the hermetic seal of the coaxial connection at the balun transformer once again!
Moisture irrecoverably increases coaxial cable loss when persisting for prolonged periods and it could result
in electric breakdown in both coaxial cable and either coaxial connector.
This completes the antenna assembly. You must get acquainted with and observe the producers, safety
requirements and installation instructions about your rotator and permanent tower structure before to
continue with lifting the antenna.
END
1mm=39.37mil 1cm=10mm=0.3937” 1m=100cm=3.281ft 1kg=2.205lbs 1m =10.764sq.ft
1km/h=0.62137mph 5
2