Assembly Instructions: Bencher Skylark
Tools Required:
Pop Rivet Tool
Tape Measure
Hex Wrenches
Screwdriver
Several Disposable Rags
Two Saw Horses
Several boxes or bowls to hold fasteners and small parts
Sharpie Marker Pen or the Equivalent
Acid Brush or stiff quarter-inch brush
Assembly Note: Jet Lube SS-30 is an effective antiseizing agent. A small amount of it should be put on the threads of all screws and bolts
prior to putting lock washers and nuts on. This is especially so for the U-bolts and the
boom to mast hardware. This will allow easy removal at a later date should it be
necessary to do so.
The small brush specified in the tools required list is the easiest way to apply the Jet Lube
both on element assembly and on bolt and screw threads.
Boom Assembly
Refer to the boom drawings and be sure you understand it. There are three inner sleeves
of 48” X 1 7/8” diameter, and 4 outer sleeves, 2” X 48”. Each of the 7 boom pieces has
holes precision drilled, and all holes should line up perfectly.
Note that the 4 pieces of 2” lengths have letters, A, B and C, marked in black. The letters
refer to the junction points, so there is Junction “A”, Junction “B” and Junction “C”.
The inner tubes also have marked letters, in red.
Take a 2” OD tube with the black letter “A” stenciled on end – place the piece on a flat
surface so that the “A” is upright and to the right end of the tube as you face it. Take the
1-7/8” tube with a red “A” stenciled on it, hold it so the red “A” is right side up, and slide
the left end of that tube into the end of the 2” tube marked with a black “A”. Notice the
hole left of the red “A”; slide the inner tube so that the hole lines up with the hole in the
outer sleeve. Pass a 2 ¾” bolt through the hole, and put a nut on it a few turns to hold the
assembly captive.
Find the 2” outer sleeve with a black “A” stenciled on one end, and a black “B” stenciled
on the other end. Slide the “A” end down over the 1-7/8 sleeve from the first section.
Rotate until the holes line up, and pass a 2 - 3/4” bolt through and add a nut for a few
turns.
Take the 1-7/8” tube marked with a red “B”, holding it so the “B” is upright. Slide the left
end of that tube into the right end of the existing assembly. Note that there are two sets of
holes. Pass a 2 ¾” bolt through one set and add a few turns of a nut.
Take the 2” tube marked with a black “B” on one end and a black “C” marked on the
other. Slide the “B” end over the right end of the boom assembly, and line up the holes;
pass a bolt though and put a nut on a few turns.
The remaining section of 1 7/8” tubing should be marked with a red “C”. Hold the tubing
so that the “C” is upright. Slide the left end of the tube into the assembly, line up the
holes and put a temporary bolt through as before.
The last piece of 2” tubing is marked “C”. With the “C” upright, slide the left end of the
tube onto the assembly and use a temporary bolt and nut.
This completes the initial assembly of the boom.
There are seven aluminum element platforms. These are mounted at the seven element
stations. In many cases, there is already a temporary bolt through the boom where the
element platform will mount. When mounting these platforms it is necessary to remove
the temporary bolt first. The platform station numbers are based one the distance from the
reflector end of the boom in inches, starting at the “A” end of the boom. Stations are
mounted so that the flat plate area is down. The first station is the 17 meter reflector,
which is about 19” in from the end of the boom. Remove the temporary bolt and nut, slip
an element platform over the boom tube, as shown in the picture, slide a 2 ¾” bolt
through, add a lock washer and nut and tighten.
In the same manner, mount the other six element platforms. Use a tape measure to
confirm the station element locations. Besides the first platform mounted at 19”,
platforms should be mounted at 46”, 90”, 94.5”, 159.75”, 177 inches and 183”. Make
sure that the stations are correct. Note that the first station may not be exactly 19” in from
the end; this is OK. However, to measure the rest of the stations, place the 19” mark of
your tape measure exactly centered on the hole of the first station. All other stations
should be exactly correct.
Element Assembly
The integrity of this antenna depends on the stainless steel aviation grade pop rivets
supplied. It is beyond the scope of this manual to cover how to pop rivet. Though the
process is neat and simple, you do want to be sure you get it done right! If there is any
question, get assistance from someone who has experience. Also, the internet has several
different instructional aids. A short video on pop riveting is at:
http://www.askthebuilder.com/Pop_Rivet_Tool_Video.shtml
Do note that sometimes in pop riveting it is necessary to pull up on the rivet by squeezing
the riveter handle, then releasing pressure on the handle, pushing the rivet tool down
further and then squeezing the handle again. If you have never done pop riveting before it
would be time well spent to try three or four rivets on a couple pieces of sheet metal.
In assembling the elements, you will be using the Jet Lube SS-30 anti-seize,
which is a copper bearing grease paste. This insures a good electrical connection between
element segments. Some people believe that copper bearing grease paste is a problem
because of galvanic action. However, galvanic action requires dissimilar metals AND
water or another liquid electrolyte. The grease in Jet Lube SS-30 prevents water from
getting involved, so there is no galvanic reaction.
In any case, note that if Jet Lube SS-30 gets on your clothes, it is virtually impossible to
remove the stain. For this reason, we strongly recommend you wear clothing for which
permanent stains will not be an issue. Also, you will want rags for wiping away excess
Jet Lube SS-30, and these rags are probably best thrown away when the project is
completed.
The Skylark has seven elements – four for 12 meters, and three for 17 meters. One of the
17 meter elements is insulated in the middle – this is the driven element. It should be
assembled last.
Note that all elements have their holes drilled in such a way that you can not make an
error in assembling nested pieces, as long as you simply insure that the rivet holes for an
outer tube and for an inner tube line up and have the same number of rivet holes.
Do not open more than one element bag at a time. Open one bag, assemble that element
per the instructions below, then progress to the next bag and the next element.
The 12 meter elements are to be assembled first. All the twelve meter elements are
identical except for tip length. Note that the 12 meter driven element is not split – the
design utilizes a solid element.
Open the plastic sleeve for one of the 12 meter elements. Find the center tubing section,
which is ¾” OD X 4’, which is the largest piece and for which there is only one piece of
that diameter.
Take one of the 5/8” diameter by 36” pieces of tube from the sleeve, which should have
three holes drilled at each end. Apply Jet-Lube SS30 to the outside of one end of this tube.
Apply a small amount of the paste from the tip of the tube to a point parallel to the hole
closest to the center of the tube, about 3” long.
Insert the tube into the end of the ¾” tube, twisting as you slide it in so that the paste is
smeared around the junction of the two tubes. Then, line up the three holes on the two
pieces of tubing. Insert a pop rivet and set it with the tool, then put in the other two rivets.
Detail of a pop riveted joint. Note that this element uses 4 pop rivets; some use 3,
some 4, and some with different hole spacing to avoid assembly errors.
Repeat with the other 5/8” tube at the other end of the 3/4” tube.
Insert the ½” tube into the 5/8” tube. Jet Lube SS-30 then rivet. Repeat on the
other half element assembly.
Insert the 3/8” tube into the ½” tube. Apply Jet Lube SS-30 then rivet. Repeat on the
other half element assembly.
Now, take the 5/8” end of one of the assemblies and insert it into the ¾” tube. Apply Jet Lube
, then rivet. Repeat on the other half element assembly to the other side of
the ¾” tube. This completes an element. Mark the element number on the tubing with the
marker, and set the element aside.
Assemble the other three 12 meter elements in the same way.
Open the bag for element #1, the 17 meter reflector. Separate the tubes. Note that one
5/8” tubing has a red paint splash on it, and has the rivet holes in the middle of the
element. This piece is the inside stiffener sleeve for the center of the element. Take one of
the ¾” tubes, and slide it over the 5/8” piece, apply Jet Lube SS-30, and rivet.
Now, using a marker such as a Sharpie Pen or the like, make two lines ½” from each side
of the center of the element. Slide one of the plastic insulating sleeves down the element
to that line. Because the sleeve has to go over two of the rivets it is not easy to slide at the
end, and having the sleeve warmed in the sun or in hot water will surely make the
operation much easier. Again, if you find it impossible to get the sleeve in place, it is
permissible to cut a slit down the length of the sleeve and put the sleeve in place.
Set the center section assembly aside, and assemble the rest of the element. Take one of
the 5/8” tubes, and note that one end has four holes in it, the other end three holes. Note
that the ½” tubes also have four holes on one end and three on the other. Insert the three
hole end of the ½” tubes in to the three hole end, of the 5/8” tube, apply Jet Lube SS-30,
and rivet.
Insert the 3/8” tube into the four hole end, apply Jet Lube SS-30, and rivet.
Now repeat procedure for the other side of the element.
Complete the element by attaching the two tip assemblies to the center section, applying
Butter-It’s-Not, and riveting. Mark the element “#1, 17 Meter Reflector”, and set aside.
Repeat the complete procedure for Element #6, the 17 meter Director.
Assembly of 17 meter driven element, #3:
Open the bag of tubing parts and separate.
There are two 5/8” X 2’ pieces of tubing, with a single hole at one end and no hole at the
other end. Set these aside.
Assemble each half element in the same way that you assembled the earlier elements.
Now, take one of the 5/8” X 2’ tubes. Smear a little Jet Lube SS-30 around the end
inside of the single hole set. Slide the tube into the end of one of the driven end halves, so
that the holes line up. Center the hole with a pop-rivet tail. Take the white fiberglass
insulator and slide it inside the assembly. While doing so, keep the pop-rivet tail through
the hole so that the 5/8” tube does not get pushed in further. When the fiberglass insulator
rod reaches the hole, partially withdraw the tail enough to let the insulator continue on in,
but without permitting the inner aluminum tube to slide in. Align the holes, and put a
#8 X 1 3/8” screw through the assembly. Put a lockwasher and nut on the screw and
tighten, then put another nut on and also tighten..
Bring up the other half of the driven element to the other side, and assemble it in the
same manner. Make sure that the pop rivets are in line on both sides of the driven
element.
Be sure there is no trace of Jet Lube SS-30 on the center of the white insulator. If any
found its way there, be extra sure it is all removed.
This completes element assembly.
Antenna Assembly
Final assembly of the antenna is best done close to the base of the tower that the antenna
will be mounted, as assembled antennas are difficult to move any distance.
Put the boom across two saw horses, with the flat sides of the boom platforms up. On
each element saddle, attach two element clamps, using the ¼” X 1” bolts, with lock
washers and nuts. Note that the holes in the element clamps are NOT centered – align the
element clamps so that they are flush with the element saddles. For the moment, only put
the nuts on a few turns. See picture for detail – note that the boom is tilted in the picture
for clarity.
Slide each element into the element clamp assembly, being sure to get the correct element
at each station. Be sure the element is centered on the boom. Turn the pop rivets so that
they are facing up. Then tighten the nuts holding each element. The 17 meter driven
element should be done last.
To mount the 17 meter driven element it will be necessary to temporarily remove the
element clamps. Set the element on the saddle, with the screw length up, then re-attach
the element clamps, using only a few threads on the nut.
You will likely need to slide the insulator tubing pieces a little to get them to align
underneath the element clamps. Be sure to get this right – the balun will be feeding RF to
the two screws making the element “hot, so you want to be sure the element is clear of
the element clamps and properly insulated.
Picture of partially assembled driven elements. Note that the 12 meter element may or
may not have a gap in the middle of the insulation – this is unimportant.
Make sure all the rivets are on top, then tighten all element-clamping screws. It is a good
idea to have someone else check to be sure that all screws are tight.
Measure the length of each of the elements:
Table – Skylark Element Lengths
17 Meter Reflector Station 19 332 inches
12 Meter Reflector Station 46 242.5 inches
17 Meter Driven Station 90 322 inches
Special note – driven element - this dimension does not include the space for the center
insulator for this element – be sure to add the open space for the overall dimension.
12 Meter Driver Station 94.5 240.5 inches
12 Meter First Director Station 159.75 223.5 inches
17 Meter Director Station 177 308 inches
12 Meter Second Director Station 183 232.5 inches
Important Note – Unlike traditional monoband yagis, the second director for 12 meters is
supposed to be longer than the first director!
Slide a PVC spacer over the ends of the driven element cell, set it close to the end of the
12 meter element, and tighten the locking screws. The locking screws are made of nylon,
which does not do well in UV. To protect the screws, after they are tightened cover them
well with electrical tape.
Final Assembly
Final assembly of the antenna is best done close to the base of the tower that the antenna
will be mounted, as assembled antennas are difficult to move any distance.
Put the boom across two saw horses, with the flat sides of the boom platforms up. This
makes assembly easier. However, note that the antenna will be mounted with the
elements hanging DOWN not up, so you will be turning the antenna over.
Place the boom to mast saddle over the boom, and align with the two holes at station
101” and 104.5”. Be sure that the flat side is on the side you want for when it goes onto
your tower. Remember, Station 0” is the reflector end. Put two 2 ¾” screws through the
boom and saddle, and add lock washers and a nut, tighten, then add another nut and
tighten.
Mount the 5” X 6” aluminum plate to the flat side of the boom to mast saddle, using the
#10-32 X 3/8” round head screws and lock washers. Make sure the screws are tight.
Insure that the four ¼” threaded holes all have clearance through the flat plate and the
boom saddle. If they do not, align the plate so that they do.
Screw the two ¼” X 1 ¼” hex head bolts into the bottom two holes of the flat side of the
boom-to-mast plate. Screw the bolts in only far enough that the ends are flush with the
boom saddle on the other side. The bolts will be still sticking out of the flat plate about
1”. When you are installing the antenna on the mast, these bolts will be entering the key
hole on the mast plate.
Put the impedance matching coil across the feed point screws, with the coil on the side
closer to the mast. Then add lock washers and nuts.
Attach the balun, as shown below.
Balun Mounting Detail –Note that the antenna is upside down for this picture.
The antenna is now ready to put up.
There are at least several different ways to get a yagi onto the mast at the top of the
tower. For what it is worth, here is how we did ours:
Install the Skylark mast plate on the mast at the desired level. Line up the plate so that it
points at the desired direction, then tighten the u-bolts.
Install, temporarily or permanently, a pulley at the top of the mast, with a rope through it
that has at a minimum several hundred pounds of strength.
Stand the antenna up on the boom so that it is leaning against the tower.
Tie one end of the rope around the mast.
Tie a short rope from the top end of the vertical boom loosely around the antenna raising
rope. This will serve to keep the antenna from rotating out of control while it is being
pulled up.
While the antenna is being raised, the person at the top of the tower is responsible to keep
the antenna pushed out enough from the tower that it does not bump into the tower.
When the top end of the boom is high enough to reach the person at the top of the tower,
he or she should remove the rope at the top end of the boom. Now, that person will
maneuver the antenna around and into position, engage the two bolts on the antenna
boom to mast plate into the keyholes on the mast plate and let the antenna drop into
place.
Tighten the two bolts, then screw in two more bolts in the lower holes. Put lock washers
and nuts over all 4 bolts and tighten securely.
Attach the coax and enjoy!
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