Build the Antenna 2

8/18/2019 Build the Antenna 2

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build the antenna 2Saturday, November 09, 20134:07 AM

Step 1: Cut the EMT conduit in half

Using a hacksaw, cut the 10-ft EMT conduit into two 5-ft sections.You'll only need one of the halves, so set the other half aside foranother project.

It helps to use a vise to hold the conduit while cutting (see Figure1). If you don't have a vise, you can use clamps or your foot.fter you've cut the conduit, !riefly sand or file the cut ends to

remove any of shards of metal.gain, one of the "#ft sections of conduit will serve as the antenna's!oom. igu!e 1: Cut the 10-ft EMT

conduit into two 5-ft sections.

Step ": #!aw guide lines along the length of the $oo%

The ne&t step is to d!aw two lines along the length of the $oo%,one line on the top, and one line on the $otto%. $hese lines willserve as guides to help ensure that the elements are aligned (seeFigure %).

$o draw the top line, place your straight edge along the length ofthe !oom, clamp the !oom to the straight edge (or step on the!oom to prevent movement), and then follow the straight edge withyour mar&er, drawing a line on the !oom.$o determine the location of the !ottom line, use your ruler tomeasure 1 mm down from the top line (the diameter of 1% *+$conduit is 1 mm). +ar& this location. $hen, flip the !oom over anduse the straight edge and mar&er to draw the !ottom line##startingat your mar#in the same fashion used for the top line.

igu!e ": Draw top and bottom guidelines along the length of theboom.

Step ': Ma!k the positions of the ele%ents

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The ne&t step is to %a!k the position of each ele%ent on the$oo%.sing your ruler and mar&er, measure along one of the guide linesand mar& the positions of the elements according to the Yagi-alculator datasheet. epeat this process for the other guide line.$hus, you should have mar&s for the elements on !oth sides of the

!oom (i.e., along !oth guide lines)./ote0 $he idea is to have mar&s...

Figure shows a screenshot of the datasheet for 23 4$* with theelement positions highlighted in yellow.

• $he reflector is to !e located 5 mm from the !eginning of

the !oom.

• $he radiator (driven element) is to !e spaced 67 mm from

the reflector, which is 157 mm from the !eginning of the!oom.

• For the directors, the 8paced column indicates the spacing

from the previous element. $he 9oom position columnindicates the position relative to the !eginning of the !oom.

Figure 2 shows an illustration of the relative position (8paced) anda!solute positions (9oom position) of the first four elements./ote0 nless you happen to have a metric ruler...

Figure " shows the !oom with the mar&ed positions. $he F: standsfor folded dipole; this is the driven element (radiator).

igu!e ': Screenshot of ! "TE#agi datasheet with positionshighlighted.

igu!e (: Diagram of the relati$eand absolute positions of the first four elements based on the ! "TE #agi datasheet.

igu!e 5: Mar% the position ofeach element along the guidelines on both sides of the boom.

Step (: #!ill the holes fo! the !eflecto! and di!ecto!s

The ne&t step is to d!ill holes th!ough the $oo% fo! the !eflecto!and di!ecto!s. (/o hole is needed for the driven element !ecause itwon't !e mounted through the !oom).

$o &eep the drill#!it from drifting during drilling, use a center punchto ma&e an indentation at each mar&ed position (e


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/e6.7 mm long (round to 1> mm).

• For the directors, the 4ength column indicates the length

of each director (again, you can round these to the nearest

millimeter).$he datasheet states that the elements lengths must !e within onemillimeter of the stated lengths.

igu!e +: Screenshot of ! "TE#agi datasheet with lengthshighlighted.

http://bcbj.org/antennae/imgs/lte_ya40.jpghttp://bcbj.org/antennae/imgs/lte_ya40.jpghttp://bcbj.org/antennae/lte_yagi_diy.htm#softwarehttp://bcbj.org/antennae/imgs/yagi_design_2.pnghttp://bcbj.org/antennae/imgs/yagi_design_2.pnghttp://bcbj.org/antennae/imgs/yagi_design_2.pnghttp://bcbj.org/antennae/imgs/lte_ya40.jpghttp://bcbj.org/antennae/imgs/lte_ya40.jpghttp://bcbj.org/antennae/imgs/lte_ya40.jpghttp://bcbj.org/antennae/lte_yagi_diy.htm#softwarehttp://bcbj.org/antennae/imgs/yagi_design_2.png


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se a pair of metal#cutting di&es or a hac&saw to cut your elements.You can remove !ends !y gently pounding them out with a hammer.9e sure to cut each element a !it long, and then file the elementdown to the correct length. $his filing also helps remove jaggededges from the cut ends.Figure > shows one of the elements, stripped, straightened, andthen cutfiled to length. $he element shown is :irector 1, which

has a length of 16 mm. Figure 15 shows the reflector and all 1%directors cut to length.fte! all of the ele%ents a!e cut to the p!ope! lengths, %a!k the%idpoint of each ele%ent. lso mar& half the !oom diameter (>mm for 1% *+$) away from !oth sides of the midpoint; see Figure11. $hese mar&s will later serve as guides when mounting theelements to the !oom. $he particular element shown in Figure 11 isthe reflector, which has a length of 1> mm, a mar& at the midpointof >> mm, and flan&ing mar&s at >5 mm and 15 mm./ote0 It's wise to la!el the elements...

igu!e : Cut each element a bitlong' and then file it down to thecorrect length.

igu!e 10: (ll 1) elements cut tolength and organi*ed.

igu!e 11: Mar% the midpoint andtwo +-mm-awa&-from-midpoint points.

Step ): Measu!e and cut the d!ien ele%ent

/ow its ti%e to tackle the folded dipole that will $e used as thed!ien ele%ent.$he driven element is argua!ly the most crucial piece of the entireantenna. It's the only element that's directly connected to the coa<feed; all other elements serve to focus the signal onto the drivenelement. $he driven element's length will affect the antenna'sfre?uency tuning, and its shape and placement will affect theantenna's impedance.$he Yagi -alculator datasheet lists the specs of the folded dipole, ascreenshot of which is shown in Figure 1% (for 23 4$*) with the mostimportant parts highlighted. s stated in the datasheet, thedistances should !e measured from the insides of the !ends (inneredge on one side to inner edge on the other side).For the 3 version of the antenna, the lengths will !e shorter!ecause the design fre?uency is higher##refer to the actualdatasheet @:F.$o create the folded dipole, cut a length of your metal slightly

igu!e 1": Screenshot of ! "TE#agi datasheet with mostimportant folded dipoledimensions highlighted.

igu!e 1': ,llustration of folded

http://bcbj.org/antennae/imgs/lte_ya48.jpghttp://bcbj.org/antennae/imgs/lte_ya48.jpghttp://bcbj.org/antennae/imgs/lte_ya133.jpghttp://bcbj.org/antennae/imgs/lte_ya112.jpghttp://bcbj.org/antennae/imgs/lte_ya112.jpghttp://bcbj.org/antennae/imgs/lte_ya112.jpghttp://bcbj.org/antennae/imgs/de.pnghttp://bcbj.org/antennae/lte_yagi_diy.htm#softwarehttp://bcbj.org/antennae/imgs/fd.pnghttp://bcbj.org/antennae/imgs/de.pnghttp://bcbj.org/antennae/imgs/lte_ya112.jpghttp://bcbj.org/antennae/imgs/lte_ya133.jpghttp://bcbj.org/antennae/imgs/lte_ya48.jpghttp://bcbj.org/antennae/imgs/lte_ya48.jpghttp://bcbj.org/antennae/imgs/lte_ya133.jpghttp://bcbj.org/antennae/imgs/lte_ya112.jpghttp://bcbj.org/antennae/imgs/lte_ya112.jpghttp://bcbj.org/antennae/imgs/lte_ya112.jpghttp://bcbj.org/antennae/imgs/de.pnghttp://bcbj.org/antennae/lte_yagi_diy.htm#software


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longer than the datasheet's $otal rod length (25 mm). $hen, mar&the distances AI and 3F (65 mm). /e


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9ecause we'll !e soldering the directors to the !oom, we need toprep the surfaces to ensure that they accept the solder. $o do this,sand around each hole on the !oom (see Figure 1")./ow, for each director0

1. @lace the element through its hole in the !oom.%. *nsure that the element is centered !y using the >#mm#

away#from#midpoint mar&s drawn previously in 8tep " (seeFigure 17). You can also measure the amount !y which theelement protrudes from each side of the !oom. It's centeredwhen these protrusion amounts are e?ual.

. pply a generous amount of flu< around the joints.

4. Solder the element to the boom. To do thi, !rttou"h the iron to the #oint, $ait everal e"ond %orthe #oint to heat&u', and then %eed the older ontothe #oint.

Barning0 $he elements will get hot...

Figure 16 shows a close#up of one of the solder joints. +y solderingjo! in Figure 16 is poor. $here is way more solder than is needed.Aowever, I had a wea& %" B soldering iron that would not stay hotfor more than a few seconds after contact with the !oomelements.I had to let the iron reheat for 1"#5 seconds after each application,and thus the messy soldering jo!. It helps to have a more powerfuliron or a propane torch.fter you've soldered all of the directors, sight down the !oom tochec& that the directors are aligned (see Figure 1). 9end thedirectors as needed to correct for inevita!le misalignments.

igu!e 1*: Closeup of solder /oints the&re not perfect' butthe&re uite solid2.

igu!e 1+: Sight down the boomto ensure alignment of the

elements3 bend the elements asneeded to correct.

Step +: Mount the folded dipole to the $oo%

The ne&t step is to %ount the folded dipole to the $oo%.$he folded dipole needs to !e insulated from the !oom. $his meansno metal#to#metal contact and a vertical separation of at least halfa !oom diameter away from the !oom (as a rule of thum!). $hus, tomount the folded dipole, we need some form of insulated standoff.Figure 1> illustrates how the folded dipole will !e positioned aroundthe !oom. 9ecause our folded#dipole's !end diameter is 6 mm, and!ecause the !oom diameter is 1 mm, the re?uired standoff heightis >." mm. slight deviation from this height is CD (e.g., 15#11 mminstead of >." mm); it will simply result in the folded dipole not!eing perfectly centered. I have done this in the past with nomeasura!le effect on performance.$o use the @E- $#fitting as the standoff, do the following0

1. 8lide the $#fitting onto the !oom, measure >." mm up fromthe top of the !oom, and then mar& and drill a hole from eachside (see Figure %5).

igu!e 1: ,llustration of the general idea behind using a plasticstandoff.

http://bcbj.org/antennae/imgs/lte_ya71.jpghttp://bcbj.org/antennae/imgs/lte_ya65.jpghttp://bcbj.org/antennae/imgs/lte_ya142.jpghttp://bcbj.org/antennae/imgs/lte_ya142.jpghttp://bcbj.org/antennae/imgs/lte_ya89.jpghttp://bcbj.org/antennae/imgs/standoff.pnghttp://bcbj.org/antennae/imgs/lte_ya79.jpghttp://bcbj.org/antennae/imgs/lte_ya79.jpghttp://bcbj.org/antennae/imgs/standoff.pnghttp://bcbj.org/antennae/imgs/lte_ya89.jpghttp://bcbj.org/antennae/imgs/lte_ya142.jpghttp://bcbj.org/antennae/imgs/lte_ya71.jpghttp://bcbj.org/antennae/imgs/lte_ya65.jpghttp://bcbj.org/antennae/imgs/lte_ya142.jpghttp://bcbj.org/antennae/imgs/lte_ya142.jpghttp://bcbj.org/antennae/imgs/lte_ya89.jpghttp://bcbj.org/antennae/imgs/standoff.pnghttp://bcbj.org/antennae/imgs/lte_ya79.jpg


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%. $rim the ends of the $ so that the fitting can slide intoplace without hitting the first driven element. (You really onlyneed to trim one end of the $##the end that will face towardthe first director.)

. 8lide the folded dipole through the drilled hole as shown inFigure %1 (you may need to temporarily unfold the dipole to

get it around the curves).

2. :rill two holes for mounting screws, and then mount thefitting folded dipole onto the !oom using these two screws(see Figure %%). *nsure that the folded dipole lines up withyour previous position mar& for the driven element (you mayneed to rotate the $#fitting to see this mar&).

(. )end the folded dipole as needed to !e as straight aspossi!le, and then apply epo


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Step 10: C!eate and attach the $alun and coa& connection

The final step is to c!eate and attach the $alun and coa& pigtailto the antenna.$he Yagi -alculator software creates a picture of the !alun andpigtail, which is shown in Figure %2 for 3"> coa< with polyethylene

insulation. Aere, I will demonstrate using 3"> !ecause I had aremnant piece with a pre#attached F#type connector.

/ote0 You can choose the coa< type...

$o construct the !alun and coa< pigtail, first cut and strip thepieces as shown in Figure %". $he top piece will !e used to createthe !alun, and the lower piece will !e used for the pigtail./ote0 $he length of the !alun's loop...

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Build the Antenna 2