Original article from: Wayne Sarosi 
 Reposted by Rob Dennis,Moderator HAM_TECH,for use of the FIDO HAM_TECH echo.
  THIS POST/SERIES NOT TO BE USED IN ANY CDROM COMPILATIONS FOR COMMERCIAL
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06 June 1991
FROM: Wayne M. Sarosi
      AFA2GN,PAFB MARS Team,Patrick Air Force Base,FL
To:  All MARS operators.
SUBJECT: Log Periodic Dipole Array (LPDA) Design
DISCUSSION:
 This antenna was designed to operate from 13.8 MHz to 28.8 MHz. The antenna
was to cover the majority of the USAF MARS frequencies yet give the operator
a smaller log periodic than the commercial types,that had reasonable gain,and
was cost effective to build.
 All design formulas are taken from the ARRL Antenna Manual.
 The antenna did not turn out as planned.
 The frequency range actually went from 13.5 MHz to 29.5 MHz with SWR less
than 1.8:1. Most SWR readings were less than 1.5:1 across the band.
 The weight was a surprize also.
 I expected 100 pounds plus,but actually was under 63 pounds.
SPECIFICATIONS:
 Boom: 22-ft, 3-in diameter, aluminum.
 Number of Elements: 10
 Feed: Balanced
 BALUN: 4:1
 Weight: 62-lb
 Windload: near 9 sq.ft.
 Cost: About $200.00
 Note:
 $150 for element insulators from HY-Gain. $50 for misc. Tubing,boom,etc from
old antennas discarded by fellow hams,CBers,and field day.
 Time: 80-hrs, including install.
 Design Bandwidth: 13.8 MHz to 28.8 MHz
 Actual Bandwidth: 13.5 MHz to 29.5 MHz*, Highest my TS-430S would go.
 SWR MAX: 2.1:1
 SWR AVE: 1.4:1
 SWR LOW: 1.1:1, all taken on an MFJ-986 Differential-T Tuner/SWR/PWR meter.
 EST GAIN: 6dB
 PWR Handling: Max Legal.
 Turning radius: same as 20m, 3 element Yagi
 Height off the ground: 35-ft minimum for best results (half wave at 14 MHz).
ELEMENTS: (Half element lengths given and quantity)
Note: Elements start at rear,longest first.
 L10: (492/13.8)/2 = 17.826-ft, quantity (2)
 L09: L10 * 0.9 =    16.043-ft, quantity (2)
 L08: L09 * 0.9 =    14.439-ft, quantity (2)
 L07: L08 * 0.9 =    12.995-ft, quantity (2)
 L06: L07 * 0.9 =    11.696-ft, quantity (2)
 L05: L06 * 0.9 =    10.526-ft, quantity (2)
 L04: L05 * 0.9 =     9.473-ft, qauntity (2)
 L03: L04 * 0.9 =     8.526-ft, quantity (2)
 L02: L03 * 0.9 =     7.673-ft, quantity (2)
 L01: L02 * 0.9 =     6.906-ft, quantity (2)
ELEMENT SPACING: d(L10-L09) = 2*(.5(L10 - L09) cot(0.5 * apex angle))
                 The cot(0.5 * apex angle) = 2.
                 Thus: d(L10-L09) = (L10 - L09)*2
                 AND: d(L09-L08) = d(L10-L09) * 0.9
d(L10-L09) = 3.566-ft
d(L09-L08) = 3.209-ft
d(L08-L07) = 2.888-ft
d(L07-L06) = 2.599-ft
d(L06-L05) = 2.339-ft
d(L05-L04) = 2.105-ft
d(L04-L03) = 1.895-ft
d(L03-L02) = 1.706-ft
d(L02-L01) = 1.535-ft
0.5 * Apex angle: 26.565
cot(0.5 * apex angle): 2
 Further detail is given in the ARRL Antenna Book under Log Periodic Dipole
Array.
 Mounting: 1/4-in aluminum plate 10-in X 10-in
          (4) U-bolts to fit 3-in boom & mast
          1/2-in stainless steel bolt,spacers,lockwashers and nuts.
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 Bolt through center allows for pivoting of mast for element placement or
repair.
 Bolt configuration: Nut-L.Washer-Washer-Boom-Washer-Nut-Washer-Plate-Nut
 Any questions, please feel free to contact me at the following address:
                    Wayne Sarosi
                    995 Alabama Street
                    Titusville, FL 32796
-WS
--- GoldED 2.42.G1219
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