CQ REVIEWS:

The Cushcraft ASL 2010Log-Periodic Antenna

BY PAUL CARR ' , N4PC

The completed antenna ready 10 take on Ihe world. Is anyone listening?

W ell, spring vacation finally came. and Itwas a welcome renet trom my classroom du­ties, I had been looking forward to this breakbecause it would give me a chance to assem­b le and build a new antenna. Waiting in mygarage was the new Cusncrat t ASL 20 10 log­per iodic system. Since then I have had lime toevaluate the system.Here are the resultsofthatevaluation.

What Is ALog-Periodic Antenna?

A log-periodic antenna is a treqoercv-moe­pendent antenna system. These antennas arecapable of bandwidths that were impossible afew years ago. This particular system has a 2:1bandwidth of better than two octaves. This isaccomplished by the choice of element length,spacing. and phasing . (All of the elements arefed simultaneously.) The element lengths varyfrom slightly greater than a half-wave length atthe lowest frequency to just less than a half­wave length at the highest frequency. The re­sulting gain is about constant, and the nomi­nal impedance IS about 200 ohms. By using a4:1 bahJn an impedance of approximately 50ohms results. Now for a few specifics aboutcusncratrs design.

The ASL 2010

Mechanically , the specifications for thebeam area boom lengtho118 feet, witha boomdiameter of 2 inches. The longest element is38 feet. and the turning radius is 19.25 feet.The beam accepts a mast diameter of 1.5-2inches, and the total weight is 55 pounds. Thewind load ing 10. 1square feet All the hardware

is of the highest quality stainless steel, whiChwe have come to expect from Cushcraft.

Assembly

As you can see from the pic ture, the antenna

The ASl2010 is a new product from Cushcratt,and it covers 20, 17, 15, 12, and 10 meters.The antenna consists of eight elements in alog-periodic dipole array. The antenna is fedthrough a single 50 ohm coaxial cable to a 4: 1balun matching unit (mounted on the boom).The beam IS rated at 2000 wans.

The electrical 2:1 bandwidth of the antennaas specified by Cushcrafl is from 13.5 MHz to32 MHz. As I indicated earlier, this is a prop­erty of the log-periodic design. I used an MFJ259 to make SWR measurements across thespectrum and on each of the amateur bands.Never did the SWA exceed 2: 1 across thespectrum. The most variat ion in SWRoccurredon 20 meters. The maximum SWR of 1.7:1wasat 14.0 MHz, and the minimum of 1.3:1 was at14.25MHz. TheSWRresultson 10meters wereamazingly flat. never exceeding 1.4:1 acrossthe entire band (see fig. 1).

The published gain figure lor the antenna is6.4 dBd It is extremely difficult to verily gainligures withOut acalibrated antenna range, butcomparing the results I received with other an­tennas, I feel the gain figure is about right. Therated front- to-back ratio is stated to be 15- 20dB. I fou nd no place throughout the spectrumwhere I ten this information was inaccurate.

"91 West Point Road, Jacksonville, AL 36265

26 • CO • August 1995

As you can see, there afe enough paris here to keep you busy for ar reasr a day. Please notethatlhe flower pots ere not included.

Say You Saw It In CO

Th ings will go easier and faster if you can coerce some ttienas into helping you out. Here Ralph,KE4UAK, puts the finishing touches on some connections. while Harold. W4ZS, supervises

the handiwork

has a very high parts count. Your success de­pends on you r ability to do an accurate inven­tory of the parts and organize the parts fo r easyaccessibility during the construction phase. Ifyou are working alone dur ing the initial co n­struction phase, allow about one davto assem­ble the elements and the boom.

There are seven steps listed in the instruc­tion manual. Assemble the boom first. This willg ive you practice working with hand tools andwill ie! you become used to the way the instruc­tio ns are written. The boom is in three sec tions ,with the end sections made so they will slip intothe center section fo r a predetermined leng thand then slop. All that is necessary is to p lacetwo locking screws and l ighten the compres­sion hose clamps. Place the plastic end cov­ers, and you are finished .

The element construction is next. Begin withthe longest element. Carefu lly measure theoverlap specified on the d iagram. The total e le­ment length is dependent on the proper mea­surement and assembly of the elements . Con­tin ue the element construct ion as specified inthe instruction sheet. Verify the element lengthsat least twice.

Now you have a decision to make. If youintend to fully assemble the antenna be fore youplace it on the mast, follow the instructions inthe booklet. I have a crank-down/t ilt-over tow­er , and I chose to depart from the instruc tions.Following is how to accomplish the installation.

Carefully measure and mark the location ofeach element and the boom-to-mast bracket.Next mount the boom-to-mast bracket. Thenmove all the assembly components tome mast

location. Turn the antenna rotor so that it w illdi splay the proper d irection when the tower isti lted to allow installation. Moun t the boom tothe mast, verify a ll the steps, and tighten themo unting hardware .

Moun t the longest e lement, and check forproper alignment. Follow by p lacing the nexttwo longest e lements. After yo u are satisfiedthat the elements are in the proper position.place the phasing straps in accordance with

2.0

Fig.

a:~ 15<f>

1- These are the SWR curves for each band as I derived themfrom my OTH.

1.514.514.414.2 14.3Frequency

1.0':-::----;-:'-:----;-!-;:---,-!-::---:+::--.,.f;~14.0 14.1

(A) 20 METERS

20 24.94 24.99 25.04Frequency

25.09 25.14

(0) 12 METERS

a:~ 1.5

1.0 2.018.069 18.118 18.168 19.068 19.11 8 20.068Frequency

(B) 17 METERS0:~ 1.5

1.5 en0:~en 1.0

1.0 28.0 28.5 29.0 29.5 30.0 30.521.0 21.1 21.2 21.3 21 .4 21.5 Frequency

Frequency (E) 10 METERS(C) 15 METERS

28 • CO • August 1995 Say You Saw It In CQ

AUQust 1995 • CO • 29

3" (7.6 em)

I - 38' .. '(11,58 m) I

~ IT~

ff I , k ! . • • .

I Be "46-318"

117.8 cm)

33'-3.5" ,If2\

(10.15 m).

38"(96,5 em)

28'-3,25" ,I(8.62 m)

3 • .

16-1 ;2" -(41.9 em)

M:~33"(83.8 em)

24'-3.5" "I4'

(7.4 m)

28-112"(72.4 eml

I 20'·11.5" -Il'f\ =@

(6.39 ml

24·518"(62.5 em)

' I: I 18'-3.5"(5.57 m]

~~I.

21-1/4"(54 em) -I~

16'·2,75"(4.95 m)

7[ 3" (78,ml

18-1/4"(46.4 em)

1

1 13'-10.5",(4.23 m\_I 8 ""it.

f

Fig.2 The overall configuration and element description for the Cushcraft ASL 2010 log-periodic antenna.

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13,5-32 MHz86.4 dBd15-20 dB18 ,5MHz2000 watts65 deg E plane18 ft , (5.48 m)2.0 in. (5.08 cm)as n. (11.58 m)1.25 in,(3.18cm}19.25 ft, (5.86 m )1.5-2 in. (3.18-5.08

10.1 tt.2 (,93 m2)55 lb . (25.5 kg)

FrequencyNo, of elementsForward gainFront-to-bec k ratio2:1 BandwidthPower rating3 dB Beam widthBoom lengthBoom diameterLongest elementElement center ceTurning rad iusMast size rangeem)Wind loadWeight

the antenna under such ccooncos. and I amhappy10 report that the antenna handled thesewinds with no problems, II I were describing asailboat, I would report that she rides well inthe water ,

If I may insert an aesthetic observation, I ama mathematician by protession, and I find thegeometry to be espec ially pleasing . My XYLshares my opinion. She remarked that shettlOught it was the prettiest antenna I had everhad . and she has seen plenty of antennasthrough the years!

The ASL2010 is maoutactueeo by CusncrattCorp , 48 Perimeter Road. Manchester, NH03108 (phone 603-627-7877; FAX 603-627­1764). The retail price of the ASL 2010 is S8OO,

TabJe I-ASL 20 10 anfenna specIfications,

Specifications For The ASL 2010the instruction booklet. You now should havethree elements in place. and phasing linesbetween two of the elements. Raise the mastto the vertical posi tion and visually check lorproper eerreor-to-toon alignment.

Rotale the assembly 180 degrees. and low­er the antenna so that the assembly can becompleted Continue by plac ing the elementsand phasing lines in a longest to shortest pat­tern untillhe antenna is completely assembled.Recheck allhardwareand elements, Mount thematching network and connect the networkoutpu t to the antenna. Connect the coax to thematc hing network (be sure to leave a drip loop )and route the coax to the shack. Raise the an­tenna to its vertical position and check for prop­er element alignment. Make any corrections asnecessary , You are now ready for preliminarytests.

Test Results

I have made many tests on auue bands. andalthough band conditions have been less thandesirable. I am we ll pleased with all results Ireceived. I feel the antenna performs great.and a plus is the fact that you have instantband-change capabilities. This is a definitebe nefit if you are interested in multi-band con­tests such as the CO World-Wide. For an all­around ante nna with good pe rformance andmaximum flexibil ity, I fee l that this antennawould be hard to beat

Iwould like to add a word about the mechan­ical stability of the beam. In my part of mecoun­try we do not expe rience great straight-linewinds that are seen other places: however, wedo experience tremendous rotat ing winds as­sociated with thunderstorms. I have observed

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