I bring the description of logoperiodic aerial, calculated,

constructed and established by me in 1999 year.

The modern requirements to the radioamateur aerial of own manufacturing can be reflected in several items:

·      to provide work on several HF bands, including WARC.

·      To have amplification (in relation to dipole) not less than 5-8 db and suppression back not less than 25 - 30 db.

·      The constructive performance of aerial should be simple, not requiring large capital inputs. (If the radioamateur has means he can buy industrial made aerial).

·      The aerial must have minimal SWR on all working bands. This requirement is especially urgent for work on transceivers, not having automatic antenna tuner.

·      The electric system must be closed, as least subject to electrostatic atmospheric noise.

·      The aerial works without additional adjustment after raise because, in practice this adjustement is diffcult or impossible.

The logoperiodic antenna is more suitable to these requirements. The aerial is executed on usual tubular boom.

The elements are executed from easy aluminium tubes. In my design from four-section aerials. Sections are inserted one into another and are latched by spring locks. The similar aerials represent uncommon and the radioamateurs can approach to manufacturing elements, proceeding from available materials. The diameter of pipes hasn't the large meaning (that also is advantage of aerials Logoperiodic) and can be made from antenna wire . The similar designs with antenna wire are described in the literature.

The isolation of elements is following: a kapron profile of square section,is applicable in which set in aluminium tubes by a diameter of 17 mm. In them are inserted and fixed tubes of elements. In middle of capron structure are drilled two apertures with diameter of 8 mm for fastening to boom by a collar. The collar is used from television aerials and has thorns interfering turning of an element. The fastening of elements can be carried out by a traditional way on isolators platforms.

The aerial receives supply by standard symmetric (collective) line executed by a copper wire with section not less of 1.5 mm in high-quality isolation and has one agreeing line:

·      Behind (in relation to a direction of radiation) closure, determining easing back. This line in addition transforms the aerial in closure system, that corresponds to item 5 of the general requirements.

·      The antenna is connected to cable through HF transformer, having factor of transformation 1:1. Balun is reeled - up on a ferrite ring HH 600 two braided wires in high quality of isolation. Quantity of coils - 6.

·  The accepted designations:

·  L1- length of an element.

·  S1- Distance between elements.

·  LS- Agreeing made circuit line.

·  B - In Length of boom.

·  K - To Settlement factor.

·  t - Factor of a progression.

·  l - Length of a wave.

·  N - Quantity of elements.

The aerial was assembled and lifted on height of 12 meters about a wooden country house through an easy telescopic mast. The cheap rotating mechanism of the Chinese manufacture intended for rotation of television aerials.

The received technical parameters can be estimated as exceeding given in the beginning (except for 14 mHz, since height of rise for this range is small). The measurements of parameters were carried out on all ranges, switching WARC with the radioamateur who is taking place on distance 15 kms of direct visibility. The received characteristics on the average Front / Beck - 54/56; Front / Side - 52; Front / Direct - 59 + 20 db

Factor of the reflected wave in all a range from 14 up to 29 mHz has appeared constant 1.3 in any measured point of the specified range. On frequencies 13.2 and 30 mHz it aspired to infinity. The gauging was carried out indicator SWR of transceiver Icom - 746.

It is necessary to note large criticality of the aerial to located beside to metal subjects and height of rise. The aerial at first was tested at height of 7.5 meters and the result of tests on frequency 18 mHz has shown, that at such height the forward petal is dim also ratio F/B no more than 5-8 db.

Some short wave men negatively concern to aerials of a type Log Yagi, considering them " by the collectors of noise ". I agree with them under one condition is has a place, if the receiver with preselector, having a wide range and weak dynamic range is applied. Usual Yagi itself works as preselector with good quality and reduces the requirements to the characteristics of the receiver. Therefore I advise radioamateurs at use Log Yagi to apply additional preselector or receiver with the high characteristics, it completely will remove problems caused by the application Log Yagi.

For short wave men who desire to calculate the aerial are give formulas of account according which are resulted the described design . Quantity of elements and bottom frequency get out arbitrary. It is not recommended, at a range of the aerial 14 -28 mHz, the quantity of elements less than 5/6 - efficiency of the aerial sharply falls.

L1 = l/2; at the rate of the bottom working frequency (14.0 mHz).

Ln = 405 sm for the top frequency 29 mHz, proceeding from the review of industrial and radioamateur designs (that contradicts the theory, but the practical gaugings prove a choice on measured SWR).

L2 = L1* t; L3 = L21* t; etc.

S2 = S1 * t; S3 = S2 * t; etc.

t = n-1Ö ^-Lmin / Lmax ;

K= 1 + t + t² + t³ .. + t^n-2

S1 = B / K ;

LS = 0.95 * S1 ;

In connection with reception many of E-mail of the letters with questions concerning a design, parameters and account of the aerial, I created the program of automatic account logoperiodic antenna. The program is created under Excel and automatically compute all parameters of the aerial and its amplification.

Can will change:

·  Top and bottom frequency;

·  Length of boom;

·  Quantity of elements from 5 up to 18.

The demo program can be taken from http://www.qsl.net/ru3uj/logyagi.zip

For reception of the working version write to me ru3uj@mail.ru

73 Roman RU3UJ

PS: Excuse for my bad English language.

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