HRS type antennas

Encyclopedia : H : HR : HRS : HRS type antennas

Contents

0.1 What are HRS type antennas
0.2 How to interpret HRS notation
0.3 Notes on HRS notation
0.4 Azimuth beamwidth
0.5 Vertical launch angle into the Ionsphere
0.6 How many variations of HRS antennas are there
0.7 Transmission system optimisation dependend on geopolitics
0.8 Cost issues of HRS antennas
0.9 Innovations in HRS antenna design

What are HRS type antennas

The curtain antenna is a dipole array, consisting of rows and columns of dipoles.

The curtain antenna is a high gain directional antenna, that is designed for medium and long range shortwave communications.
The HR(S) notation is as follows
* HR Rows/Columns/Wavelength(s) -- Above Ground

HR 2/2/1 the most basic HR antenna type, commonly used in tropical band broadcasting.

How to interpret HRS notation

An HR 4/4/1 antenna has the following characteristics

4 rows
4 columns
is 1 wavelength Above Ground (with respect to mid-band transmission frequency)

Syntax note: HRS

The S means is that the antenna's pattern is electrically steerable.
Electrical steering is typically done in the vertical orientation.
Electrical steering of the antenna beam typically is limited to (-/+) 15°.

Notes on HRS notation

HRS transmission systems can be "double sided", but in this case HRRS notation is used. The extra R meaning "Reversible". Very few HRRS antenna systems are in use worldwide.

HRS antennas of type HRS 1/1/1 are undefined.
HRS antennas of type HRS 1/2/1 and 2/1/1 exist, but see little practical use in broadcasting.
The number of rows can be 2, 3, 4, 6, 8 or 12.
The number of columns is usually 2, 3, 4, 6 or 8.
The dipoles are ALWAYS horizontally polarized.
A reflector screen is placed behind the dipole array so as to provide a directive beam.

Mathmatical model of an HR 4/4/1 antenna

Azimuth beamwidth

For a 2-wide dipole array, the beamwidth is around 50°
For a 3-wide dipole array, the beamwidth is around 40°
For a 4-wide dipole array, the beamwidth is around 30°

The main beam can be slewed by 15° or 30° so that a maximum coverage of 90° can be achieved.

Vertical launch angle into the Ionsphere

The number of dipole rows and the height of the lowest element above ground determine the elevation angle and consequently the distance of the service area.

A 2-row high array has a typical takeoff angle of 20°
* is most commonly used for medium range communications.
A 4-row high array has a typical takeoff angle of 10°
* is most commonly used for long range communications.
A 6-row array is similar to a 4-row, but can achieve 5° to 10° takeoff angles. This antenna type can be used in shortwave communications circuirts of 12000 km, and is highly directive.

How many variations of HRS antennas are there

Curtain antennas are available in two sizes.

A low band array typically covers the 6, 7, 9 and 11 MHz bands.
Low band antennas are typically larger and taller.
A high band array typically covers the 11, 13, 15, 17 and 21 MHz

bands (or 13-26 MHz bands).

High band antennas are typically smaller and shorter.

HR 4/4/1 the most common HR antenna type, it can be found at most shortwave relay stations.

Transmission system optimisation dependend on geopolitics

Occasionally an international broadcasters may use, for reasons

of geopolitical necessity -- a highband, midband as well as lowband HRS curtain arrays.

Using 3 HR curtain arrays to cover the HF broadcasting spectrum

creates a highly optimized HF transmission system.

Cost issues of HRS antennas

HF transmission systems using 3 or more curtain arrays can be costly to build and maintain.
Since the mid 1990s no new HF relay stations have been built.
Existing HRS shortwave transmission systems (built before 1992) will likely remain in use for at least another 50 years. The modern HRS antenna design thankfully has a long lifespan.

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Innovations in HRS antenna design

ALLISS is a rotatable antenna system for high power shortwave radio broadcasting.

Three HRS array antennas types are available for broadcasting in the traditional shortwave broadcasting bands.

For tropical and lower frequency shortwave broadcasting

HR 4/2/1 (using low band antenna)
HR 2/4/1 (using low band antenna)
HR 2/2/1

For traditional shortwave broadcating

HR 4/2/1
HR 4/4/1

For highly directional shortwave broadcasting

HR 6/4/1
HR 6/2/1

The HRS 6/4/1 is not available for use in the 26 MHz band.

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