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krs_inputs


Once logged in, the layer will render several different features; a banner in the top left corner showing session information, a layer of green rectangles over the earth showing server terrain coverage (each tile is 1 degree latitude/longitude) and an orange button in the centre of the screen. The orange button appears after the view has changed and settled and will only appear once the view has focused and zoomed into a country as opposed to a continent.
To perform a calculation, click the orange button.
The pop-up calculation form contains a tabbed input form with a wide range of options of varying importance and can also be opened up in any javascript enabled web browser via the ‘open in web browser’ hyperlink. This can be beneficial to users with multiple monitors who can keep their Google earth view clear of visual obstructions. The hyperlink opened is unique to the logged in user and expires after several hours.
There are two modes of operation for the interface: Basic or Advanced to cater for tactical radio users and strategic radio engineers alike. Novice and new users should start in Basic mode which enables only three of the six input tabs. Experienced users should select the Advanced option to enable all tabs and features.
The geographic location used for the calculation will be the centre of the screen view. The co-ordinates can be manually edited within the second ‘Transmitter’ tab.

Keep your Google earth view looking straight down to keep the button in the middle.

Calculate options


The first tab contains the most important values and the calculate button which is used to perform the calculation.

Template

The template box will list saved templates created using the ‘save template’ button (star icon). The templates can be selected with a click and will automatically populate the relevant fields within the form with saved values. To save a template, click the star icon. For more on templates, see the data section.

Save your settings as a template by clicking the star icon

Name

The calculation description field allows for up to 25 characters to describe a calculation, for example ‘Repeater2’. This name is visible in both the archive and the KML layer within Google earth. Spaces are removed so underscores (_) are advised. If left as ‘Tx’ it will result in the default filename of date, time and Tx. The date in every filename is in the format YYmmddHHiiss so it is unique.

Frequency

Enter the channel frequency of the radio system in megahertz (MHz). Acceptable values are 20 to 100,000MHz (100GHz) with 3 decimal places accuracy eg. 446.025.

ERP

Enter the total effective radiated power (ERP) of the radio system in Watts. Novice users should just enter their radio’s wattage as per its specification eg. 5W. Advanced users can enter transmitter power (W) and antenna (isotropic) gain (dBi) to automatically calculate the ERP on the antenna’s tab (#3). Maximum value is 2MW (2,000,000W).

Bandwidth (Advanced mode)

Select the system’s bandwidth in MHz from the drop down list to represent wideband high capacity data bearers. Any bandwidth greater than 1MHz will cause a reduction in received power proportionate to the bandwidth. A signal of 10MHz bandwidth is twice as weak at the received site as 5Mhz as the power is spread across twice the spectrum.

Radius

Enter the maximum distance in either kilometres or miles for the coverage plot. This should be no more than the range of the most distant station. To change distance units, click metres or feet within the second transmitter tab. The maximum value possible is determined by the server’s available memory (300km on cloudrf.com).

Calculate

The calculate action button executes the calculation. Whilst running, it will be greyed out and cannot be clicked until the calculation completes.

Transmitter options


The second tab contains geographic and units information including the transmitter’s location, heights for the transmitter and receiver (above ground level) and distance units.

Antenna location

Enter the location of the emitter in either Decimal degrees, Degrees-minutes-seconds or NATO Military Grid Reference System (MGRS). Entering a value within one row will automatically result in a conversion to the others. By default this is the centre of the main view in Google earth when looking straight down.

Antenna heights (above ground)

Enter the height of the transmitter (Tx) and receiver (Rx) antennas above the ground. The metres or feet toggle next to it will also change distance units for all other distance measurements within the form including radius and clutter height(s).

The metres or feet toggle will change distance units for heights, clutter and radius

Antenna options

Keyhole Radio Google earth

The third tab contains advanced settings related to antenna radiation patterns. It allows a choice between pre-made 3D templates or a custom 3D pattern based upon user supplied values. For both methods, there will be two adjacent images shown which depict the horizontal (bird’s eye view) and vertical (side on) radiation patterns. Most users should find a template to suit their needs and will only need to rotate the antenna by defining the ‘direction’ (degrees from north) field.

Antenna Templates

Templates are stored in a database in .ant v3 format (360 rows of horizontal values, 360 rows of vertical values) compatible with other popular planning applications. A template is selected by choosing it from the drop-down menu. New templates can be uploaded in as .ant files. If you have a .pat format, there is a script to convert it to .ant located at /API/antennas/pat2ant.php. To see all patterns in detail click the ‘Add’ link to open the antennas dashboard. All antenna patterns are referenced to 0dB (100% radiation) so an omni-directional pattern with 0dB all round would be radiating at full power in all directions.

Novice users should select ‘Dipole.ant’ (Omni-directional)

Custom

The custom option allows users to create a pattern on the fly by defining key fields (Azimuth, down-tilt, horizontal beamwidth, vertical beamwidth, forward gain and front-to-back ratio). As values are changed within these fields, the pattern will automatically update. You can download the pattern in ant format via the hyperlink underneath the images.

Save your pattern by downloading the .ant file in the middle

Polarisation

Antenna polarisation (US: polarization) describes the physical orientation of the antenna relative to the ground. Most broadcast and handheld systems are vertical, whilst some data systems are horizontal to reduce (vertical) interference. The default is vertical.

Direction

The horizontal angle (azimuth) the antenna is pointing referenced to grid north. Values of 0-360 are allowed. Not to be confused with beamwidth.

Down tilt

The down-tilt is the vertical angle the antenna is pointing relative to the horizon. Acceptable values are -10 to (+)90 degrees where angles above the horizon (pointing up) are negative and angles toward the earth (pointing down) are positive. A directional antenna parallel to the ground would be 0 degrees. This value is used typically when a directional antenna on top of a hill is pointing down toward low ground. It would have a positive downtilt. A similar antenna down in a valley would have a negative downtilt as it would be looking up the hill. Default is zero (no tilt).

Horizontal Beamwidth (Custom mode)

This describes the angle in degrees between the two half power (-3dB) points of a directional antenna in the horizontal plane. For example, a directional ‘one third’ panel on a GSM cell tower would have a beamwidth of 120 degrees. This setting can only be applied in ‘custom’ pattern mode.

Vertical Beamwidth (Custom mode)

This describes the angle in degrees between the two half power (-3dB) points of a directional antenna in the vertical plane. For example, the previously mentioned 120 degree (horizontal beamwidth) GSM panel may have a smaller vertical beamwidth of only 30 or 45 degrees, otherwise it will be wasting energy radiating the sky above it. This setting can only be applied in ‘custom’ pattern mode.

RF Input Power

Transmission RF power in watts is the amount of power supplied by a radio and is normally smaller than the total effective radiated power (ERP) of a directional antenna system. It is used along with the gain to calculate the total effective radiated power (ERP) of the system.

Max Gain

The directional gain of an antenna measured in dBi. This is a numerical value between 0 and 50. For 1:1 gain (no additional power) then a default figure of 2.15dBi should be used. A high gain antenna would be greater than 10dBi. Adjusting this will result in an automatic adjustment to the ERP value on both the antenna tab and the initial ‘calculate’ tab. If you have losses you need to offset, subtract them from the gain value. For example, a system with 9dB antenna gain and 3dB loss could be said to have a positive gain of 6dB.

Front to back ratio

This ratio measured in dB relates to the difference in power between the front and the back of the antenna. A value of 3dB would mean the antenna was twice as powerful to the front as to the rear. This defaults to twice the forward gain so a 5dBi antenna would have a 10dB FBR. Maximum value is 70dB.

ERP

Effective Radiated Power (ERP) is the total RF output of a system and is automatically calculated using the following formula. Losses can be factored in by removing them from the antenna gain value.

ERP = Transmitter Power * Feedline Loss * Antenna Gain

This value, once changed is automatically set on the first ‘Calculate’ tab as well.

Receiver options

The fourth tab contains advanced settings relating to the receiver(s) settings. An incorrect value here can result in unrealistic output.

Propagation model

This drop down selection allows the planning algorithm to be selected. There are different models optimised for different parts of the radio spectrum and geographic scenarios. For example the free space path loss model is well suited to a SHF point to point microwave link where there are no terrain obstacles whilst the Hata urban model is especially designed for UHF cellular planning in urban areas where tall buildings are present. Picking the right model will enhance accuracy. Picking the wrong one will deliver inaccurate results. If in doubt, choose the ‘Irregular Terrain Model’.
ModelFrequencyDescription
Irregular Terrain model (ITM)20-20,000MHzUS NTIA general purpose model used by the FCC
Line of Sight (LOS)All Line of sight model used to determine existence of obstacles.
Okumura Hata (Urban)150-1500MHzCellular model optimised for urban areas where transmitter is >30m AGL.
ECC33150-3500MHzECC33 model for cellular and microwave communications
SUI (WiMax)1900-11,000MHzStanford University Interim for WIMAX
COST231-Hata (Urban)1500-2000MHzEuropean GSM1800 and CDMA2000 cellular model optimised for urban areas where transmitter is >30m AGL.
Free space path loss20-100,000MHzITU-R P.525 model which assumes no terrain obstacles exist in the path.
Irregular Terrain model with obstructions (ITWOM)20-20,000MHzDebatable enhancement to ITM model with increased loss
Ericsson cellular150-11,000MHzEricsson model for cellular communications up to 11GHz

The ITM model is an advanced general purpose model ideal for most users

Knife edge diffraction

Where a terrain obstacle like a hill is present, diffraction and shadowing will occur on the far side of it. Not all the propagation models factor this in by default so you can manually enable this effect. This option is not necessary for the default Irregular Terrain model where it is a core feature. The diffraction algorithm used is a custom linear model which uses the obstacle’s height, distance and angle from transmitter to determine the resultant diffraction impact.

Receiver height

The height above ground level of the receiver(s). Distance units are defined on tab two. For a man holding a handheld radio or phone, set this to 2 metres.

Units of measurement

The output units determine how to represent the propagation. Selecting dB (decibels) will ignore the Power output (ERP) and depict the path loss caused by the terrain. Handy for identifying high loss blackspots in the terrain. Selecting dBm (decibel milliwatt) will factor in all variables and depict the radio coverage. This should be used as standard or when uncertain. Selecting dBuV/m (Decibel microvolts per metre) will show the electrical field strength present in the ground and is best used for scientific surveys relating to RF radiation levels.

Receiver sensitivity

The coloured key and selected value changes according to the measurement units selected above it. For all units, a strong signal is to the left (yellow) and a weak signal is to the right (blue). An optimistic result can be achieved by setting the slider to -120dBm whilst in 'received power' mode. A strong signal limit of -75dBm would provide a more pessimistic result and can be increased further to simulate losses associated with urban environments where ground clutter is not available to simulate concrete screening and absorption. If you do not know your receiver sensitivity then -80dBm is a good limit. If you want to factor in a fade margin eg +15dB then just add it to receiver sensitivity so -90dBm plus fade becomes -75dBm.
ModeUnitsDescription
Path LossdBIgnores RF power. Used for showing terrain loss
Received powerdBmShows received signal based on all options
Field StrengthdBuV/mShows electric field strength based on all options
Bit Error RateBER (%)Digital comms. Converts to a dBm value by looking up modulation mode and SNR.

The Bit Error Rate (BER) mode will reveal two hidden input values for modulation and noise floor

Modulation (BER mode only)


Different modulation modes have different error rates at a given signal to noise ratio (SNR). To calculate the SNR, the mode and noise floor must be selected.
ModeDescription
QPSKWorks with low SNR
4PAMLow SNR
16PSKMedium SNR
64QAMHigh SNR
32PSKRequires highest SNR

Noise floor (BER mode only)

The noise floor is used to calculate the SNR which in turn is used to extract the BER. A low noise floor in the countryside might be -130dBm but in a typical suburban environment this will be higher (-120dBm) and for a busy city higher still (-115dBm). Noise floor varies by location, time of day and year.

The receiver sensitivity is very important and must be set carefully to create accurate output, Use -80dBm if you are not sure


1 Watt repeater with -125dBm receiver sensitivity

Same site with -75dBm receiver sensitivity

Environment options

The fifth tab lists advanced options for defining man made obstacles (clutter) and ground conductivity. The features here will help advanced users achieve the most realistic coverage plot for an area, especially in suburban or extreme climatic environments.

Random clutter (height above ground)

Buildings can be rapidly simulated using the slider, up to 50 metres (150 ft) high. This will increase the ground height all around the site to simulate a layer of buildings above ground level.
The width of each clutter item is determined by the output resolution. For the default resolution of 1200 pixels per degree this is 90m wide.

Database clutter

A much more precise simulation of man-made buildings can be done by uploading an overlay of points to mark building locations via the ‘Upload KML’ hyperlink.
This overlay should be a KML overlay containing either placemarks, polygon corners, line points with heights in metres defined in the point properties.
A quick way to define a row of wind turbines is to use the Google earth 'path' feature and click once per turbine then set the path’s altitude to 30 metres in Google earth (Relative to ground). Save off the path as a .kml file and upload it using the 'Upload a KML' link.
A single click will create a 90mx90m wide building. To define a larger building, click each corner.
Clutter OptionMeaning
NoneNo clutter
PersonalOnly my clutter items
AllEveryone's clutter items

Ground conductivity

The conductivity slider allows you to compensate for different environments using a dielectric value which describes electrical conductivity through the ground. A city has very poor conductivity whilst a wet marsh has very high conductivity. This is relevant for radio systems which operate at ground level such as hand held radio.

If your system's antenna is low or at ground level (Groundwave propagation), the terrain type will greatly affect signal attenuation

GroundDielectric constantAttenuation
Water80Very low
Good ground25Low
Farmland, Forest15Average
Mountain, Sand13Higher
City5High

Radio Climate

The radio climate slider allows you to compensate for different environments using a climate code which affects propagation through space. This is relevant for radio systems which operate high up such as over the horizon microwave links.

If your system's antenna is high above the ground (Spacewave propagation), the radio climate will affect signal attenuation

Radio climate
Equatorial
Continental subtropical
Maritime subtropical
Desert
Continental temperate
Maritime temperate (Land)
Maritime temperate (Sea)

Layer options

The sixth tab’s options do not affect actual propagation results with the slight exception of resolution which changes the granularity of the output. They determine formatting of results after calculation.

Resolution

This option relates to the pixels per degree of output files. A high resolution employs 1200 pixels for each degree on the earth which at the equator is about 90 metres. This figure reduces towards northern latitudes. A medium resolution is 600 pixels so twice the distance and low is half again (300 pixels). Calculation time is affected significantly by the resolution.

Speed up your calculations by selecting a lower resolution

Transparency

The transparency/opacity slider applies to the Google earth ground overlay. This value can also be manipulated post calculation manually within the layer’s properties.

Colour schema

The colour of the output file can be set here. For single colours like ‘Reds’ a range of dark and light reds will be used to denote strong and weak signals. A key is supplied with each layer for reference.
The number in brackets is the number of colours in that scheme.

Greyscale terrain background

Enabling this will draw the terrain background for the overlay which can be helpful when sharing the layer with other users or viewing it on systems with limited mapping. This feature greatly increases resultant filesize.

Path Profile Analysis

The Path Profile Analysis (PPA) feature allows a point to point (P2P) study from the transmitter (Tx) which generates a 2D profile graph and text report highlighting obstructions. To use the PPA feature select a radio coverage layer and then focus the viewer on to a point within the coverage area where you would like to have a receiver (Rx). Expand the layer’s components within the left hand layer tree to reveal the ‘Path Profile Analysis’ network link, select it and press Ctrl-R to run a PPA. (Alternatively, right click the layer then select ‘refresh’)
After a brief delay, a signal strength icon will appear on the map centred on the centre of view with a value representing the signal strength. Click this icon to view the report and 2D graph with Fresnel zones.

krs_inputs.txt · Last modified: 2016/09/01 21:01 (external edit)