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Our native Android app is no longer under active development due to it being replaced by the HTML5 Web app.

Keyhole Radio™ for Android

0.Getting an account
2. Map view
3. App Menu
4. Key settings
5. Mast settings
6. Antenna settings
7. Receiver settings
8. Environment settings
9. Layer settings
10. Template settings
12. Offline usage
13. Filenames and archive
14.Trouble Shooting
15. Do's and Dont's

0. Getting an account

This app requires a server based account. If you have your own server you should use the Keyhole Radio username and password you would use for the server / Google earth layer. If you do not have your own server you can sign up for a free public account with a valid email address and password either on the app or on the website at An account allows you to store personal layers, templates and clutter online for use with the Web, Google earth and Android interfaces.

Registration ( users only)

When you open the form or archive for the first time you will be challenged for a login. Enter your email address and a password unique to CloudRF here (NOT your email password) then click 'Register', ensuring the 'Server' field remains at ''. A request will then be made to the server which will email you immediately. Check your spam folder if you don't see the email within a minute. In the email is an activation link which you must follow. If successful, you will be told your account is registered after which point you can press 'Login' on the app. This is one time only. If you make a mistake or want to register under a new email (limits apply), open your menu and click 'reset' then 'clear settings'. This will flush your identity.
Once activated your account can be used on the website immediately. Here you can change both your username and request password resets.

Login (All)

If you have an account on your Keyhole Radio server or at, enter either your username (eg. user1234) OR your email (eg. and your password. Next ensure the 'Server' field is set to the IP address of your server eg. then click login.

Credits ( only)

The service operates a credits system for calculations. New users are given 100 credits to play with which can be topped up manually by logging in to your account

1. Quickstart

1) Site your antenna by panning and zooming the map so it is centered on it OR press menu > settings and enable GPS within settings to use your location.
2) Press either the Center key or tap the icon in the bottom right to open the calculate form. More settings are available with the MENU key in here.
3) Enter your Transmitter's key parameters: Frequency, Power and Height (above ground).
4) If you need to change any advanced parameters, press MENU then click settings.
5) Finally, click the Big orange button in the middle and wait for your overlay to appear.
Note: Your request will be passed to a server where calculation takes place. The result will then be downloaded by your phone. The time this takes depends on your calculation radius, internet connection speed and server usage / other users. An average calculation should take no more than ~8 seconds.

You can support this service by
rating this app

2. Map view

Upon loading you will have a Google map with an antenna icon in the middle. The location of the antenna determines your Transmitter location and is visible at the bottom of the screen in decimal degrees. At the top of the screen is a colour key which depicts signal strength colours using the currently selected units of measurement. Orange is strong and purple is weak. A calculate button is available in the bottom right to create a new calculation.

3. App Menu

The menu is accessed from the map view with the MENU button. There is a second menu within the calculate form which is accessed also with the MENU button.
CALCULATE - To create a new coverage calculation.
HELP - This page.
ARCHIVE - Internet connection required. This will be your private archive at Also accessible at
MAP - The map can be switched from Map to Satellite.
RESET - Clear the map and/or settings.
QUIT - Exit the application.

4. Key Settings

The tabbed settings menu contains a variety of options that govern the Apps functionality, extra information is available on each by pressing the 'i' next to it.
FILENAME - Optional field for assigning a nickname to this calculation. This is handy for recovering it later on another interface eg. Repeater11
FREQUENCY - Frequency in MHz between 20 and 100,000MHz.
E.R.P - Effective Radiated Power in Watts. From 0.1 to 2,000,000W
RADIUS - Calculation radius measured in either Km or Miles. Max value is 50km on the app.
CALCULATE BUTTON - The big orange button will calculate the coverage once all settings are adjusted.
FAVOURITE BUTTON - The save template button will offer to save your settings for quick recovery. Give them an easy to recall name.
LOAD TEMPLATE BUTTON - The load template button will allow you to search your saved settings to find parameters you can reuse.

5. Mast settings

USE GPS - By selecting this, you can have the app center on your location which is handy for mobile radio users. You will be prompted to enable/disable GPS yourself as the app is not allowed to do this.
LOCATION - Transmitter location in decimal degrees.
MEASUREMENT UNITS - Antenna Heights and Radius can be either Metric (Metres / Kilometres) or Imperial (Feet / Miles). Changes take effect for the next calculation.
TRANSMITTER (TX) HEIGHT - The Transmitter height (above ground) will make a big difference.
RECEIVER (RX) HEIGHT - The Receiver height (above ground) will make a big difference.

6. Antenna settings

ANTENNA RADIATION PATTERN - Choose an antenna pattern. You can view them all at ANTENNA POLARISATION - An Antenna is typically either vertical or horizontal. For Line of Sight (LOS) paths, the Transmitter (Tx) and Receiver (Rx) must be of the same polarisation otherwise Signal degradation will occur. A handheld VHF is vertical, US TV Broadcasts are Horizontal.
ANTENNA AZIMUTH - The horizontal direction in degrees of the main lobe.
ANTENNA DOWN TILT - The angle in degrees of the antenna toward the earth. Positive values are looking downhill.

7. Receiver settings

COVERAGE TYPE - There are three output types available in the full version. The colour key will automatically update when the type is changed.
Path Loss is measured in decibels as a ratio (dB). This displays signal attenuation over the earth and varies with height and frequency but power is NOT a factor. This is useful for getting a feel for the conductivity of the surrounding terrain.
Received Power is measured in decibel milliwatts (dBm) as a negative ratio. On a mobile Phone 1 bar would equate to about -100dBm and 5 bars would be greater than -60dBm. This is useful for finding out where you can get a good signal.
Field Strength is measured in decibel Micro Volts per metre (dBuV/m). This is the actual electrical power present in the earth at a given point.
RECEIVER SENSITIVITY For 'Received power', the sensitivity is measured in decibel milliwatts (dBm) as a negative ratio with -73 being strong and -100 being weak. Enter -75 for a cynical calculation and -110 for an optimistic one. -90 is workable. Anything beyond the limit you set will not be shown. Be careful with this as an incorrect value here could easily result in nothing been shown!

8. Environment settings

RANDOM CLUTTER - The random clutter slider simulates trees, buildings and vehicles which will affect propagation.
UPLOADED CLUTTER - Precision obstacle overlays can be uploaded as KML files (Polygons,Lines or placemarks...) and included or ignored for calculations. Clutter Tutorial:
GROUND CONDUCTIVITY - The ground conductivity will make a big difference when you're using groundwave propagation. If you're using VHF/UHF and your antenna isn't above the
MEH then this will affect you.
RADIO CLIMATE - The radio climate determines atmospheric effects on OTH spacewave emmissions. Expert users only.

9. Layer settings

RESOLUTION - The output resolution will greatly affect computation time. Choose a lower resolution to speed up calculations and reduce overlay size. Tile resolutions vary with latitude and values shown are based upon 40 degrees N/S where High=70m,Medium=140m and Low=280m.


TRANSPARENCY - Adjust the opacity of the next overlay only.
COLOURS - Reduce the file size of your overlays by dropping the colours from rainbow to a primary colour scheme. Ideal for users on low bandwidth connections or with limited memory.

10. Templates

Within the calculate form, press MENU to see the load and save templates options.

Saving a template

Click save template to open a form. Within this form, your key technical parameters are already loaded and taken from your last calculation. Give your device a name eg. IC-M24 and then categorise it properly so VHF > Marine VHF. Next, give it a useful description so others can find it: "ICOM IC-M24". Finally submit your template to the server. If you completed correctly you will be notified.

Loading a template

To open a template, click load template to open a search form. You can search by keyword and frequency. Enter some values and click the filter icon to the right. To use a search result, click it from your results list to open a dialogue box. You then click 'use' to populate the settings in your phone, ready for your next calculation. Always pay attention to what settings your loading in, especially with things like sensitivity.

11. Technical

The algorithm used on the server is the Irregular Terrain Model (ITM) commonly known as the 'Longley Rice' model. This planning model was developed in the US for TV Broadcasting and is optimised for 20-20,000MHz (VHF-UHF-SHF). It's incorporated into an open source program called Signal Server which is a server optimised version of SPLAT!. This program performs the calculations on a high performance server containing elevation data for the entire world. The elevation data used is NASA SRTM2 which has a resolution of 90m and 99% global coverage between -/+60 degs latitude. Additional high latitude tiles have been added for Norway,Sweden, Finland and Northern Russia. Much more detail about this service is available through

Minimum Effective Height (MEH)

Spacewave / LOS propagation is much better suited than groundwave for VHF frequencies due to ground attenuation. To determine if your antenna is high enough for spacewave you need to work out the wavelength. So for 30MHz, divide 300 over 30 and get 10m. For 145MHz: 300/145 = 2m.

12. Offline use

You will be viewing the overlay in the app on Google Maps so you need to think about your map cache. Fortunately, the map cache is pretty good and so long as you've looked at your target area recently at the right scale, you'll be able to revisit that place later offline. File name conventions use the year/month/day/hour/minute/second_Frequency. These files are also available
on the server.

13. Unique filenames and archive

You will be given the option on the first tab of saving it with a distinct nickname eg. 'repeater3'. This name will help you recover it later in your archive and also appears within the KML overlay so when viewed in Google earth, each icon is tagged with a nickname. The nickname is appended to the time stamp already in the filename (year/month/day/hour/seconds) eg. 120113140033_repeater3.kml. Only alpha numeric characters are allowed.

14. Trouble Shooting

Map is slow

Using a ground overlay on a smartphone map is very resource intensive as the bitmap must be redrawn and layered every time the map moves slightly to keep it aligned with the earth. You may notice after a few calculations that navigating the map becomes slow, this is normal. Clearing the map with the RESET button from the menu or restarting the app will help this.

Nothing happens

First check you have an internet connection and that you're supplying valid input so check your settings: If you've tried a dB 'Path loss' calc with a receiver sensitivity of 80 you won't see anything. Try 'Received Power' instead with a receiver sensitivity of -100dBm. If you've entered an incorrect value it will generate a brief alert prompt on your phone so check you're not getting these. If the input is ok, check for any errors after calculation. A tell tale sign of a calculation error is an alert prompt ''. To test if the server is OK, open up the following service status URL in a web browser:
Alternatively it's possible your phone is being lazy when drawing the overlay, rotate the screen 90 degrees to initiate a redraw then back again to see if that helps. If you still can't get it working, get in touch with your handset model at the link below.

Crashed after completing a calculation

This app is by it's nature, resource intensive, especially when performing large calculations. If your device is low on memory you will run the risk of crashing the app when trying to overlay a large calculation. Drop the resolution to low and try to free up memory where possible but if the problem persists, email the location, radius and handset model to dev at address below. You can see the filesize in kilobytes for each overlay by tapping the antenna icon in the centre of the coverage.

Crashed after an update

If it crashed after an update or when you clicked settings do this:
Open your phone's settings, then Applications, find 'RF Signal' under installed apps and clear it's data, or if you've got the latest version, use the reset settings option from the menu. This will remove config files from the old version and wipe the slate clean.

No terrain data for my area?

The terrain data on the server covers 99% of the World's land mass but typically stops at 60 degrees north and south with exceptions for Scandanavia.

I don't like the new version. I want the old one back!

You won't find old versions in Market but the APK files can be emailed on request.

15. Do's and Don'ts


Take your time with your input and double check each value you pass to the server.


Try to do as many calculations as fast as you can. You will violate the Terms and Conditions of this service and your device will be blocked.


Learn all the advanced features. You will get a more accurate calculation.


Use this app with a non stock keyboard. You could enter an illegal character (not a number!) - which will crash it.


Turn on the GPS if you want it to use your location


Leave your GPS on after use. It will drain your battery

app.txt · Last modified: 2016/09/01 22:01 (external edit)