The Receiver section of the web interface has a small number of controls for specifying signal receiver characteristics. It is important to ensure these values are correct to obtain realistic outputs.
The Receiver panel can be expanded and collapsed by clicking on its tile [1]. It will automatically collapse when you open any other calculation panels. Here you'll find the Height AGL field [2], Gain [3], a Units of Measurement drop-down menu [4], and a sensitivity slider bar [5]:
Height AGL
Just like the transmitter height, this value is measured above the ground so a 4m antenna that is 100m above sea level will simply be 4m AGL. Important: the distance units used here (feet or meters) is defined within the Transmitter section. To simulate a man holding a hand-held radio or phone, for example, you'd set this to 1.5 meters.
Receiver Gain
Much like the transmitting (Tx) antenna gain, the receiver (Rx) gain is a ratio of directional gain measured in decibels relative to an isotropic radiator (dBi). The default value is 2.14dBi. A high gain 5.8GHz receiving dish would be 5dBi or greater. This value will be added to the Tx gain on the server to produce a total link gain. Losses can be deducted directly from these values so with Tx 10dBi, Rx 10dBi and 3dB losses the server would use a final 'link budget' value of 17dB net gain.
Units of Measurement
The Receiver Unit of Measurement selection determines how to represent the propagation. Each selection has it's own
| Mode | Units | Description |
|---|---|---|
| Path Loss | dB | Ignores RF power / ERP. Used for showing terrain losses to locate black-spots. |
| Received power | dBm | The most common selection, it factors in all variables and depicts the radio coverage. |
| Field Strength | dBuV/m | Shows electric field strength present in the ground based on all options. |
| Bit Error Rate | BER (%) | Reveals a hidden input value fields. Used for digital communications. 50% = 0.01, 60% = 0.001, 70% = 1E-4, 80% = 1E-5, 100% = 1E-6. |
Selecting the Bit Error Rate (BER) mode will reveal hidden input options for Noise Floor, Modulation, and Bit Error Rate.
Noise Floor
The noise floor is critical for calculating the effective range of a digital waveform and is limited to between -90 and -105 dBm on the Web Interface. If your noise floor is greater than -90 dBm please email us at support@cloudrf.com or use the API which allows noise floor values from -120 to -60dBm. The noise floor is fixed at -114dBm for a 1MHz wide signal.
Modulation
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 first be selected:
| Mode | Signal-to-Noise |
| 4QAM | 11 dB |
| 16QAM | 16 dB |
| 64QAM | 18 dB |
| 256QAM | 24 dB |
| 1024QAM | 29 dB |
| BPSK | 11 dB |
| QPSK | 11 dB |
| 8PSK | 14 dB |
| 16PSK | 18 dB |
| 32PSK | 24 dB |
| LoRa | -20 dB |
Bit Error Rate
The Bit Error Rate is used for digital communications. A good bit error rate is very small, with 100% link reliability. A poor error rate is one error in every 100 bits (0.01).
| Link Reliability | Value |
|---|---|
| 50% | 0.01 |
| 60% | 0.001 |
| 70% | 0.0001 |
| 80% | 0.00001 |
| 100% | 0.000001 |
Sensitivity
The sensitivity slider will be hidden if Bit Error Rate is selected.
The coloured key and selected values change 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 general limit.
If you want to factor in a fade margin (e.g. +15dB) then just add it to receiver sensitivity. So for example -90dBm plus fade becomes -75dBm. A 1-watt handheld PMR may have a pessimistic -70dBm receiver sensitivity, while an optimistic number would be -120dBm receiver sensitivity. The receiver sensitivity is very important and must be set carefully to create accurate output, Use -80dBm if you are not sure.
And as always, if you have any comments or questions please reach out to us at support@cloudrf.com.