VComm Scanner

ID:  2083

Object Description

The VComm Scanner object can be used in conjunction  with one or more VComm Radio Scan Channel to simulate the operation of a radio that scans multiple frequencies. Although there are many variations in how such radios work, in general, such a radio will silently scan all of its frequencies until a signal is detected on one of them. Upon signal detection, the radio will dwell (i.e., stay) on that frequency until the signal ceases. During the dwell, the radio operator listens to the transmission. After the signal ceases, the radio stays on the dwelled frequency for a period of time to allow the radio operator to transmit a reply. After a period of inactivity on that frequency (i.e., no signals detected and no transmissions made), the radio resumes scanning. The VComm Scanner object provides many static input parameters to allow the behavior of the object to be customized.

Use of this object is best described via the example provided in the figure below:

State Machine Operation

The operation of the state machine is described in the following tables. There is a table for each state in the VComm Scanner state machine. The Description explains the operation of the state. The Transition In describes how the state is entered. The Transition Out describes how the state is left. The Rx Settings and the Tx Settings describe how the Rx and Tx output pins are set on the VComm Radio Scan Channel objects. The Effect of PTT describes how enabling the Push To Talk input pin on the VComm Scanner object affects output settings.

Input Pins

Radio

The Radio pin is currently unused. Any value provided at this pin will be ignored.

Enable

The Enable pin when set to 0 disables the object. Any non-zero value enables it.

Threshold

The Threshold pin is used to specify the minimum signal strength level required for an incoming signal to be detected. The Threshold value must be provided in units decibel-milliwatts (dBm).

Reset

The Reset pin is used to reset the object’s internal state machine. A transition from any value to 1 will cause the state machine to reset. Resetting the state machine causes it to go to the Scanning State.

PTT

The PTT pin is used to provide the state of the scanning radio’s push to talk switch. This must be provided to the object as it affects the operation of the state machine. A zero indicates that the PTT is not enabled.  Any non-zero value indicates that the PTT is enabled.

Output Pins

Handle

Each VComm Scanner object produces a unique scanner Handle. This output pin must be connected to the Scanner input pin on each VComm Radio Scan Channel object associated with this scanner.

State

The State pin provides the current state of the state machine as follows:

0 – Disabled State

1 – Initializing State

2 – Scanning State

3 – Dwell State

4 – Wait State

Channel

The Channel pin provides the channel number of the locked channel. If no channel is currently locked then this pin is set to -1.

Static Data

Scanning Method

This value is currently unused.

Initial Channel

This value specifies the channel on which the scanner first dwells when enabled and before starting to scan (i.e., during the Initializing State). If the channel number is set to -1, then no channel is dwelled upon during the Initializing State.

Initial Delay

This value specifies the duration of the Initializing State in milliseconds. A value of zero will result in the scanner starting to scan as soon as it is enabled. A value less than zero will result in the scanner staying in the Initializing State until it is reset using the Reset pin.

Reply Wait

This value specifies the duration of inactivity during the Wait State before the scanner resumes scanning. The value is specified in milliseconds. A value less than zero will result in the scanner staying in the Wait State until it is either reset using the Reset pin or until it re-detects a signal on the locked channel and re-enters the Dwell State.

Scanning Transmit Channel

This value specifies a specific channel that is to be used for outgoing transmissions during the Scanning State. If the channel number is set to -1, then outgoing transmissions are disabled during the Scanning State.

Dwell Transmit Channel

This value specifies a specific channel that is to be used for outgoing transmissions during the Dwell State. If the channel number is set to -1, then outgoing transmissions are enabled on the locked channel.

Wait Transmit Channel

This value specifies a specific channel that is to be used for outgoing transmissions during the Wait State. If the channel number is set to -1, then outgoing transmissions are enabled on the locked channel.

Wait Override Transmit Channel

This value specifies a specific channel that is to be used for outgoing transmissions during the Wait State when the PTT has been engaged multiple times. If the channel number is set to -1, then this override feature is disabled.

Enable Receive While Scanning

This value determines whether reception on all channels is enabled in the Scanning State. A value of 0 disables reception. Any non-zero value enables reception.

Example

The example below presents a design for a scanning radio with three channels. Each channel is represented by a  VComm Generic Radio, V8 DIS/HLA  object (VComm Generic Radio, V8 DIS Only  objects may be used as well). The VComm Scanner object is associated to each one of its channels via a  VComm Radio Scan Channel  object. The channels must be numbered uniquely using the Channel static data value of each VComm Radio Scan Channel object. Several static data values in the VComm Scanner object refer to these channel numbers.

The VComm Scanner object monitors incoming signal levels on all of its associated radios. Based on the incoming signal levels the object controls an internal state machine and controls the Rx (Receive) and Tx (Transmit) output pins on the VComm Radio Scan Channel objects. Those output pins are then used to control the volume and the PTT on their associated radio. It is important to note that although this is a simulation of a single scanning radio, it requires as many radio objects as there are channels to scan for the radio.