What Does a Microwave Downlink Do?

The primary mission of a Microwave Downlink is to send video from the aircraft to the ground so that people on the ground can see what the aircraft sees. Downlinks can also send audio and data to the ground.

Why Do You Need Microwave Downlinks?

There is no better way to describe something to someone than to show it to them. A picture is worth a thousand words and live video is worth so much more. Video is a universal language. It shows those on the ground exactly what is happening without misinterpretations.

Pilots can give no better description.

Recipients receive the best possible description.

Seeing is believing.

BMS’ microwave downlink systems consist of a receive side and a transmit side, and are explained in the following sections.

A microwave downlink system simply transmits live video from your aircraft (transmit side) and sends it down to the ground (receive side) so that people on the ground can see what you see. If your job is in part to be an aerial observation platform and you must describe what you see to people on the ground, there is no better way of doing so than to share a live video of it.

BMS offers four types of receive systems:

• Central Receive: These include Silhouette and diversity tracking systems.
• Mobile Command Post: These include the MTD II and DiversaPod products.
• Vehicle: These include the Mobile-Viewer™ and Briefcase Viewer.
• Portable: These include handheld products like the Carry-Viewer™ III receiver.

Central Receive

The Silhouette Tracking System consists of the SCU322 receiver, a large high-gain antenna in a radome, and the MC5 software. The system is a large fixed receive site system for auto-tracking and is suitable for fixed sites such as mountain tops or tall building installations. The antenna pod is mounted on top of a tall building.

The MC5 is the user interface of the remote control which controls the receiver and the antenna pod from the MC5 location.

Mobile Command Post

The MTDII is a small lightweight mobile antenna tracking system used on a mobile command vehicle or for a temporary installation where mobility is required. This self-contained, compact and rugged ground tracking antenna pod and remote control is intended for use wherever mobility and ease of use are required. The antenna is easily transported and deployed on a tripod, permanently mounted on top of a vehicle, or mounted on top of a telescoping air mast.

Vehicle

The BMS Mobile-Viewer™ LE (MV-LE) is a COFDM digital vehicle-mounted two-way diversity microwave receiver that is suitable for law enforcement, public safety and homeland security applications. Small and affordable, the MV-LE is easily installed in any vehicle, and allows instant viewing of down-linked or surveillance video. The Briefcase Viewer is similar to the CVIII but has a larger monitor and is installed in a small briefcase. Often, it is used by law enforcement to determine a plan of action, because it can be used on top of a squad car.

Portable

Portable systems are among the simplest systems to operate, because they consist of an omni-directional receive system and are lightweight and highly portable. BMS’ Carry-Viewer™ III handheld consists of a DeCoder II receiver and uses two omni-directional antennas for true diversity reception. It operates for three hours on a single battery charge. Video record and playback are standard features. A unique Geo-Point™ option uses metadata from the video source and displays the bearing and distance to the location shown on the screen, all in real time!

Microwave Downlink Operation

All microwave systems require a line of site between the transmitter and the receiver for a guaranteed reception at the receive site. Obstructions such as buildings and trees can interfere with line of site. The aircraft should also be above the horizon and be in line-of-site.

With an omni system, if the aircraft is above or below by 11º, the line of sight is limited. With a high gain system, the aircraft must be within 25º to be in line of site. Banking will create a limitation, so the aircraft must be in line of site without banking. Banking at an angle looses gain and energy is lost when the line-of-site is pointed at an angle.