Accessories

Telecommunications Accessories ensure reliable power supply, signal transmission and mounting of communications equipment. These include antenna bases, coaxial cables, connectors, connection adapters, microphone holders and mounting brackets. A damaged antenna connection or poor earth point can cause the same symptoms as a faulty transceiver. Always check the entire connection chain before replacing communications equipment.

• Antennas and antenna Accessories: GPS/GNSS antennas, mobile communications antennas, antenna bases and seals.
• Cables and wiring harnesses: coaxial cables, data cables and power cables.
• Connectors and connection adapters: plugs, couplers and vehicle-specific connection adapters.
• Power supply Accessories: power adapters, voltage converters and fuse holders.
• Holders and mounting hardware: device holders, mounting brackets and vibration-resistant fasteners.
• Vehicle interfaces: CAN and FMS interface adapters for accessing vehicle data.
• Cable protection and feedthroughs: protective sleeving, cable grommets and strain relief.

Always identify parts using the vehicle's chassis number, together with the identification details of the installed telecommunications system. Visual comparison or selection based on the model name alone is never sufficient. For retrofitted equipment, the manufacturer, model number and wiring diagram are also essential. Check the supply voltage, pin assignments, connector keying and mounting dimensions: an adapter that fits mechanically does not guarantee electrical compatibility.

Roof feedthroughs, mounting positions and cable routes can differ on MAN TGS with M-, L- or LX-cabs and MAN TGX with XL-, XLX- or XXL-cabs. The same applies to Mercedes Actros with Lang StreamSpace or Lang GigaSpace cabs. For buses and vans such as Citaro, Sprinter and TGE, use the vehicle-specific installation data; connections and roof structures are not necessarily interchangeable.

Distinguish between passive antenna Accessories, active antenna components requiring power and mechanical mounting parts. For coaxial connections, check the characteristic impedance, typically 50 ohms for radio transmission, the frequency range and the permissible cable attenuation. For power adapters, the key factors are a nominal input of 12 or 24 volts, voltage tolerances, continuous output current and protection against voltage spikes. For holders, check the hole pattern, thread, fit and vibration resistance. Corrosion-resistant metal fasteners and suitable elastomer seals help prevent loosening and water ingress.

Dropped calls, insufficient transmission range, crackling noises and equipment restarting do not necessarily have a single cause. Common problems include corroded connector contacts, broken cables at pivot points, holders loosened by vibration and moisture in antenna bases. A kinked coaxial cable can also cause additional signal loss even when the outer sheath appears intact.

1. Record when the fault occurs: during transmission, with the engine running, after rain or when the cab moves. Inspect connector locks, seals, cable sheaths and strain relief.
2. Use a multimeter to measure the supply voltage directly at the connection, including under maximum load. Then measure the voltage drop across both the positive supply lead and the earth connection. Compare the results with the equipment specifications.
3. Isolate the system from its power supply and disconnect both ends of the cable. On individual passive coaxial cables, check the continuity of the centre conductor and shielding, and check for short circuits between them. Bear in mind that some antenna designs intentionally appear short-circuited at DC.
4. For transmitting systems, measure the SWR (Standing Wave Ratio) with a suitable meter at the operating frequency. An abnormal reading calls for checks of the antenna tuning, cables and connectors. If necessary, assess cable attenuation with a network analyser; a continuity test alone does not confirm proper high-frequency signal transmission.

Replace moisture-damaged coaxial connections and worn connectors rather than simply cleaning them. Use suitable crimp contacts, the specified tools and tightening torques. Observe the minimum bend radius and keep signal cables away from sources of interference such as power converters. Check whether antenna bases require a conductive ground plane; a plastic roof may require an antenna designed for that application.

Prevent further roof leaks with the correct seal and protect cable feedthroughs against abrasion. After installation, check reception, transmission where permitted, power supply stability and quiescent current after switching off. This helps prevent recurring communications problems and battery drain caused by incorrectly connected accessories.