Technalogix TAVD-500, Руководство пользователя

Страница: 23 / 76

Technalogix Ltd TAVD-500 Transmitter
IV-5
Filter
The passive bandpass filter rejects spurious and harmonic output products and passes the VHF
channel RF output. The cavity resonator uses aperture coupling and is a linear resonator design.
Typical insertion loss is 0.6 dB to 1.0 dB depending on channel frequency. Average roll off is –33
dBc at a point 4.5 MHz below the peak visual carrier frequency and –30 dBc 9.0 MHz above the
peak visual carrier frequency. The filter is DC grounded on both the input and output for additional
lightning protection.
Directional Coupler
The Technalogix dual directional couplers provide DC voltages proportional to forward and reflected
RF power monitoring. These analog voltages are converted for processing using analog-to-digital
converters and provide the control system with valuable data for monitoring purposes. Output
power should be set following the operating procedure found elsewhere in this manual. The
directional coupler has a typical insertion loss of 0.5dB and its Type N connectors can handle
1,500-watts peak while the 7/16” DIN connectors can handle over 3,000-watts peak.
Isolator
The power amplifier pallets are protected in part by the isolator located in the power amplifier
enclosures. It is actually made up of a circulator and 50-ohm dump resistor. The circulators’
specifications include an insertion loss of less than 0.2dB with an isolation rating better than 20dB.
Any reflected power gets dumped into the flanged power resistor. Even though the flanged power
resistor is rated for only 150-watts, and there could potentially be 500-watts being reflected back
into the circulator, the software will recognize quickly that reflected power is present and turn the
carrier off. This way, there is instantaneous protection due to the isolator setup and long term
protection due to the software.