Tektronix RFA300A, Руководство пользователя

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Installation
1- 14
RFA300A Measurement Set 8VSB
RF Connections
The quality of the input signal path is critical in obtaining the full-specified
performance of the measurement set. Therefore, you must connect the measure-
ment set to your transmitter using high quality cable and connectors. The
following list provides the requirements needed for the RF connection:
H
Hold the nonflatness of the input signal to approximately 0.05 dB peak-to-
peak or less over the width of the channel.
H
Keep the station’s radiated signal to at least 63 dB down from the sampled
signal in the line by using appropriate shielding.
H
The cable with connectors must have a return loss of at least 26 dB
(VSWR
±
1.10) over the channel width and a loss tilt of less than .02 dB
over the channel width. This assumes that the tap used to obtain the signal
has a return loss of
²
30 dB (VSWR
±
1.065).
High quality cable and connectors are required to meet the listed requirements.
The connectors should be precision grade at both ends of the cable. The best
cable type is dependent on the run length and operating frequency. The return
loss requirement is hardest to meet at high frequencies, and the loss tilt is hardest
to meet at low frequencies. In either case, minimize the difficulties by using only
a few feet for cable length. Longer lengths (50 ft. or more) place extreme
requirements on cable quality specifications.
The rear panel provides two RF input connectors for your transmitted signal.
Refer to Figures 1--9 and 1--10 to connect the measurement set to your transmit-
ter and for other connections.
Transmitter Channel filter
RFA300A
Power input
Figure 1- 9: Transmitter connection
Connect the measurement set to your transmitter in a manner that ensures the
instrument will receive only one channel. If the input signal strength is more
than 1 watt, install the external 10 dB attenuator (the input signal strength cannot
be more than 2 watts).