BIRD 43 - Frequency Response

Bird Model 43 Wattmeter
14
unknown line to the wattmeter. The measured
φ is the attenuation
for two passes along the line (down and back). The attenuation can
then be compared with published data for line type and length
(remember to halve N
db
or double the line length to account for the
measurement technique).
This measurement should be supplemented by either time domain
reflectometry or dc continuity and leakage checks, since the
attenuation measurement alone cannot account for faults such as
open or short circuits partway down the line.
 NOTE: Very small attenuations require allowance for normal
instrument errors. Make sure to note exact readings, or their
difference, on the initial equality check, and correct for this.
Frequency Response
Bird Plug-In Elements have a flat frequency response over their
specified operating range. A sample set of curves is shown in Figure 6.
Notice that for the low power element, the rolloff outside its frequency
band is more pronounced than for the high power elements. For
example, at 40 MHz the 10C element will have a loss of 4 dB, giving a
reading of about 40% of the true value For the 100C, the loss will only
be about 1 dB, for a reading at 80% of the true value, and the 500C
should be within the normal 5% of full scale tolerance.