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AM-55 / Sep 2015
A M - 5 5 G U I
If desired, the transmission system’s high frequency pulse response may be analyzed
using the tools contained within the AM‑55 to determine if HF correction needs to be
applied.
The procedure is as follows.
1. With the AM‑55 connected to the transmitter to be tested…
2. Connect the transmitter to your antenna system.
3. Turn on the AM‑55 test oscillator. Adjust it to a frequency of 1kHz. Adjust the
Test Oscillator Level control and the TX#1 or TX#2 output (whichever is feeding
the transmitter under test) until approximately 60% modulation is indicated on
your modulation monitor. Ensure that, at this point, the
HF Corr EQ
“L” (level)
controls are set for 0dB.
4.
Turn on the AM‑55 Tilt Test
by clicking the check box.
5.
Using an oscilloscope connected to a low level RF sample of the transmitter
output, observe the resulting RF waveform.
6. If the transmitter has adequate HF response the waveform will appear similar
to figure C.
7.
If it has LESS than adequate HF response, the waveform will appear similar to
figure A.
8. Depending on the magnitude of HF correction required, the appearance may be
between figures A&C.
9. If the response of the transmitter does not resemble the perfect high frequency
response represented by figure C, alternately adjust the
HF Corr EQ
“F” (Fre
‑
quency), “Q” (Bandwidth) and “L” (Level) controls in order to achieve the flattest
top and bottom waveforms, and reduce overshoot on the waveform’s leading edge.
