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AM-10HD / Aug 2008
A M - 1 0 H D G U I
required signal swing! Most AM transmitters require approxi10dBu for
100% modulation which leaves plenty of headroom (…in the AM‑10HD anyway!)
to reach 200% positive peaks.
Wheatstone is not responsible for damage to your equipment or transmission
facility that may result from using the AM–10HD’s incredible modulation ca-
pabilities in an “aggressive” manner! Nor is it liable for interference to your
adjacent channel neighbors!
Digital Output
Adjusts the peak audio output level at the AM analog chain’s digital output. The
resulting peak output levels in dBFS
are indicated by the front panel and
remote GUI bargraph meters. This
control can be set to OFF or adjusted
over the range of ‑35.95dB to 0.00dB.
DeEmphasis
Sets a complementary de‑em‑
phasis to that set in the AM Limiters
screen and applies it only to the AES3 digital output of the analog side processing
chain.
PreDelay
Allows the AES3 output of the analog side processing chain to be taken prior to
the Diversity Delay. This feature would be used when the transmitter includes its
own Diversity Delay for the analog side of the AM signal.
LF Tilt
This section contains the three controls that are used for compen‑
sating the infrasonic frequency response of the AM transmitter in
order to compensate for inadequacies in its low frequency response.
Such inadequacies typically manifest in the inability to accurately
control modulation on low frequency waveforms that have been
peak limited by clipping.
Low Frequency Tilt Correction can help to correct for the low
frequency response inadequacies of older style AM transmitters
where inter‑stage transformers and/or coupling capacitors limit the
frequency response at low frequencies due to their “high‑pass, DC‑
blocking” nature.
Because high waveform fidelity is required for good peak con
‑
trol, and because transmitters with such inadequacies do not have
frequency response extending down to near DC, the clipped waveforms generated
by the audio processor will not pass through such transmitter without undergoing
low frequency losses and phase shift. This causes the waveform to “tilt,” which can
cause the top of the clipped waveform to exceed 100% modulation, but only at low
frequencies. In order to prevent over modulation on such waveforms the audio level
into the transmitter must be reduced, which results in lost loudness and coverage.