innomar SBP smart - HF (100 Khz) Data Channel; How Can I Switch off the HF Channel; How Can I Switch off HF Data Recording; How Can I Reduce the HF Transmit Power

User’s Manual INNOMAR Parametric Sub-Bottom Profilers / SESWIN 159
Innomar Technologie GmbH (2023-01) 159
13.2 HF (100 kHz) Data Channel
13.2.1 How can I switch off the HF channel?
Q1: I do not need the data from the HF channel, I’m interested in the LF data only. Thus, I
would like to switch off the HF channel entirely and transmit LF only.
Q2: The HF channel causes interference with my multibeam, I need to switch this channel
off to improve MBES data quality.
The HF channel cannot be switched off independently from the LF channel. The high (primary)
frequencies (~100kHz) are necessary to generate the low frequencies (LF channel) used to
penetrate the seabed and get sub-seafloor information. If no HF ping is transmitted, there is no
LF ping produced.
To reduce acoustic interference, see section 13.1.5 on page 154.
13.2.2 How can I switch off HF data recording?
Q: I do not need the data from the HF channel, I’m interested in the LF data only. If I cannot
switch off the HF channel, can I switch off data recording for this channel to save storage
space?
The INNOMAR data formats contain both, LF and HF data in one file. Switching off one channel is
not possible.
If the INNOMAR data files are converted to third-party data formats, like SEG-Y, you can select
which channel(s) to convert.
For the (new) SES3 INNOMAR data format it is possible to split the data files into their separate
channels to separate SES3 files for each data channel. Afterwards you may delete the unwanted
data files.
13.2.3 How can I reduce the HF transmit power?
Q1: In my multibeam data I see artefacts caused by acoustic interference from the INNOMAR
SBP HF channel, especially in shallow water. How can I reduce the HF transmit power in
shallow water?
Q2: In extremely shallow water the HF data amplitudes are too high and clipped. How can
I reduce the HF transmit power to avoid this?
The LF transmit power depends on the HF transmit power. To ensure best performance for the
LF channel, the HF ping is transmitted at the highest possible power.
With the latest “medium-100” models it is possible to reduce the HF power. Please note, that
reducing the HF power by 6dB (signal amplitude 50%) will cause the LF power to drop by 12dB
(signal amplitude 25%). This will seriously affect seabed penetration.
To reduce acoustic interference, see section 13.1.5 on page 154.