Philips Avalon CTS M2720A, Service Manual, Page: 74 / 110

7 Troubleshooting RF Interference
68
Using the Service Support Tool
How to proceed:
1 Connect the base station to the fetal monitor.
2
Switch on the fetal monitor’s recorder.
3 Connect the PC loaded with the Service Support Tool software to the base station using the PC
interface cable (M1360-61675).
4 Register the transducers to the base station, so that they are active.
5
Use the Service Support Tool software to display the RSSI signals, for all slots, and additionally the
amount of squelch noise for slots 1 and 2. Refer to the
Service Support Tool Help for details.
6 Go to a different room within the intended operating area and place the fluid-filled bag there. You can
place the bag in a bath tub to get a realistic indication of the area of reach when monitoring underwater
(a metal bath tub and underwater monitoring both reduce the operating range).
7 Go back to the PC and check the RSSI signal displayed by the Service Support Tool. If the RSSI bar is
yellow or green, then the signal quality is adequate. Poor quality, or loss of, RF signals will result in a
low, red RSSI signal, together with a high amount of squelch. See the
Service Support Tool Help . Check
for frequent mode annotations on the recorder trace. Loss of RF signal will show as dropouts on the
recorded trace. This indicates that you are close to the operating limit of the RF signal range.
8
Repeat to cover the whole area of intended operation. This is the limit of the range where the system
can transmit and receive parameter measurements reliably.
RF Interference
You may encounter RF-related problems other than those associated with the area of reach. Problems
concerning RF link stability are due to RF interference. There are two categories of interference:
• On-channel or narrowband interference
• Broadband interference
One-Channel or Narrowband Interference
This is defined as an interference source that occupies the same bandwidth as the transmitter and only
interferes with one channel or two frequency adjacent channels.
It is likely that the channel is set to the same frequency as another telemetry unit, or there is interference
from an external source, such as a broadcasting station. Be sure to check for adult and fetal telemetry
channels. Also check for other radio devices such as walkie-talkies, paging systems, ambulance systems,
and so forth.
If you encounter narrowband RF interference you can:
• Identify the “problem” frequencies or frequency ranges (see “Scanning the Available Frequency Range”
on page 69).
• Exclude these frequencies or frequency ranges (see “Excluding Frequencies” on page 70).
• Set the base station or the transducers to fixed frequency operation (see page 70).