On the field intensity measurement in the car using the signal analyzer MSA538 or the application software MAS9501, the location of the antenna can effect to the result.
We investigated to find the best antenna location to make the measurement in the car.
AM/FM radio wave measurement
We used the system below to make the field intensity measurement in the car. The antenna location is changed to find the best place.
The frequency related parameters and the information of the radio station are shown in below.
- AM Measurement Center Frequency:594kHz
- AM Measurement Span:50kHz
- AM Radio Station:NHK 1st Station (Kuki-city in Saitama)
- F M Measurement Center Frequency:79.5MHz
- FM Measurement Span:10MHz
- FM Radio Station:NACK5 (Hiki - county in Saitama)
Antenna Location and the Waveform (AM)
Antenna Location and the Waveform (FM)
Conclusion
The test results are concluded as follows.
| AntennaLocation | AM FieldIntensity | FM FieldIntensity |
|---|---|---|
| Luggage Space Window (Photo1A, 1F) |
46.8dBμV/m (Fig.1A) |
54.9dBμV/m（Fig.1F） |
| Luggage Space（Photo2A,2F） | 37.5dBμV/m（Fig.2A） | 49.0dBμV/m（Fig.2F） |
| Rear Seat（Photo3A,3F） | 52.4dBμV/m（Fig.3A） | 56.3dBμV/m（Fig.3F） |
| Front Seat（Photo4A,4F） | 56.5dBμV/m（Fig.4A） | 52.7dBμV/m（Fig.4F） |
| Out of the car（Photo5A,5F） | 67.5dBμV/m（Fig.5A） | 71.5dBμV/m（Fig.6F） |
For the case of AM, the best place is the front seat. On the other hand, the best place for FM is the luggage space window with the consideration of the noise floor. Comparing the out of the car, AM degraded around 11dB and FM degraded around 15 dB or more.
For the case of AM, the best place is the front seat. On the other hand, the best place for FM is the luggage space window with the consideration of the noise floor. Comparing the out of the car, AM degraded around 11dB and FM degraded around 15 dB or more.
It is recommended to apply the software correction when the measurement should be calibrated for the value at outside of the car.
Appendix–AM loop antenna is located on the dashboard in flat
The additional experiment was performed with AM antenna is located on the dashboard in flat as shown in Photo 6A.
On this case measured field intensity is as strong as the one when the antenna is located out of the car. Since the loop antenna responds to the strength of the magnetic field, the iron components around the antenna should be minimum for the best location.
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