Digital BC signal measured with field strength meter for analogue
Because I had only the electric field strength meter for the analogue, it thought whether the electric wave of the terrestrial digital broadcasting was able to be measured by this though the electric wave of digital broadcasting on the present place and the electric wave of the ground analog broadcasting were transmitted. The correction value became +7dB. Electric field strength was comparing measured by using the Spectrum analyzer.
What is the Spectrum analyzer?
Spectrum analyzer takes the frequency in a horizontal axis (X axis), and is a measuring instrument in the spindle (Y axis) like to the oscilloscope that displays decibel (dB) as for the voltage or the electric power waveform. It is called spectrum analyzer for short. There is no distinction between the voltage and the electric power because it is decibel (dB) display. (For instance, it is ten times in the voltage, and 100 times in the electric power in case of 20dB. )
It is a measuring instrument that can see the frequency element to be brief. It is called a spectrum analyzer.
Comparing digital broadcasting wave and analog wave seen with spectrum analyzer(RBW:300kHz)
This shape of waves is comparing waveform of the terrestrial digital broadcasting electric wave and the analog electric wave seen with spectrum analyzer. The range of RBW:300kHz and 485MHz-685MHz is measured.
It becomes a result of a measurement equal with what measured with the electric field strength meter that measures a past, analog electric wave. It became an equal result of a measurement ..952 type TV/SAT electric field strength measuring instrument (RBW:280kHz) of the leader whom I was handling...
23CH: television [setouchi] and 25CH: the Inland Sea broadcasting and 35CH: Television Okayama is electric wave of the ground analog broadcasting (transmitting power 20kW). It is an electric wave of the voice that the electric wave under each channel is about 6dB in the upper part of 4.5MHz small in the image.
18CH: television [setouchi] and 20CH: the West Japan broadcasting and 21CH: the San-yo broadcasting and 27CH: television Okayama and 30CH: the Inland Sea broadcasting and 32CH: NHK General and 45CH: NHK Educational is terrestrial digital broadcasting (transmitting power 2kW). The terrestrial digital broadcasting is OFDM (Orthogonal Frequency Division Multiplexing) In the method, several thousand careers are very adjacent to full bandwidth of 5.57MHz and queue up. Because the electric power is distributed in the entire band, the measurement of electric field strength should measure the sum total of one career electric power channeled all.
Correction value of measurement in field strength meter for analogue
(Resolution Band Width)(bandwidth of IF filter of Spectrum analyzer)It is 300kHz in case of [gakono]. It is necessary to measure the terrestrial digital broadcasting by 20 times this band because it sends it with one channel about 6MHz. In a word, 20 times correspond to 13dB in the electric power. (10*log20= about 13)What added to this shape of waves by about 13dB becomes electric field strength of the terrestrial digital broadcasting. When 13dB is added to measurements of digital broadcasting above (about -65dB of the screen), it becomes about -52 a dB on the screen. Because this becomes a value that fell more than the analog broadcasting by about 10dB, and is almost corresponding to the difference 10dB of the broadcasting electric power, I understand this is correct.
It is necessary to do by -6 the dB to correct a cusp value of the electric field strength meter for the analogue to the mean value because it seems that electric field strength of the terrestrial digital broadcasting is displayed by the mean value (Because it is all electric powers in intraband, it must be good in the mean value). Then, +13 -6 It is understood to only have to add the correction of =+7dB. (Please teach if these ideas are wrong. )
When electric field strength of the ground digital electric wave is measured with the electric field strength meter (cusp value demodulation and RBW:280-300kHz) that measures a past, analog electric wave, it is understood to have to correct +7dB to the measured value. If this is understood, it seems not to have to buy the electric field strength meter for the terrestrial digital broadcasting especially for the time being.
However, items such as MER (Modulation Error Ratio: modulation error margin ratio) and BER (Bit Error Rate: bit error rate) cannot be measured with the equipment for the analogue. If it is an antenna system that makes unquestionable in a past analog broadcasting even if this cannot be measured, the terrestrial digital broadcasting doesn't have the problem either. It only has to adjust the antenna and the booster according to this policy.
Comparing digital broadcasting wave and analog wave seen with spectrum analyzer(RBW:1MHz)
This shape of waves is comparing waveform of the terrestrial digital broadcasting electric wave and the analog electric wave seen with spectrum analyzer. The range of RBW:1MHz and 485MHz-685MHz is measured.
It is the one that above-mentioned RBW was changed from 300kHz to 1MHz. The level of the terrestrial digital broadcasting is growing more than the above-mentioned one by about 5.2dB because it increases RBW(Resolution Band Width) (bandwidth of the IF filter of the Spectrum analyzer) by a factor of about 3.3.
In addition, it is necessary to measure the terrestrial digital broadcasting by six times the band because it sends it with one channel about 6MHz. In a word, what added to this shape of waves by about 7.8dB becomes electric field strength of the terrestrial digital broadcasting. It doesn't measure it in bandwidth 6MHz this time.
Because even the next channel is measured when RBW is widened any further, it is not significant. Actually, the verge part has disappeared in the adjacent channel of 20CH and 21CH because of the next channel.
The main specification of FSL18 of Rohde-Schwarz R&S
- Range of frequency: 9kHz-18GHz
- I/Q recovery bandwidth: 28MHz
- 1.2dB of level measurement precision :< (With 18GHz. )
- Resolution bandwidth: 1Hz-10MHz(It is 20MHz by 0 spans. )
- Fast measurement:
Measurement speed: 80 sweeps/second(By 0 spans. )
The frequency counter: It is < 50ms in resolution 0.1Hz.
- Various measurement functions: Gain measurement, AM/FM/PhiM recovery, and another power measurement and noise factor/by power sensor connection
- Size (W x H x D): 342.3mm 158.1mm 367.0mm(The steering wheel is excluded. )
- 8kg in weight