SDRplay Community Forum

RECEIVING SYSTEM ASSESSMENT @ 3.8 MHz

Noise Floor assessment for the 3.8 MHz band is as follows:

Wavelength Wl @ 3.75 MHz: Wl = 300/3.75 = 80 m
Ratio L/Wl: R = 135/80 = 1.69
From "Beverage Antenna gain Vs. wavelength", Figure 1 in the cited reference: G = -2.5 dB referred to the isotropic.
Balun insertion loss is 0.5 dB. Total loss is 3 dB. To compare the measurement with data and criteria of Table 3, we must correct by adding 3.0 dB to measured noise values.

The graph shown below carries the raw measurements in ligt blue and the corrected measurement in red, compared to the noise leve ranges of "Rural" and "Quiet Rural". The Rural decile range extends for +/-3.5 dB, while the Quiet Rural range extends for +/- 3 dB. The noise peaks shown 22/10 to 25/10 and 28/10 to 29/10, caused by electrical activity due to stormy weather, are present at this frequency also.

In general, under average weather conditions, we can classify the receiving system under examination as located mid-way between Quiet Rural and Rural.

RECEIVING SYSTEM ASSESSMENT @ 7.2 MHz

Noise Floor assessment for the 7.2 MHz band is as follows:

Wavelength Wl @ 7.2 MHz: Wl = 300/7.2 = 43 m
Ratio L/Wl: R = 135/43 = 3.15
From "Beverage Antenna gain Vs. wavelength", Figure 1 in the cited reference: G = +1.5 dB referred to the isotropic.

Balun insertion loss is 0.5 dB and total gain is: 1.0 - 0.5 = 1.0 dB. Therefore the Noise Floor measurements taken with this antenna show a noise level of 1.0 dB more than the level we should have obtained if the measurement had been taken with an isotropic antenna. To compare the measurement with data and criteria of Table 3, we must correct by subtracting 1.0 dB to measured noise values.

The graph shown below carries the raw measurements in ligt blue and the corrected measurement in red, compared to the noise leve ranges of "Residential", "Rural" and "Quiet Rural". The Residential decile range extends for +/- 4 dB, the Rural range extends for +/- 3.5 db, while the Quiet Rural range extends for +/- 3 dB. The noise peaks shown 23/10 to 24/10 and 28/10 to 29/10, caused by electrical activity due to stormy weather, are present at this frequency also.

In general, under average weather conditions, we can classify the receiving system under examination as located in a Rural situation.

RECEIVING SYSTEM ASSESSMENT @ 14 MHz

Noise Floor assessment for the 14 MHz band is as follows:

Wavelength Wl @ 14 MHz: Wl = 300/14 = 21.4 m
Ratio L/Wl: R = 135/21.4 = 6.3
From "Beverage Antenna gain Vs. wavelength", Figure 1 in the cited reference: G = +5.0 dB referred to the isotropic.

Balun insertion loss is 0.5 dB and total gain is: 5.0 - 0.5 = 4.5 dB. Therefore the Noise Floor measurements taken with this antenna show a noise level of 4.5 dB more than the level we should have obtained if the measurement had been taken with an isotropic antenna. To compare the measurement with data and criteria of Table 3, we must correct by subtracting 4.5 dB to measured noise values.

The graph shown below carries the raw measurements in ligt blue and the corrected measurement in red, compared to the noise leve ranges of "Residential", "Rural" and "Quiet Rural". The Residential decile range extends for +/- 4 dB, the Rural range extends for +/- 3.5 db, while the Quiet Rural range extends for +/- 3 dB. The noise peaks shown 23/10 to 26/10 and 28/10 to 29/10, caused by electrical activity due to stormy weather, are present at this frequency also.

In general, under average weather conditions, we can classify the receiving system under examination as located mid-way between Rural and Quiet Rural situations.

RECEIVING SYSTEM ASSESSMENT @ 21.5 MHz

Noise Floor assessment for the 21 MHz band is as follows:

Wavelength Wl @ 21.5 MHz: Wl = 300/21.5 = 13.9 m
Ratio L/Wl: R = 135/13.9 = 9.7
From "Beverage Antenna gain Vs. wavelength", at the extreme of Figure 1 in the cited reference, we extrapolate: G = +7.5 dB referred to the isotropic.

Balun insertion loss is 0.5 dB and total gain is: 7.5 - 0.5 = 7 dB. Therefore the Noise Floor measurements taken with this antenna show a noise level of 7.0 dB more than the level we should have obtained if the measurement had been taken with an isotropic antenna. To compare the measurement with data and criteria of Table 3, we must correct by subtracting 7.0 dB to measured noise values.

The graph shown below carries the raw measurements in ligt blue and the corrected measurement in red, compared to the noise leve ranges of "Residential", "Rural" and "Quiet Rural". The Residential decile range extends for +/- 4 dB, the Rural range extends for +/- 3.5 db, while the Quiet Rural range extends for +/- 3 dB. The noise peak shown 23/10 to 26/10, caused by electrical activity due to stormy weather, are present at this frequency also.

In general, under average weather conditions, we can classify the receiving system under examination as located in the Rural situation.

RECEIVING SYSTEM ASSESSMENT @ 29 MHz

Noise Floor assessment for the 28/29 MHz band is as follows:

Wavelength Wl @ 29.0 MHz: Wl = 300/21.5 = 10,34 m
Ratio L/Wl: R = 135/13.34 = 13
Figure 1 in the cited reference does not go all the way up to 13 length to Wavelengt ratio, so I consider a worst case guess of : G = +8 dB referred to the isotropic.

Balun insertion loss is 0.5 dB and total gain is: 8 - 0.5 = 7.5 dB. Therefore the Noise Floor measurements taken with this antenna show a noise level of 7.5 dB more than the level we should have obtained if the measurement had been taken with an isotropic antenna. To compare the measurement with data and criteria of Table 3, we must correct by subtracting 7.5 dB to measured noise values.

The graph shown below carries the raw measurements in ligt blue and the corrected measurement in red, compared to the noise leve ranges of "Residential", "Rural" and "Quiet Rural". The Residential decile range extends for +/- 4 dB, the Rural range extends for +/- 3.5 db, while the Quiet Rural range extends for +/- 3 dB. The noise peak shown 23/10 to 26/10, caused by electrical activity due to stormy weather, are present at this frequency also.

In general, under average weather conditions, we can classify the receiving system under examination as located between the Rural and Quiet Rural situations.

NOISE FLOOR DATA FOR THE FIRST 15 NOVEMBER DAYS

In this and subsequent posts I am uploading data measured 1 to 15 November. Previous data taken in October shows the noise floor increase and instability due to stormy weather in Southern Europe, which caused big damages, as reported by the International Press. The last 15 days have seen weather gradually going to calmer and calmer states and this reflects on the settled noise floor data recorded in the second week.

NOISE FLOOR DATA FOR THE FIRST 15 NOVEMBER DAYS

Collected data for 7 and 14 MHz

NOISE FLOOR DATA FOR THE FIRST 15 NOVEMBER DAYS

Collected data for 21 and 29 MHz