ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

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glovisol
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by glovisol » Thu Sep 27, 2018 6:13 am

There are many methods to determine the noise figure of a receiver and they are all valid, provided they give the right result. For instance another practical method is to use a noise figure meter.

The methods you propose give a noise figure of 15 dB @ 14 MHz.

In my revised Table 1 (revised RX noise table) you find a 14 MHz noise floor value of -127 dBm, which corresponds on Table 2 (TABLE 2 – Conversion between noise floor and receiver’s noise figure) to a Noise Figure: (15.4-13.4)/2 = 14.4 db.

In conclusion there is no controversy or contradiction among the various methods, nor I do imply that the one I propose is superior to another: in my opinion it seems merely quicker and simpler, because based on tabular data.

Finally let us not forget that the main point of of this thread is not to discuss the best method to assess receiver's noise figure, which we have seen to be of marginal importance in this development, but rather to propose a way to statistically assess the quality of a receiving system with respect to antenna noise in order to have some knowledge of the noise environment in which our receiving system is operating.

Thanks, I do appreciate your suggestions and assistance,

glovisol

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glovisol
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by glovisol » Thu Sep 27, 2018 1:20 pm

MORE ON NOISE FIGURE ASSESSMENT

Hi Roger,

Concerning measurement of noise figure, I do not seem to be able to confirm the results of your proposed methods which would appear to disagree with each other and ask you to kindly help me. Here are my findings on my standard RSPduo. FFT method always with Rectangular FFT window and using all your proposed settings and the 1 KOhm termination on the Hi Z input, of course. Even measuring Tuner 1 at the coxial input with 50 Ohm termination discrepancies still exist.

Frequency 1900 KHz
METHOD 1
Noise Floor: -130 dBm
-130 -10*LOG10(2000) = -130 - 33 = - 163
174 - 163 = 11 db NF
METHOD 2
Noise Floor: -145 dBm
RBW = 26.86Hz
10*LOG10(26.86)= 14.29
-145-14.29 = 159.29
174-159.29 = 14.71 dB NF

Frequency 3750 Hz
METHOD 1
Noise Floor: -130.2 dBm
-130 -10*LOG10(2000) = -130.2 - 33 = - 163.2
174 - 163.2 = 10.8 db NF
METHOD 2
Noise Floor: -141.2 dBm
RBW = 67.14Hz
10*LOG10(67.14)= 18.27
-141.2 - 18.27 = - 159.4
174-159.4 = 14.6 dB NF

Frequency 7200 Hz
METHOD 1
Noise Floor: -126.5 dBm
-126.5 -10*LOG10(2000) = -159.5
174 - 159.5 = 14.5 db NF
METHOD 2
Noise Floor: -140.3 dBm
RBW = 40.28 Hz
10*LOG10(40.28)= 16
-140.3 - 16 = - 156.3
174-156.3 = 17.7 dB NF

Frequency 14200 Hz
METHOD 1
Noise Floor: -125.7 dBm
-125.7 -10*LOG10(2000) = -158.7
174 - 158.7 = 15.3 db NF
METHOD 2
Noise Floor: -139.3 dBm
RBW = 47 Hz
10*LOG10(47)= 16.72
-139.3 - 16.72 = - 156
174-156 = 18 dB NF

Kind regards,

glovisol

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Roger
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by Roger » Thu Sep 27, 2018 5:19 pm

glovisol wrote:MORE ON NOISE FIGURE ASSESSMENT

Hi Roger,

Concerning measurement of noise figure, I do not seem to be able to confirm the results of your proposed methods which would appear to disagree with each other and ask you to kindly help me. Here are my findings on my standard RSPduo. FFT method always with Rectangular FFT window and using all your proposed settings and the 1 KOhm termination on the Hi Z input, of course. Even measuring Tuner 1 at the coxial input with 50 Ohm termination discrepancies still exist.

Frequency 1900 KHz
METHOD 1
Noise Floor: -130 dBm
-130 -10*LOG10(2000) = -130 - 33 = - 163
174 - 163 = 11 db NF
METHOD 2
Noise Floor: -145 dBm
RBW = 26.86Hz
10*LOG10(26.86)= 14.29
-145-14.29 = 159.29
174-159.29 = 14.71 dB NF


Frequency 14200 Hz
METHOD 1
Noise Floor: -125.7 dBm
-125.7 -10*LOG10(2000) = 125.7 -33 = -158.7
174 - 158.7 = 15.3 db NF
METHOD 2
Noise Floor: -139.3 dBm
RBW = 47 Hz
10*LOG10(47)= 16.72
-139.3 - 16.72 = - 156
174-156 = 18 dB NF

Kind regards,

glovisol

Here are a couple of tests at the frequencies that you used and my results along with screenshots. They were done using the HI-Z port terminated with a 1K resistor. The Rectangular Window was selected under SETT and the FFT average was 128. 1800 Hz. filter in USB.

When selecting the 160m band in SDRuno the LO will be at 1900 Hz so this is not a good test frequency. You need some offset. Here are my results. I have adjusted the scale under SETT to zoom in on the noise floor. The baseline noise floor is selected with the cursor in SDRuno.

Frequency 1930 KHz.
1900.png
1900.png (108.31 KiB) Viewed 4208 times
METHOD 1
Noise Floor: -132.5 dBm
-132.5 -10*LOG10(2000) = -132.5 - 33 = - 165.5
174 - 165.5 = 8.5 dB NF

METHOD 2
Noise Floor: -151.2 dBm
RBW = 26.86Hz
10*LOG10(26.86)= 14.3
-151.2-14.3 = 165.5
174-165.5 = 8.5 dB NF

Frequency 14.200 KHz.
14200.png
14200.png (110.12 KiB) Viewed 4208 times
METHOD 1
Noise Floor: -127.0 dBm
-127.0 -10*LOG10(2000) = 127.0 - 33 = 160.0
174 - 160 = 14.0 dB NF

METHOD 2
Noise Floor: -143.1 dBm
RBW = 47 Hz
10*LOG10(47)= 16.7
-143.1 - 16.7 = - 159.8
174 - 159.8 = 14.2 dB NF

Roger

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Roger
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by Roger » Thu Sep 27, 2018 5:59 pm

glovisol wrote:2. PREDICTED ANTENNA NOISE FLOOR

Table 3, together with the fully calibrated RSP receiver Noise Floor dBm display, is an invaluable tool that lets you immediately determine the noise characteristics of your antenna and the quality of the area in which your antenna is operating. To fully qualify a Receiving System, several tests on as many days will be required, but nevertheless this method allows quick and easy determination of system noise parameters. An example will demonstrate the value of this operating procedure.

26/09/18 - Examples below have been amended and measured values now correct.

EXAMPLE 3
On Sept. 23, 2018, at 15:00 GMT, our RSP receiver, connected to a Beverage antenna with N-S orientation and located in a rural area, provides the following measurement data.

F = 1.950 MHz / SR=3.52 / DEC=16
IF AGC= ON / RF AGC=OFF/30
GAIN=65.7 dB
NOISE FLOOR = -110 dBm
Looking at Table 3, we see that this value is even better than the best in the 1.8 MHz row, even considering the “old” galactic noise value of -104.5 dBm plus the rural decile deviation of -3.5 dB for a total noise floor of – 108 dBm. On the other hand the antenna is only 135 m long and therefore it is possible that the low level of received noise is due to excessive antenna loss at this frequency.

F = 3.600 MHz / SR=2.2 / DEC=4
IF AGC= ON / RF AGC=OFF/30
GAIN=57.2 dB
NOISE FLOOR = -93 dBm
Looking at Table 3, we see that this value belongs to the “Rural” location: -94.2 (Noise Floor) +3.5 (decile deviation) for a total of -97.7 dBm.

F = 7.200 MHz / SR=2.64 / DEC=8
IF AGC= ON / RF AGC=OFF/30
GAIN=42.8 dB
NOISE FLOOR = -105 dBm
By looking at Table 3, we are in the “Rural” ballpark.

These measurements and comparisons obviously cannot be made when in presence of rainstorm/lightning noise, but apart from this precaution, several measurements over a significant period of time will provide a firm assessment of Receiving System noise performance. The above example, if confirmed with several tests, would evidence that my receiving system and Beverage antenna are installed in a quiet area, leaving me little or no room for improvement. If you are in doubt about the noise performance of your antenna, or suspect your area to be too noisy, then this proceure will immediately give you an idea of what the ideal situation should be.
You bring a number of interesting points to light about the effect of different types of noise on the reception of HF signals. Noise studies have been reported in the technical literature for over 75 years. The report you mentioned has been updated many times with the last version released in 2016. The Radio Society of Great Britain (RSGB) is also studying noise with a focus on man-made noise which is getting worse due to the proliferation of electronic consumer devices.

Unfortunately your conclusions about how to use the data in ITU-R P.372-13 are not entirely correct. You cannot make a comparison with noise received on your antenna and the RSP with that obtained during ITU tests without considering several factors:

- The data in the ITU report was calculated based on a lossless monopole over perfect ground. This reference antenna is omni-directional and no resistive wire loss. When making these kinds of tests a short monopole is used over a substantial ground plane (copper mesh and radials) and a correction factor is applied to the data (obtained using calibration equipment.) The transmission line between the antenna site is also measured. When using dBm we are using 50 ohms as a reference and there also has to be compensation for the impedance of the antenna used.

- When using any other antenna one has to consider the Gain, Directivity and impedance match at the frequency band of interest in order to make valid calculations and comparisons. Even a simple dipole over ground (not free space) can have up to 8 dB of gain over an isotropic radiator. While Beverage antennas have excellent directivity, because they are close to lossy Earth, they do not produce absolute gain; their gain is typically from −20 to −10 dBi. https://en.wikipedia.org/wiki/Beverage_antenna#Gain



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glovisol
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by glovisol » Fri Sep 28, 2018 8:55 am

I could not agree more with what you say.....the point is I still have to complete this series of posts, as stated in my # 3 post...
In the next post we shall see how to use the above expressions and tabled data.
But I was diverted by your Noise Figure observations. The questions you are addressing will be covered in the next post, now that the N.F. issue has been put to bed.

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glovisol
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by glovisol » Mon Oct 01, 2018 2:00 pm

4. ASSESSING ANTENNA DEPENDENT SYSTEM NOISE PERFORMANCE


Revised 03/10/2018: Below I have changed the denomination of the antenna characteristic constant from k to r, otherwise there would be confusion between this constant and Boltzmann's constant shown in part 3, MATHEMATICS. Apologies for any inconvenience caused.

To recap, the power Pn in dbW shown in (7) and (8) is the mean noise power available from an equivalent loss free antenna at the temperature of 17°C or 290°K. Thus the Noise Floor dBm values Pd, calculated by (6) and shown in Table 3, while providing a basic guideline, do not take antenna characteristics into account. To obtain more accurate data, we must consider the equivalent Noise Field Strength En whose value also depends on the Antenna Effective Aperture. The general expression relating En to Fa is as follows:

En = Fa + (20*LOG10(f)) + B - r [db(uV/m)] (10) (*)
with f in MHz, B=10*LOG10(b) and r is a constant depending on antenna characteristics.
Or, solving for Fa:
Fa = En – (20*LOG10(f)) – B + r [dBm] (11)

This means that the constant r (antenna characteristic constant) to find the the r.m.s. value of the Field Strength can also be used to correct the value of the Noise Floor.

The ITU recommendation gives values for two antenna types as follows:
r = 95.5 for a short vertical monopole over perfect ground plane and
r = 96.8 for the reference isotropic antenna in free space.

Therefore for a short vertical monopole the correction constant r’ = 96.8 – 95.5 = 1.3 db and all Noise Floor values in Table 3 will be corrected by -1.3 dB (higher noise level).
Constant r does not take into account transmission line loss between antenna and receiver and this datum, easily found/calculated, must be factored in to determine the final Noise Floor value.

Correction expressions and constants for various HF “thin with respect to λ” antenna types, such as long wire and dipoles, will be given in the next post.

(*) Derivation of this formula will be given in the "appendix" post

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Roger
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by Roger » Mon Oct 01, 2018 11:08 pm

glovisol wrote:
The ITU recommendation gives values for two antenna types as follows:
k = 95.5 for a short vertical monopole over perfect ground plane and
k = 96.8 for the reference isotropic antenna in free space.

Therefore for a short vertical monopole the correction constant k’ = 96.8 – 95.5 = 1.3 db and all Noise Floor values in Table 3 will be corrected by -1.3 dB (higher noise level).
You do not have to correct the values in Table 3 for the short monopole. They were calculated using a lossless short monopole based on a Gain of -1.25 dBi. ITU defines a lossless antenna as one with no power losses (resistive or ground) so that (antenna power out)/(antenna power in) =1. An adjustment does have to made to compensate for gain if any other antenna is used.

If you use a half-wave dipole in free space (Gain of 2.15 dBi) k is 98.9. For a dipole over ground with a typical gain of 7.5 dBi k would be 104.3. As the gain of the antenna increases the observed noise floor on the receiver will increase. For example, a ham using a 20m dipole would have to add 8.75 dB (104.3-95.5) to the ITU 372 Fa numbers to compensate for the additional antenna gain.

Directivity and polarization are also factors to consider. An antenna with gain will have directional characteristics so man-made noise may appear lower on the receiver with a directional antenna than a vertical with an omni-directional pattern (if the directional antenna is pointed away from the noise source). If the antenna main lobe is pointed towards the noise source (i.e. a house full of noisy consumer devices) the noise floor may be higher than the vertical. The elevation angle of the antenna also needs to be considered. Some observers have stated that man-made noise tends to have more vertical polarization (although this is subject to debate.)

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glovisol
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by glovisol » Tue Oct 02, 2018 5:45 am

First of all there is a question of method. It is impossible to carry on a meaningful series of posts if you persist in posing problems at every step, so it becomes hard for readers to follow a complete tractation especially while my work is in progress. I politely did not complain, but what was the purpose of your interruption on the methods to assess receiver's noise figure, when the emphasis was elsewhere? It looks just as useless polemics to me...

Second, if you are such an expert, why you do not research and write an analogous tractation yourself?

Third, forgive me, but you are wrong in your arguments and do not understand what ITU and other researchers are doing. See for instance Radio Science, Vol. 42 among literally tens of different publications with which, no doubt, you are also acquainted.

Fourth, in my last post the main POINT IS THAT YOU CAN CORRECT THE CALCULATED N.F. VALUES DEPENDING ON THE CHARACTERISTICS OF THE INDIVIDUAL ANTENNA, NOT WHAT IS THE REFERENCED ANTENNA (even if the reference is the isotropic!). This is looking at your finger and missing the moon, just for the sake of polemizing.

One voice in the crowd: Radio Science, Vol. 42, RS4026, 2007 by Anthony C. Fraser-Smith
……Given a particular antenna, the gain factor is usually combined with the constant 96.79 to give an antenna-dependent constant. For example, for a short vertical monopole above a perfectly conducting ground plane, the gain G is -1.25 dB and (-G - 96.79) in equation (4b) is replaced by the new constant 1.25 - 96.79 = - 95.54. A list of these constants for a variety of electric field antennas is provided in the study by Hagn and Shepherd [1984]…..
Fifth ( to look good, perhaps?) you again anticipate what I have still to expose: e.g. the criteria and methods to be used to obtain the corrections. Again, if I do not meet this constant provocation, it seems I am wrong, if I meet it, then the reader will not be able to make head or tails of what is going on.

To conclude, it is not worthwhile to carry on under such pestering: nor the Community Forum, nor myself have anything to gain by this constant polemizing. You are free to carry on and finish this work, as you would seem keen to do. At the end of the day politeness, courtesy and spirit of service and cooperation are much more important than expertise on radio noise.

Kind regards,

glovisol

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Tech_Support
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by Tech_Support » Tue Oct 02, 2018 8:20 am

Gentlemen,
I sincerely hope that this doesn't become an acrimonious exchange. This has been a fantastic thread with tremendously valuable information to widest possible community of radio listeners and not just RSP owners.

Glovisol, I want to thank you for starting this thread and for the fabulous effort and information that you have put into it. It is very easy when becoming enmeshed in the technical details for comments to appear brusque when they are not intended. I don't believe for a second that Roger intended to offend you, but was probably just enjoying the exchange of valuable knowledge.

I greatly hope that you will both continue to share your outstanding experience and knowledge on this and other forums as it is a great service to the community of RSP users.

Sincerely

Tech_Support

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glovisol
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Re: ASSESSING THE PERFORMANCE OF THE RSP RECEIVER SYSTEM IN HF

Post by glovisol » Wed Oct 03, 2018 11:12 am

Thanks Tech_Support, for your words of encouragement.

In my last post, PART 4, I have changed the denomination of the antenna characteristic constant from k to r, otherwise there would be confusion between this constant and Boltzmann's constant shown in part 3, MATHEMATICS. Apologies for any inconvenience caused.

PART 5 will follow shortly.

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