Hi Ernst,
I can not confirm or say it is not so regarding your measurements as I have to stop the testing. As I said files has been normalized.
Voice Rx level sensitivity testing
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Well, i can tell that i hear level 24 , even 27, but only that it is there, just a bit over the noise. If i was meant to understand level 24, i would fail. So I voted 21.
So to really determine how deep you can hear in the noise, random words do the trick. 73, martin
I vote 18 but 21 is Q3 ...
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I found your signal even more useful than expected, while testing link margin during a thunderstorm. I know I lost at least 15dB at its worst, and that happened while the streets were still dry. I could "see" the thunderclouds drifting towards the sat path. When the rain started, signals went up
Using WebSDR, I saw that my own signals were not attended as much which is strange (2.4 is the max water absorption frequency ?!?)
Having longer signals at a level would be useful. "zero" is short to measure.
Is 0dB the beacon level? I don't think it is, but propagation is strange right now.
I any case, this is useful, but perhaps t needs to be there structurally. Good stuff!
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I found your signal even more useful than expected, while testing link margin during a thunderstorm. I know I lost at least 15dB at its worst, and that happened while the streets were still dry. I could "see" the thunderclouds drifting towards the sat path. When the rain started, signals went up
Using WebSDR, I saw that my own signals were not attended as much which is strange (2.4 is the max water absorption frequency ?!?)
Having longer signals at a level would be useful. "zero" is short to measure.
Is 0dB the beacon level? I don't think it is, but propagation is strange right now.
I any case, this is useful, but perhaps t needs to be there structurally. Good stuff!
If you lose so much signal then it is probably water on the feed or whatever, if you have a canopy on the feed then you won't don't see such attenuation levels during rain. Contrary to impossible to erase believe, 2.4 GHz is NOT a water absorption frequency. The earliest water vapor resonance frequency is 22 GHz.
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Maybe try this calculator in excel or matlab. In excel specify your set-up in the yellow fields, don't change the green fields and in the end it returns in orange the SNR in dB which is probably the best you can achieve on the waterfall. Filled in is already my setup.
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I do not understand the calculation results of the excel table.
At the moment when you receive the transponder noise, should the SNR change only insignificantly with larger antenna diameters?
A twice as large antenna area (so a 1.414 times larger diameter) yields 3 dB which is a factor two. See also https://www.electronics-notes.…enna-gain-directivity.php
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A twice as large antenna area (so a 1.414 times larger diameter) yields 3 dB which is a factor two
Yes, I know, but will not double the SNR if the TP noise was received before....
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Yes, I know, but will not double the SNR if the TP noise was received before....
The size of the dish will not do that, why?
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... but your excel sheet does that ..
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The size of the dish will not do that, why?
The excel sheet calculates the expected signal to noise ratio (SNR) in dB of your transmission that is received by the satellite, all parameters in yellow affect that SNR since a bigger dish means that you have a higher gain so more signal (but not noise) arrives at the satellite. The analogy is: a better pointer makes a brighter spot.
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Spotted the first rain cell anomaly when a weather front passed over my station. Conclusion is that the signal normally varies by +/- 0.5 dB which seems related to relative humidity, and that during severe rain (you need pouring rain of several mm per hour) results in 1,5 dB signal loss.
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Hi together,
last days we had extreem rain about 40lit in 1 hour. No TV-Rx with 80m dish from Astra. The upper beacon from qo100 falls down about 7dB.
73 Wilhelm dl6dca
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Hi together,
last days we had extreem rain about 40lit in 1 hour. No TV-Rx with 80m dish from Astra. The upper beacon from qo100 falls down about 7dB.
73 Wilhelm dl6dca
Wow! We can get a lot of rain in the Netherlands but 40mm in one hour is really exceptional.
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Dear OMs,
I performed S/N ratio measurement on 29/07/2021 using a R&S FSP38 Spectrum Analyzer. I have a 1.2m dish with dual-band coaxial feed fitted with a SPCR5300 LNB (measured noise figure 0.9 dB). An AOR AR5000A receiver with AGC off was used for these measurements. I measured on Rx's IF output – 10.7 MHz.
The channel power measurement for 2500 Hz bandwidth (SSB) was performed. As a signal source I used a middle PSK beacon. For noise power density measurement, I used clear free frequency, 10 kHz below mid beacon. I used an RMS detector, since there is no correlation between the peak value of the video voltage and noise power. The resulting S/N ratio was 16.49 dB with fluctuation a few tenths of dB. For the different bandwidth (BW), for example 1 Hz, the result must be corrected by 10 · log (ChanBW), i.e. 10.log(2500) = 33.98 dB. So, my measured result for 1 Hz bandwidth is giving S/N ratio 50.47 dB. The achieved results very well correspond with Goonhilly and IS0GRB Earth Station S/N values.
As was formerly written by Achim, Peter and others, when transponder noise is dominant over the Rx noise, then there is no room to improve S/N ratio and the above described test is becoming a hearing test or operator capability test, not an equipment test.
73 & BR, Rasto OM6AA
