Magic Number?

04-21-2005

What is the magic number 149? What is magic about it w.r.t NS?

streaker69 · 04-21-2005

Quote:

Originally Posted by adonis

What is the magic number 149? What is magic about it w.r.t NS?

Ever consider using the search feature? If you'd use it, you'd get your answer. It's about the 4th thread displayed.

04-21-2005

Yes I searched the FAQ and everywhere. There was one place where Thorn says that 149 should be subtracted from SNR, sig and noise if the readings are taken from an orinoco device.

However after that SNR=sig-noise is not true anymore!

streaker69 · 04-21-2005

Data format

I think that explains it.

04-21-2005

This link says that 149 is to be subtracted from only the sig and noise. However here SNR, Signal & Noise Thorn subtracts 149 from all the three values.

Thanks

streaker69 · 04-21-2005

Quote:

Originally Posted by adonis

This link says that 149 is to be subtracted from only the sig and noise. However here SNR, Signal & Noise Thorn subtracts 149 from all the three values.

Thanks

The subtraction is to give the displayed values in dB.

04-21-2005

I thought 149 is to offset a reading difference.

The sig and the noise level are in dBm i.e. w.r.t 1mw baseline.

In log scale SNR=sig-noise which is in dB. Hence 149 should be subtracted only from the signal and the noise.

Why I am confused is because Thorn asked to subtract 149 from all the three values here SNR, Signal & Noise

Did he just miss it or am I missing something?

Thanks in advance.

Thorn · 04-21-2005

Quote:

Originally Posted by adonis

I thought 149 is to offset a reading difference.

The sig and the noise level are in dBm i.e. w.r.t 1mw baseline.

In log scale SNR=sig-noise which is in dB. Hence 149 should be subtracted only from the signal and the noise.

Why I am confused is because Thorn asked to subtract 149 from all the three values here SNR, Signal & Noise

Did he just miss it or am I missing something?

Thanks in advance.

It's a mistake. Subtract 149 from the Signal and the Noise, not the SNR. The SNR figure will be accurate whether or not the Signal and Noise figures are converted to dB.

04-21-2005	#1 (permalink)
adonis Posts: n/a	Magic Number? What is the magic number 149? What is magic about it w.r.t NS?

04-21-2005	#4 (permalink)
streaker69 Psychic Amish Stumbler Join Date: Jul 2004 Location: Virginville, BlueBall, Bird In Hand, Intercourse, Paradise, PA Posts: 11,798	Data format I think that explains it. __________________ "One of these days, I'm going to cut you to pieces." If you're offended by this post, please feel free to report it to one of the many helpful moderators of this forum. Thank you.

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04-21-2005	#3 (permalink)
adonis Posts: n/a	Yes I searched the FAQ and everywhere. There was one place where Thorn says that 149 should be subtracted from SNR, sig and noise if the readings are taken from an orinoco device. However after that SNR=sig-noise is not true anymore!

04-21-2005	#5 (permalink)
adonis Posts: n/a	This link says that 149 is to be subtracted from only the sig and noise. However here SNR, Signal & Noise Thorn subtracts 149 from all the three values. Thanks

04-21-2005	#7 (permalink)
adonis Posts: n/a	I thought 149 is to offset a reading difference. The sig and the noise level are in dBm i.e. w.r.t 1mw baseline. In log scale SNR=sig-noise which is in dB. Hence 149 should be subtracted only from the signal and the noise. Why I am confused is because Thorn asked to subtract 149 from all the three values here SNR, Signal & Noise Did he just miss it or am I missing something? Thanks in advance.