History, but interesting to brows, if you have free time
Anyone working with the new x86 Raspbian
Run Piaware from Win/Mac Laptop/Desktop - Absolutely No Software Installed on Hard Drive
History, but interesting to brows, if you have free time
Anyone working with the new x86 Raspbian
Run Piaware from Win/Mac Laptop/Desktop - Absolutely No Software Installed on Hard Drive
Now, just to be clear, lets see a real antennas installation.
If everything else is identical and you’re confident it isn’t a power or software problem, then I’d go for the “except computing device” bit - the receiver is in two different RF noise environments. Maybe your laptop is unusually noisy.
That’s not how it works; amplifiers generally don’t consume power proportional to gain.
I’m not clear what your point was.
Ehm… decibells and “times” are linked exactly proportional decimal logarithmic law, and real power consumption including the another basic law… damn, dunno appropriate Eng word… Ideal operating coefficient? Perpetum mobile staff, you got it. More power you consume, more power you dissipate to nothing (LNA at dongle heats just like any other electronic. More gain - more pain).
That is how it work exactly. And there are no any other phisycs in our universe =)
So real RPI installation cannot show more than 25 db of onboard LNA gain because its datasheet limits. Otherwise - normal USB 2.0 may handle up to 40, but dongle gonna be melted.
Here’s a stackexchange answer that may help explain: Is amplifier power consumption relative to signal gain, or output volume? - Electrical Engineering Stack Exchange
The TL;DR is that for many amplifiers (and specifically class A is probably what we’re interested in here for a LNA), the power consumption is dominated by the static power consumption and does not depend on output power much at all. Also, it depends on output power, not gain, and there is a design limit on output power where the amplifier stops being linear and you can’t get more gain out of it.
FWIW the R820T has something like 50dB of configurable gain (as used by librtlsdr, anyway) and I can assure you that there is not a factor-of-100000 difference in power consumption between the two ends of the gain range.
And again - I don’t see any reason to struggle against statistics =) Just linked to USB 2.0 (real, not such as op RPIs) of old laptop and got about 30-50% data traffic encreased and twice larger “line of sight”. Just look at my profile.
My bad English… I mean exactly the power consumed and and power went out. Don’t try to catch a grammar mess. 10 times are 1 db only, 100 times are 10 db.
You say up to 50 db LNA can give. Yes, it can. But do you really sure that RPI USB may give 100 000 times more power? =) Even if LNA takes 1microAmps for zero ratio, than 50db are 0.1 A wich is already at the top border of RPI, but real signals a bit (actually, 50-100 times) more, and only a real USBus may handle more than 1A.
See? Oh, whatever, I got much more planes and distance, so that experimental and normal theoretical-based data is competely correct so there are no reasons to discuss =)
No, because it doesn’t need to.
The R820T datasheet is sorely lacking in useful data, but here is an example from another variable-gain LNA (Analog Devices AD8330):
Vdbs is the gain control voltage, nominally 30mV/dB (so this graph shows a gain control range of approx 0dB - 50dB). There is not much change in supply current (maybe 10%) across the entire gain control range - certainly nothing logarithmic there.
The “LNA wants more power” argument is a complete red herring. I’m not disagreeing with your observed numbers, but your explanation for why they changed makes no sense.
I get way more variation than that without making any changes - this is the past few days
The gain is on the antenna input (analog signal), not on the power input from USB. As in nano W levels of antenna power.
Example: http://otadtv.com/digital_tv/signals.html
The operating power used by any computer is generated by the digital transistors switching on/off and it’s wasted as heat.
Surely plausible and normal deviations.
But look here and pay attention to dates. I knew and been expected such result, I got it.
With all respect and best regards, I’m here not to discuss definitions i know in my native language and may translate wrong a little, but to gain (is it correct word usage now?) better result with less pain. I got it now just as planned by me and ruled by physical laws we all know. Nuff’said (is this correct “mic drop” synonym? )
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