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Ricardo Romanowski spam at rocketri.deHi Marcus, thanks for the Information! Though it might seem (and the temperature rise of ~40 degrees (i measured) between no power supply and a active chipset propably has *some* impact on the signal recieved) heat is not my main concern. My application is a raspberry zero with a oled screen and a battery attached that's a portable and slim sdr scanner. The raspberry performs superb battery-lifetime-wise (7 hours of idle/4 hours under 100% cpu load on a 1Ah single cell lipo) and i'm looking for the longest battery life that i can possibly archieve (as well as smallest size). I've continued searching for info on that topic after i sent the mail and found that there are indeed big differences between chipsets: https://www.reddit.com/r/RTLSDR/comments/2e9u7v/power_consuption/ which means that the E4000 uses (very) roughly 1/3rd of the energy of a R820T chipset. To bring that into some relation: for the raspberry to last 4 hours under full load on a 1000mAh battery (voltage regulator losses included) it propably draws ~250mA. Attaching a 300mA usb dongle would propably mean that i would get 1.8 hours of lifetime, while IF the E4000 only uses 110mA i'd get 2.7 hours of lifetime. Thats a significant difference (for me). So much for describing my application and concerns a little further. All the numbers are unproven so far (except for the 7h /4h lifetime of the zero, i did measure that), meaning that i need to experiment a little further and examine some chipsets power-consumption-vise myself.. As a sidenote, the battery has nominal 1Ah on 3.2V (lipo) meaning that after upconverting the voltage to 5V though a regulator (+loss) for that lifetime the pi zero propably draws even less current than 250mAh, thus increasing the impact of the power consumption of the rtl-sdr device for my battery life even further. Thank you so much for the description of temp-increase vs. signal quality - in order to understand it completely i propably have to dive a little deeper into general RF as you suggested. Maybe somebody is able to confirm the numbers for current draw, or even point me towards more energy-efficient rtl-sdr hardware (with a small form factor) Best regards, Ricardo On 06.02.2017 18:55, Marcus Müller wrote: > Hi Ricardo, > > I don't think so. Anyway, I'd doubt you can do much but tweaking gains > when it comes to the tuner – and really, the power consumption of that > would be in the milliwatts (datasheet [1] says 118mW typ); and > seriously, in a device that's typically supplied 1.5 V generated using > linear regulators from USB's 5V, I'd say your tweaking will have little > to barely measurable effect. > > However, you seem to be more worried about heat than power, actually – > so what's your problem with the heat? At least the datasheet claims a > Noise Figure of about 4.5 dB worst-band, presumably at room temperature. > Going up from 20 °C to 85 °C (max rec. operating temp, assuming your > device doesn't get higher) will increase your noise floor by the > temperature-weighted Boltzmann constant, i.e. k·𝚫T, so something like > -180 dBm/Hz; I'd have my doubts that this becomes a relevant problem, > even assuming a full noise-equivalent filter bandwidth of 8 MHz (= 66 > dBHz -> a noise floor increase by -114 dBm), since we're in a 8-bit > sampling regime (which means the Signal-to-Quantization-Noise-Ratio is > about 50dB (=1.76 dB + 6.02 dB · bits)). Of course reducing temperature > *does* increase SNR, especially in low-signal-power scenarious; however, > the thing you'd probably want the least in that situation is to reduce > the gain of the LNA. > > As usual, it's usually easier to help people when you know what exactly > they want to do – I can only guess your heat concern is noise-related. > Maybe it isn't. > > In any case, your wording indicates you might want to ask general RF > operation questions, and I'm not 100% sure this mailing list is the > perfect place to do so. > > Best regards, > > Marcus > > [1] https://www.nooelec.com/files/e4000datasheet.pdf > > On 02/05/2017 06:54 PM, Ricardo Romanowski wrote: > >> Hi, >> >> has anyone yet tried to optimize the rtl drivers towards using less >> energy on the chipset (cpu doesn't matter for my purpose). I just >> noticed that the r820 tuner gets awful hot when used normally or even >> when the device is just inserted into the usb port thus supplied with >> power. I also have multiple E4000 Tuner based dongles, but these do >> seem to heat up pretty well also. My hackrf stays quite cold compared >> to that. >> >> Are there chipsets known for less power consumption (thus less heat)? >> I doubt software could really do much about the chip design, but i'm >> not deep enough into the rtl chipset to judge whether it's more of a >> software- or hardware-issue. >> >> Any ideas on that topic? >> >> Thanks!! >> >> >> Best regards, Ricardo >> >>