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
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
Hi 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
Hi Ricardo,
My guess is that it's power supply is a linear type, necessary due to the radio frequency hash that would appear as noise if a higher efficiency switching supply is used. So, the dongle has to dissipate 3.3 times 118 milliwatts (389.4milliwatts) instead of 118 milliwatts. The point is that 66.6 percent of the 'heat' you feel is not coming from the chip itself!
As far as a practical solution, you can build a switching supply and build it in the cable run between the punchbox and the unit. You can't locate them extremely close to each other if a switching supply is used.
Or, you can locate the linear power supply very close to (but not inside of) the enclosure for the chip. Today, linear power supplies can almost fit on the head of a pin, provided that the amount of power they dissipate is low.
With radio questions related to SDR, check out the softrock mailing list on yahoo where you will find many hams, who have extensive exposure to radio communication and with SDR.
GL, I hope to get one of these little beauties someday soon, and I hope that someone is working on the companion SDR based transmitter, that generates an rf output from an audio input....basically doing the reverse of what the SDR receiver does.
Regards.
Art
A switching supply could be made outboard from the On 02/06/2017 12:55 PM, 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
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Art -
Marcus Müller -
Ricardo Romanowski