5 Feb
2017
5 Feb
'17
5:54 p.m.
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
6 Feb
6 Feb
5:55 p.m.
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
9:39 p.m.
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
>
>
10:25 p.m.
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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days inactive
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days old
3 comments
3 participants
participants (3)
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Art -
Marcus Müller -
Ricardo Romanowski