6 Feb
2017
6 Feb
'17
11:25 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