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uhoh
uhoh
2:51 AM
2
Q: Did any of Voyagers' receivers' front ends take advantage of the "cold of space" to lower noise?

uhohMost of the Voyagers' electronics are kept warm by electrical heaters powered by their RTG's, and presumably protected by some amount of insulation from the "cold of space" which means loss of heat via blackbody radiation. This is done because the carrier density in semiconductors (both intrinsic...

communication voyager deep-space-network antenna electronics
4
Q: Why is the operating temperature for the Voyagers' receiver noise calculation about 1550K?

uhohIn line 10 of Table 5.2 of DESCANSO IV - Voyager Telecommunications it shows a value of the uplink receiver noise spectral density of -166.7 dBm/Hz, which is 196.7 dBW/Hz which is 2.1E-20 Watts/Hz = $k_B T$. With $k_B$ = 1.381E-23 J/K that's a temperature of about 1500 K (which seems really hot!)...

voyager radio-communication deep-space-network
I've just added bounties to both
 
 
14 hours later…
Mike Waters
Mike Waters
5:07 PM
3
Q: How to measure quartz crystal motional parameters using a VNA?

S.s.I want to measure quartz crystal motional parameters with a VNA, unfortunately all Google searches I've done have lead me to nothing in concrete. I know how to get an impedance curve and measure the parallel and series resonant frequencies but I dont know how to extract the motional parameters fr...

filter crystal-radio
 
 
1 hour later…
SEJPM
SEJPM
6:18 PM
Hi guys, I've got a short question for you. Assumingt the following question would be posted onto EE.SE, would you vote to close it?
0
Q: Do VAES (wide multi-block AVX and AVX512 AES instructions) cause thermal throttling just like other AVX512 (and some AVX2) instructions can?

Adam IerymenkoThis is a CPU architecture question but it's cryptography extension specific so I figured I'd ask here. I know that AVX512 and also sometimes AVX2 instructions can cause X64 chips to down-clock due to thermal and power issues. This is a well known issue with some of these wide vector extensions, ...

aes performance cpu
(with minor edits to remove the part where it explains why it posts to Crypto.SE)
^^^ (randomly choosing) @Shalvenay (or anyone else willing to answer)
 
Shalvenay
Shalvenay
@SEJPM that's a good question -- I'm not sure
 
SEJPM
SEJPM
@Shalvenay thanks for looking at it, perhaps @W5VO has a clearer feeling?
 
 
2 hours later…
Bartek Banachewicz
Bartek Banachewicz
8:01 PM
When bitbanging I2C via GPIO, do the pins need to be repeatedly changing between inputs and outputs? Asking from a perspective of an Arduino user used to program-wide pinMode.
 
W5VO
W5VO
yes, but why aren't you using the I2C peripheral?
 
Bartek Banachewicz
Bartek Banachewicz
@W5VO ESP8266
I was just curious how that's done, I flashed NodeMCU there which has Lua which has a ready I2C driver that does all the work for me.
the more I read about I2C the more I dislike its complexity
 
W5VO
W5VO
@SEJPM A reasonable question, but normally these require too much specialized knowledge - either specific experimental data or insider knowledge - for them to be good SE questions.
@BartekBanachewicz Everything is a tradeoff. A lot of people want I2C to do things that it was never intended for, and then are frustrated with the added effort. I would have seriously reconsidered my selection of an I2C component if my MCU didn't have a hardware I2C interface
 
SEJPM
SEJPM
@W5VO thanks for the evaluation!
 
Bartek Banachewicz
Bartek Banachewicz
@W5VO I don't think it's ideal either but in this case (talking to BME280 sensor every minute or so) I think I can live with it - especially given that the ESP boards with hardware I2C are much more pricey
the older, small ones are awfully limited and have completely useless pinout, but the price is quite frankly amazing
 
W5VO
W5VO
8:16 PM
Randomly searching, the BME280 has SPI - why not use that?
 
Bartek Banachewicz
Bartek Banachewicz
I only get two pins.
well, technically I could probably repurpose the serial ones
 
W5VO
W5VO
It feels like you've painted yourself into a corner with component selection
I suppose I2C isn't the worst protocol to bit bang from the electrical/CPU side, but it's certainly not the simplest protocol.
 
 
1 hour later…
Bartek Banachewicz
Bartek Banachewicz
9:39 PM
@W5VO I agree, and I really wouldn't like to implement it myself
it's an evaluation more than anything anyway
if it turns out I'll need to buy a board with more pins, so be it
or I can just add another MCU to the picture to act as a bridge and only use the ESP as a WIFI connection and not actual MCU - this could be advantageous as i could cut power to it and only power it on when actually sending data, but I suppose sleeping the wifi module would accomplish that too
 

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