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SteveSh

 Discussion on question by Allfadern: …

Imported from a comment discussion on electronics.stackexchang...
SteveSh
Dec 8, 2024 01:40
@Envidia - There are techniques to "synthesize" an LFM pulse with a wide bandwidth (say 2 GHz) out of 10 200 MHz LFM pulses, and then successfully process the 10 pulses as if they were one long 2 GHz pulse. Go back and read my comment from Nov 21.
SteveSh
Nov 21, 2024 12:35
That should be RF output, not IF output in the first sentence.
SteveSh
Nov 21, 2024 12:33
This is a common problem, solved with complicated frequency synthesizers, when you're trying to synthesize a wide instantaneous bandwidth (IBW) waveform (say 2 GHz) with hardware that only supports a fractional IBW of that range, say 200 MHz, which wold require 10 chirps each with a different frequency slope.
SteveSh
Nov 21, 2024 12:33
You need a more intelligent VCO to do what you want. In addition to just changing the frequency, you need to be able to control the starting amplitude and phase of the VCO's output, so that of chirp n ends at 1V and 235 deg, chirp n+1 starts at 1V and 235 deg.
SteveSh
Nov 21, 2024 12:28
These discontinuities are an artifact of using the stepped chirp waveform. You are trying to stitch together phase and amplitude information from one chirp to the other. In order for this to work properly, the IF output step-to-step needs to be continuous.
SteveSh
Nov 20, 2024 17:20
Here's a potential source of your problem. Look at your yellow trace, the 1.7 KHz (?) If output. Note that it is not continuous chip to chirp. That is, the end point of chirp n does not match up with the starting point of chirp n+1. That discontinuity will show up in any frequency analysis - like a FFT - you do of the IF.
SteveSh
Nov 20, 2024 17:14
If you change the chirp time - increase or decrease the slope of the VCO input - and keep everything else the same, you should see the IF frequency change accordingly.
SteveSh
Nov 20, 2024 17:14
Looking at the 'scope traces, they make some sense to me now. The yellow that overlays the purple is 1 cycle (actually, a smidgen less) of the 1.3 KHz IF output. So if you move the target, you should see the IF output (yellow) change in frequency. That is, see more or less "cycles of the IF output during the chirp.
SteveSh
Nov 20, 2024 17:14
@Envidia - Yes, I think the purple trace is the voltage input to the VCO.
SteveSh
Nov 20, 2024 17:14
I did a quick back of the envelope estimation. Your chip is 138 MHz (2.4V) in 770 us (1.3 KHz). If you put a target 5' away, the round trip time is ~ 10 ns (1 ns/foot). So the IF output should be 1.8 KHz (the frequency change in your signal over 10 ns). Is this what you measure?
SteveSh
Nov 20, 2024 17:14
If you have a fixed target at zero range, your IF output should be close to DC. As you move the fixed target further away, the IF output should increase, proportional to the 2-way range and your sweep rate, MHz per us, or whatever.
SteveSh
Nov 20, 2024 17:14
@Marcus - I agree, something doesn't look right with the waveforms shown. The RF sweep should be ~150 MHz with a chirp input range of 2.4 V. Something about the yellow trace doesn't make sense.
 

 Discussion between SteveSh and sina bala

Imported from a comment discussion on electronics.stackexchang...
SteveSh
Feb 3, 2024 02:42
Only reason I can think of for the 10 ns rise time number is that OP is planning on using this signal to drive the gate of a switching MOSFET,and he thinks he will get lower switching losses with 10 ns than with, say 50 ns rise time. But this is just a WAG.
SteveSh
Feb 3, 2024 01:59
My point was that you don't have to treat this signal/interface like a super high-speed one. 35 MHz BW for this particular interface (30 KHz PWM signal & 10 ns rise/fall times for a switching power supply) should be fine.
SteveSh
Feb 3, 2024 01:53
No. It starts with a square wave signal with 0 ns rise & fall times. We know that in order to accurately represent this we need the fundamental plus an infinite number of harmonics. Now we start eliminating higher harmonics, turn that frequency domain signal back into a time domain signal, plot that signal and measure the 10%-90% rise time of the signal.
SteveSh
Feb 3, 2024 01:53
sina bala - All you really need to get a good 10 ns edge (10%-90%) is 35 MHz BW.
SteveSh
Feb 3, 2024 01:53
And I don't think a lot of the effects you mentioned - resistive losses, skin effect, dielectric losses - are much in play at the frequencies involved here - 30 KHz and 10 ns edge times.
SteveSh
Feb 3, 2024 01:53
A 10 ns rise time does not have a 100 MHz bandwidth.
 

 Discussion on answer by Lundin: Cable…

Imported from a comment discussion on electronics.stackexchang...
SteveSh
Nov 14, 2023 17:23
If I knew what "raw UART" is...
SteveSh
Nov 14, 2023 17:23
@Lundin - As Tim Williams hinted at, the noise immunity of RS-422/485, or LVDS for that matter all go out the window if the common mode range of the receiver is exceeded.
 

 Discussion on question by MyCarGoesHi…

Imported from a comment discussion on electronics.stackexchang...
SteveSh
Nov 9, 2023 11:27
And I would also look closely at your DIN to 4 RCA plug cable. It's really tricky to maintain good shielding integrity with a 4-way Y connection like that. A break or opening in the shield can render the entire cable useless from a shielding standpoint.
SteveSh
Nov 9, 2023 11:27
That may just be a red herring. This is where a detailed diagram of your setup, with all the interconnects and grounding, would help a lot. Every one of us here probably has a different mental image of what your setup is.
SteveSh
Nov 9, 2023 11:27
I'm thinking that you don't have ground loop, but rather there may be a problem with your cables that are allowing radiated emissions (RE) from the ignition system to couple onto the cables and then into the amp. That would be consistent with your observation that when the speakers are hooked up directly to the head unit, you do NOT hear the whine.
SteveSh
Nov 9, 2023 11:27
So you go from a DIN connector at the head unit to 4 RCA connectors into the amp (in the trunk), right? Try unplugging the RCA connector from your amplifier. That is, leave the amp inputs open and see if that affects your symptoms. If it does, connect the RCA plugs to the amp, but leave the DIN connector unplugged and see what that does. For the later test, you may want to connect the shield to GND/Chassis at the DIN connector.
SteveSh
Nov 9, 2023 11:27
Yes. Maybe I was mis-interpreting the "as long as it can handle enough current" part of your comment.
SteveSh
Nov 9, 2023 11:27
Using shields of cables to carry power return currents is not a good idea, and, in general, is not recommended.
SteveSh
Nov 9, 2023 11:27
Why do think it's a ground loop and not some other source of interference, like radiated (through the air) or conducted (on the power lines)?
 

 Discussion on question by Kevin: How …

Imported from a comment discussion on diy.stackexchange.com/qu...
SteveSh
Jul 15, 2023 13:48
Looks like you have two kinds of exterior wall treatment. Vinyl siding on one side (where the J-channel is), and some T-111 (maybe) on the other side. Is this accurate?
 

 Discussion on question by David Molon…

Imported from a comment discussion on electronics.stackexchang...
SteveSh
Jan 21, 2023 17:25
While I agree that many of these suggestions are possible, none of them are very practical for a consumer level product. If you short an unprotected 100 A or 200 A source, bad things are going to happen. You can't protect against stupidity.
SteveSh
Jan 21, 2023 17:25
While not an answer to your question, we had a PCB flamed because of a short between the VCC and GND planes. Root cause was some GND to VCC plane smear when a hole was drilled through the board as part of a rework process. The VCC supply, 5V, was a 200 amp switcher. Needless to say, the board was toast (pun intended). This was maybe 40 years ago.
 

 Discussion on question by ChrisD91: H…

Imported from a comment discussion on electronics.stackexchang...
SteveSh
Jan 3, 2023 15:57
@ChrisD91 - It might be a worthwhile to run the Radiated Field Immunity test again, but this time with coax cables disconnected and the coax connectors capped off. This might help you isolate the problem.
SteveSh
Jan 3, 2023 15:57
@ChrisD91 - It is common practice to exclude from EMC testing frequencies that are naturally used by the system. For example, and X-band radar system (~10 GHz), does not have to meet a Radiated Emissions, or Radiated Susceptibility requirement at it's intended frequencies of operation.
SteveSh
Jan 3, 2023 15:57
@ChrisD91 - Can you notch out/filter, at the receive end, any frequencies other than what you are transmitting?
SteveSh
Jan 3, 2023 15:57
@ChrisD91 - When you test your box, are the transmit and receive coils connected? If not, what are you doing with the coax connectors for those coils? They should be capped off to prevent leakage into you box that may be interpreted as a "detect".
SteveSh
Jan 3, 2023 15:57
@Lundin is correct. Reading OP's post, the unit is failing the equivalent of a radiated susceptibility (RS) test. To me, that eliminates power supplies from the problem space.
 

 Discussion on question by Jose Leon: …

Imported from a comment discussion on diy.stackexchange.com/qu...
SteveSh
Aug 1, 2022 18:01
Where is this switch relative to the kitchen? If it's close, you just replace this 3-way with 2 individual SPST switches, one for the closet & one for the kitchen.
SteveSh
Aug 1, 2022 18:01
@Jose - Did you read my comment above, and the comments from the others? Looks like this is a mistake as it doesn't make sense (that I can see) for a switch to do what this one does.
SteveSh
Aug 1, 2022 18:01
Oh, and BTW - nice picture of the switch with the wires visible. Good job for your first question.
SteveSh
Aug 1, 2022 18:01
OP's photo looks like it's a switch. Yeah, I know he said receptacle, but...
SteveSh
Aug 1, 2022 18:01
Sounds there may not be another 3-way switch involved. It could just be that the two travelers (one black, one red) from the switch you showed go to two different loads. One load is the closet light; the other is the kitchen light, fan, and receptacle.
 

 Discussion on question by Nick: Signa…

Imported from a comment discussion on electronics.stackexchang...
SteveSh
May 26, 2022 05:06
@Nick - Yes, the 2 frequencies add in a sense. But they also separable at the destination. Back to th square wave for a moment. When someone generates square wave digitally, they do that just by switching a transistor, or pair of transistors ON and OFF. It's not done by combining a bunch a sine waves.
SteveSh
May 26, 2022 05:06
Plus, your old AM radio would never have worked if signals combined the way you think they do in a medium, like a wire. All of the stations picked up by the antenna are separable by the tuners and filters that follow.
SteveSh
May 26, 2022 05:06
But it's simpler than a lot of these comments. Two or more signals (frequencies) in a linear system do not mix or combine. This is the key. And that's what a wire is - a linear system. At the receiver, you just need a way to separate, or differentiate between the various signals. If they are different in frequency, all you need, notionally, is just a bunch of bandpass filters each one tuned to the frequency of interest.
 

 Discussion on question by drabsv: Do …

Imported from a comment discussion on workplace.stackexchange....
SteveSh
Apr 18, 2022 20:03
@ David R - I agree, somewhat. But again the basis of my comment was how - what measure (or measures) are they employing - are they determining if one layout is better then another? Employee feedback is one thing (whether they like one layout over another), but does not address my question. If you can't measure it, then you're just fooling yourself if you think rearranging desks are making any difference, productivity-wise.
SteveSh
Apr 18, 2022 20:03
@Helena - Sorry, can't get to any of the researchgate.net publications. I get the following error message "We've picked up some unusual traffic from your network and have temporarily blocked access from your IP address." This is the only site that gives gives me such a warning. No, I'm not going to waste my time figuring out the problem.
SteveSh
Apr 18, 2022 20:03
@Helena - I was asking about productivity, which seemed to be the point of OP question.
SteveSh
Apr 18, 2022 20:03
I want to know how they measure productivity.
 

 Discussion on question by Vivek Mahar…

Imported from a comment discussion on diy.stackexchange.com/qu...
SteveSh
Dec 21, 2021 15:00
@Vivek - Has your neighbor applied for a variance? That should be the first approach. Like others have said, almost all jurisdictions have a process whereby bulk requirements (like building setbacks) can be waived. It happens all the time in my neck of the woods.
SteveSh
Dec 21, 2021 15:00
I know people who have been allowed to put AC units on a public sidewalk because of a "hardship" plea.
SteveSh
Dec 21, 2021 15:00
And if everything OP said is true, the local jurisdiction is basically telling OP's neighbor that she can't have an AC unit on the ground outside her house, but OP can. That just doesn't sound right to me. Maybe OP's neighbor just hasn't tried hard enough, like seeking a variance from the planning/zoning people.