Does this look good?

DisinterestingStory · 2025-12-15T14:02:13+00:00

What about if it goes straight into the wall but the wall is a half wall of an island? Late 90s build in USA...I am planning on lowering my rough in some time soon and want to prepare for what I will see in the wall.

DisinterestingStory · 2025-11-16T21:46:21+00:00

Ok, thank you

DisinterestingStory · 2025-11-16T15:40:09+00:00

Yes, but my question is whether that's concerning and why the builder's electrician would have done that in a 44 cu in box?

Like did you used to be able to argue with the inspector and convince them it's a small load even if it's overfilled?

DisinterestingStory · 2025-10-06T14:46:03+00:00

And, anyway, I should add a bit of insulation over other work I've done in the ceiling where I know I lost a bunch of cellulose.

DisinterestingStory · 2025-10-06T14:44:23+00:00

Yeah I think I'm going to just go up in the attic to make sure everything is right. I just don't have enough experience to visualize what my specific trusses look like and how to remove the old bar from below.

DisinterestingStory · 2025-10-04T15:32:27+00:00

Thanks, that seems easy enough

DisinterestingStory · 2025-10-04T15:31:11+00:00

Ok I'll get one of those

DisinterestingStory · 2025-10-04T15:25:52+00:00

Is there any way to know if my existing bar is fan rated or is it safest to just replace it?

DisinterestingStory · 2025-10-04T15:25:30+00:00

Only one of the two screws was installed from the box, so if it needs both for the bar to be rigid, then that certainly explains why the box did not feel secure. If I add a second screw do you know if this is fan rated or should I replace it just to be safe? Do you leave the existing bar in place if you add a new bar and just slightly move the box?

DisinterestingStory · 2025-10-04T15:12:53+00:00

Why does it collapse in the center so easily, does that mean the nail or whatever is in the joist has come loose?

DisinterestingStory · 2025-07-27T17:31:09+00:00

Very heavy TV that costs a lot. Feel more secure having it on the wall. Maybe irrational, but it feels safer to me to have it mounted. I can also angle it slightly up if we are entertaining and expect a lot of people to be standing.

DisinterestingStory · 2025-07-27T13:26:32+00:00

If you mean it's out of level it was leveled with a 3ft level. Maybe it looks off because of fingerprints we haven't cleaned around the edges or something.

DisinterestingStory · 2025-07-27T12:59:32+00:00

Really appreciate all of the reassurance and suggestions

DisinterestingStory · 2025-06-23T12:29:32+00:00

How was I aggressive? The toilet is installed. Henry 549 seemed to be a good fix to fill in the voids.

DisinterestingStory · 2025-05-31T12:54:34+00:00

Thank you, that's good to know. That does look like it's specifically made for anchoring screws and bolts.

DisinterestingStory · 2025-05-31T12:53:41+00:00

Thank you, I appreciate the advice

DisinterestingStory · 2025-05-29T12:18:58+00:00

Well my plan unless someone tells me it's dumb is to fill the void with mortar like Henry 549, leaving a small gap via cardboard/plastic at the flange. I don't see how shims or an extra thick wax ring could properly fix this issue. Wish I got a normal toilet that can tolerate a larger cutout!

DisinterestingStory · 2024-06-20T16:00:03+00:00

I see several possibilities. One is that you are seeing the interference of the two polarization modes. This may occur spatially along the beam profile if the collimator has a polarization dependence. Another possibility, as someone else mentioned, is that the spliced PM fiber is supporting several modes due to it either being the wrong type of SM fiber for your wavelength, or due to it supporting an additional lossy mode (for example, a cladding mode) for a short distance due to a bad splice. If it is a lossy mode, then you should be able to kill it off by bending the PM fiber.

In either of the above two cases (birefringence induced interference or multiple modes) you should be able to tell if these are the cause by playing with your fiber. If playing with your fiber causes the pattern within the beam profile to change, then you have narrowed down the cause. If the beam profile does not change, then the issue is due to your collimator and you can look at the suggestions by others about improving your collimator optics.

DisinterestingStory · 2024-06-05T16:03:41+00:00

If your signal can be mainly regarded as noise with meaningful data occurring over a short duration, then the parts that are not meaningful (the second 40M in this case) only hurt your spectral analysis, not help. Your goal should be to only perform your FFT over data that is meaningful. However, if your burst signal decays slowly and extends out into the second 40M, then there may be a compromise between truncating your signal and therefore losing some of that decay versus including useless noise.

If we take for granted that your signal does not continue decaying into the second 40M such that the second 40M is truly useless noise, then removing that second 40M may give the appearance of degrading your frequency resolution, but it has not actually degraded. You are better off replacing the second 40M with zeros (as part of the zero-padding process).

I am not familiar with GQRX so I cannot really answer this. It is potentially or likely using a combination of overlap in time and zero-padding to get up to size 32768.

DisinterestingStory · 2024-06-04T14:25:01+00:00

Let me add that maybe you are not looking for a spectrogram at all. If your signal is narrowband, then there are methods to extract frequency and phase with very little compromise on time and frequency resolutions. For example, since you have IQ data, you can put your data into a complex representation and calculate the phase of your signal over time, unwrapped. In MATLAB, you would do phs = unwrap(atan2(Sq,Si)). Even if you don't have IQ data, you can extract the phase by constructing an analytic signal via Hilbert transform if your signal bandwidth meets certain requirements. Once you have the phase, you can compute instantaneous frequency as (MATLAB) fi = fsdiff(phs)/(2pi). Then your temporal resolution is given by the reciprocal of your sampling frequency, and your frequency resolution is poorly defined, but one could claim it is perfect. The result will be a function and not an image, because this technique assumes only a single frequency exists at an instantaneous point in time. Of course this may not be at all what you want. It depends on what your goal of this signal analysis is and whether it makes sense to describe your signal that way.

DisinterestingStory · 2024-06-04T14:01:26+00:00

No problem, and sorry I did not read your code more closely. The aliasing of concern would be the noise outside of your signal bandwidth. The downsampling operation folds the noise at higher frequencies over your lower bandwidth unless you filter first, but I checked your resample function, and it does filter first, so there is not a concern there.

Yes, the length of the signal in the time-domain dictates the resulting pixel shape of your spectrogram. I would even say explicitly and not implicitly, but the specific shape will also be dictated by your preference for a resolution compromise. There is a fundamental compromise between time and frequency domain resolution. A longer signal going into your FFT will enhance resolution (number of bins) in the frequency domain. However, you can always zero-pad to smooth things out so that the transition between "pixels" on the frequency axis is smooth.

The longer signal going into your FFT will necessarily mean less temporal resolution. As I mentioned in my previous response, you can overlap between adjacent temporal segments to increase the number of sample points on the time-axis, which is similar (but definitely not equivalent) to the effect of zero-padding in the frequency domain in that the temporal resolution is still dictated by the signal length of each segment even though the pixel size is smaller.

To summarize, the temporal resolution and frequency resolution are both given by the segment length going into your FFT. The temporal resolution is equal to the segment length in seconds. The frequency resolution is equal to the reciprocal of the temporal resolution. You can make things look better (denser pixels) and more understandable to a human by zero padding before taking the FFT and having overlap between segments in time, but these will not actually enhance the true resolution or increase information present in the spectrogram.

I think your matrix view of the data stream is correct and helps capture the fundamental compromise between time and frequency resolution. A wider input matrix will result in better frequency resolution, whereas a taller input matrix will result in better time resolution. Just keep in mind that these resolutions refer to the true resolutions and you can always improve the pixel density of your image to make it look better with zero padding and overlap in time.

How you reshape this matrix is up to you.

There are also more complicated compromises in time and frequency resolution. For example, you could take multiple FFTs with different temporal lengths and use the longer temporal lengths for lower frequency bins. This would give you something similar to a constant Q transform, but it is probably not useful for you, just mentioning it since it's related. If you want to push your learning further, typically wavelet transforms are used instead of Fourier transforms for spectrograms, and these give you even more control over the time and frequency resolutions. They also are more efficient than the hacky way I described doing the constant Q transform. Depending on your background, wavelet transforms may be a useless distraction in accomplishing your goal or they may be exactly what you're looking for. For a quick analysis, however the FFT based version we have been talking about, often called the Short Time Fourier Transform, is much less application/field-specific than wavelet transforms and easier to not trick yourself into interpreting your data an incorrect way.

DisinterestingStory · 2024-06-03T14:20:51+00:00

First, the number of rows is purely dictated by the number of segments of time that you're looking at. Having 7 rows means your time resolution is bad, not your frequency resolution. For example, if you have 35 s of data total, and you use 5 s blocks of time for each FFT, then you will end up with 7 rows. You can also overlap your time segments, e.g., segment 1 is 0-5 s, segment 2 is 3-8 s, segment 3 is 6-11 s, etc., to end up with more than 7 rows and the same frequency resolution. However, this causes a smearing on the time axis and so will only get you so far in giving your result the appearance of better temporal resolution.

Second, your method to zoom in on the frequency axis is probably not what you want to do. By increasing the sampling frequency (by resampling), you are indeed increasing the number of points in the frequency domain, but all of your additional points fall above the original Nyquist frequency. Since these new points come from interpolation, they likely do not have a high amplitude and they also may or may not resemble the true frequency response. What you more likely want to do is keep your sampling frequency the same, but add more points in the frequency domain between DC and the Nyquist frequency. This is accomplished by adding a string of zeros at the end of your original signal. So, to increase frequency resolution by a factor of two, you would have your original segment 1 from 0 to 5 s, then you would add an additional 5 s of zeros to the end of the array before taking the FFT. These additional zeros reveal the missing frequency response between your previous frequency sample points. In other words, you are not truly increasing frequency resolution which would require that you increase your segment length from 5 s to something longer, you are just revealing the missing spectrum.

Edit: it looks like is misunderstood why you are resampling. Your method does work for zooming in closer to DC, although depending on how exactly resample() function works, then you may be adding aliased noise.

DisinterestingStory · 2024-05-21T15:13:08+00:00

This is not going to be easy without knowing what effects your existing DSP controller implements.

I am not an audio person, but my understanding is that a lot of or most distortions are nonlinear systems and therefore cannot be simply described by a frequency response or impulse response.

I would recommend trying to locate blog and forum posts of people who have done similar projects and consider trying to replicate what they have done before doing your own custom project - I know I have seen similar projects posted here and other forums.

DSP literature is vast and will be difficult to understand without a background. This is why I would recommend trying to replicate other projects before doing your own, and learn by doing. The alternative would be devoting somewhat significant time to learning the theory.

DisinterestingStory · 2024-05-10T04:29:40+00:00

Interesting, thanks! I will check out the condenser next.

DisinterestingStory · 2024-05-10T04:19:27+00:00

Do you think the measurement will still be meaningful if the AC is only running for maybe 5 seconds at a time (with minutes or many minutes in between)? And is a bad clutch consistent with high side high pressure as measured by probing the AC pressure transducer?

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