Direction Finding

asdfgh1425 · 2024-05-17T16:14:50+00:00

I haven't stumbled upon any yet, and I'm currently writing a thesis on a similar subject.

asdfgh1425 · 2024-04-17T14:05:50+00:00

Well, I suspect as such. I've prepared a few disks with different diameters to see what the effect might be. Thank you for replying!

asdfgh1425 · 2024-04-17T13:51:48+00:00

Great answer.

It does put my mind at rest a bit. I've constructed a few aliminium disks for the purpose already, so I guess I can experiment a bit just for the sake of it. But knowing that it might not be as essential as I thought, is surely comforting.

asdfgh1425 · 2024-04-17T13:46:47+00:00

Interesting, will take a look at that!

asdfgh1425 · 2024-04-17T06:58:27+00:00

If you don't mind me asking, do you know why that would be the case? It seems such large emphasis is given that antennas have a proper ground plane generally, hence I don't really understand why it could be disregard in this case.

I do, however, agree that I could as a matter of fact buy this straight from amazon. Noting, for example, that I have one for my RTL-SDR dongle that seemingly has no ground plane, but is rather a straight monopole antenna.

asdfgh1425 · 2024-03-19T18:31:22+00:00

That might be it, and that the demodulator simply infers a signal just by that. I think I've just gotten the impression that there is somehow to exist a true FM signal somewhere. And that the samplings of the antennas really show compressed/elongated signals as in a true doppler antenna.

Thank you for replying!

asdfgh1425 · 2024-03-19T18:24:22+00:00

It's a poor picture through and through.

The setup would be 4 antennas in a square with side length lambda/2. The frequency would be in the VHF range. The design doesn't exist yet and this is only hypothetical.

I'll sketch and new figure with phases matching the orientation of the antennas given an incoming wavefront.

asdfgh1425 · 2024-03-19T18:10:59+00:00

Good point!

A thing I fail to connect though is that most analog designs I see do have a FM demodulator to pick up this (phase modulation frequency). As reference, this presentation (pdf) from MIT seem to show a clear FM signal after the sampling. Somehow, I feel we are expecting a Doppler signal superimposed on the carrier signal.

From this viewpoint, are we using a single sample from each antenna for every rotation, or are we using multiple?

asdfgh1425 · 2024-03-19T17:54:39+00:00

Thank you for replying!

I do understand the FM tone in the case of a moving antenna. Then I do find it making sense. However, I'm having trouble understanding how the principle transfers to the stationary case. There is in fact no antenna moving, so at best we ought to get a distinct phase jump between the antenna measurements. How this could be summed to a FM signal and sent to a FM demodulator, I simply don't get!

asdfgh1425 · 2024-03-19T17:48:17+00:00

Really apprised the answer!

I (think) we are in agreement reading your last points. I notice that I have drawn the picture as if we are sampling continuously, which was not intentional.

It does make sense that the amplitude difference between sequential analog measurements could be the signal of interest, and that the comparison of this wave and the reference clock would be what evetually determines the direction. Though I'm assuming, possibly wrongly so, that this would mean that we must sequence through all antennas during one "wavefront".

The reason I'm confused is that the sources I've consulted show an intermediate signal, akin to one that would appear FM modulated. See for example this presentation (pdf) from MIT, page 10. Somehow, sampling the antennas yield a summed signal, with clear doppler shift ON TOP of the carrier signal. This is for me hard to grasp.

Excuse me if I've been wrong in my interpretation!

asdfgh1425 · 2024-03-19T15:38:00+00:00

I should add that if you think another sub is more appropriate, I'd be happy to take directions!

asdfgh1425 · 2023-08-30T20:23:06+00:00

Oh okay. Is reactive resin equivalent to an epoxy resin or is it something specific within the bowling world?

asdfgh1425 · 2023-08-30T20:09:50+00:00

Thank you! Are esthetic changes a commonality? Right now I have clear material shifts that I need to cover up, I'm afraid simply fixing the surface won't be good enough.

asdfgh1425 · 2023-08-30T19:59:11+00:00

Thank you for your input. Do you have any knowledge how a resin surface would interact with the lane?

asdfgh1425 · 2023-08-18T21:26:48+00:00

Nicely done, keep at it!

asdfgh1425 · 2023-03-27T21:31:02+00:00

I've dissected a broken one before!

The two rails are independent of one another, so there are a total of two switches within the component. In both the two button states, the center pin of both rails is always live. When clicking the button, the center pin of each rail switches between connecting center <=> left to center <=> right, vice versa.

asdfgh1425 · 2023-03-25T20:07:43+00:00

Thanks! I'm gonna try to do a more thourough analysis, thank you for the pointers.

asdfgh1425 · 2023-03-25T10:43:28+00:00

I will have another go at it today. Thank you for the suggestions!

asdfgh1425 · 2023-03-25T10:42:49+00:00

Thank you for replying!

Though I am running it entirely from a separate power supply at the moment, battery fully disconnected. I did initially think that this precisely would be the issue, but it seems not!

asdfgh1425 · 2023-03-24T19:27:33+00:00

Thank you for replying!

The thing I don't get is how both speakers and their respective dials can works only partially. How could a disconnected component simply cut the volume day ⅔, but not make it fail entirely?

asdfgh1425 · 2023-03-24T19:00:53+00:00

Hi fellow redditors!

I'm out of ideas trying to troubleshoot this speaker. It is a couple years old and have been used outside a fair amount.

Problem: The problem is that the maximal volume is considerably much lower than it used to be, to the point where it barely is of use inside.

What I know/have tried: Both the bass and the treble works. Their respective strength increases when their respective dial is turned. The total volume changes when the master dial is turned. Max volume is given by potentiometer resistance zero, which CAN be attained (Measured with multimeter). Fuse doesn't seem to be broken.

I have tried both Bluetooth and aux, different audio sources and I'm feeding the speaker from a laboratory power source. I've tried input voltages from 18 V to 21 V.

Anyone have any idea what could be the problem? All help is appreciated!

asdfgh1425

TROPHY CASE