@Asmyldof Now that you ask... I had to restart the scope and I think i that case it always loses the 20MHz BW setting... but for single captures like that I don't think it made a difference
(I was fighting a lot yesterday with rigols ultrabench software to get i to display anything, and it makes the scope hang a lot. Also the "screenshots" you do are black text on white background with the selected colour, which is yellow in this case)
dc/dc artifacts might be a reason why it vanishes when run into 50ohm... though the input impedance of line in of devices should be a rather high, shouldn't it? a headphone is likely low enough to get the same effect
I really need better cabling to not get noise from everywhere a round on top of it, even the "cleaner" trace when into 50ohm is terribly noisy and I don't know if its a cable thing or just the signal
maybe this evening I have more time (and now that this software runs without constantly crashing) to get a cleaner picture of it
also any tips on how to better trigger on that? it jitters around quite som µs depending on where the first spike of that "block" happens tobe
@PlasmaHH If the SPS rating is high enough you can trigger on pulse smaller than X or try to trigger on flank speed, though to my knowledge no Rigols have a flank speed option.
@PlasmaHH Good probes and/or good mini-coax is the key to getting good noise measurements out of anything.
I have finally managed to convince some people of that here as well, we now have a spool of 25m micro-coax and appropriate 2GHz bandwidth BNCs
But you can attach a 500 Ohm resistor to the pin in a loose connector and then attach a coax cable to that and ground, terminate neatly at 50 Ohm and set to 1:10
I would prefer a load about as low as the input of e.g. the mixer I would probably be running it into, need to check what it is, expect it to be in the order of tens, maybe hundreds of kΩs
hm, only the higher end model has it actually specified, but its likely to be the same on the one I have, which would then be 10kΩ
is it unreasonable to boost a single 18650 lithium battery up to 16-18V for use in a mono-channel class D amplifier on a 20W rated 8 ohm speaker? Short and loud pop sounds (rather than continuous full-range music) is the intended use of the speaker.
expected current draw from the speaker is 1-2A max, on the 16-18V audio voltage rail, so i expect the switching currents on the boost converter would be up around 12-15 amps
if 3V to 18V @ 2A out was the goal, worst-case scenario
can these lithium cells handle that kind of brutal treatment? Obviously I'd have as many capacitors as possible, but space might only allow 1mf to 1.5mf worth of bulk capacitance
yeah ideally i'd get a smaller, 2 cell battery and it becomes a lot more reasonable
its just so much more convenient with single cell batteries for charging and sourcing and integration into a product. There are no nice integrated 2-cell chargers that take a simple USB 5V input is there?
Keeping the input voltage somewhat stable at around 3V would be a challenge in itself, and then on top adding a boost factor of 6 isn't that easy either, especially not with that amount of currents involved.
yeah so realistically I should drop the idea of high capacity single cell 18650 style and go for smaller capacity 2-cell configuration - still aiming for the same Watt-hours though. Will reduce the circuitry requirements for operation, just annoying for charging
You want short loud bursts of noise like sound, so why keep a lossy booster running the whole time, rather than just driving a low impedance 1:10 transformer at 3V with a high current amplifier chip?
In which case you can have 10mF at 3V of bank, which may actually catch the brunt of the jolt
@Asmyldof that's a good point, if i stack low voltage capacitors and decouple the battery a little bit (series resistor maybe, and can use as a current monitor at the same time) I can let the boost converter or transformer handle the pulsed loads
are there tiny little transformers for this kind of task? I haven't ever used or designed anything with transformers so i'm unfamiliar with expected size/current handling
@KyranF Depends on the frequency of interest. The higher the frequency the likelier you may find something in ferrite
If you want a 10kHz square-wave to "pop"/"squelch" you can use an LF DC/DC ferrite and just a simple H-bridge and with some toying/tweaking may find a perfectly service-able solution with the transformer normally used for 3W LF
Hello, lads. Quick simple question for anyone who is familiar with RF basics: why does the coaxial cable leading to an antenna not contribute to the antenna length and screw up the resonant frequency?
depending on your definition of "screw up" it does, and assuming the impedance is prfectly match it doesn't really make any difference at what phase the wave to be radiated arrives
unless you have the experience to determine it on your own (which you probably don't have, hence asking here) you describe the setup to someone who has the experience and ask if it matters.
or you go and study the stuff until you have teh experience
What I basically want to do is to replace a trace antenna on a PCB with an external antenna. It's for a 433.92Mhz alarm that has awful range. Is this as simple as one could think and can the coax cable leading to the external antenna ruin this idea?
My assumption would be that the existing antenna is already horribly matched, it doesn't sound like top notch equipment, so if you know the impedance and have the coax, connectors and antenna look "perfectly" that impedance, then I would expect it to work fine
it also sounds like a case that you can just try out with minimal testing just fine
It's an OEM automotive alarm, it may be intentionally designed to have a short range. Or not, sometimes it just seem painfully short, possibly when I am around other RF sources. I am guessing I'll have to cut the trace antenna and the impedance matching circuit to be able to connect a dedicated 50ohm antenna, so not screwing it up would be nice.
@Asmyldof in this case, some level of 'audio' is still needed in the output, not purely 'noise' as such
Does anyone have any recommended manufacturers of precision inclinometers (tilt sensors)? I've found Sherbourne and Jewell so far, any major ones I'm missing somehow?
by precision, i'm talking in the 1 or less arc-second resolutions
@KyranF they do, but much more. Specialized in all kinds of precision optics and measurement devices. We used a laser tracker to measure spots of a planes fuselage to micrometer precision
@Asmyldof intresting little thing I noticed: when playing with the triggering options, I sometimes get a somewhat stable triggering and the hardware frequency counter shows 192kHz, the max frequency of the DAC
could you do the following... setup say 2khz sine wave 10mV or so and fiddle together a way to attach the scope probe in 1x setting to the funcgen
then wiggle the 1x/10x switch on the probe, espcially near the extremes, switch position and also orthogonal to the switch direction and see if anything changes
(besides obviosuly when it switches)
at my place I see some changes, but I am not sure if this is due to the cobbled together thing the probe is attached to and I am moving that despite my best efforts not to, or if the switch really does something
@Shalvenay maybe, but I am seeing huge differences, in amplitude as well as noise pickup, and I am wondering where it actually comes from, and since I don't have a trust funcgen setup...
even more wiggling and I had a situation where in the 1x setting the signal looked as if it was in 10x setting, and now I have the case where the noise is almost completely gone with one probe, including the class d amplification aartifact noise I talked about earlier today
so I would say it is deifnetly massively reducing the bandwidth somehow
I am interested in the ESP32 family, but I could not find a full feature table for ESP32... and ESP32 Wroom / ESP32 Wroom2. Do you know a link with a table for comparization?
