More on wifi range - Pi PICO W Oil level sensor

Seeed sells the "LiPo Rider Plus". After checking several brands of 'solar charge controllers' these were the ones I chose to power my field projects. Most of the others did NOT cap the voltage very well, or at all, so the sun comes out bright and you might send 6+ into your 3.1v device.

Combined with a 3 to 5 watt panel they'll keep even intermittent non-nano-power projects going.

Beware the quality of the batteries though ... got some no-names, about 50x50x10mm square, that were generally good - but one DID explode on me, inside the office building, when I barely touched it. Had not been charged for months either. Oh well, nothing to do but watch the big crimson flame .......

Fire control IS a priority with lithiums.

I once made a bi-directional client/server setup, first Python, then 'C'. One variant was TCP, the other UDP. Probably could have used a config file or defs ... but I never got to it.

On a clean LAN, both worked perfectly. However with some outdoor devices (Pi2 + wifi dongle as best I recall) both approaches had issues kind of similar to what you described.

TCP, while "error resistant", was often VERY iffy. UDP - well - easier/smaller to send. You could scan each packet for obvious errors and, if a fail, could ask for it again or just let the pgm work around to sending that data again.

For almost all modern apps, TCP is best by far. However iffy situations CAN still exist, so UDP you add some IQ to MIGHT be better.

As I've said elsewhere, wifi can sometimes be black magic. Weird RF shadows and multipaths can be anywhere and it's very hard to tell what's perfect placement.

Hmm ... apparently CANbus can be sent over wifi - but you lose some error-checking so there's no gain. There are various dongles for lower-freq data transmission too, but never got around to trying them. Fidelity might be worth losing some speed.

Huh. That's not good when the thing is intended to be near a oil tank.

Ah, pity. Many AP have external antenas that are screwed on a socket.

Barely :-)

Yeah, well.

Of course, that is enough.

You can aproximate the chord with a rectangle. If you divide the chord in two, it is two rectangles. Up to a thousand rectangles, or a million. The numerical result is close to the real result with a math formula. Kind of Runge-Kutta.

:-D

Or ask ChatGPT for the formula. I sure don't remember it, I doubt I ever saw it.

Actually it is a slot antenna. There is a gap in the ground plane which is equivalent to a dipole. It works remarkably well for its size.

John

Also Google cutoff frequency and see that the Pringle tube is too small in diameter to be effective at 2.4GHz.

Of course, designs on the internet do not have to follow the laws of physics! :-)

Assuming that is a relevant issue.

Shouting down a pipe whose diameter is way less than the wavlength of voice frequencies, still works....

..especially for people who don't fully understand them...

Indeed. And I'm sure you are perfectly well aware of the difference between longitudinal sound waves propagating down a narrow pipe and transverse electromagnetic waves in a waveguide. If a Pringles can were highly conductive it would have a cutoff frequency of close to 2.4GHz so the attenuation would be very high. However, a very thin layer of aluminium on the inside of a cardboard tube will be so resistive that it will not make a lot of difference. For many purposes a well made half-wave dipole or quarter-wave monopole gives excellent results which are far better than anything that can be achieved with small pcb antennas.

A quarter wave monopole made from relatively thick wire or rod can be an excellent match to 50 ohm coax so long as the ground plane is at least a few wavelengths across.

A half-wave dipole combined with a coaxial balun can also be a very good match but has a slightly narrower bandwidth due to the frequency dependency of the coax balun. The choice of which one to use depends mostly on how the antenna is to be mounted.

An almost omnidirectional antenna with very low losses can be more effective than a lossy directional one.

John

An antenna is not a waveguide.

A statement which clearly contradicts the well known skin effect of conductirs at high frequencies.

Sure. Most routers come with wavelength sized wobbly penises that give you a few dB.

Nevertheless I have seem that sort of design work. I worked around radar antennae briefly in the 1960s.

What I learned was that theory is too simplified to actually be able to design a real antenna: All our designs were field tested and adjusted.

I am not advocating Pringle cans. I wouldnt use one myself. But I am not so quick to rubbish them as you are.

RF propagation is tricky, and real world objects of no apparent value often have enormous effects.

Prsumably you're saying Mythbusters-style "not proven"?

I am saying that a blanket denial 'because the theory says no' is not good enough for me, personally.

To make a waveguide, which is analysable, is quite tricky. To throw something in place that 'does something' and clearly is *not* a waveguide, and is essentially unanalysable, is another matter.

With Gigahertz, as with Heffalumps, you never know...

As a wireless applications engineer, I have always shaken my head at the pringles can antenna, which if well made can have a gain up to at most 8 dBi or so. For less than $50, you can buy a professinally made flat patch antenna with 8 dBi gain at L-com.com. Apparently, you can find used ones on eBay for under $30, but why take the risk? If you need circular polarization, it will be closer to $75.

Some of us do know.

Yep, once you get into gHz things get really weird.

"Solutions" here can work for NO GOOD REASON, pure chance, funky reflections.

Moved a unit literally four inches the other day and the data rate went up nearly 5X.

Yes, a cheapo foil-lined tube CAN be a a waveguide, but the math has to work out.

Me, I can't use waveguides because I need an OMNI signal the way things are spaced out in my home. I use one, sometimes two, wifi repeaters instead. Fairly cheap, work well.

True, but the benefits of impedance matching with a megaphone were discovered long ago.

Some of us have worked with RF.

-- “I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives.”

― Leo Tolstoy

If you need a different diameter and know what diameter you need, any decent hardware store or home improvement big-box store in the US and perhaps elsewhere will have a wide assortment of sizes of PVC, ABS, and metal pipes and round conduits. Some adhesive and copper foil would seem likely to be useful for making the plastic types useable.