In comp.os.linux.misc The Natural Philosopher <tnp@invalid.invalid> wrote:
On 09/12/2025 11:57, Andy Burns wrote:
The Natural Philosopher wrote:Umm. Well now the rain has gone and the wind died down a little I am
might be dependent on where I parked the car
Monitoring within the appliance bays of multiple fire stations,
certainly shows signal levels exhibiting high and low levels depending
whether the truck is in or out ...
getting +6dB better signal. I could move the car...
I'll park that one (sic") till I use the car again, then I'll move it ...
Water greatly absorbs 2.4Ghz signals, so it is not surprising you see stronger signals once the extra "water" is no longer in the signal
path.
On 09/12/2025 11:57, Andy Burns wrote:
The Natural Philosopher wrote:Umm. Well now the rain has gone and the wind died down a little I am
might be dependent on where I parked the car
Monitoring within the appliance bays of multiple fire stations,
certainly shows signal levels exhibiting high and low levels depending
whether the truck is in or out ...
getting +6dB better signal. I could move the car...
I'll park that one (sic") till I use the car again, then I'll move it ...
The Natural Philosopher wrote:
might be dependent on where I parked the car
Monitoring within the appliance bays of multiple fire stations,
certainly shows signal levels exhibiting high and low levels depending whether the truck is in or out ...
The Natural Philosopher wrote:
might be dependent on where I parked the car
Monitoring within the appliance bays of multiple fire stations,
certainly shows signal levels exhibiting high and low levels depending whether the truck is in or out ...
c186282 wrote:
If monitoring 'emergency vehicles/installations'
˙˙ is critical, maybe consider something using lower
˙˙ frequencies than wi-fi ???
Nah, it was mostly "for interest" to gather a few more values from kit that's already being monitored. Someone else mentioned water (presumably
as rain) don't forget the fire appliances carry around their own water,
but hopefully it's low down for CoG reasons, while the access points are mounted higher up.
c186282 wrote:
˙˙ Now if real, legal, 'security' was an issue
˙˙ then you'd want a solid connection all of
˙˙ the time ... and one wi-fi point likely won't
˙˙ provide that.
Only the largest couple of stations have multiple APs in the bay.˙ The building and individual vehicles have 4G, and the buildings form a
meshed POCSAG network between neighbouring towns (or parts of cities).
Everybody thoughtReminds me of a brand new factory in Jo'burg. Solid concrete walls and a
˙ that the 1950s were the pinnacle of modern civ ...
˙ "What else WOULD you need to add in ???".
First of all thanks to all those who responded on my first efforts to
put a battery power Pi Pico W outside and have it phone home.
Having eliminated temperature and supply voltage as issues, I delved
into wifi and router logs, and it was clear that it was sometimes
getting a DHCP lease and even occasionally opening a TCP/IP connections
and sending data. And might be dependent on where I parked the car and
the weather.
I tried putting a tin tray behind the router and that made it worse.
Now the layout was that a ground floor router through the window and the garage was not very good at about 30m range.
Then I remembered I had put an Ethernet port in an upstairs bedroom by
the window in case I wanted to use it as an office.
It was further away - 35m or so - but much less cluttered path. It just
had to go through a corner of the garage.
Instantly the router reported about 8-10dB more signal and almost
reliable comms resulted.
And I knew all that trig would come in handy one day :-)
On 10/12/2025 10:02, c186282 wrote:
On 12/10/25 04:14, Andy Burns wrote:I stated for te record and for the interest of others doing outside wifi coupled IOT shit that rain wind and possibly cars made a difference.
c186282 wrote:
˙˙ I think it was you ... said how a cam wouldNo, maybe TNP said his oil level monitor would drop out?
˙˙ more or less drop out when the Big Red Truck
˙˙ was there.
˙˙ Posting traffic has considerably increased of late,
˙˙ partly my "fault" ... but COSLM was kind of dying
˙˙ and that would have been tragic. Forgive the sort
˙˙ of off-topic stuff, but it DOES keep minds alive -
˙˙ you can't ALWAYS think about Linux without kind
˙˙ of seizing up :-)
Someone else remarked that so did fire trucks.
The downside of the new oil monitor is that is is so accurate - to
within a litre it seems - that I can visibly see how much a shower or washing the dishes costs me, and a cold night is very expensive. :-)
LOL.
Now off to write the software that will look at it for me and warn me of things by email.
So I can get on with the next project.
On 11/12/2025 04:12, c186282 wrote:
Everybody thoughtReminds me of a brand new factory in Jo'burg. Solid concrete walls and a
˙˙ that the 1950s were the pinnacle of modern civ ...
˙˙ "What else WOULD you need to add in ???".
tin roof. And nnot a single socket or light that worked.
The contractor brought in to fix it spent 20 minutes looking and then
said 'Fuck that - get the Kangas' and simply chipped new channels for *everything*. Laid in pipe conduit and got wiring.
Before the days of computers that was, let alone networking. We used Telex.
˙ I've had to skip subject threading because of all
˙ the new postings ... just datetime sorting now.
The Natural Philosopher wrote:
the sensor I built on the tank has no power except batteries: So it
only wakes up occasionally and draws nanoamps in between.
I have completed the warning software that looks for low oil levels,
loss of communication, a failing battery and unexpected changes in oil
level, BUT it cannot do that in real time as the unit is only powered
up for a minute or so every couple of hours.
Depending on how long the batteries last I may increase the frequency
of operation.
Worth trying to send the data as UDP rather than TCP? if it fits in a
single packet,the receiver doesn't have to track the position within a stream ...
On 2025-12-10 11:24, The Natural Philosopher wrote:
On 10/12/2025 10:02, c186282 wrote:
On 12/10/25 04:14, Andy Burns wrote:I stated for te record and for the interest of others doing outside
c186282 wrote:
˙˙ I think it was you ... said how a cam wouldNo, maybe TNP said his oil level monitor would drop out?
˙˙ more or less drop out when the Big Red Truck
˙˙ was there.
˙˙ Posting traffic has considerably increased of late,
˙˙ partly my "fault" ... but COSLM was kind of dying
˙˙ and that would have been tragic. Forgive the sort
˙˙ of off-topic stuff, but it DOES keep minds alive -
˙˙ you can't ALWAYS think about Linux without kind
˙˙ of seizing up :-)
wifi coupled IOT shit that rain wind and possibly cars made a difference.
Someone else remarked that so did fire trucks.
The downside of the new oil monitor is that is is so accurate - to
within a litre it seems - that I can visibly see how much a shower or
washing the dishes costs me, and a cold night is very expensive. :-)
LOL.
Now off to write the software that will look at it for me and warn me
of things by email.
So I can get on with the next project.
You mentioned thieves stealing fuel. You can also monitor for that. You would need a fuel flow meter on the fuel line, or a sensor telling when
the furnace is working. Compare with the tank level decreasing rapidly.
On 11/12/2025 21:06, Carlos E.R. wrote:
On 2025-12-10 11:24, The Natural Philosopher wrote:
On 10/12/2025 10:02, c186282 wrote:
On 12/10/25 04:14, Andy Burns wrote:
c186282 wrote:
Now off to write the software that will look at it for me and warn me
of things by email.
So I can get on with the next project.
You mentioned thieves stealing fuel. You can also monitor for that.
You would need a fuel flow meter on the fuel line, or a sensor telling
when the furnace is working. Compare with the tank level decreasing
rapidly.
The problem is that the sensor I built on the tank has no power except batteries: So it only wakes up occasionally and draws nanoamps in between.
I have completed the warning software that looks for low oil levels,
loss of communication, a failing battery and unexpected changes in oil level, BUT it cannot do that in real time as the unit is only powered up
for a minute or so every couple of hours.
Depending on how long the batteries last I may increase the frequency of operation. But it can never be 'real time'
Two ideas.
Some routers can steer the signal horizontally; the technology is called "MIMO" (https://en.wikipedia.org/wiki/MIMO). You notice because the
router has multiple antenas, maybe four.
Then you can replace the antena on the router
directional WiFi antena.
Home made with a box of Pringles. just google
for "pringles wifi antenna". I made one and it actually works. But maybe they are sold, too.
On 2025-12-09 11:47, The Natural Philosopher wrote:
First of all thanks to all those who responded on my first efforts to
put a battery power Pi Pico W outside and have it phone home.
Having eliminated temperature and supply voltage as issues, I delved
into wifi and router logs, and it was clear that it was sometimes
getting a DHCP lease and even occasionally opening a TCP/IP
connections and sending data. And might be dependent on where I parked
the car and the weather.
I tried putting a tin tray behind the router and that made it worse.
Now the layout was that a ground floor router through the window and
the garage was not very good at about 30m range.
Then I remembered I had put an Ethernet port in an upstairs bedroom by
the window in case I wanted to use it as an office.
It was further away - 35m or so - but much less cluttered path. It
just had to go through a corner of the garage.
Instantly the router reported about 8-10dB more signal and almost
reliable comms resulted.
Two ideas.
Some routers can steer the signal horizontally; the technology is called "MIMO" (https://en.wikipedia.org/wiki/MIMO). You notice because the
router has multiple antenas, maybe four.
Then you can replace the antena on the router or the remote with a directional WiFi antena. Home made with a box of Pringles. just google
for "pringles wifi antenna". I made one and it actually works. But maybe they are sold, too.
...
And I knew all that trig would come in handy one day :-)
You can calculate it numerically on a computer, by calculating the aproximate integral ;-)
On 2025-12-12 11:26, The Natural Philosopher wrote:
On 11/12/2025 21:06, Carlos E.R. wrote:
On 2025-12-10 11:24, The Natural Philosopher wrote:
On 10/12/2025 10:02, c186282 wrote:
On 12/10/25 04:14, Andy Burns wrote:
c186282 wrote:
Now off to write the software that will look at it for me and warn
me of things by email.
So I can get on with the next project.
You mentioned thieves stealing fuel. You can also monitor for that.
You would need a fuel flow meter on the fuel line, or a sensor
telling when the furnace is working. Compare with the tank level
decreasing rapidly.
The problem is that the sensor I built on the tank has no power except
batteries: So it only wakes up occasionally and draws nanoamps in
between.
I have completed the warning software that looks for low oil levels,
loss of communication, a failing battery and unexpected changes in oil
level, BUT it cannot do that in real time as the unit is only powered
up for a minute or so every couple of hours.
Depending on how long the batteries last I may increase the frequency
of operation. But it can never be 'real time'
Ah.
What about a small solar panel and rechargeable batteries?
The Natural Philosopher wrote:
Well the daemon runs under xinetd...for sheer laziness. I guess I
could make it UDP.
But I don't know what problem that would solve.
The data would arrive if a single packet got through the fog, whereas
with tcp at least dour packets on sequence need to make it (or get
retried) with UDP you could afford to spray each packet half a dozen
times and if one of them makes it, you're good ...
The Natural Philosopher wrote:
Well the daemon runs under xinetd...for sheer laziness. I guess I
could make it UDP.
But I don't know what problem that would solve.
The data would arrive if a single packet got through the fog, whereas
with tcp at least dour packets on sequence need to make it (or get
retried) with UDP you could afford to spray each packet half a dozen
times and if one of them makes it, you're good ...
On 11/12/2025 21:18, Carlos E.R. wrote:
Two ideas.
Some routers can steer the signal horizontally; the technology is
called "MIMO" (https://en.wikipedia.org/wiki/MIMO). You notice because
the router has multiple antenas, maybe four.
Then you can replace the antena on the router
What antenna on the router?
It's just a wifi bridge with an internal something or other.
https://www.netxl.com/wifi-access-points/mikrotik-routerboard- rb951ui-2nd-wifi-4-access-point/
Its actually very very cheap and has been 'good enough'
or the remote with a
directional WiFi antena.
That gets complicated. I am trying easy shit first :-)
P Pico W doesn't have an 'antenna' either. Just some PCB traces.
Home made with a box of Pringles. just google for "pringles wifi
antenna". I made one and it actually works. But maybe they are sold, too.
Everything is possible. I am lazy. I do what is necessary to achieve
desired result and no more.
For now I seem to have adequate connectivity.
On 12/12/25 06:19, Carlos E.R. wrote:
On 2025-12-12 11:26, The Natural Philosopher wrote:
On 11/12/2025 21:06, Carlos E.R. wrote:
On 2025-12-10 11:24, The Natural Philosopher wrote:
On 10/12/2025 10:02, c186282 wrote:
On 12/10/25 04:14, Andy Burns wrote:
What about a small solar panel and rechargeable batteries?
˙ 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.
On 11/12/2025 21:18, Carlos E.R. wrote:
On 2025-12-09 11:47, The Natural Philosopher wrote:I sorta tried that without huge success, In fact I am getting up to 12dB variation in signal due to who knows what?
First of all thanks to all those who responded on my first efforts to
put a battery power Pi Pico W outside and have it phone home.
Having eliminated temperature and supply voltage as issues, I delved
into wifi and router logs, and it was clear that it was sometimes
getting a DHCP lease and even occasionally opening a TCP/IP
connections and sending data. And might be dependent on where I
parked the car and the weather.
I tried putting a tin tray behind the router and that made it worse.
Now the layout was that a ground floor router through the window and
the garage was not very good at about 30m range.
Then I remembered I had put an Ethernet port in an upstairs bedroom
by the window in case I wanted to use it as an office.
It was further away - 35m or so - but much less cluttered path. It
just had to go through a corner of the garage.
Instantly the router reported about 8-10dB more signal and almost
reliable comms resulted.
Two ideas.
Some routers can steer the signal horizontally; the technology is
called "MIMO" (https://en.wikipedia.org/wiki/MIMO). You notice because
the router has multiple antenas, maybe four.
Then you can replace the antena on the router or the remote with a
directional WiFi antena. Home made with a box of Pringles. just google
for "pringles wifi antenna". I made one and it actually works. But
maybe they are sold, too.
The setup is all somewhat experimental. At least˙ for now the software
is more or less stable - I have a few hanging daemons if the link goes
down mid message - but that is easily fixed .
...Huh? it can be as exact as your measurements are.
And I knew all that trig would come in handy one day :-)
You can calculate it numerically on a computer, by calculating the
aproximate integral ;-)
No 'approximations' here...
˙˙˙˙˙˙˙ diameter= tankDepth - offset;
˙˙˙˙˙˙˙ radius = diameter * 0.5;
˙˙˙˙˙˙˙ y = echoDepth - offset -radius;
˙˙˙˙˙˙˙ theta = asin( y / radius);
˙˙˙˙˙˙˙ x = radius * cos(theta);
˙˙˙˙˙˙˙ pie= radius * radius * theta;
˙˙˙˙˙˙˙ delta = x * y;
˙˙˙˙˙˙˙ area= (M_PI * radius *radius)/2 - (pie + delta);
˙˙˙˙˙˙˙ volume=(area/(M_PI * radius *radius ))*tankVolume;
That is about ultimately three days of work. It is redundant but I think
gcc can optimise out the intermediary variables that I used to make sure even I could understand it.
What has been encouraging is the pinpoint accuracy of the measurements.
Once in a stable environment the ultrasonics are very precise. something like a mm or two in a couple of metres. Probably more precise than the
speed of sound in air of variable pressures would justify, or indeed the expansion of the oil in warmer temperatures.
LOL.
Maybe I have built the world's most complicated barometer.
On 2025-12-12 12:28, The Natural Philosopher wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:
Two ideas.
Some routers can steer the signal horizontally; the technology is
called "MIMO" (https://en.wikipedia.org/wiki/MIMO). You notice
because the router has multiple antenas, maybe four.
Then you can replace the antena on the router
What antenna on the router?
It's just a wifi bridge with an internal something or other.
Ah, pity. Many AP have external antenas that are screwed on a socket.
https://www.netxl.com/wifi-access-points/mikrotik-routerboard-
rb951ui-2nd-wifi-4-access-point/
Its actually very very cheap and has been 'good enough'
Barely :-)
or the remote with a
directional WiFi antena.
That gets complicated. I am trying easy shit first :-)
P Pico W doesn't have an 'antenna' either. Just some PCB traces.
Yeah, well.
Home made with a box of Pringles. just google for "pringles wifi
antenna". I made one and it actually works. But maybe they are sold,
too.
Everything is possible. I am lazy. I do what is necessary to achieve
desired result and no more.
For now I seem to have adequate connectivity.
Of course, that is enough.
Home made with a box of Pringles. just google for "pringles wifi antenna".
On Wed, 24 Dec 2025 14:23:45 +0000
The Natural Philosopher <tnp@invalid.invalid> wrote:
[]
What I learned was that theory is too simplified to actually be able toPrsumably you're saying Mythbusters-style "not proven"?
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.
On 11/12/2025 21:18, Carlos E.R. wrote:
Home made with a box of Pringles. just google for "pringles wifi antenna".
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! :-)
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.
On 24/12/2025 07:58, mm0fmf wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:Assuming that is a relevant issue.
Home made with a box of Pringles. just google for "pringles wifi
antenna".
Also Google cutoff frequency and see that the Pringle tube is too
small in diameter to be effective at 2.4GHz.
Shouting down a pipe whose diameter is way less than the wavlength of
voice frequencies, still works....
Of course, designs on the internet do not have to follow the laws of
physics! :-)
..especially for people who don't fully understand them...
On 24/12/2025 12:16, The Natural Philosopher wrote:
On 24/12/2025 07:58, mm0fmf wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:Assuming that is a relevant issue.
Home made with a box of Pringles. just google for "pringles wifi
antenna".
Also Google cutoff frequency and see that the Pringle tube is too
small in diameter to be effective at 2.4GHz.
Shouting down a pipe whose diameter is way less than the wavlength of
voice frequencies, still works....
Of course, designs on the internet do not have to follow the laws of
physics! :-)
..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 cutoffA statement which clearly contradicts the well known skin effect of
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
On 11/12/2025 21:18, Carlos E.R. wrote:
Home made with a box of Pringles. just google for "pringles wifi
antenna".
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! :-)
On 24/12/2025 12:16, The Natural Philosopher wrote:
On 24/12/2025 07:58, mm0fmf wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:Assuming that is a relevant issue.
Home made with a box of Pringles. just google for "pringles wifi
antenna".
Also Google cutoff frequency and see that the Pringle tube is too
small in diameter to be effective at 2.4GHz.
Shouting down a pipe whose diameter is way less than the wavlength of
voice frequencies, still works....
Of course, designs on the internet do not have to follow the laws of
physics! :-)
..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
With Gigahertz, as with Heffalumps, you never know...
On 24/12/2025 20:07, The Natural Philosopher wrote:
With Gigahertz, as with Heffalumps, you never know...
Some of us do know.
On 2025-12-24, mm0fmf <none@invalid.com> wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:
Home made with a box of Pringles. just google for "pringles wifi antenna". >>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! :-)
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.
On 24/12/2025 17:00, Kerr-Mudd, John wrote:
On Wed, 24 Dec 2025 14:23:45 +0000I am saying that a blanket denial 'because the theory says no' is not
The Natural Philosopher <tnp@invalid.invalid> wrote:
[]
What I learned was that theory is too simplified to actually be able toPrsumably you're saying Mythbusters-style "not proven"?
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.
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...
On 11/12/2025 21:18, Carlos E.R. wrote:
Home made with a box of Pringles. just google for "pringles wifi antenna".
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! :-)
On 25/12/2025 03:25, Robert Riches wrote:
On 2025-12-24, mm0fmf <none@invalid.com> wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:
Home made with a box of Pringles. just google for "pringles wifi antenna".
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! :-)
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.
If I felt that a design of any sort could be connected to a Pi Pico W I would 3D print it.
But in the end the simpler approach was to create a wifi point higher up.
Signal strength varies wildly, but enough transmissions get through...
On 2025-12-24 15:23, The Natural Philosopher wrote:
On 24/12/2025 14:04, John R Walliker wrote:
On 24/12/2025 12:16, The Natural Philosopher wrote:
On 24/12/2025 07:58, mm0fmf wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:Assuming that is a relevant issue.
Home made with a box of Pringles. just google for "pringles wifi
antenna".
Also Google cutoff frequency and see that the Pringle tube is too
small in diameter to be effective at 2.4GHz.
Shouting down a pipe whose diameter is way less than the wavlength
of voice frequencies, still works....
Of course, designs on the internet do not have to follow the laws
of physics! :-)
..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.
An antenna is not a waveguide.
If a Pringles can were highly conductive it would have a cutoffA statement which clearly contradicts the well known skin effect of
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.
conductirs at high frequencies.
For many purposes a well made half-wave dipole or quarter-waveSure. Most routers come with wavelength sized wobbly penises that give
monopole gives excellent results which are far better than anything
that can be achieved with small pcb antennas.
you a few dB.
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
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.
I just say that once I built a Pringles antenna at a training course,
and it does work. Inside the tube there is a threaded metal rod with a number of nuts and washers that had to be put at precise distances
according to the instructions we followed.
Black magic.
We did not have any tool to measure gain, but indeed the router read a higher signal that with its manufacturer antena. And it was directional.
I can not give any number because I don't remember where my notes are.
Back to the original subject of the thread and to topic; Some of the
designs out there just put an USB dongle inside the tube, and they work, somehow. No need to actually have a wifi card with socket for the
antenna. If the Pi is small enough (I have no idea) there will be
designs out there using it.
On 24/12/2025 14:04, John R Walliker wrote:
On 24/12/2025 12:16, The Natural Philosopher wrote:
On 24/12/2025 07:58, mm0fmf wrote:
On 11/12/2025 21:18, Carlos E.R. wrote:Assuming that is a relevant issue.
Home made with a box of Pringles. just google for "pringles wifi
antenna".
Also Google cutoff frequency and see that the Pringle tube is too
small in diameter to be effective at 2.4GHz.
Shouting down a pipe whose diameter is way less than the wavlength of
voice frequencies, still works....
Of course, designs on the internet do not have to follow the laws of
physics! :-)
..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.
An antenna is not a waveguide.
If a Pringles can were highly conductive it would have a cutoffA statement which clearly contradicts the well known skin effect of conductirs at high frequencies.
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-waveSure. Most routers come with wavelength sized wobbly penises that give
monopole gives excellent results which are far better than anything
that can be achieved with small pcb antennas.
you a few dB.
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
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.
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