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Recent Experience With RF "Modem-ish" Data Links ?

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  Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-05-25 01:46 -0400
    Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-05-25 17:56 +0000
      Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-05-26 01:27 -0400
        Re: Recent Experience With RF "Modem-ish" Data Links ? TheLastSysop <thelastsysop@dev.null> - 2026-05-26 22:11 +0000
          Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-05-26 23:04 -0400
            Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-05-27 03:21 +0000
              Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-05-27 00:18 -0400
                Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-05-27 07:09 +0000
                  Re: Recent Experience With RF "Modem-ish" Data Links ? Nuno Silva <nunojsilva@invalid.invalid> - 2026-06-04 17:40 +0100
                    Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-04 14:43 -0400
                      Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-06-04 23:09 +0000
                        Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-04 23:14 -0400
                          Need for new personal ID numbers Lars Poulsen <lars@beagle-ears.com> - 2026-06-04 20:46 -0700
                            Re: Need for new personal ID numbers c186282 <c186282@nnada.net> - 2026-06-05 01:29 -0400
                          Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-06-05 04:53 +0000
                            Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-05 02:13 -0400
                          Re: Recent Experience With RF "Modem-ish" Data Links ? Andy Burns <usenet@andyburns.uk> - 2026-06-05 09:26 +0100
                            Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-05 05:24 -0400
                            Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-06-05 17:36 +0000
                              Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-06 00:16 -0400
                                Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-06-06 06:08 +0000
                                  Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-06 02:43 -0400
                                    Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-06-06 20:19 +0000
                                      Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-07 05:54 -0400
                                        Re: Recent Experience With RF "Modem-ish" Data Links ? rbowman <bowman@montana.com> - 2026-06-07 19:43 +0000
              Re: Recent Experience With RF "Modem-ish" Data Links ? The Natural Philosopher <tnp@invalid.invalid> - 2026-05-27 14:14 +0100
        WiFi range ... Lars Poulsen <lars@beagle-ears.com> - 2026-05-31 21:19 -0700
          Re: WiFi range ... TheLastSysop <thelastsysop@dev.null> - 2026-06-01 04:26 +0000
            Re: WiFi range ... Lars Poulsen <lars@beagle-ears.com> - 2026-06-01 22:44 -0700
          Re: WiFi range ... Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-07-31 23:00 +0000
            Re: WiFi range ... c186282 <c186282@nnada.net> - 2026-07-31 23:34 -0400
              Re: WiFi range ... rbowman <bowman@montana.com> - 2026-08-01 05:15 +0000
                Re: WiFi range ... c186282 <c186282@nnada.net> - 2026-08-01 21:30 -0400
                  Re: WiFi range ... rbowman <bowman@montana.com> - 2026-08-02 04:13 +0000
                    Re: WiFi range ... c186282 <c186282@nnada.net> - 2026-08-02 01:23 -0400
                  Re: WiFi range ... "Carlos E. R." <robin_listas@es.invalid> - 2026-08-02 14:26 +0200
                    Re: WiFi range ... The Natural Philosopher <tnp@invalid.invalid> - 2026-08-02 15:00 +0100
                      Re: WiFi range ... rbowman <bowman@montana.com> - 2026-08-02 19:46 +0000
                    Re: WiFi range ... c186282 <c186282@nnada.net> - 2026-08-02 22:57 -0400
                  Re: WiFi range ... Robert Komar <robk@robpc4.robk-home.org> - 2026-08-02 11:59 -0400
                    Re: WiFi range ... rbowman <bowman@montana.com> - 2026-08-02 19:44 +0000
        Re: Recent Experience With RF "Modem-ish" Data Links ? Andy Burns <usenet@andyburns.uk> - 2026-06-01 08:10 +0100
          Re: Recent Experience With RF "Modem-ish" Data Links ? TheLastSysop <thelastsysop@dev.null> - 2026-06-01 07:33 +0000
            Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-02 01:35 -0400
          Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-02 01:15 -0400
            Re: Recent Experience With RF "Modem-ish" Data Links ? Lars Poulsen <lars@beagle-ears.com> - 2026-06-01 22:50 -0700
              Re: Recent Experience With RF "Modem-ish" Data Links ? c186282 <c186282@nnada.net> - 2026-06-02 03:04 -0400

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#87579

On Sat, 6 Jun 2026 00:16:45 -0400, c186282 wrote:

>    Why order a $90 display for like an Ard Uno or equiv ?

https://www.amazon.com/dp/B0GBVWBWCR/

I splurged and went for the $7 version rather than the 4 for $10. That was 
a couple of years ago so maybe the Chinese weren't fully cranked up.

https://toptechboy.com/using-the-ssd1306-oled-with-an-arduino/

You can do Lissajous curves easily. Try that with your 2 line LCD.

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#87584

On 6/6/26 02:08, rbowman wrote:
> On Sat, 6 Jun 2026 00:16:45 -0400, c186282 wrote:
> 
>>     Why order a $90 display for like an Ard Uno or equiv ?
> 
> https://www.amazon.com/dp/B0GBVWBWCR/
> 
> I splurged and went for the $7 version rather than the 4 for $10. That was
> a couple of years ago so maybe the Chinese weren't fully cranked up.
> 
> https://toptechboy.com/using-the-ssd1306-oled-with-an-arduino/
> 
> You can do Lissajous curves easily. Try that with your 2 line LCD.

   Well, for my particular need right now, ONLY need
   a slow stats scroll. Better the 3-for-$9.95 displays.

   Job, needs, Why Spend More ?

   Did you ever use SeeTron or equiv "serial"
   displays ? If it could do RS-232, even by
   crude bit-banging, it would work. LCD was
   kinda new back then - most were VFD. Got
   one to work with a PIC-12xxx chip once.

   Tried to look up SeeTron lately ... does not
   seem to have a real page any more alas. It's
   mentioned, but not REALLY there.

   DO like VFDs ... they still make 'em - crude
   or even bit-addressable.

   Got in the equip to make a bigger square hole
   in that fancy aluminum ZERO case previously
   mentioned. The big hole added 10% to the wifi
   signal, this should add another 10%. Have some
   fiberglass tape to cover the hole. Case top will
   still be maybe 60% there to dissipate heat and
   provide mechanical protection.

   One step at a time.

   Now gotta remember how to wire 'parasite mode'
   on a DS temperature unit ......

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#87619

On Sat, 6 Jun 2026 02:43:15 -0400, c186282 wrote:

>    Did you ever use SeeTron or equiv "serial"
>    displays ? If it could do RS-232, even by crude bit-banging, it would
>    work. LCD was kinda new back then - most were VFD. Got one to work
>    with a PIC-12xxx chip once.

I don't think so. The handheld pH meters had a custom LCD, but I can't 
remember the interface. If I did it with an 8049 it wasn't very complex. 

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#87643

On 6/6/26 16:19, rbowman wrote:
> On Sat, 6 Jun 2026 02:43:15 -0400, c186282 wrote:
> 
>>     Did you ever use SeeTron or equiv "serial"
>>     displays ? If it could do RS-232, even by crude bit-banging, it would
>>     work. LCD was kinda new back then - most were VFD. Got one to work
>>     with a PIC-12xxx chip once.
> 
> I don't think so. The handheld pH meters had a custom LCD, but I can't
> remember the interface. If I did it with an 8049 it wasn't very complex.

   Well, RS-232 is so BASIC ... ergo those devices
   would work with almost ANYTHING - even PIC-12xxx
   if needed.

   But they weren't cheap.

   Got in my LCD displays ... suprisingly actually a
   tad LARGER than a PI-0. Gotta find DOCS though,
   nothing in the box.

   Anyway, five, six, maybe seven slow-scrolling lines
   of basic stats - that's ALL I want. Quick ref. The
   displays are super-cheap ... ideal for the use .....

   I2C displays work. NOT sophisticated or fast but
   FUNCTIONAL and generally just 4 wires. Lots of
   libs for them - Ards/PIs/BBBs/etc.

   And yea still, I really kinda LIKE the look of VFDs.
   They used to be IT ... now they're more an 'option'
   and more expensive. The LCDs will serve my immediate
   need however.

   Will post on a 'web-cam' I got ... TRIED to cheat
   the automatic IR-LED/lens-switch by pulling plugs
   (hey, I always take such things APART). No good.
   Fair cam - but, as said, need tricks. For NOW just
   taped black cardboard over the IR LEDs .....

   As for "seetron" ... appears to be mostly defunct.
   Kinda sad.

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#87660

On Sun, 7 Jun 2026 05:54:51 -0400, c186282 wrote:

>    Got in my LCD displays ... suprisingly actually a tad LARGER than a
>    PI-0. Gotta find DOCS though, nothing in the box.

The ones i have are 2.25 x 3.75 inches OA. Some of that is the circuit 
board. Unlike the old days you don't get a data sheet with anything. There 
are libs for Arduino, MicroPython, and CircuitPython to handle all the I2C 
bit banging.

https://randomnerdtutorials.com/micropython-i2c-lcd-esp32-esp8266/

Even the SSD1306 OLEDs are easy with the libraries though you do have to 
do more work for graphing etc. 

For your next project:

https://hackaday.com/2026/06/06/pi-pico-demos-therefore-it-is/

My eyes glassed over about 15 minutes in but then I never liked screwing 
around with OpenGL. Still, it's impressive and the guy knows his way 
around a 2340. I like the part about using a debug flag to intercept the 
GPIO output without using the pins.

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#87196

On 27/05/2026 04:21, rbowman wrote:
> On Tue, 26 May 2026 23:04:18 -0400, c186282 wrote:
> 
>>     Now, can I do LoRa with like a higher-end Ard ? PIs are nice but
>>     they're power hogs, can't 'sleep'. Haven't looked into the
>>     BeagleBones recently ... DO have a BBB in The Heap somewhere though.
> 
> https://store.arduino.cc/products/arduino-mkr-wan-1310
> 
Pico Pis can me made to sleep with the addition of a TPL5110 nanotimer.

I am looking at over a year battery life on 3xAA  lithium primaries.


-- 
“The urge to save humanity is almost always only a false face for the 
urge to rule it.”
– H. L. Mencken

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#87319 — WiFi range ...

On 2026-05-25 22:27, c186282 wrote:
> On 5/25/26 13:56, rbowman wrote:
>> On Mon, 25 May 2026 01:46:15 -0400, c186282 wrote:
>>
>>> Anyway ... NOW I may have a use for RF "modems",
>>> a link to a kind of far-off property site. Do not need video, MAYbe the
>>> odd still image. The low speed isn't relevant, just the range. WiFi
>>> isn't gonna cut it at all.
>>
>> How far off? 
> 
> 
>    About 1000 meters.

My company's high reliability radios use essentially 20 year old WiFi 
technology, and we have customers than routinely run them over distances 
of 5-10 km. It is not the technology per se that limits distance; it is 
the cheap off-the-shelf gear that is crap.

We use an 802.11b modulator, in 900 MHz or 2400 MHz bands, at speeds 
from 100 kbps effective data transfer rates to 8Mbps. We do NOT us the 
802.11 MAC layers, because we WANT to be guaranteed to be incompatible 
with WiFi. We pair this modem chipset with a very good front-end (low 
noise receive amplifier and very clean, very linear power amplifier. And 
then we put good directional antennas on them. We have one customer who 
runs a 100km radio link with a 27dBi antenna at 500mW (27 dBm) power 
output. For years.

I bet many commercial WiFi radios if paired with a decent front-end and 
a good antenna, even an 18dBi panel antenna, would give you a reliable 
link over 5km/3miles, so long as you have a clean line of sight. Its not 
really that hard.

-- 
Lars Poulsen - an old geek in Santa Barbara, California

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#87320 — Re: WiFi range ...

>On Sun, 31 May 2026 21:19:08 -0700, Lars Poulsen <lars@beagle-ears.com> wrote:
>On 2026-05-25 22:27, c186282 wrote:
>> On 5/25/26 13:56, rbowman wrote:
>>> On Mon, 25 May 2026 01:46:15 -0400, c186282 wrote:
>>>
>>>> Anyway ... NOW I may have a use for RF "modems",
>>>> a link to a kind of far-off property site. Do not need video, MAYbe the
>>>> odd still image. The low speed isn't relevant, just the range. WiFi
>>>> isn't gonna cut it at all.
>>>
>>> How far off?
>>
>>
>>    About 1000 meters.
>
>My company's high reliability radios use essentially 20 year old WiFi
>technology, and we have customers than routinely run them over distances
>of 5-10 km. It is not the technology per se that limits distance; it is
>the cheap off-the-shelf gear that is crap.
>
>We use an 802.11b modulator, in 900 MHz or 2400 MHz bands, at speeds
>from 100 kbps effective data transfer rates to 8Mbps. We do NOT us the
>802.11 MAC layers, because we WANT to be guaranteed to be incompatible
>with WiFi. We pair this modem chipset with a very good front-end (low
>noise receive amplifier and very clean, very linear power amplifier. And
>then we put good directional antennas on them. We have one customer who
>runs a 100km radio link with a 27dBi antenna at 500mW (27 dBm) power
>output. For years.
>
>I bet many commercial WiFi radios if paired with a decent front-end and
>a good antenna, even an 18dBi panel antenna, would give you a reliable
>link over 5km/3miles, so long as you have a clean line of sight. Its not
>really that hard.

For a 1 km link, I would start with the boring purpose-built gear rather than
trying to make ordinary indoor WiFi stretch that far.  A pair of outdoor
CPE/bridge units with directional panels will usually be far less fiddly than
routers plus random antennas.

The practical checks are mostly RF geometry, not Linux-specific:

* clear line of sight, including some Fresnel-zone clearance;
* fixed mounting and careful alignment at both ends;
* outdoor-rated cable/enclosures and proper grounding/lightning protection;
* enough margin for rain, leaves, and future clutter in the path.

If only low-rate data and the occasional still image are needed, backing the
link down to a slower modulation/rate can buy a lot of reliability.  Once the
bridge is up, Linux just sees an Ethernet path, which is the nicest possible
outcome.

-- 
TheLastSysop <thelastsysop@dev.null>
"I survived the great rm -rf / rehearsal and all I got was this .signature."

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#87354 — Re: WiFi range ...

On 2026-05-31 21:26, TheLastSysop wrote:
>> On Sun, 31 May 2026 21:19:08 -0700, Lars Poulsen <lars@beagle-ears.com> wrote:
>> On 2026-05-25 22:27, c186282 wrote:
>>> On 5/25/26 13:56, rbowman wrote:
>>>> On Mon, 25 May 2026 01:46:15 -0400, c186282 wrote:
>>>>
>>>>> Anyway ... NOW I may have a use for RF "modems",
>>>>> a link to a kind of far-off property site. Do not need video, MAYbe the
>>>>> odd still image. The low speed isn't relevant, just the range. WiFi
>>>>> isn't gonna cut it at all.
>>>>
>>>> How far off?
>>>
>>>
>>>     About 1000 meters.
>>
>> My company's high reliability radios use essentially 20 year old WiFi
>> technology, and we have customers than routinely run them over distances
>> of 5-10 km. It is not the technology per se that limits distance; it is
>> the cheap off-the-shelf gear that is crap.
>>
>> We use an 802.11b modulator, in 900 MHz or 2400 MHz bands, at speeds
>>from 100 kbps effective data transfer rates to 8Mbps. We do NOT us the
>> 802.11 MAC layers, because we WANT to be guaranteed to be incompatible
>> with WiFi. We pair this modem chipset with a very good front-end (low
>> noise receive amplifier and very clean, very linear power amplifier. And
>> then we put good directional antennas on them. We have one customer who
>> runs a 100km radio link with a 27dBi antenna at 500mW (27 dBm) power
>> output. For years.
>>
>> I bet many commercial WiFi radios if paired with a decent front-end and
>> a good antenna, even an 18dBi panel antenna, would give you a reliable
>> link over 5km/3miles, so long as you have a clean line of sight. Its not
>> really that hard.
> 
> For a 1 km link, I would start with the boring purpose-built gear rather than
> trying to make ordinary indoor WiFi stretch that far.  A pair of outdoor
> CPE/bridge units with directional panels will usually be far less fiddly than
> routers plus random antennas.
> 
> The practical checks are mostly RF geometry, not Linux-specific:
> 
> * clear line of sight, including some Fresnel-zone clearance;
> * fixed mounting and careful alignment at both ends;
> * outdoor-rated cable/enclosures and proper grounding/lightning protection;
> * enough margin for rain, leaves, and future clutter in the path.
> 
> If only low-rate data and the occasional still image are needed, backing the
> link down to a slower modulation/rate can buy a lot of reliability.  Once the
> bridge is up, Linux just sees an Ethernet path, which is the nicest possible
> outcome.

Bravo. You are hitting all the requirements for it to work.

My point was that it is not the RF technology (modulation, frequency 
band etc) that limit the range of WiFi, just a general sloppiness in the 
way 99.9% use the gear with no respect for microwave propagation 
characteristics.

-- 
Lars Poulsen - an old geek in Santa Barbara, California

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#89372 — Re: WiFi range ...

On Sun, 31 May 2026 21:19:08 -0700, Lars Poulsen wrote:

> My company's high reliability radios use essentially 20 year old WiFi
> technology, and we have customers than routinely run them over distances
> of 5-10 km.

In the early days of wi-fi, when many people were using it to set up
point-to-point links to extend access to those limited early broadband
deployments, it was common to use an empty Pringles chip can as a
high-gain antenna.

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#89374 — Re: WiFi range ...

On 7/31/26 19:00, Lawrence D’Oliveiro wrote:
> On Sun, 31 May 2026 21:19:08 -0700, Lars Poulsen wrote:
> 
>> My company's high reliability radios use essentially 20 year old WiFi
>> technology, and we have customers than routinely run them over distances
>> of 5-10 km.
> 
> In the early days of wi-fi, when many people were using it to set up
> point-to-point links to extend access to those limited early broadband
> deployments, it was common to use an empty Pringles chip can as a
> high-gain antenna.

   Saw an article where somebody spliced in a REAL antenna
   to a RPi - and got a HUGE range increase. Probably illegal
   but, really, nobody's checking.

   WiFi has pretty shitty range. The 2ghz band tends to
   work better - 5ghz is more blocked by obstacles.

   I have a big enough property where I had to buy
   an 'extender' to improve coverage to out-buildings.
   Not expensive, several makers have them, work OK.
   Had best success with TP-Link. Setup can be a bit
   weird, counter-intuitive, but you'll get it.

   Some of the older data links - 400 or 900mhz band -
   do have kilometer+ range. However the data rate
   might not meet modern needs. Ya ain't gonna be
   streaming 8K over them.

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#89376 — Re: WiFi range ...

On Fri, 31 Jul 2026 23:34:54 -0400, c186282 wrote:

>    Some of the older data links - 400 or 900mhz band -
>    do have kilometer+ range. However the data rate might not meet modern
>    needs. Ya ain't gonna be streaming 8K over them.

I am a little curious where the outdoor temperature/humidity so I can 
thank the provider. They transmit on 433 MHz so who knows?

rtl_433/Accurite-600TXC/185: {
"time":"2026-08-0105:01:44",
"model":"Acurite-609TXC",
"id":185,
"battery_ok":1,
"temperature_F":75.38,
"humidity":45,
"status":2,"
mic":"CHECKSUM"}

There is another one but it doesn't have humidity so I don't pass it to 
the mqtt broker. I wonder if it's near a lawn sprinkler. weather.gov has 
Humidity 28% and 81°F.

https://github.com/merbanan/rtl_433

It handles a load of protocols but I specified 11 so I only see the 
Accurite data. I should run it wide open and see what else is lurking 
around.

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#89421 — Re: WiFi range ...

On 8/1/26 01:15, rbowman wrote:
> On Fri, 31 Jul 2026 23:34:54 -0400, c186282 wrote:
> 
>>     Some of the older data links - 400 or 900mhz band -
>>     do have kilometer+ range. However the data rate might not meet modern
>>     needs. Ya ain't gonna be streaming 8K over them.
> 
> I am a little curious where the outdoor temperature/humidity so I can
> thank the provider. They transmit on 433 MHz so who knows?
> 
> rtl_433/Accurite-600TXC/185: {
> "time":"2026-08-0105:01:44",
> "model":"Acurite-609TXC",
> "id":185,
> "battery_ok":1,
> "temperature_F":75.38,
> "humidity":45,
> "status":2,"
> mic":"CHECKSUM"}
> 
> There is another one but it doesn't have humidity so I don't pass it to
> the mqtt broker. I wonder if it's near a lawn sprinkler. weather.gov has
> Humidity 28% and 81°F.
> 
> https://github.com/merbanan/rtl_433
> 
> It handles a load of protocols but I specified 11 so I only see the
> Accurite data. I should run it wide open and see what else is lurking
> around.

   As said, I'd be a little skeptical about the accuracy
   of the humidity reading. I tested a number of units
   when working on some field-conditions dataloggers and
   wasn't pleased with any of them. There are some theoretical
   ways to detect water vapor, but they don't seem very good,
   at least not in affordable little devices.

   Now you CAN make a wet/dry-bulb unit using two DS
   18b20 temperature sensors - one kinda wrapped in a
   light wet cloth. Suggest dipping both sensors in epoxy
   to enhance water resistance. DO adjust the reported
   temperatures, dry, to be the same. The Dallas 1-wire
   devices are GOOD, but no two of them will read
   EXACTLY the same. Calibrate at the bench, using a
   scientific conventional thermometer as reference.

   Now the wet bulb, how the hell do you KEEP it wet ?
   This can be a PROBLEM depending on environment. Where
   I was, there was surely a little rain every 7-10 days.
   A cheepo reservoir was easy to rig. It's also possible
   to lace the wet cloth with a chemical, ammonium nitrate
   for example, which is extremely hydroscopic - but the
   chosen salt WILL affect the reading and compensation
   will be needed.

   Anyway, wet+dry will give you a very real figure, but
   at added complexity.

   Do you really NEED super-accurate humidity readings ?
   For like a big commercial greenhouse, YES. For yer
   back-yard, close-enough may be close-enough.

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#89434 — Re: WiFi range ...

On Sat, 1 Aug 2026 21:30:22 -0400, c186282 wrote:

>   Do you really NEED super-accurate humidity readings ?
>    For like a big commercial greenhouse, YES. For yer back-yard,
>    close-enough may be close-enough.

Idle curiosity. The 45% surprised me. right now it's reporting 
"temperature_F":81.5,"humidity":21

which is more in line with the NOAA figure. A front is moving in. No rain 
but it's supposed to be high 70s Sunday and Monday. That will feel like 
winter after the high 90s.

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#89437 — Re: WiFi range ...

On 8/2/26 00:13, rbowman wrote:
> On Sat, 1 Aug 2026 21:30:22 -0400, c186282 wrote:
> 
>>    Do you really NEED super-accurate humidity readings ?
>>     For like a big commercial greenhouse, YES. For yer back-yard,
>>     close-enough may be close-enough.
> 
> Idle curiosity. The 45% surprised me. right now it's reporting
> "temperature_F":81.5,"humidity":21
> 
> which is more in line with the NOAA figure. A front is moving in. No rain
> but it's supposed to be high 70s Sunday and Monday. That will feel like
> winter after the high 90s.

   For cheap you can buy a wet/dry bulb unit with
   a nice little chart on it. My granny had one
   on her porch. That was 1960s.

   It might be interesting/informative to compare
   yer device readings with the Gold Standard.

   But, as said, for "home" stuff, close enough
   might be close enough.

   Ah, my Momma had two funky things. One was
   "horse-hair" actuated - little figures would
   come out depending on high/low humidity. The
   other was a kind of "stick", made of wood
   that's sensitive to humidity. If it curled
   down it meant low, if straight out it meant
   high.

   Variances in how various frequencies of light
   are absorbed according to water-vapor percentage
   make "match-box" folded-path metrology possible.
   Ya have two laser diodes - one on a high-absorbsion
   frequency, the other for low. Mirror strips inside,
   turns the 'matchbox' into like a meter-long path.
   Comparing freq 'A' to 'B' can give you a fair reading.

   I think most modern mini-devices just have a sort
   of semi-hydroscopic layer - you measure the resistance
   across the layer. Alas there are a number of ways that
   can become rather imprecise.

   Now, as also said, for like a big commercial greenhouse,
   more exact humidity readings may be rather critical so
   'scientific management' is possible.

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#89466 — Re: WiFi range ...

On 2026-08-02 03:30, c186282 wrote:
>    Now the wet bulb, how the hell do you KEEP it wet ?

And fungi free?

>    This can be a PROBLEM depending on environment. Where
>    I was, there was surely a little rain every 7-10 days.
>    A cheepo reservoir was easy to rig. It's also possible
>    to lace the wet cloth with a chemical, ammonium nitrate
>    for example, which is extremely hydroscopic - but the
>    chosen salt WILL affect the reading and compensation
>    will be needed.


-- 
Cheers,
        Carlos E.R.
        ES🇪🇸, EU🇪🇺;

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#89471 — Re: WiFi range ...

On 02/08/2026 13:26, Carlos E. R. wrote:
> On 2026-08-02 03:30, c186282 wrote:
>> Now the wet bulb, how the hell do you KEEP it wet ?
> 
> And fungi free?
> 
>> This can be a PROBLEM depending on environment. Where I was, there
>> was surely a little rain every 7-10 days. A cheepo reservoir was
>> easy to rig. It's also possible to lace the wet cloth with a
>> chemical, ammonium nitrate for example, which is extremely
>> hydroscopic - but the chosen salt WILL affect the reading and
>> compensation will be needed.
> 
> 
AI Overview:

Humidity sensors measure water vapour in the air using capacitive,
resistive, or thermal conductivity methods. They track changes in
electrical properties or heat patterns when moisture is absorbed.

Capacitive Sensors
============
Structure: A moisture-absorbing (hygroscopic) material sits between two
metal plates (electrodes).

Action: The material absorbs water from the air, which changes its
ability to store an electrical charge.

Output: The sensor measures this change in capacitance and turns it into
a relative humidity percentage.

Resistive Sensors
===========

Structure: A pair of electrodes is coated with a material like a
conductive polymer or salt.

  Action: Absorbed moisture breaks down into ions, which changes the
electrical resistance across the coating.

  Output: Lower resistance means higher humidity, which the device
calculates into a reading.

Thermal Conductivity Sensors
===================

Structure: Two small heat-producing parts (thermistors) are used.

Action: One part is sealed in dry gas while the other is exposed to the air.

Output: Moisture in the air cools the exposed part differently than the
dry one, and the difference in resistance measures absolute humidity.
---------------------------------------------------------------------

Presumably any hygroscopic elements are soaked in fungicide at manufacture

-- 
The difference bweteen a psychopath and a saint is that the psychpoath
takes what he can and gives only what he must, but the saint gives
everything he can and takes only what he needs.

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#89477 — Re: WiFi range ...

On Sun, 2 Aug 2026 15:00:53 +0100, The Natural Philosopher wrote:

> Resistive Sensors ===========
> 
> Structure: A pair of electrodes is coated with a material like a
> conductive polymer or salt.
> 
>   Action: Absorbed moisture breaks down into ions, which changes the
> electrical resistance across the coating.
> 
>   Output: Lower resistance means higher humidity, which the device
> calculates into a reading.

fwiw, that's the technique used in the DHT11 and other cheap sensors.

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#89487 — Re: WiFi range ...

On 8/2/26 08:26, Carlos E. R. wrote:
> On 2026-08-02 03:30, c186282 wrote:
>>    Now the wet bulb, how the hell do you KEEP it wet ?
> 
> And fungi free?

   Zinc chloride. A little dab 'll do ya.

   DO keep it off the wires though, hence
   my 'epoxy-dip' rec  :-)

>>    This can be a PROBLEM depending on environment. Where
>>    I was, there was surely a little rain every 7-10 days.
>>    A cheepo reservoir was easy to rig. It's also possible
>>    to lace the wet cloth with a chemical, ammonium nitrate
>>    for example, which is extremely hydroscopic - but the
>>    chosen salt WILL affect the reading and compensation
>>    will be needed.

   The "KEEPING it wet" can be more of a problem.

   Fine if the unit is on your back porch, but what
   if it's an environmental station 90 miles back
   into the hills ?

   As said, there ARE some - kinda iffy - ways to
   detect water vapor that can fit into a kinda
   small/cheap package. It just depends on HOW
   accurate you need to be. If plus/minus 15%
   is functionally OK then ......

   But I did do work for a commercial greenhouse
   long long back ... for max yield they needed
   more accurate figures.

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#89474 — Re: WiFi range ...

c186282 <c186282@nnada.net> wrote:
> 
>   Now you CAN make a wet/dry-bulb unit using two DS
>   18b20 temperature sensors - one kinda wrapped in a
>   light wet cloth. Suggest dipping both sensors in epoxy
>   to enhance water resistance. DO adjust the reported
>   temperatures, dry, to be the same. The Dallas 1-wire
>   devices are GOOD, but no two of them will read
>   EXACTLY the same. Calibrate at the bench, using a
>   scientific conventional thermometer as reference.
> 
>   Now the wet bulb, how the hell do you KEEP it wet ?
>   This can be a PROBLEM depending on environment. Where
>   I was, there was surely a little rain every 7-10 days.
>   A cheepo reservoir was easy to rig. It's also possible
>   to lace the wet cloth with a chemical, ammonium nitrate
>   for example, which is extremely hydroscopic - but the
>   chosen salt WILL affect the reading and compensation
>   will be needed.
> 
>   Anyway, wet+dry will give you a very real figure, but
>   at added complexity.
> 
>   Do you really NEED super-accurate humidity readings ?
>   For like a big commercial greenhouse, YES. For yer
>   back-yard, close-enough may be close-enough.
> 
Back when I was an student in the 80's, one mechanical engineering
professor described doing wet/dry bulb measurements.  The thermometers
were tied to lanyards, and you would whirl them around in the air at
a certain rate to get more air flow over the bulbs during the
measurement.  It increased the difference between the wet and dry
readings for better accuracy, and the tables were adjusted for that
affect.  My old thermodynamics textbook has a Psychrometric Chart in
the back that you could use for calculating the absolute humidity from
the temperatures.  It doesn't say whether the bulbs should be whirled
around or not, maybe that was common knowledge back then.

Cheers,
Rob Komar

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