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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: WiFi range ... c186282 <c186282@nnada.net> - 2026-08-03 00:12 -0400
        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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#89476 — Re: WiFi range ...

On Sun, 2 Aug 2026 11:59:29 -0400, Robert Komar wrote:

> 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.

https://ktagage.com/product/sling-psychrometer/

The video shows the use of the charts. Barometric pressure comes into play 
too. I assume that takes into account elevation. The side by side types 
probably are good enough although with no motion the air around the wet 
bulb will be affected by the evaporation.

Digital hygrometers measure the capacitance or resistance of a moisture 
sensitive material. The common DHT11 uses resistance which isn't as 
accurate as capacitance but what do you want for $3? One of the Accurite 
pages mentions both methods but doesn't say which is used. In both cases 
onboard processing handles the raw measurements of the thermistor and 
humidity sensor 

I suppose I could build a 70 cm Yagi and go fox hunting to find the 
Accurite unit but whoever owns it probably wouldn't be happy with me 
taking it apart.

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#89494 — Re: WiFi range ...

On 8/2/26 11:59, Robert Komar wrote:
> 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.

   "Whirl-around" IS best.

   However, for a fixed unit these days, maybe the
   best is a tiny PI fan that sucks air over the
   thing. Start the fan like 60 seconds before you
   make the reading. Doesn't need MUCH power.

   Anyway, kind-of EXACT humidity readings are a sort
   of black art. A number of cheepo approaches, some
   small and low $$$, but expect at least a 15% variance
   from reality.

   I did lots of environmental field units, tried a
   bunch of 'solutions'. None of the 'cheap' ones were
   very good - though kinda sorta "good enough". The
   one diff was for a commercial greenhouse, good yield
   required precise monitoring. Just for humidity I had
   to use a $250 unit to get 'precise'. They DID pay,
   but didn't LIKE it. Faked a wet/dry unit on some
   field units I did later using dual 1-wire DS
   temperature sensors. Cheaper but still Good Enough.

   Greenhouse, if humidity too low, you sent pulses to
   a 'mist' unit - sprayed water mist into the air.
   Wait 30 minutes, test again.

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#87325

c186282 wrote:

> rbowman wrote:
> >> c186282 wrote:
>>
>>> 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.
>    NO power utilities there.
Maybe look at specialised WiFi?  802.11ah HaLow

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#87326

>On Mon, 1 Jun 2026 08:10:41 +0100, Andy Burns <usenet@andyburns.uk> wrote:
>c186282 wrote:
>
>> rbowman wrote:
>> >> c186282 wrote:
>>>
>>>> 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.
>>    NO power utilities there.
>Maybe look at specialised WiFi?  802.11ah HaLow

For 1000 m and no mains, I would split the question into "link budget" and
"power budget" before buying anything.

If there is clean line of sight, a pair of outdoor point-to-point CPE radios
(Ubiquiti/MikroTik/TP-Link CPE type kit) is usually simpler than old-style RF
modems and can be throttled down to very little traffic.  The catch is that the
remote end still needs a small panel, battery, charge controller and a
weatherproof enclosure, so idle power matters more than peak throughput.

If it is not line-of-sight, or if the remote end is just sending occasional
sensor data/status and maybe not images, then LoRa/LoRaWAN-type gear is worth a
look.  It is much easier to run from a small battery/solar setup, but it is not
a substitute for an IP-ish link with images.

HaLow sits between those worlds.  I would check local regulatory limits and the
actual antenna options before assuming it beats a boring directional 2.4/5 GHz
bridge at only 1 km.

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

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#87353

On 6/1/26 03:33, TheLastSysop wrote:
>> On Mon, 1 Jun 2026 08:10:41 +0100, Andy Burns <usenet@andyburns.uk> wrote:
>> c186282 wrote:
>>
>>> rbowman wrote:
>>>>> c186282 wrote:
>>>>
>>>>> 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.
>>>     NO power utilities there.
>> Maybe look at specialised WiFi?  802.11ah HaLow
> 
> For 1000 m and no mains, I would split the question into "link budget" and
> "power budget" before buying anything.

   The LINKS - several variants - seem to be affordable.
   At 400/900mhz seem to have good range and obstacle
   immunity.

   The power budget - always a tricky equation. Plenty
   of lithium chargers that plug into PV panels. The
   "Seeed" brand, "LiPo Rider Plus", are the best - no
   voltage spikes even at low/no demand.

   My old dataloggers could get by on a 5w panel just
   fine. However they didn't xmit anything, just
   recorded to a card. Came out of sleep every 15
   minutes.

   However transmitting can use up a lot more power.
   Anything 'on demand' like a camera frame will
   use up more, transiently.

> If there is clean line of sight, a pair of outdoor point-to-point CPE radios
> (Ubiquiti/MikroTik/TP-Link CPE type kit) is usually simpler than old-style RF
> modems and can be throttled down to very little traffic.  The catch is that the
> remote end still needs a small panel, battery, charge controller and a
> weatherproof enclosure, so idle power matters more than peak throughput.

   My line-of-sight is NOT "clean" ... ergo the interest
   in lower-freq links.

> If it is not line-of-sight, or if the remote end is just sending occasional
> sensor data/status and maybe not images, then LoRa/LoRaWAN-type gear is worth a
> look.  It is much easier to run from a small battery/solar setup, but it is not
> a substitute for an IP-ish link with images.
> 
> HaLow sits between those worlds.  I would check local regulatory limits and the
> actual antenna options before assuming it beats a boring directional 2.4/5 GHz
> bridge at only 1 km.

   Still looking in to What's Out There these days.
   A few possibly good options - also a few that,
   on consideration, probably won't cut it.

   Gotta run a few numbers yet, then I'll decide.

   PIs are OUT ... massive power hogs. Good
   microcontrollers give much more control.

   Anyway, fun project ! Tired of not knowing
   what's going on at my other property too.
   If it's on fire I wanna know. If squats
   set up a camp, I wanna know. If shits are
   dumping trash, I wanna know.

   I know a guy with a bucket-truck - for a few
   bucks he could screw an instrument package to
   one of the tall trees. Olive-drab canvas
   strips with an odd splurt of 'primer' brown
   and it'd look perfectly natural unless you
   actually climbed the tree. The panel can go
   on top, angled up maybe 40 degrees, kind of
   invisible. Have had to use 'disguise' before
   in semi-public areas.

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#87352

On 6/1/26 03:10, Andy Burns wrote:
> c186282 wrote:
> 
>> rbowman wrote:
>> >> c186282 wrote:
>>>
>>>> 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.
>>    NO power utilities there.
> Maybe look at specialised WiFi?  802.11ah HaLow

   "Lo-RA" ? That's been recommended for the described
   range and need. Am looking into it.

   A few other suggestions too. 900mhz band may be
   the 'best' - less speed but more range and more
   immunity to common obstacles. Old days (and a
   few are still sold) 400mhz might also meet my
   modest needs with even better obstacle immunity.
   Clearly "live audio", which would be a NICE
   option, is gonna be just too much bandwidth.
   Can live without that.

   Anyway, need a few little weather sensors and
   the ability to request video FRAMES on demand.
   That's kinda do-able at about a mile's range
   without licenses or such govt BS. It has to run
   on maybe a 10-20w solar panel (easy to hide).
   Don't need constant data, just kinda "on demand".

   I've done multi-sensor dataloggers before, know
   how to code it, wire 'em down to the chips etc.
   Made a dozen based on the Ard 2560 - good
   'sleep'/low-power lib. They didn't xmit though,
   just saved to an SD card. Worked for many years.
   Got by on just a 5w panel.

   Somebody here said their company/group made
   really good 802.11 RF links - but did not
   name the maker.

   Long back such devices didn't even pretend to be
   network connections - just serial modems. That
   worked and was less complicated. Linux still has
   all the needed utils to cope with serial comms.

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#87355

On 2026-06-01 22:15, c186282 wrote:
>    Somebody here said their company/group made
>    really good 802.11 RF links - but did not
>    name the maker.

You would not want to buy ours. For starters, we'd charge
you about $3K per node. And we are planning to close the business in a year.

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

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#87359

On 6/2/26 01:50, Lars Poulsen wrote:
> On 2026-06-01 22:15, c186282 wrote:
>>    Somebody here said their company/group made
>>    really good 802.11 RF links - but did not
>>    name the maker.
> 
> You would not want to buy ours. For starters, we'd charge
> you about $3K per node. And we are planning to close the business in a 
> year.

   At $3k I can see why :-)

   Another old govt/industrial "solution" idiots
   would vastly over-pay for ???

   There are MUCH cheaper LoRa and related to be
   found online these days.

   2.4 is too obstacle-sensitive for my need, but
   900/400 can work.

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