Weather Station Discussion

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#2766689 25-Aug-2021 20:34

neb:
Technofreak:

A 20° or greater variance might not matter to you but I can think of situations where it would matter to someone else. For example if I was setting it up on an airstrip 20° degrees can be the difference between showing a head wind to a tailwind.

Sure, but in that case I'd be going for a proper METAR source, not a crowdfunded project some geek has slung up on the garage roof :-).

(Mine's actually bolted to the top of the pergola, easier access there).

For someone with their own private airstrip, which what I was thinking of when I posted that comment, this is perfectly adequate bearing in mind there is no legal requirement for them to have a weather station.

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#2766692 25-Aug-2021 20:39

Technofreak: For someone with their own private airstrip, which what I was thinking of when I posted that comment, this is perfectly adequate bearing in mind there is no legal requirement for them to have a weather station.

Sure, I thought you might be referring to something like that. But in that case I'd also be using a real compass for orientation, not a cellphone wiggled in a figure-eight a few minutes before the reading was taken, and for that use I assume the CAA will have a precise definition of what constitutes "north".

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#2766719 25-Aug-2021 21:13

neb: Sure, I thought you might be referring to something like that. But in that case I'd also be using a real compass for orientation, not a cellphone wiggled in a figure-eight a few minutes before the reading was taken, and for that use I assume the CAA will have a precise definition of what constitutes "north".

No not really, North is North just need to be sure whether you want True North or Magnetic North.

In my experience most phone compasses are pretty accurate providing they have been through the calibration process and are clear of any ferrous items and free of interference. The same things that apply to any compass.

I had four devices outside today on a wooden table. Three gave a reading within a degree of each other, the fourth was within 3 to 4 degrees of the other three.

I guess most people setting something like this up on a private airstrip would use an aircraft compass which is probably only accurate to within a couple of degrees or an orienteering compass which wouldn't be any better. At least an aircraft compass has to be checked every two years.

One advantage of a cellphone/tablet with the True North function built in is there's no chance of stuffing up the variation calculation, including adding instead of subtracting.

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Ge0rge

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#2766874 26-Aug-2021 09:56

Technofreak:
One advantage of a cellphone/tablet with the True North function built in is there's no chance of stuffing up the variation calculation, including adding instead of subtracting.

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Sorted ;)

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#2766878 26-Aug-2021 10:02

Ge0rge:
Technofreak:

One advantage of a cellphone/tablet with the True North function built in is there's no chance of stuffing up the variation calculation, including adding instead of subtracting.

Machine Gun Ammunition
GrandMa's Socks

Sorted ;)

Sorry, you lost me there, but East is least, West is best.

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aaristotle

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#2766949 26-Aug-2021 11:52

Having an issue with my new Tempest weather station, and just wanting to check what rssi signal levels others are seeing.

The station ran fine for 12 days 75m from the hub at about -78 rssi then started to cut out (go offline) and report rssi of -89. Reset the hub and "Replaced Device" to re-pair and it came right. A day later it lost connection again and when I retrieved the station the LED was flashing green, which according to the troubleshooting guide it should need a button press to activate the LED status. After doing some range / signal level tests I pressed the button to confirm the status but the LED stayed dark, even though it was still connected and working.

Weatherflow agreed the station is both behaving strangely regarding the LED and that 300m line of sight should be able to be achieved, so are sending a replacement unit.

Measurements I recorded:

In a temporary location 25m from the hub, 6.5m high (through a window) rssi: -51

Placed next to hub 5cm rssi: +8

Hub placed outside window for testing so no walls/windows, direct line of sight to Tempest station,

0.5m rssi: -18,

65m rssi: -74 to -85 over a 5 minute period.

Can anyone else provide their rssi reading and station/hub distance, along with any obstacles so I see how impaired my station currently is?

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#2766951 26-Aug-2021 11:55

@aaristotle My tempest is literally 15m away from the hub so I can't be of too much help here but that is showing -58 RSSI.

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#2766976 26-Aug-2021 12:58

My hub sits inside while sensor is on roof. Probably about 8m apart with the usual walls, ceiling, roof obstacles between the base and the weather station - RSSI is -74.

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#2766996 26-Aug-2021 13:38

I assume the RSSI figure is in dB? I might be telling you how to suck eggs here, but here goes anyway.

Signal strength in a situation like this will reduce at the inverse square law, i.e at double the distance from the source you will get 1/4 of the power. All assuming there is nothing creating a screen, like a steel roof, reinforcing steel in a concrete wall etc in the way.

dB is logarithmic. i.e. a doubling or halving (2 times change) of the power gives a 3 dB change. A 4 times change is 6 dB change.

Based on your two examples I'd expect to see around -46 in the first example at 25 metres and -60 at 65 metres in the second example. Both are around 6 dB higher than you measured which is possibly within the bounds of reasonableness with the gear that's being used to do the measurements.

There's a very handy tool here for doing calculations. http://hyperphysics.phy-astr.gsu.edu/hbase/Acoustic/isprob2.html It's for acoustic measurement but the same principle applies for radio signals as it applies to this situation.

It probably doesn't matter where you take your measurements unless you have something screening out the signal. It's going to be the power coming from the base unit that really matters. Is the power dropping off over time?

If you can get a sample of measurements from various users that are all measured at the same distance in the same conditions (no walls or roof in the way) then you will get an idea how your unit is performing.

Another thought. There has to be two way communication between the units. Could it be the other end the is giving you the problem?

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Technofreak

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#2767008 26-Aug-2021 13:59

michaelmurfy:

@aaristotle My tempest is literally 15m away from the hub so I can't be of too much help here but that is showing -58 RSSI.

Based on the figures measured by aaristotle at 0.05 m (5 cm) and 0.5 m I'd expect to see between -41 dB and -47 dB at 15 m. Just shows the vagaries of trying to get useful figures. Would be interesting to know your figures at 0.5 m.

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wally22

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#2767011 26-Aug-2021 14:03

Technofreak:

If you can get a sample of measurements from various users

I'm in lockdown with time on my hands. How do I do this?

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#2767042 26-Aug-2021 15:07

wally22:

Technofreak:

If you can get a sample of measurements from various users

I'm in lockdown with time on my hands. How do I do this?

Sorry can't help you there. I don't have a Tempest.... yet. I have assumed from what @aaristotle and @michaelmurfy have posed that there is a way within the device or its desktop where these measurement can be made.

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#2767049 26-Aug-2021 15:24

Technofreak:

Based on the figures measured by aaristotle at 0.05 m (5 cm) and 0.5 m I'd expect to see between -41 dB and -47 dB at 15 m. Just shows the vagaries of trying to get useful figures. Would be interesting to know your figures at 0.5 m.

My hub is sitting under my desk so there is normally a body of water sitting between the hub and the Tempest with multiple walls in the way also. Still doesn't hinder it.

You ordered a Tempest yet? It seems like you really want one. I found that Meteobridge supports it so now have a Raspberry Pi sniffing the local data and uploading it to several places:

Local dashboard: https://weather.interwebz.nz/
PWS Weather: https://www.pwsweather.com/station/pws/48466
Weather Underground: https://www.wunderground.com/dashboard/pws/IPARAP24

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#2767094 26-Aug-2021 16:08

michaelmurfy:

Technofreak:

Based on the figures measured by aaristotle at 0.05 m (5 cm) and 0.5 m I'd expect to see between -41 dB and -47 dB at 15 m. Just shows the vagaries of trying to get useful figures. Would be interesting to know your figures at 0.5 m.

My hub is sitting under my desk so there is normally a body of water sitting between the hub and the Tempest with multiple walls in the way also. Still doesn't hinder it.

You ordered a Tempest yet? It seems like you really want one. I found that Meteobridge supports it so now have a Raspberry Pi sniffing the local data and uploading it to several places:

Local dashboard: https://weather.interwebz.nz/
PWS Weather: https://www.pwsweather.com/station/pws/48466
Weather Underground: https://www.wunderground.com/dashboard/pws/IPARAP24

Which probably explains the difference between my calculations and your readings.

Remember that aaristotle at 65 m has less than 1/16 of the power you do at 15 metres.

No, not ordered yet but have decided to get the Tempest. Saw they had a 'Labor Day" bundle special which looked very good. I can't justify spending money on a weather station right now. Been off work, no income for 4 months, hopefully back shortly if the lockdown doesn't slow things down.

Thanks for the links. Keen on the Raspberrry Pi feeding a local screen as well, which I think WeeWx can do.

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aaristotle

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#2767139 26-Aug-2021 18:16

wally22:

I'm in lockdown with time on my hands. How do I do this?

If you go to the status page for your Tempest you will see a rssi figure for the device at the bottom of the page (not to be confused with the hub rssi for the wifi). This is the link to my Tempest status page (which you can also get to from the main weather stats page by clicking on the green online dot at the bottom of the page.). This updates once a minute so move the weather station, wait a minute and then refresh.

From the rssi stats supplied so far my figures don't look too out of the ordinary. Rather than a signal strength problem the issue with my weather station is looking more like an intermittent loss of pairing that it can't recover from so has to be manually re-paired to the hub.

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