Re: [weewx-user] Signal Strength vs Rainfall

[Bob DeMattia]

Has anyone else seen this behavior?  Is there an explanation?:

[Kevin Davis]

Rain would certainly attenuate RF signals.

On Mon, Nov 16, 2020 at 10:50 AM Bob DeMattia <rjd...@gmail.com> wrote:

Has anyone else seen this behavior?  Is there an explanation?:

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[Bob DeMattia]

Quite a bit of attenuation!   The sensor is located approximately 8 feet horizontally and fifteen feet vertically

from the display.  It must be the wet roof!

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[Greg Troxel]

Bob DeMattia <b...@demattia.net> writes:

> Quite a bit of attenuation! The sensor is located approximately 8 feet
> horizontally and fifteen feet vertically
> from the display. It must be the wet roof!

Not sure what you have for station hardware. That graph suggests Davis
VP2 or Vue, and there I am pretty sure 'signal quality' is a recent
average of the fraction of packets successfully received vs what should
have been received.

Assuming Davis:

Davis at the 8'/15' should be very solid. It's 915 MHz, and it is very
slow FH, AIUI one data packet on a frequency and a new frequency for the
next packet rotating among a set of 51 (US). That protects against
narrowband interference. So I am skeptical that this is just due to
increased path loss.

I don't look at signal strength on my VP2 often, but I used to see a dip
from 100 to 98% occasionally, and the time pattern was suggestive of
some other transmitter, but I haven't figured it out. But it was a
brief dip to 98%, not hours at 25%. I just checked and last night with
the temp peak/rain event it was mostly 99.1/99.9% with an occasional
97ish%. I can perceive no patterns. Console/sensor distance is
probably 20' horizontal, 10' vertical, so not so different.

Therefore, I would be suspicious of broadband noise happening because of
the rain, although I admit that at 900 the level needed to explain this
does not make a lot of sense. Speculating wildly and beyond the point
of reason, it could be arcing of a powerline insulator when wet.
Perhaps listen at 450 MHz during the next rain, or at 900 if you have an
SDR set up that can function as a spectrum analyzer (rtlsdr/gqrx?).

You can also use rtldavis to listen to the packets:

https://github.com/lheijst/rtldavis

with an RTL-SDR dongle. That might be useful information.

Greg

[Tom Keffer]

I've also seen signal strength drop inexplicably on my Davis Envoy, although I've never correlated it with rain. Sometimes it doesn't come back for days. In those cases, I reset the Envoy by taking the batteries out. Here's one example:

I should note that I also have a VP2 console. I haven't noticed it happening with the console, but then it only runs occasionally when I'm working on WeeWX. There's definitely no correlation between the console and the Envoy, so it must be a receive-side problem.

-tk

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[Bob DeMattia]

Yes, I should have mentioned the hardware.

This is an Acurite 15036 which uses 433 MHz.  The batteries are brand new lithium batteries installed 

about one month ago.  The sensor is located in a rural area, in a summer cottage 

that is unoccupied, as are all the ones around except one house two doors away.  

I guess the good news is it seems to come back.  Hopefully it will make it through the winter without

needing any attention.

Thanks,

Bob

[Greg Sinclair]

My Acurite does not do well on lithium batteries. It seems to prefer long lasting alkaline batteries.

Signal strength was an issue for me for a while after switching from a Pi3 to a Pizero and upgrading weewx. They were both attached directly to the Acurite's base station. I eventually solved the problem by changing the channel used between sensors and the base station. My thought is changing the Pi caused an interference problem.

Greg