[TowerTalk] Weather Stations that don't transmit near the 70 cm band?

[Larry McDavid]

All these weather monitors (the ones in this price range, anyway) have 
rotating  anemometer cups and rotating wind vanes (more expensive 
systems can use ultrasonics for these measurements) and thus have moving 
parts. Those parts need bearings and most are "shielded" spherical ball 
bearings that are continuously outside and exposed to weather 
conditions. "Sealed" ball bearings are available but have rubber seals 
that drag on the ball races and would load the cups or vanes of the 
weather sensors. Thus, you can expect to have lifetime issues with these 
bearings.

So, an issue is how easy it is to service these parts. I can speak only 
for Davis Instruments Vantage Pro 2 systems now. Davis has an *exchange* 
program that ships you a replacement anemometer/wind vane sensor-set to 
install and then ship back the old sensors. I have done that once in 
about 9 years due to some light drag on the wind vane; I never had any 
difficulty with the anemometer bearing (yet).

Outdoor radiation shields for the temperature and humidity sensors can 
be static or aspirated, and fan aspirated radiation shields can be 
daylight only or 24-hour (with a rechargeable battery of some kind). In 
all cases, air currents flow through the radiation shield and bring 
debris that must be cleaned out occasionally. I clean mine every 18 to 
24 months by complete disassembly. In my 24-hour aspirated radiation 
shield, an unusual dc fan is used, and it has no markings to indicate 
operating voltage. Overnight, it operates on about 2.4 volts from two 
NiCd "C" cells but it gets higher voltage during the day from a separate 
solar cell that powers only that aspiration fan. I replaced that fan 
once when I found it ran during the day but not at night when on the 
NiCd battery. The fan is easy to replace when the radiation shield is 
disassembled for cleaning and the replacement already has the required 
connector installed. Not cheap, however.

Wired weather monitors will have long wires that simply act as antennas 
in a strong local RF field. Shielding and ferrite chokes can help but 
local high power ham stations may still be a problem. I have not had a 
wired system in about 10 years and I don't now remember if there were 
any RFI issues with the old Davis Instruments "Weather Monitor" model 
system. My Davis Vantage Pro 2 wireless system, which uses 
frequency-hopping diversity, has always performed flawlessly for me.

One advantage to using Davis Instruments weather monitors is that phone 
technical support (and excellent, knowledgeable support it is!) is 
immediately available at no cost beyond the phone call.

I won't argue against using a wired weather monitor. Each of us has to 
consider many factors when selecting such high-tech things! Cost is one 
issue but so is reliability and ease of service. The convenience of 
wireless comms between the display console or computer and the sensor 
suite is significant. And, with wireless, I can have multiple display 
consoles around the house.

I frankly don't know if a 900 MHz wireless spread spectrum wireless 
weather system will affect weak-signal reception in that same band. I am 
confident it would not affect any other band.

However, I would not want to put a weather monitor sensor suite up on a 
ham tower; I expect the tower itself and the beam antennas above would 
affect measurements of wind and rain. I have my Davis sensor suite about 
6 feet above the peak of my house roof and in the clear, in an area that 
is easy to access. National Weather Service standards for location of 
weather sensors would have them only in clear, grassy fields; in 
Southern California typical residences, that is simply not possible so 
some trade-off is necessary.

Is all this weather monitoring really necessary? Surely not! But, it is 
interesting and can provide useful data. Many will say that Los Angeles 
does not have "weather." I agree we don't receive much rain! I might get 
8 inches in moderately wet year. But rain here often comes in brief, 
heavy rainfalls so measuring those is interesting. I find I look often 
at the weather monitor solar radiation sensor and compare its daily 
curve shape to that of my home photovoltaic solar system; curiously, 
they are not always the same! Unexplained dips and peaks happen and are 
often inconsistent between the two systems. Makes me wonder if there are 
pterodactyls flying about...

Best wishes,

Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)

On 9/19/2022 8:57 PM, Kim Elmore wrote:
> As a research meteorologist, this topic is nearvand dear. I had a Peet Bros. station for some time and truly liked it. It has in particular a heated rain gauge. But, critters kept chewing on wires, so I chose to replace it with a Davis Vantage Vue. It’s been pretty good over the past 10 - 15 y. Be had to replace the anemometer unit twice due to bearing failures. At the 10 m level on my tower, It isn’t bothered by 1500 W on any HF band and is RF silent. The supercapacitor on mine became leaky enough that it started eating the lithium 123 cells used to keep it going at night after the supercapacitor has been discharged. The supercapacitor is potted and so not serviceable. I decided to replace the lithium cell with two D cells at the base of my tower and have had no further issues.
> 
> Colleagues like the Ambient Weather systems.
> 
> Kim N5OP
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