Five minute wonder

My  Nevada WH3080 weather station has turned out to be a five minute wonder. Barely 3 months since we installed it, it has quit working. The base unit is no longer receiving information from the sensors.

We checked the batteries. The batteries in the sensor unit, which are supposed to be charged by solar power, were almost dead. We replaced them by some ordinary alkaline cells. But there is still no communication.

I think it is going in the garbage bin. It was whilst trying to reset the unit that I fell over in the garden and flattened some of Olga's plants. It is cheap Chinese rubbish.If I don't throw it in the trash I expect Olga will.

To theit credit Nevada did offer to exchange it for a new replacement when we couldn't get the rainfall gauge to work. But I threw away the packaging so we couldn't take up the offer. Either I can go back to using the one I built myself fom a kit which only recorded temperature, humidity and pressure, or abandon the idea of having a weather station altogether.

Summer has arrived

Another warm, sunny day. It really seems as if summer has arrived. But it's not the weather for sitting in the shack operating the radio. It actually gets a bit unbearable in the shack on warm days with all the equipment (not to mention the operator!) radiating heat.

The weather forecast is for fime weather on the next few days. I'm not complaining but dare I say it, Olga and I have been wishing for some rain - Olga to water the garden and me to see if the rain gauge of the new weather station is really working!

With some freshly charged batteries in the KX3 I thought I would see what I could hear from out in the garden. The answer was - not much. Band conditions seem to be pretty dire at the moment. True, the antenna I was using out there (a WonderWand L-Whip) is not the most efficient I could find but it is easy to tune and usually receives OK. But today I could hear almost nothing.

Sunny weather

I hope I don't jinx it by writing this, but I think my weather station is now working. Everything is showing the values expected, including the rain which shows 0 mm as we haven't had any. Trust the Cumbrian weather to not rain when you want it to.

It was actually Olga who got everything working. I had lost patience with it and was all for sending it back. Olga patiently went through the manual (which she found was poorly written) and double-checked everything. She even used my test meter to check the voltage of the newly installed batteries. She found that the rechargeable alkaline batteries supplied for the sensor/transmitter unit were only giving 1.3V each. So she took them out and replaced them with some new Energizer alkaline cells. And everything including the rain sensor started working!

The manual says "Insert 2xAA 1.5V rechargeable batteries into the battery compartment of the remote sensor and immediately afterwards 3xAA alkaline batteries in the base station." It didn't say anything about charging them first. If I had provided my own rechargeable batteries I would obviously have charged them first. But as they came shrinkwrapped in the box I assumed they were ready to use. False assumption! It was as simple as that!

The case of the disappearing weather objects.

I have just spent what seems like several hours trying to find out why my weather station data sent by Cumulus to the APRS network vanishes without trace. I have tried using the wxnow.txt method of generating APRS weather objects in APRSISCE and that does work, but unfortunately it messes with the MYCALL setting in my Kenwood TM-D710 converse mode TNC. So I thought that I would avoid the problem by getting Cumulus to send the data to APRS-IS directly.

The data packets were being sent but they never showed up on aprs.fi. I produced debug logs for both Cumulus and APRSISCE. These showed the packets being sent. So where did they disappear to?

To cut a long story short, Cumulus was sending the data packet with a path of TCPXX*. This is listed as "deprecated" in the APRS spec but it is actually blocked by the APRS-IS network software. The CWOP (Citizens Weather Observer Program) which I believe runs on an older version of the software, is not so picky so no-one had encountered the problem before. Can you believe that I must be the first person to try sending weather data to the APRS network using the Cumulus software?

A new weather station

Yesterday Olga and I set up a new weather station in the garden. It is a Nevada WH3080 SOLAR. It took a while for me to figure out how to put it together but I got there in the end with a bit of help from Olga (who took the radical step of reading the instructions!)

The sky is always blue in Cumbria!

We had a bit of trouble mounting the weather station in the garden. The manufacturer supplies two large hose clips (you can see them in the picture) which are not the ideal hardware for attaching a pole to another pole. But they did the job, if not very elegantly.

There were no problems receiving the weather station on the control panel sitting on the shack PC 10m away. This Nevada weather station transmits on 868MHz so no interference from or to 70cm amateur transmissions. No problems with the software either, not with EasyWeather nor with Cumulus which is what I will be using.

The software setup went so easily that I couldn't see how it was working. When I plugged the display console into a USB port the PC went "ding dong" to acknowledge a new USB device had been connected but I couldn't find the new device anywhere. I expected it would appear as a serial port in Device Manager but no new ports were added. I didn't have to specify a COM port in either program either. How the console talks to the weather software is a mystery. I'm not planning to write my own software to process the weather data but I'm still curious as to how the software gets the data.

Using the example web pages provided with Cumulus I set up a Cockermouth Weather page very easily. Cumulus creates a wxnow.txt file which APRSIS32 uses to generate an APRS weather object. However I have just noticed that Cumulus can send updates to the APRS network directly. That would be a simpler way of doing it, but that way the weather object would not get transmitted to the local APRS network. I've since discovered an issue when using APRSIS32 to generate a weather object via a converse mode TNC, but hopefully Lynn KJ4ERJ the author of APRSIS32 will come up with a fix for it.

What weather station?

A few days ago my Fox Delta WX1 Micro Weather Station stopped working. As it turned out, I just had to switch off the power and switch it on and it started working again . But while I was waiting for the rain to stop so I could go out and look at the device I began thinking about getting a better weather station - one that measures wind speed and direction and rainfall as well as temperature, humidity and pressure.

When you start to look at weather stations the choice is overwhelming. My first priority was that it should work with APRSISCE and generate the file wxnow.txt that it uses to update weather objects. That requirement led to the stipulation that it should be compatible with the free weather software Cumulus, which creates the required file. There is a list of weather stations that work with this software, which narrowed the choice down a little. After reading many reviews the best choice seemed to be the Davis Vantage Vue. Unfortunately this cost about four times more than I was willing to pay, so it was back to the drawing board.

The weather stations made by the Chinese firm Fine Offset and sold under the Watson brand name seemed to meet my criteria at a more reasonable price. However, browsing through the reviews on Eham.net and elsewhere there were quite a high proportion of dissatisfied users. Complaints about anemometers that stopped rotating, poor wireless reception and so on. With weather stations as with everything else, it seems, you get what you pay for.

Despite the reviews I am tempted to get one of the Watson W6861 solar weather stations. But before I did I thought I would take the opportunity to ask my readers for their experiences. Many of you must have home weather stations. So which ones are good, which are bad and which should be avoided at all costs? I await your comments with interest.

Snow!

This was the scene that greeted me when I looked outside this morning! Nothing to what folks in the USA get, of course. But considering that it used to be unusual to have any snow at all during the winter here in West Cumbria it's still noteworthy.

I hope we don't get any more, though. Apart from the hassle factor of slushy slippery pavements, a thick layer of snow on the roof won't help my attic antennas to get out.

WX-1 baud rate fix

On Thursday I wrote about how my WX-1 APRS weather station was not being received by my TH-D72 and the PIC TNC because the baud rate was slightly fast, and of my unsuccessful attempt to fix it. Glenn W9IQ offered to take a look at the PIC source code and see if there was an easy fix. I sent him a link to the code and a day later I got a reply back. Glenn's suggestion solved the problem perfectly. But he didn't just tell me what to change, he explained what the code did and how it worked. I thought that his explanation would be of interest to anyone trying to understand how packet tones are generated using a PIC, so with his permission I am copying it here.

"The baud rate is determined by an interrupt service routine. The interrupt is driven by Timer 0 (TMR0) that is configured to use the instruction clock as its input (frequency of Y1 divided by 4). The input of TMR0 is also initialized to have a divide by 32 prescaler (the code comment says 16 but that is wrong). So at this point the timer is being driven by the frequency of Y1 divided by 128 or (20 MHz / 128) =  156.25 kHZ or a period of 6.4 uS.

Now the math and routines get a little more complicated. The interrupt is serviced by the code in the "packet" file. This code sets the TMR0 count to start at a value of 127. This TMR0 count will tick up one count every 6.2 uS (the clock from the output of the prescaler). When the timer count rolls over from 255 to 0, the interrupt is triggered.

At first glance, it would appear that this would generate an interrupt every 129 counts or 825.6 uS (6.4 uS * 129). That would seem to put the interrupt at roughly 1211 Hertz ( 1/825.6 uS). But this is not correct due to the way the author wrote the interrupt routine plus a small nuance of how a PIC handles the reset of the prescaled interrupt timer.

The interrupt service routine in "packet" executes 6 instructions before resetting the interrupt timer to a value of 127. Each instruction takes 4 clock cycles so this adds another 1.2 uS to the time between interrupts. In addition, when the prescaled interrupt timer register is written, there are another 4 instruction cycles of delay before the timer starts to run again. This is another 0.8 uS added to the interrupt time. So we now have an interrupt cycle of 825.6 uS + 1.2 uS + 0.8 uS totaling 827.6 uS or 1208 Hz. I believe this is what you measured as the current baud rate from your board.

Improving this is fairly straight forward. The interrupt goal is 1200 Hz or 833.3 uS. If we change the TMR0 count to 126 instead of 127, this will add another 6.4 uS to the interrupt period. This would give us 827.6 uS + 6.4 uS = 834 uS. Then if we eliminate one instruction in the interrupt routine, we eliminate a 0.2 uS delay for a total interrupt time of 834 uS - 0.2 uS = 833.8 uS or 1199.3 Hz.

This change is effected in the code located in the "packet" file. Look for the following code fragment:

        movlw        0x80        ; 128 decimal

        sublw        0xFF        ; subtract 128 from 255 to get TMR0

        movwf        TMR0        ; move it to the TMR0 register

Change this code fragment to read like this:

        movlw        0x7E        ; 126 decimal

        movwf        TMR0        ; move it into the TMR0 register

Recompile everything and reload the processor and you should see the baud rate drop as described."

When I ran the modified code the baud rate dropped from 1207/8 baud to 1198/9 baud which is pretty much just as Glenn predicted. The weather station is now being received by the Kenwood TH-D72 as well as my other APRS radios. It can also now be received using the PIC TNC though the level of the receiver audio is critical and unfortunately not the same as that needed to decode the VX-8R. I think that is because the maximum deviation I can get out of the Radiometrix transmitter module is a bit on the low side.

I had an anxious couple of minutes when I found that although the D72 was decoding the packets it was rejecting them as invalid. This turned out to be because the position co-ordinates had a lower case n for North and w for west: In my haste to see what effect the changed code had I had entered the settings carelessly, though the other radios didn't seem to mind. That was soon fixed.

The WX-1 weather station is now back in position beaconing the temperature, humidity and pressure as G4ILO-5. I would like once again to express my thanks to Glenn W9IQ for acting in the finest spirit of ham radio and helping me out with this.

Weather station

As I was not making any progress on other projects for one reason or another I decided to build the Fox Delta WX1 weather station kit that had been sitting in a drawer for the past couple of months. For several years I have had a simple wireless weather station that tells me the outside temperature, humidity and pressure. Since getting into APRS I wanted to be able to put this information on the network. Most of the weather station products I've seen interface with a PC using some proprietary software, which ties you down to a particular operating system. It also typically interfaces with APRS using some proprietary method that works with UI-View but is not supported by APRSISCE. The elegant solution would be a weather station that transmits the weather information as an APRS packet using a low power RF link, which would then be received by my VHF IGate. When I discovered that the WX1 produced 1200baud AFSK audio output and a PTT signal to control an external transceiver to do exactly that it seemed just the solution I was looking for.

Unfortunately the WX1 was no longer for sale from the Fox Delta website. I contacted Dinesh, the proprietor of Fox Delta and he explained that although he still had a couple of boards and most of the parts for the WX1, the kit needed to be redesigned to support the latest 1-Wire anemometer so he had taken it off the market. I told him I didn't want an anemometer. Our garden is so tiny and surrounded by houses, trees and bushes that I would never get an accurate reading anyway. Besides I didn't think Olga would be thrilled to have an anemometer planted in the middle of her flowers. And from what I've read, most of these home weather station anemometers fail after a year or so. So Dinesh agreed to sell me a kit and I had to take up the offer there and then even though it hadn't been something I'd planned on doing right away.

The weather station turned out to be quite easy to build despite the fact that there are no detailed step by step instructions, just a parts list, a schematic diagram and the silk-screened PCB to show you where each component goes. Most of the parts were supplied in individually labelled small polythene bags which helped a lot. I had a nasty moment after I soldered in a crystal X1 and then realized the second crystal on the board was also labelled X1. But the two devices were in a completely different form factor and would not match the outline in the wrong place so there was little chance of a mistake. Amazingly, for something built by me, it worked first time.

I set up the weather station running standalone in our unheated conservatory and I was disappointed to find that the temperature readings were several degrees on the high side. I was also disappointed that the configuration software provided no way to change the display of temperature from Fahrenheit to Celsius. The sensors for temperature, humidity and pressure are all mounted on the board itself. I had thought that I would be able to extend them via a cable so the sensors could be outside and the weather station inside but on closer examination I could see that was not going to be practical.

The temperature sensor chips are actually underneath the LCD display and it appeared that the LCD backlight may have been contributing a bit of local heating. Given that the unit will have to live out of doors, the display will not be particularly useful. In fact, the instructions state that if you want you can take it off to save power. So the problem of high readings and the Fahrenheit display can be resolved simply by removing the LCD, which as it is a standard display panel, can probably be used in another project. I tried it on my EasyPIC5 development board and it displayed some demo text.

The plan is to use the Radiometrix TX1 10mW transmitter module that I recently bought for the 144.800MHz RF link. However to get the weather station on the air quickly I made up a cable to try it with my old Kenwood TH-205E. I put them in the garage to get close to the outside temperature, and one problem quickly reared its head. As with the FoxTrak I found that the PIC-based circuit is extremely vulnerable to RFI. Even 0.5W into a short Nagoya dual band antenna on the Kenwood was enough to cause loud buzzing on the audio and once to lock up in transmit and corrupt the atmospheric pressure calibration. The rather poorly made case provided by Fox Delta offers very little in the way of screening, especially with the aperture for the LCD display. Hopefully the 10mW produced by the Radiometrix module won't necessitate the elaborate screening measures that were required by the FoxTrak.

Weather station

After I removed my Ascot weather station due to the interference it caused on the 70cm band, I didn't have a clock in the shack. I searched for a long time to find a radio controlled digital clock with a nice 24 hour LED display capable of showing UTC but couldn't find anything suitable. Whilst browsing I found something interesting. It was a Meteotronic WM5100 weather station made by La Crosse, reduced from £49.99 to £17.49. As I still liked the idea of having a weather display in the shack, I decided to get one.

The Meteotronic is interesting as it is not, in itself, a weather station. It is a radio, tuned to receive transmissions from the German time and frequency standard station DCF77 on 77.5kHz. Besides an accurate time signal, DCF77 transmits weather forecast data for 90 different regions of Europe for up to 4 days ahead. This information is received by the device and displayed on its LCD, as you can see in the picture.

Some of the weather regions are quite large. I am in the region "northern England" which covers the whole area north of Birmingham to the Scottish border. But the forecasts are probably still better than predictions based simply on atmospheric pressure trends, like most home weather stations.

I'm coming to realize that this is a pretty poor location for reception of radio signals of any type. The unit had difficulty receiving the DCF77 transmission, although I am well within the maximum distance at which reception is possible. You need to experiment with different locations to get the best reception.

Although the unit doesn't have a UTC time option, you can set a time zone offset, so I can set this to -1 during the summer to compensate for the effect of daylight savings time.

More snow!

We had almost lost all the snow that fell over the previous couple of weeks. But last night there was a fresh snowfall and we awoke to a couple of inches of the white stuff.

It does make for a nice picture - the photo above is the view from our front door this morning - but I had hoped we had seen the last of it and that we might return to the mild temperatures we normally get. (I can remember winters when we hardly ever had a frost.)

The streets where we live have not been gritted and as you can see from the picture we are on a hill. Fortunately we don't have to go anywhere except for into the town now and again for supplies which we can do on foot. Otherwise I think I would be starting to regret exchanging the Suzuki 4x4 that we had for our present small lightweight two wheel drive Hyundai which is not really designed for such conditions.