Daily Archives: 3rd January 2015

Ham Radio

Electrical Interference – The hunt with my mate Billy.

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I have had a problem of a really strong pulsating radio interference signal lifting my noise floor, the strongest signal were at 350Mhz, 521.5Mhz, 924.7 Mhz, 990.3Mhz, 1.802Mhz, 145.537Mhz and 145.000Mhz detected by my trusty AM radio, Billy.

SAM_5244 (Large)Billy the Fish with a broken gill.

Preliminary investigations walking around the house and outside pointed to it being the neighbours solar panels as when I got near to his garage where the inverter is located, Billy went nuts, it was as though it was radiating out everywhere, putting Billy over my buried radials in lawn amplified this signal up, even putting the radio near the earthed outside tap picked the interference up.

As I was convinced the interference was from outside of my house, the only way to prove this was to turn the power OFF to the house, so with Billy in hand, I turned the power OFF expecting the radio to go quiet, but it didn’t!

Looking around in the garage, where I turned the power off, for a source of the noise, I saw the UPS for the PC was ON, turning this OFF the noise reduced, but still did not stop, walking around with Billy the interference was still very evident.

Went inside the house and heard two other UPS bleeping, the first one is in a room directly above the garage and as soon as I turned this OFF the majority of the noise stopped.

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The next visit was to a room off my home office where my network kit is installed, the main UPS is fitted there, turning this off and the radio went dead quiet, so much for my theory of blaming the neighbours solar panels!!

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So now to start turning things back on, with all the breakers off, I turned the main power switch ON, and the radio stayed quite, turning the breakers ON one by one, I didn’t get very far until the radio kicked off again.

First breaker causing a problem was the garage sockets, turning the switches on the sockets OFF in turn, I came to one which stopped the noise when turned off, it was a 12v switched mode power supply for a camera causing the interference.

The next breaker to cause me a problem was the one to the house sockets, switching this ON, yet again caused the radio to detect interference, back into the house with Billy, the hunt was on!

It turned out to be right under my nose in the office, it was the Blitzortung lightning detection controllers power supply unit.

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I will investigate sourcing a low noise 5v DC linear PSU as well as making improvements to the controllers earthing as I don’t want to disable the unit.

I do have background hum from the power supplies feeding the Netgear switches and other small load items, but it’s nowhere near as bad as it was and I know what’s causing it, which is good, total elimination is the optimal solution, but proberbly unrealistic, so bit by bit I’ll chip away and get the noise floor as low as I can.

Weather Site

Web Site – Alerting of Inaccurate Data

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Data has to be accurate and reliable, this is especially true of weather data, Chatteris Weather uploads in ‘Rapid Fire’ mode its data status for a whole range of variables every 2.5 seconds, this allows the gauges and wind speed and direction to seem so responsive, so how do you when the site its not updating or putting it another way, how do you know if the data is stale?

Here at Chatteris Weather, we use three ways (excluding the status update page).

First –

If the site is going to be down for maintenance, we will post up description and predicted down-time, this message will be displayed in a yellow warning box at the top of each page.

Second –

The Weather PC uploads a changed file each and every time, this file is called clientraw, a script within the weather template compares the time of last clientraw arrival with the current time, if no change has taken place, a yellow alert box will open on the home page and it will say that an error has occurred and the clientraw file has not updated for x minutes.

This works really well, however, as I have an older PC running numerous weather related programs, when one which is particularly heavy on processing starts, the clientraw error might appear until this program finishes and PC resource are again available, an example of a short duration, but high processor usage is the creation of the movie files used in the time-lapse playback pages.

It may well be that clicking on refresh, will clear the error message.

The clientraw error message is fine to let site visitors know of a problem, but I need to know if something’s not right without constantly being sat on the site, I have done this in a number of ways, one is using a free service provided by Pingdom, this checks the accessibility of Chatteris Weather and sends me an e-mail if it gets no response, I have set the check time to every 15 minutes, the downside to this method is that Pingdom has to visit the site in order to determine if its available and consequently my ‘Whos-Online’ script counts it as a visitor, hence installing the RevolverMap as this discounts these ‘bot’ visits.

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ping1Example of Pingdom status report.

Pingdom alert e-mail examples (The check-time was originally set to 1 minute before I relaised the impact on visitor numbers) –

PingdomAlert DOWN:
Http://www.chatteris.biz (www.chatteris.biz) is down since 12/08/2014 08:49:37AM.

PingdomAlert UP:
Http://www.chatteris.biz (www.chatteris.biz) is UP again at 12/08/2014 08:58:37AM, after 9m of downtime.

Third –

An additional way of alerting site visitors is with script ‘Flatline-check.php’, this offers an alert message to site visitors that a problem exists and that it has been escalated, this script not only reads the clientraw file, but crosschecks that certain key sensors are working, it does this by creating a file called flatline-status.txt, this file display a range of readings:-

1) Average Wind Speed
3) Wind Direction
4) Outside Temperature
6) Barometer
72) Dew Point Temperature

The parameter numbers relate to clientraw table as above. Every 30 minutes a schedule (cron job) runs on the Go Daddy server which compares the latest ‘flatline-status.txt’ file to the earlier version, if they have changed indicating a healthy upload, no action is taken, if a problem is detected i.e. no changes made, I get an alerting e-mail, the next time data is refreshed, I get a further e-mail informing me that service has been restored.

‘Flatline-status.php’ actual alert e-mails –

Weather Data Appears Flatlined.
01-03-15 2:16 pm now. Last data change recorded at 01-03-15 1:35 pm (0.0 26 3.9 1017.1 3.2)

Weather Data Back Online.
Back active at 01-03-15 3:14 pm (4.1 329 4.2 1018.9 3.4)

error2Alert messages – this was after a planned power outage.

The top message was generated by ‘clientraw.php’ script, the lower messages based on ‘Flatlines-status.php’ would have appeared some 27 minutes later followed by an alerting e-mail, these are the ones pasted above.

Well, that’s how I do it so hopefully the data displayed is current, if not, at least two of us will know 😉