Order Tray | Contact Us | Home | SIG Lists

[aprssig] HF noise measuring campaign reports via APRS

Curt, WE7U curt.we7u at gmail.com
Fri Sep 14 19:36:36 UTC 2012


On Fri, 14 Sep 2012, Heikki Hannikainen wrote:

>> Does anyone foresee a problem with this?
>
> There's at least one small problem: there's no fixed identifier anywhere 
> which would allow detecting that this is a telemetry packet from your 
> software. It's just a status packet with some numbers there. A protocol ID 
> string in the beginning of the data would make it possible for software to 
> easily figure that hey, there might be noise level data in here.
>
>> If anyone can think of a better way to do it I'm open to ideas.
>
> If there's at most 5 frequencies monitored by a given station, you could 
> transmit it as standard APRS telemetry, and it would be graphed automatically 
> by all APRS receiving stations without any code changes in the receiving end. 
> Like this:
>
> http://aprs.fi/telemetry/a/OH7LZB-14
>
> You can also transmit channel names for each graph.

Great ideas all the way around so far, but I'm wondering how an antenna/feedline system can be "calibrated" and how local noise is taken into account?

Here's a "fer instance":  I'm in an apartment complex with 100's of units.  My S-meter runs S7 to S9 until most of those people go to sleep and start shutting off their electronics.  There's no way I could contribute useful data to a project like this.  I realize this is an extreme case, but everyone else will have some lesser degree of the same type of problem.  Often it will be caused by electronics in their own house.

Plus:  Various antenna systems have different radiation angles, polarization, and directivity.  Not to mention hams are always messing with things by their nature.  Their feedline routing, type and length of feedline, antenna height, and other antenna parameters will be constantly changing.  Those will show up as step functions in the data which will have no apparent explanation.

Think of installations like METAR weather stations out at airports:  They have fixed design parameters so that the weather info coming from the instruments are trusted.  Then you get into things like the Citizen's Weather program where they're _not_ trusted...  If readings are similar to other readings in the area then they're used.  If not, readings are ignored for weather prediction purposes.  I doubt most of those stations are built to any kind of standard, even though a reasonable standard exists.

If one were putting up a receiving station with fixed characteristics out in the middle of nowhere (no local noise sources, no obstructions), then I could see it as somewhat scientific.  If not, then you have to take all of the readings with a grain of salt, and expect many of them to change over time just due to station changes and local noise source changes, not necessarily due to changes in noise coming over the HF bands from elsewhere.

Maybe I'm looking at this all wrong though and the measurement intended to be made _is_ local noise?  In that case I'm a perfect candidate!  hi hi

-- 
Curt, WE7U.        http://wetnet.net/~we7u
APRS Device Capabilities:  http://wetnet.net/~we7u/aprs_device_capabilities.html



More information about the aprssig mailing list