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[aprssig] HF noise measuring campaign reports via APRS

Chris Moulding chrism at crosscountrywireless.net
Fri Sep 14 20:57:10 UTC 2012


Curt,

All good points.

The idea behind the noise measuring campaign is to look at HF noise in a 
range of different environments e.g. rural, suburban, urban, industrial 
and noisy.

For instance your observation about the level of local noise changing as 
equipment is switched off at night is just the sort of information that 
the measuring campaign will reveal.

I would expect one or two receivers to be placed in an ideal location to 
look at galactic or solar background noise but the real value of the 
tests would be prove just how much more RF noise is present in the real 
locations where we live.

Regarding antennas I'm also developing a HF voltage probe antenna so 
maybe one of those could be connected to the SDR receiver so that it's 
left to run on it's own as a known reference antenna without the usual 
ham antenna changes. That's also one of the reasons for the peak noise 
level measurement to record local ham activity on site or nearby static 
crashes.

73,

Chris, G4HYG

On 14/09/12 20:36, Curt, WE7U wrote:

> 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
>



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