[time-nuts] manmade interference was Re: Russian Timing Service ?

jimlux jimlux at earthlink.net
Tue Aug 21 14:46:16 EDT 2018


On 8/21/18 11:37 AM, Poul-Henning Kamp wrote:
> --------
> In message <a6d1b0da-19ab-3b85-d928-e0e8bf8f6153 at storm.ca>, Martin VE3OAT write
> s:
> 
>> A very good system, unlike anything used in the Western world.
> 
> Except you will be incredibly challenged to receive it anywhere
> because of all the man-made noise at those low frequencies.
> 
> And as I said, they don't seem to be on air much these days...
> 

Speaking of which, does anyone have any pointers to "modern" 
measurements of RFI in the lower frequency ranges (up to a few MHz, 
perhaps).

There's the ITU report with the "urban" and "rural" curves, but those 
are fairly old.  And they don't give any sample "power spectral density" 
curves.


In the days of analog power supplies, choosing your broadcast time 
standard to be at a round number (like 60 kHz or 10 MHz) made a lot of 
sense. But now with switchers, maybe that's not such a good idea?  Or 
where do all those spurs tend to lie?  Maybe CHU at 3330, 7335 and 14670 
works out better.

I know I find receiving WWV/H at 10 or 20 MHz is troublesome because of 
all the other 10MHz sources I have running around.  ( I usually wind up 
looking at the 100 Hz sidebands, if I'm looking for an over the air test 
signal. Most of my 10 MHz sources aren't so far off that they interfere)


Famously, one of the Omega frequencies is an exact multiple of 60Hz, 
causing trouble for its use -




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