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Re: [RFI] Weather Station on 433.92?

To: rfi@contesting.com
Subject: Re: [RFI] Weather Station on 433.92?
From: "Cortland Richmond" <ka5s@earthlink.net>
Reply-to: ka5s@earthlink.net
Date: Wed, 11 Apr 2007 20:11:04 -0400
List-post: <mailto:rfi@contesting.com>
Hi Dave!  Comments interspersed below. HTML to preserve formatting. 

> [Original Message]
> From: David Garnier <dgarnier@wi.rr.com>
> I have written about these devices before...
> Having briefly looked at Part 15 regulations for transmitting devices,
> they scary the crap out of me... I don't have to deal directly with these
> devices at work yet, the 433.92 MHz frequency sounds awfully like
> an ISM frequency slot. (Years ago we used to test product @ 3 V/m
> 80% AM modulation on our OATS site, I think that's the frequencies
> called out by CISPR11.)

Comment: Yes, IIRC, that's a European ISM frequency.    Also in that range are 
Euro PCM radios, which show up here when tourists bring their PSM radios with 
them, much as we might take FRS radios over there. Only FRS isn't on Ham 
frequencies, so they get *noticed*. Different subject.  

> My rudimentary understanding of the regs for Part 15 transmitters is
> 1) 3 meter limit for RE that "falls off" (some curve) with frequency,
> 2) Can darn near operate anywhere _however_, 3) Without causing
> "harmful interference" (whatever the FCC definition of the day is.)

Section 15.209 Radiated emission limits, general requirements.
(a) Except as provided elsewhere in this Subpart, the emissions from an 
intentional radiator shall
not exceed the field strength levels specified in the following table:
Frequency               Field Strength                Measurement Distance
(MHz)                    (microvolts/meter)          (meters)
0.009 - 0.490          2400/F(kHz)                 300
0.490 - 1.705         24000/F(kHz)                30
1.705 - 30.0           30                                  30
30 - 88                   100                                3
88 - 216                 150                                3
216 - 960               200                                3
Above 960             500                                3

> Do I got it right?  I sure there's other folks who work in a test houses
> and are more intimately knowledgeable with them than I am...  I love
> this business.  ;-)

There you go!

BTW... just TRY measuring a VLF intentional emitter at 300 meters (must use a 
loop); good luck!  Remember VDE 0871?   

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