>> The levels for man made noise that are cited in the program are:
>>
>> -110.4 dBm - industrial
>> -114.7 dBm - residential
>> -120.0 dBm - rural
>> -133.6 dBm - remote
>>
>> This presumably assumes an isotropic radiator. I am guessing this is
>> 3 kHz bandwidth.
> If I understand correctly, those numbers represent an external wide
> band noise floor. Being not a noise produced internally to a receiver
> (or by a low noise instrument like a spectrum analyzer), it has not a
> great meaning to specify a BW unless the receiver ground floor is
> actually comparable with those numbers (hopefully not).
> 73,
> Mauri I4JMY
Hello, Mauri,
Even with an external noise source, or with any exteranal or internal signal
whose bandwidth is significantly greater than the receiver bandwidth, the
bandwidth of the receiver does affect the amount of noise power than will be
present within the receiver passband. If the distribution of noise is
uniform, doubling the receiver bandwidth will result in a 3 dB increase in
the average noise power. For that reason, noise is better expressed in
dBm/Hz. If the measurement bandwidth above were 3 kHz, you could subtract
10*log(BW) from the numbers to obtain dBm/Hz.
73,
Ed Hare, W1RFI
ARRL Laboratory
225 Main St
Newington, CT 06111
Tel: 860-594-0318
FAX: 860-594-0259
Internet: w1rfi@arrl.org
ARRL Web: http://www.arrl.org
ARRL Technical Information Service: http://www.arrl.org/tis/
-----Original Message-----
From: i4jmy@iol.it [mailto:i4jmy@iol.it]
Sent: Thursday, March 01, 2001 9:21 AM
To: w1rfi@arrl.org; n4zr@contesting.com; rfi@contesting.com;
topband@contesting.com
Subject: RE: [RFI] RFI levels
> The levels for man made noise that are cited in the program are:
>
> -110.4 dBm - industrial
> -114.7 dBm - residential
> -120.0 dBm - rural
> -133.6 dBm - remote
>
> This presumably assumes an isotropic radiator. I am guessing this is
a 3
> kHz bandwidth.
If I understand correctly, those numbers represent an external wide
band noise floor.
Being not a noise produced internally to a receiver (or by a low noise
instrument like a spectrum analyzer), it has not a great meaning to
specify a BW unless the receiver ground floor is actually comparable
with those numbers (hopefully not).
73,
Mauri I4JMY
>The data caem from CCIR Report 258. The measurements made by
> ARRL showed somewhat lower levels.
>
> The program has to be just about the best IONCAP-based propagation
program I
> have played with. It can be downloaded free from:
>
> http://elbert.its.bldrdoc.gov/hf.html
>
> 73,
> Ed Hare, W1RFI
> ARRL Lab
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