[600MRG] Fwd: Re: measuring noise level ?

[Edward R Cole]

Meant this to go to the list

>Date: Sun, 17 Jul 2016 10:45:54 -0800
>To: Frank Lotito <k3dz at live.com>
>From: Edward R Cole <kl7uw at acsalaska.net>
>Subject: Re: [600MRG] measuring noise level ?
>
>Definitely.  if not specified for ham radio reports, I assume SSB bw 
>of approx. 2.5-KHz.
>Elecraft receiver MDS spec using 500-Hz which subtracts 7 dB to 
>measurements done at 2.5KHz.  e.g. MDS of -144 dBm becomes -137 dBm at 2.5 KHz.
>
>Contrary to Elecraft I make all my MDS at 2.5-KHz.  Partly because 
>JT65 sw signal level readings are referenced using 2.5-KHz.  Weak 
>signal CW operators are capable of mentally filtering to bw ~ 50-Hz 
>which means they can hear signals -17 dB from a reference at 2.5-KHz 
>(SNR=0).  Whereas JT65 signal can often be decoded at -27 dB and 
>occasionally down to -29 dB (readings on the JT65 signal level indicator).
>
>I have done sun noise measurements using my SDR-IQ + transverter + 
>preamp on 144-MHz (Y= 8 dB) and 1296-MHz (Y=16dB).  Antenna gain is 
>21-dBi on 144 and 34-dBic on 1296.  Below 50-MHz sky noise swamps 
>out sun noise on most antenna systems (excepting very large eme 
>arrays).  Bw = 190-KHz.
>
>Most HF noise variance is man-made.  I see a rise from S2 to S4/5 on 
>6m when I point NE vs SE.  City of Anchorage is NE at 98-km from me 
>(coincidence?).
>
>My noise floor using my invert-L on 495-KHz usually runs about -110 
>dBm (0.7uv) using my SDR-IQ running Spectravue in 2.5-KHz bw (SSB 
>mode).  But I have seen nights it rises to -90 dBm.  SDR-IQ without 
>antenna shows noise floor of -134 dBm.
>
>73, Ed
>
>At 09:46 AM 7/17/2016, you wrote:
>>Don't forget, the "noise"measured, be it dBm, uV, S-Units, etc. is 
>>also "bandwidth" dependent.  I would also submit, for complete 
>>receive systems, a noise measurement is also directional, such a 
>>sweeping across the path of the sun with a VHF, UHF, SHF or 
>>microwave antenna.  If the noise peaks, Great; if the noise does 
>>not peak your aim is off, or your total system is lacking.  Ditto 
>>when your HF yagi is aimed in certain directions.
>>73 Frank K3DZ / WH2XHA
>>________________________________________
>>From: 600MRG <600mrg-bounces at w7ekb.com> on behalf of Edward R Cole 
>><kl7uw at acsalaska.net>
>>Sent: Sunday, July 17, 2016 12:13 PM
>>To: 600mrg at w7ekb.com
>>Subject: Re: [600MRG] measuring noise level ?
>>
>>Most likely the poster of that noise measurement intended to say -85
>>dBm.  Spectravue provides direct level measurements of signal and
>>noise on a waterfall display.  Most SDR sw do this.
>>
>>All modern service equipment show signal level in dBm.  I hear almost
>>no one using uv anymore (unless they are audiophiles).  DBm are
>>direct measurement in power while uv is ac voltage which requires one
>>to specify the impedance if it is to relate to power.
>>
>>So would you rather S-meter reading be given - ha ha!  Show me two
>>receivers that have s-meter properly calibrated.
>>
>>73, Ed - KL7UW
>>
>>At 07:26 AM 7/17/2016, sbjohnston at aol.com wrote:
>>
>> >I did not say there was no reason to be aware of noise - far from
>> >it.  In both my amateur and my professional life the problem of
>> >radio noise is a very big deal.  I just don't get the point of
>> >sharing a figure like "-85 dB".
>> >
>> >Decibels don't mean anything unless you provide the reference level
>> >to which your measurement is -85 dB down from.
>> >
>> >And without considering the gain or loss of the complete antenna
>> >system (or the bandwidth of the receive system in which you are
>> >adding up the noise) I can't see how you can compare station A to
>> >station B in a different location.
>> >
>> >
>> >
>> >
>> >Steve WD8DAS
>> >
>> >sbjohnston at aol.com
>> >http://www.wd8das.net/
>> >--------------------------------------------------------------------
>> >Radio is your best entertainment value.
>> >--------------------------------------------------------------------
>> >
>> >
>> >
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>>
>>73, Ed - KL7UW
>>http://www.kl7uw.com
>>      "Kits made by KL7UW"
>>Dubus Mag business:
>>      dubususa at gmail.com
>>
>>
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>
>73, Ed - KL7UW
>http://www.kl7uw.com
>     "Kits made by KL7UW"
>Dubus Mag business:
>     dubususa at gmail.com

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     dubususa at gmail.com