Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w0MKaNW0026251 for ; Mon, 22 Jan 2018 21:36:26 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ediko-0001hR-Mp for rs_out_1@blacksheep.org; Mon, 22 Jan 2018 20:31:42 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1edikm-0001hI-OE for rsgb_lf_group@blacksheep.org; Mon, 22 Jan 2018 20:31:40 +0000 Received: from mail-wm0-x233.google.com ([2a00:1450:400c:c09::233]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1edikj-0006NT-GD for rsgb_lf_group@blacksheep.org; Mon, 22 Jan 2018 20:31:39 +0000 Received: by mail-wm0-x233.google.com with SMTP id i186so18702613wmi.4 for ; Mon, 22 Jan 2018 12:31:37 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=pND4v96dZXLi6j8JzOlBIVt6hHBVj9CjCmvEaEspaRE=; b=bSjn7vQm2VxcbhzBwJVhdmLERe39gvnhgQJj2XY5PuSUxXXfmv6lXasnzHon6M4r54 3xqlpsJh89Wm1nID4lipni3lSUBNFvKK0xtffJFcDYZ/Hbci1k/VJghfRMf+DlUYfqZ3 AXmRjrk9H0KmCnADwz3ukErzHY4lQMFJPTTQjlpcokMkXmg9PJAFGUTk84mWQEb5DUf/ 6pAHSwAvD6bdP2KdlSLhJTpjo+BSHkx8RfaXHs0QmJgjqx934sJRDEkolBa2GDFycdpS bdKlNltWCxc8FS7vuooiRnCCFwL42qooSlnMHfh2nVvI6mH9IYQxgfDEhE6yC6j4xLSu C9RA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=pND4v96dZXLi6j8JzOlBIVt6hHBVj9CjCmvEaEspaRE=; b=Ygmp6iigaaRWvGu2d5ieSf4bRSPeSclOTjRdt7ibqAksusq4vYwUOVUOPJL+R4ARUW QXTcoZx2y/riRsPPB1TgWuDruOub4rf3PuxGeSCafpvdQ55CBP1f08/GGiicEfC/tp+R UBtBN2EKdezhR8DcYnJ+dvgq3TXrfQSIQqA3wrHmNmxwjNFTmsuJ2R6loIGpVl10ILgt zMFbNK4u2fdIjLi6VTD9umf9PYZep0RU+s3tvFY3EuYR8A+Wyq5rfefVfM6/dysr8w8v cPnLD1dtId5ysen9kBw+CKqVaFmYHkSCtnSdiNvSQQ2QI00kxB2RbMUskek5TSo3T9Uw 3I0Q== X-Gm-Message-State: AKwxytc/+5bBKwV6tjT+qWK2I4iNvig+fpdrusggWKctgP6sWq60+3Iy 2D1g1U9yDcJ2irh2Y4Y/E4MhhWV8HA8C2LZl3Hg= X-Google-Smtp-Source: AH8x224TJWqTUsClC5nmmkVc8+4BXejRuNFiM7wSsdx6J9rKyXmcKWvrOnWhFg2ujSyl/jXNPpRl7UWUl1bwaXQJmJQ= X-Received: by 10.80.196.3 with SMTP id v3mr15435409edf.232.1516653096370; Mon, 22 Jan 2018 12:31:36 -0800 (PST) MIME-Version: 1.0 Received: by 10.80.179.198 with HTTP; Mon, 22 Jan 2018 12:31:35 -0800 (PST) In-Reply-To: <7553d9d1-2639-3846-feb9-7bffc4585597@btinternet.com> References: <7553d9d1-2639-3846-feb9-7bffc4585597@btinternet.com> From: Andy Talbot Date: Mon, 22 Jan 2018 20:31:35 +0000 Message-ID: To: LineOne X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Noise power is proportional to bandwidth At room temperature, a resistor will develop -174dBm of thermal noise or -174dBm/Hz In a 2.5kHz SSB bandwidth, the total power is therefore -174 + 10.LOG(2500) = -140dBm [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andy.g4jnt[at]gmail.com) 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 6b0411a0208d534ec13cf5eb48c0cfb7 Subject: Re: LF: 136kHz - this is how badmy system is! Content-Type: multipart/alternative; boundary="94eb2c1cd8740e854805636351bb" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false --94eb2c1cd8740e854805636351bb Content-Type: text/plain; charset="UTF-8" Noise power is proportional to bandwidth At room temperature, a resistor will develop -174dBm of thermal noise or -174dBm/Hz In a 2.5kHz SSB bandwidth, the total power is therefore -174 + 10.LOG(2500) = -140dBm When using an SDR + waterfall with 0.3Hz bins, the thermal noise per bin, and the minimum possible sensitivity is -174 + 10.LOG(0.3) = = -179dBm. Using QRSSS with a 0.01Hz bin, that becomes -194dBm Using the bin size of an FFT as the bandwidth is not strictly the case as FFTs are windowed to increase dynamic range, which has the effect of a signal appearing in adjacent bins at reduced power. So a good average to assume if you don't know the exact windowing function is that bandwidth is twice the bin size. Andy G4JNT On 22 January 2018 at 20:06, Martin Evans wrote: > > Alan - thanks for this. > Being a bear of very little brain ( I wouldn't recognise a Newton if I > tripped over one!) much of your explanation goes over my head, but I > understand well enough your conclusion that "that is not bad". > > One thing that I don't understand is the relevance of bandwidth to an SDR > receiver. > > If I short my receiver input, my baseline stands at -140dB ( that's the > lowest that the spectrum display goes); connect my antenna and my > background noise level around 137kHz is around -120dB; DCF30 is around > -70dB at the moment, and if I increase my scan width, R4 on 198kHz is > -40dB. All these measurements are taken from the spectrum display in the > Elad software. > > I don't see where bandwidth comes into the picture(!!) > > No doubt one of these days some of this will begin to make sense.... > > Thanks again, > > Martin GW3UCJ. > > ******************** > > Hi Martin, I would estimate the field strength from DCF39 in your area is >> about 0.5mV/m (from measurements done by PA0SE in the UK) and from your >> data that gives about 1.5uV at the RX input as the level of the noise. If >> that is in an SSB bandwidth that is not bad. I remember the noise plotted >> on my CFH measurements in around 2002 was in this area but in a 300Hz bw, >> on the AOR7030 (Remembering WSPR s/n is related to a 2.3kHz bw if I >> remember right) >> My minimum signal detection using a waterfall on the audio was 5nV (rx bw >> not relevant) but 0.3Hz bin size using a good sig-gen. I guess this was >> little more than 1 to 1.5dB above the noise. I think it was probably >> quieter here in East Anglia 15 years ago than it i now. >> >> I hope that helps (saves you ripping your station apart :-)) ) >> Alan >> G3NYK >> >> ----- Original Message ----- From: "Martin Evans" >> To: >> Sent: Monday, January 22, 2018 4:51 PM >> Subject: Re: LF: 136kHz - this is how badmy system is! >> >> >> >>> Watching Roger's adventures on 136kHz, I thought I'd go take a look and >>> I wondered - >>> >>> DCF39 is about 50dB above the noise at 16:44UTC. >>> >>> I'm using a 150ft inverted L, untuned, stuffed directly into an Elad >>> FDM-S2 SDR. >>> >>> Decoded G3XIZ, G4FTC, G8HUH & G4GIR between 16:12 and 16:44. >>> >>> What does this say about my setup? >>> >>> Is it deaf/average/ok? >>> >>> How far above the noise is DCF39 in an optimised "good" setup? >>> >>> Anyone tell me? >>> >>> Martin GW3UCJ Swansea. >>> >>> >> >> > > --94eb2c1cd8740e854805636351bb Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Noise power is proportional to bandwidth
At room tempe= rature, a resistor will develop -174dBm of thermal noise or -174dBm/Hz=C2= =A0 =C2=A0In a 2.5kHz SSB bandwidth, the total power is therefore -174 + 10= .LOG(2500) =3D -140dBm

When using an SDR + waterfa= ll with 0.3Hz bins, the thermal noise per bin, and=C2=A0 the minimum possib= le sensitivity is -174 + 10.LOG(0.3) =3D =3D -179dBm.=C2=A0 =C2=A0Using QRS= SS with a 0.01Hz bin, that becomes -194dBm

Using t= he bin size of an FFT as the bandwidth is not strictly the case as FFTs are= windowed to increase dynamic range, which has the effect of a signal appea= ring in adjacent bins at reduced power.=C2=A0 So a good average to assume i= f you don't know the exact windowing function is that=C2=A0 bandwidth i= s twice the bin size.

Andy=C2=A0 G4JNT
=

On 22 January 201= 8 at 20:06, Martin Evans <gw3ucj@btinternet.com> wrote:<= br>

Alan - thanks for this.
Being a bear of very little brain ( I wouldn't recognise a Newton if I = tripped over one!) much of your explanation goes over my head, but I unders= tand well enough your conclusion that "that is not bad".

One thing that I don't understand is the relevance of bandwidth to an S= DR receiver.

If I short my receiver input, my baseline stands at -140dB ( that's the= lowest that the spectrum display goes); connect my antenna and my backgrou= nd noise level around 137kHz is around -120dB; DCF30 is around -70dB at the= moment, and if I increase my scan width, R4 on 198kHz is -40dB. All these = measurements are taken from the spectrum display in the Elad software.

I don't see where bandwidth comes into the picture(!!)

No doubt one of these days some of this will begin to make sense....

Thanks again,

Martin GW3UCJ.

********************

Hi Martin, I would estimate the field strength from DCF39 in your area is a= bout 0.5mV/m (from measurements done by PA0SE in the UK) and from your data= that gives about 1.5uV at the RX input as the level of the noise. If that = is in an SSB bandwidth that is not bad. I remember the noise plotted on my = CFH measurements in around 2002 was in this area but in a 300Hz bw, on the = AOR7030 (Remembering WSPR s/n is related to a 2.3kHz bw if I remember right= )
My minimum signal detection using a waterfall on the audio was 5nV (rx bw n= ot relevant) but 0.3Hz bin size using a good sig-gen. I guess this was litt= le more than 1 to 1.5dB above the noise. I think it was probably quieter he= re in East Anglia 15 years ago than it i now.

I hope that helps (saves you ripping your station apart :-))=C2=A0 )
Alan
G3NYK

----- Original Message ----- From: "Martin Evans" <gw3ucj@btinternet.com&g= t;
To: <r= sgb_lf_group@blacksheep.org>
Sent: Monday, January 22, 2018 4:51 PM
Subject: Re: LF: 136kHz - this is how badmy system is!



Watching Roger's adventures on 136kHz, I thought I'd go take a look= and I wondered -

DCF39 is about 50dB above the noise at 16:44UTC.

I'm using a 150ft inverted L, untuned, stuffed directly into an Elad FD= M-S2 SDR.

Decoded G3XIZ, G4FTC, G8HUH & G4GIR between 16:12 and 16:44.

What does this say about my setup?

Is it deaf/average/ok?

How far above the noise is DCF39 in an optimised "good" setup?
Anyone tell me?

Martin GW3UCJ Swansea.






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