References: <CAHAQVWP9OQ-dZ0q7hEp2tjuvZzghQGi+oDVBtbwL=xUHCYZi9g@mail.gmail.com> <CAHAQVWPuCx+WeejbnDgLMmQRWonYSM4eB8yhs8kRSWe15yhDzA@mail.gmail.com> <c6200e98-35eb-bb7a-1a39-75f306816ff0@btinternet.com> <CA20351BC5E841289F19B4E51BA463FC@gnat> <7553d9d1-2639-3846-feb9-7bffc4585597@btinternet.com> <B6CB04DF2A4F4E689F98BAE674619C2C@gnat>
From: Gmail <rogerlapthorn@gmail.com>
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Date: Tue, 23 Jan 2018 08:05:15 +0000
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
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Subject: Re: LF: 136kHz - this is how badmy system is!
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Well I am glad I was persuaded to keep trying by Pete! On 136kHz WSPR 4 different stations have been received in the last day despite my totally useless setup. Thank you to everyone for the encouragement.

73s
Roger G3XBM

On 22 Jan 2018, at 23:55, "Alan Melia" <alan.melia@btinternet.com> wrote:

> Hi Martin I think Andy has answered the question for me so I wont confuse your with further facts :-))
> 
> In the days when I used to pontificate daily on propagation I tried hard to ensure the sensitivity of the rx system was reasonably constant and I did not have too much external noise. We had problems but Brian CT1DRP had a line on his waterfall we never located but was external and very constant. It provided a very good confidence boost and I believe did show Brian when his earth connection corroded and fell off. The general opinion for the source of the signal was a harmonic from a digital comms line (I think it was a harmonic of 8kHz) I came across a couple of ceramic 'bookends' the other day which I never used :-))
> 
> Happy LFing
> Alan
> G3NYK
> 
> 
> ----- Original Message ----- From: "Martin Evans" <gw3ucj@btinternet.com>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Monday, January 22, 2018 8:06 PM
> Subject: Re: LF: 136kHz - this is how badmy system is!
> 
> 
>> 
>> 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" <gw3ucj@btinternet.com>
>>> To: <rsgb_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 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.
> 
>