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From: Martin Evans <gw3ucj@btinternet.com>
Message-ID: <7553d9d1-2639-3846-feb9-7bffc4585597@btinternet.com>
Date: Mon, 22 Jan 2018 20:06:24 +0000
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Subject: Re: LF: 136kHz - this is how badmy system is!
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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.
>>
>
>