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" <[email protected]> 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" <[email protected]>
> To: <[email protected]>
> 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" <[email protected]>
>>> To: <[email protected]>
>>> 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.
>
>
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