[600MRG] Rx noise 630m

[Ed Cole]

50-ohm reference (not 500-ohm - a typo).

I'm not an expert on A/D tech and how well strange waveforms are 
duplicated in digital.

Fortunately no (known) solar panel noise around me, but noise is both 
white and non-sinusoidal (so NB don't work).

Noise on 6m is S4-S6 which buries weak-signals (6m-eme is very 
hard>impossible).  I note noise at 10m is lower than 80m so that may 
predict my 630m noise environ.

I guess I could hook up the SDR-IQ on 475-KHz to look at the noise.  No 
wire antennas are up at present.  Could try shorted coax on HF beam at 
50-foot, I suppose.

Ed

On 3/18/2023 2:08 PM, Ed Cole wrote:
> Measuring noise floor is tricky so using a 500-ohm term probably yields 
> more comparable results.  I never measured the SDR-IQ into 50-ohms. 
> Something else to-do!
> 
> SDR-IQ is currently idle but operates off a SV1AFN 50-ohm splitter with 
> my K3.  This is fed via SP5T sma relay from either 630m antenna or 
> 28-MHz IF of 144/28 or 1296/28 transverters; Two relay positions idle:
> http://www.kl7uw.com/2023_Station.jpg
> 
> 73, Ed - KL7UW
> 
> On 3/18/2023 1:08 PM, Dave Riley via 600MRG wrote:
>> TNX, Tom for another look through your prism..
>>
>> I just set the Cushman 24 up on 475kc.  With a shorted input it reads 
>> -111 db ( not sure of cal )
>>
>> Then I plug in the loop and it goes up to -5 on the Cushman or +6 db 
>> over -111 noise.
>>
>> I'd guess that the -111 is the noise floor on that meter.  It was on 
>> 3.1 kc
>>
>> I tuned off to 460 and then 490 and the noise indicated -110 db on the 
>> edges.
>>
>> Tuned to 476 kc. and it was -5  ' fairly good loop Q '
>>
>> Best I can do is 'relative'...  Think I should be using a 50 ohm load 
>> instead of a short..
>>
>> TNX summore de DaveR W1FRV
>>
>>
>>
>>
>> On 3/18/2023 4:09 PM, Tom W8JI wrote:
>>> Hi Dave,
>>>
>>> Relative performance or noise performance is very difficult to 
>>> measure in a meaningful way.
>>>
>>> 8dB is meaningless. 8 dB is just a ratio, what is the 8dB ratio 
>>> against and under what condition?
>>>
>>> The 13dB difference between a short and an antenna doesn't mean very 
>>> much of anything either. It only means the antenna is picking up 13dB 
>>> more noise than a short. That doesn't mean anything about ambient 
>>> noise or antenna receiving performance. It only means is the antenna 
>>> system has 13dB more background noise than a short in some test. It 
>>> doesn't tell us anything about how well something is working, how 
>>> poorly it is working, or what the ambient noise level is unless there 
>>> is some good reference.
>>>
>>> Now if we have some reference signal it might mean something. My full 
>>> size inverted L antenna in January was about -73 dBm in 3.1kHz 
>>> bandwidth daytime at this time of day, and -70 dBm average on a quiet 
>>> night just before sunrise.
>>>
>>> I just measured it now and it is -72 dBm in the same 3.1 kHz 
>>> bandwidth. Some digital signal on right now is -86 dBm, 14 dB below 
>>> the 3.1kHz noise floor.
>>>
>>> My guess is that is N4WLO, my level meter can't decode digital signals.
>>>
>>> Even this does not mean much.
>>>
>>> 73 Tom
>>>
>>>
>>>
>>>
>>> On 3/18/2023 3:11 PM, Dave Riley via 600MRG wrote:
>>>
>>>> Saying good bye to seasonal DX..
>>>>
>>>> Think the bulk of QRN has been nulled out here but still, the 
>>>> difference between antenna and a short is about 13db
>>>>
>>>> Not much difference in noise level with loop spun around either..
>>>>
>>>> Maybe there is 8 db ambient noise average, some say that is low..
>>>>
>>>> What you say??
>>>>
>>>> TNX Dave @ W1FRV
>>>>
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