[600MRG] Rx noise 630m

[Dave Riley]

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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