[600MRG] Relative outside noise...

[Tom W8JI]

On 7/24/2023 10:45 AM, Ed Cole wrote:
> Dave,
>
> I have been inactive for a few years but I recall trying a single wire 
> BOG of 1/4 WL at 500-KHz and it was 20-dB quieter than my Inverted-L 
> (43x130 feet).
>
> But I found the BOG about 20-dB lower on signals (using NDB's as 
> testing sources out to 1000 miles).
>
>

The above is good example of why absolute levels of noise on a receiver, 
or noise on an antenna compared to a dummy load, are useless except to 
establish the system is noise limiting on external noise.

Receiving has a different requirement than transmitting.

630M I can use a 40dB or 50dB pad when receiving on my transmitting 
antenna with no ill effect. If I was listening on the TX antenna I could 
use a feedline with 40dB loss with no ill effect on receiving.   The 
3100Hz bandwidth measured wintertime noise level on my full size 
Inverted L antenna is -74dBm daytime and -70dBm at night.  (My 
transmitting antenna is a full-size inverted L about 500 feet or so from 
any power lines and probably about 20% eff).

The consistent ~4dB noise increase on a winter night tells me noise 
propagated via sky wave is the limiting factor at night, not local 
noise, so other than making it more directional there is nothing I can 
do on the TX antenna to make it receive better. (On 40M my daytime to 
nighttime noise changes about 30dB because 40M is a quiet local band)

630M is just very noisy locally, even way out in the country.

73 Tom


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