[600MRG] Relative outside noise...

[Dave Riley]

Thanks for all your replies, am still processing.. Great brain food..

After 70 years of hamming, this subject has been one of the most 
interesting fer sure..

Here is latest 630m report showing some relative proof of performance..
VK4YFB 6:07 PM 
<https://khz-chat.slack.com/archives/CCCD8PL7L/p1690236428493789>
5720 km  DC0DX > W1FRV -26 WSPR
Fessenden noticed a lot of signal loss working Scotland from here in the 
summer months. His Elmer was Kennally ( of Kennally-Heavyside ) who told 
him what happens and to maintain a salt water connection between here 
and Scotland.. www.radiocom.net/Fessenden
He also used and researched RF loops.. Had hundreds of inventions during 
his run here in town..

1/4 db ( watching long fft ) of noise trimmed here, another one there, 
pretty soon adds up to real DX..
Today added a separate local earth ground rod for the the SDR play 
receiver which now shows 2 db less noise or 2db of more signal above 
noise on 160m..
Tonight the R75 is running off battery.. Will see..

I have no such thing as a calibrated noise source on hand, just 
comparisons..

Cushman CE24, HP 3586c level receiver, Icom R75, ic718 and two SDR rsps 
all show different noise floors.. Or MDS...

So I take approx 200 nV of RF and a step attenuator, send it to each of 
the receivers one at a time and the one RX that shows the most RF up and 
out of the noise wins...
Don't have up to date cals with the above.. Probably are in the ball park..
All is done relative here..  Today the 2 turn coax loop on 160 shows 4 
db between the loop and a 50 ohm load..  W1NMF

Too much fun...  73s from Dave @ W1FRV 'first radio voice'






On 7/25/2023 7:58 AM, Tom W8JI wrote:
> 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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20230725/81ba25cd/attachment.html>