[R-390] sensitivity

[Lester Veenstra]

And in the beginning it was:  1.3806488 × 10-23 joule/K

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y
lester at veenstras.com

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-----Original Message-----
From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Bob Camp
Sent: Friday, October 07, 2016 3:26 PM
To: Roy Morgan
Cc: R-390 Forum
Subject: Re: [R-390] sensitivity

Hi

K = a magic constant to make it all work
T = temperature
B = bandwidth of the noise

If you are at 25C you get one number, if you are at 25K (really cold) you
get another number. 
Once you try to convert the noise power into volts, the resistance involved
matters. 

Bob


> On Oct 7, 2016, at 1:46 PM, Roy Morgan <k1lky68 at gmail.com> wrote:
> 
>> ... sensitivity on all bands  as .07uV.  So the tightest filter in this
> is 300hz.  So now we are  talking incredible receiver  right?  I  have my
> suspicions on that.
> 
> Russ,
> 
> Claims of receiver sensitivity very much below one microvolt should be
> regarded with suspicion.  Some of the factors in making such measurements
> are:
> 
> - actual input impedance of the receiver with respect to the test signal
> source impedance
> - method of predicting the receiver input signal level
> - possibility (likelihood!) of leakage in the test signal generation
> system at such low levels
> - bandwidth of  the receiving system
> - overall measurement system quality and capability
> - eagerness of the operator to proclaim astounding performance for his
> receiver.
> 
> I know a fellow who owns a Ferrari Testarosa automobile.  I think it can
go
> nearly 200 miles per hours.  He seldom gets a chance to do that.
> 
> Bob Camps just-posted comment relates directly:
> "If you are dealing with an HF radio below 10 MHz, none of this is all
that
> big a deal. Any time or place
> you would ever *use* the radio, the noise into any rational antenna is
well
> above the KTB
> noise floor."
> 
> Now, I'm going to go refresh my memory about the meaning of "KTB nose
> floor".
> 
> -- 
> Regards,
> Roy
> 
> Roy Morgan
> k1lky since 1958
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