[R-390] Felton Electronic redesign of R-390A

[John Kolb]

On Thu, 4 Dec 2003, James A. (Andy) Moorer wrote:

> I have no experience with his engineering work - I am sure the receivers are
> remarkable devices, and I am sure his work is top-notch.
>
> But his reported sensitivity figure of .012 microvolts across 50 ohms can't
> possibly be true.
>
> Please refer to my "noise and sensitivity" page at:
> www.jamminpower.com/main/noise.jsp
>
> The short version is that a 50 ohm resistor at room temperature will exhibit
> a .0266 microvolt "thermal noise" voltage. This has been known for decades.
> A sensitivity measurement reports the voltage that is 10 dB above the base
> noise floor. The absolute minimum sensitivity possible with a 50-ohm load
> would be 10 dB above .0266 microvolts, which is about .084 microvolts. That
> is the theoretical limit  - the actual sensitivity is probably much higher
> than that.
>
> James A. (Andy) Moorer
> www.jamminpower.com
>
I'm not saying Mr Felton's figure is accurate - it doesn't take much
signal generator leakage at all to cause inaccurate measurements,
but his 0.012 uV figure was for minimum discernable signal with a 350
Hz IF bandwidth and 250 Hz audio filter. That should make the 50 ohm
resistor noise a little less than 0.01 uV, dividing 0.266 by the
sq rt of 3500 hz/350 hz.

My recievers routinely measured < .1 uV sensitivity with a Heathkit
Lab Generator on the other side of the room, without a connection
between the rx and the sig gen.

John

>
> P.S. - even a receiver with a 100-200 microvolt input sensitivity is an
> incredible receiver! No reason to inflate (deflate?) the numbers beyond
> physical limits.
>
>
> ----- Original Message -----
>
> > Good evening all:
> >
> > Does anyone have experience with the above mentioned company. He makes
> some
> > pretty impressive claims, but I haven't heard anyone ever mention him or
> his
> > work.
> >
> > http://www.feltondesign.com/
> >
> > Thanks for your input!
> >
> > Randy
> >
>
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