[hpsdr] Janus Lives!!

[Ahti Aintila]

On 04/07/06, Christopher T. Day <CTDay at lbl.gov> wrote:
> For what it's worth, which I suspect is nothing, the Linear Technology
> LT1128 op amps used on Janus are rated at a noise _voltage_ of
> ~1nV/root(Hz). Since I don't see off hand what resistance that's into, I
> don't know how to translate it directly to dBm, but the blurb does say
> that the amplifier's voltage noise is less than that of a 50ohm resistor
> at room temperature.
>        Chris - AE6VK
>
Hi Chris,

Go to the page 11 of the LT1028/LT1128 data sheet. Under the title
"Total Noise vs Source Resistance" you can find how to calculate it.
The input noise voltage density of the amplifier as specified is not
dependent on the input resistance, thermal noise voltage developed in
the resistor and noise voltage caused by the noise crrent through the
resistor have to be added as given in the formula.

Here is a convenient on-line tool for coversion of voltages, powers
and dB's: <http://www.analog.com/Analog_Root/static/techSupport/designTools/interactiveTools/dbconvert/dbconvert.html>

73, Ahti OH2RZ

 1152004755.0