[hpsdr] 100D Noise Figure?

[Conrad Farlow]

I totally agree with Helmut, what is needed is a Y factor calculation 
with a high ENR noise source. I doubt that the HP346A that I have would 
be any good.

Conrad G0RUZ

> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Clyde and Phil,
>
> Phil, of course your formula is correct, but I think you can also accept the
> well known formula for cascaded stages and the contribution of noise
> depending on the specific NF and gain/loss of the single stage:
>
> F = F1 + F2 -1/G1 + …..
>
> According to this formula the contribution of noise by the ADC would be so
> low or negligible for the whole system, if the supplier data for the ATT,
> filter and preamp are correct. That is a contradiction to that what the
> supplier of ADCs tell us. They recommend to calculate with noise figures of
> 30 to 40 dB.
>
> I think my both setups , one with Mercuries and the other with Hermes are
> well calibrated under fullscale condition of the ADC. Under your mentioned
> conditions( 28 MHz, 2.9 kHz, Signal avg) I can read minimum noise levels in
> the range of -127 dBm to -125 dBm (dither/random off and RX terminated
> directly at the socket on the board). This is already a difference of at
> least 3 dB to your figure.
> I’m not really sure that we can trust the readings of the noise level
> absolutely, when only a few bits of the ADC are applied, while calibration
> was done with 16 bit. When my noise source gets repaired -hopefully soon -
> I’ll make some measurements to get perhaps further insight.
>
> 73, Helmut, DC6NY
>
>
> -----Ursprüngliche Nachricht-----
> Von: hpsdr-bounces at lists.openhpsdr.org
> [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Phil Harman
> Gesendet: Samstag, 1. Juni 2013 08:13
> An: Clyde Washburn; hpsdr at lists.openhpsdr.org
> Betreff: Re: [hpsdr] 100D Noise Figure?
>
> ***** High Performance Software Defined Radio Discussion List *****
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