[Elecraft] APF measurements: FW 4.17 better results by 2 dB

[Arie Kleingeld PA3A]

Bill,

Thanks for your added comments.

As I said, I do not have the lab equipment to do this. But there are 
people in this group that have and can measure far better than I.
The APF (for me) is not about selectivity. I use it when digging into 
the noise and get a better copy of weak signals.
That is why I tried to measure S+N/N ratio the best I could. So if it is 
not exactly 2 dB (it is not), I donot care. I just measured that there 
was a _difference_ that 4.17 did a better job on s+n/n ratio.

So if one of the pro's can measure this more scientifically, that would 
be very enlighting.

If this s+n/n ratio and the passband are the same, then we can stop this 
discussion about the apf. :-)

73
Arie



>
> "Conclusions
>
> The model and the experimental results both suggest that these and similar
> multimeter are not capable of single high resolution relative measurements
> of narrowband audio noise such as measuring S/N ratios or Y factor for noise
> figure measurement due mainly to the short integration time in combination
> with narrow bandwidth.
>
> It may be possible to improve resolution by taking multiple measurements and
> calculating the root of the mean of the squares of the measurements, but
> errors in the summary process and in temporal drift become an issue."
>
> 73,  Bill
>