On Wed, Sep 18, 2019 at 11:59 AM, <qrp.ddc@...> wrote:
Andy G0FTD>> Does anyone have data on measurements taken with or without ?
yes, here is measurement. First one is without load on CH1. And the second one
with load on CH1. As you can see, with load on CH1 there is less noise
Thanks.
I'd say that there's no discernible difference for S11 measurements (expected) but the lower limit of noise floor
has been extended by about 5db.
Not got my reading glasses on for my laptop though ;-)
So being able to measure a filter's attenuation at -80db rather than -75db @ 200Mhz (your marker) I'm presuming is the practical outcome ?
I won' pass comment on that, because for some users, -75db might be good enough, depends what the operator whats.
But I suppose 5db is 5db and in some cases that could be everything.
I've had another thought on this too.
Why not do a port isolation calibration using the 50R load supplied on Ch0, and the supplied SHORT on the input of Ch1 ?
Any noise drifting around entering the port would surely be eliminated too ?
73 de Andy
