On May 16, 2025, at 15:37, Gordon Gibby KX4Z via groups.io <docvacuumtubes@...> wrote:

?If you’re able to down between the two points that you’ve got, success at -73 and failure at negative103 which are 30 DB apart, that would be a big step forward!

I wonder if the digital noise from various cables, etc., in the device are harming the basic sensitivity? ? As I remember, I think this device uses a diode mixer, and those generally can have a pretty well known sensitivity. ? ?But that could be covered up by internally generated noise. Those are things that can be fixed!

Thanks-?

Gordon kx4z?

On May 16, 2025, at 14:46, Tom via groups.io <tmoll150@...> wrote:

?

Just got my zbitx yesterday and have begun playing with it. Made a bunch of FT-8 QSO's right away on 20m last night with 2w out to a vertical, so that was interesting and pleasantly surprising.

Did some receiver testing today.

The factory Test Report card that came with the xcvr indicates a sensitivity of -105dbm.

I attached my S9 signal generator set at -103dbm (about S4) and it could not be heard on any band, even with the IF gain at 100.

With the generator set at S9 (-73dbm) it could be plainly heard on all bands with the IF gain set at 50, however, the audio heard was not

perceived to be an S9 signal. Turning the IF up to about 65 helped a lot, but the radio seems to lack audio gain as well.

The S meter on the zbitx did read approximately S9 at this setting.

?

This lack of sensitivity surprises me greatly - even my super cheap and dated technology SoftRocks easily hear better than that, as does a simple analog rig like a QCX.

Something does not seem right to me. I expected better.

The concept of this radio is really great IMO, and obviously a lot of work has already gone into its implementation, so hats off to the developer, however,

this receiver performance seems to be a serious issue to me, even at this price point.