The uptrend yesterday which can be seen on your remaining receiver is not unusual for a friday, or?
I have a similar increase as well for that day without changing anything. You might need to monitor this for at least a week.
You have also an uptrend on # of messages, but in your history you had these improvements also (e.g. 02/14)
I’m getting slightly annoyed by this so I decided to bite the bullet and ordered nanovna-h4 it should be with me in a few weeks.
Assuming I’ve built the antennas properly, the only other difference I can see is the coax. The whip is on magnetic base with 2m of RG58, while for the DIYs I’ve used RG6 but much shorter lenght, would that make such a huge difference?
For the price of the nanovna you could simply buy an optimized FA antenna.
I have no idea what issues your setup nas.
At the beginning i was the simple whip antenna, then i built a spider made from a simple coax with arms in correct length. I did not use any electronic device, however it outperformed the whip by at least 30%
Now i am using an optimized antenna i got from ebay for low price - done.
Theres a lot of ways to build them using less expensive bits, I ruined a few SO239 connectors trying to make pretty solder joints.
Here’s one I made using a simple F coupler connector, simply winding the ground plane radials onto it and tightening the nut. Simple, works fine doesnt really need to be soldered but I sweated the two pieces together.
Another I made using a copper plumbing pipe cap, drill four holes at the upper edge to solder the radials into and a center hole to insert an sma to F pigtail through it. Copper of course takes solder well. BTW, I did experiment some with the height of the ground plane on the connector and it didn’t seem especially sensitive to that.