I have a Zenith J615 (one year newer than the H511) with the extra 12BA6 RF amp stage. This makes a difference, especially in the daytime reception. One thing I did was "peak" all the IF can trimmers. I am confined at work to a brick-metal building, a literal "faraday cage , so I had a challenge to optimize daytime reception. This is the best performer in this building to date.
Jeff, if you need the Sams for the alignment procedure, PM me. It may be the last thing (after those caps) you need to do.
The other radio I used to make this daytime reception comparison is a Motorola H56, a typical AA5. I restored it at work "in the cage" over several lunchtimes, and I could barely get more than a few non-local stations after doing the standard alignment.
Now its on loan to a family member as a daily driver for the kitchen.
Motorola 56H.jpg
The Motorola does not have the RF amp stage either, so I imagine your Zenith would be slightly better.
Reece is spot on advise........ get close to a window or at least an outside wall. AM hates tunnels.
