Suggestions for a good digital converter box for maximum 4:3 format screen fill
 

Hi guys...looking for suggestions for a digital converter box useable with a vintage antenna and has a coax RF output and a screen filling or almost screen filling picture setting for the vintage 4:3 video ratio. Also, how much do you mess with a vintage TV's width and height settings for a round tube TV to maximize screen fill. My box does have ratio settings for 4:3 screen fill but it's not even close. It's a cheap Chinese unit so I didn't expect much but when I watch YT restorations, the final image restorers get is much larger than I have been able to get with my equipment. Additionally, it's obvious some of these converters are better than others for noise/buzz suppression associated with modern format so some suggestions there would also be appreciated.

I use the Zenith DTT-900, DTT-901, the LG, and Insignia rebadged of those boxes. They've got enough reception strength that 30-40 miles west of Milwaukee I can get most channels with just 6" of wire jammed in the antenna hole...They work well with a vintage antenna and a balun for it (excellent if it's a vintage UHF bowtie antenna). They have a Zoom button that lets you choose between letterbox, Cropped (the sides of 16x9 lopped off and the rest used to completely fill the 4x3 NTSC output), and Squeezed (16x9 image squished horizontally so it fills the 4x3 NTSC output without anything being invisible)....They have RF output too.
They're old 2009 models and there's a cap which fails in some (dieseljeep posted which one on this forum), but they still work great.

I prefer the Zenith boxes too and it's what I use in many of my videos on YouTube.

I can vouch for that Zenith box. Have the 2008 version, with that same cap that went bad. Replaced cap and and the unit still works like new.

How's the "buzzz" with the Zenith you get with modern text graphics on the screen or is it unavoidable with this era of TVs?

The Zenith converter box is ok on most brands of TV. Zenith TVs with the buzzomatic 6BN6 audio detector will buzz with any signal source they're not aligned to*.
Granted I mostly use my DTV converters AV jacks instead of RF to feed Blonder Tongues that then wirelessly transmit RF on any channel I want throughout my house.

*A few years ago I noticed an interesting thing with Zenith 6BN6 audio detectors...I had a video only vacuum tube RF modulator from the 50s, and a built an audio stage for it with a single tube 4.5 MHz FM osc/modulator that I could mix into the composite signal in the unit. That osc could be tuned for an offset not exactly 4.5MHz. I found on one of my buzzier Zenith's that if I tuned the RF carrier of that modulator I could completely null the buzz and get clean audio. This proves that IF alignment matters with the 6BN6.

The fact that you could null it out with just a fequency tweak seems to point to a single frequency adjustment in the Zenith that would potentially have the same effect. I wonder...