Maximum range of NDB's

I've been getting deeper into designing custom airports with the SDK and Scruffy Duck's ADE20 editor, and have discovered a couple of things about NDB's. If this info is buried in the SDK docs somewhere, and this isn't "news", my apologies, but maybe it will help someone who is struggling with getting their custom airport to work properly. 

First off, there's a lot of data on the Internet regarding the "maximum range" of NDB radio beacons. I've seen some documents listing this as 199 nm for "HH" class NDB's, so I tried 199nm as a range setting for an NDB at Howland Island (This was the mid-ocean refueling point that Amelia Earheart and Fred Noonan were trying to get to).

It turns out that MSFS 2020's SDK will build a BGL file with a 199nm range for an NDB without showing any compiler error, but when you get in your Cessna 152 and try to fly an NDB approach there, the sim seems to have a max range of 146 nm built in, that overrides the NDB range value in your XML file if you set it to anything over 146nm.

As I fly toward this "HH" type NDB, the needle on the ADF gauge swings off of the neutral position and the Morse code becaomes audible in the headphones, right about when Little Nav Map says the distance is 146nm between the aircraft and the NDB site.

This was with the Cessna 152 flying at 6,500 ft MSL. I've tried it with the DH2 Beaver, the Cessna 208, and the Beech Bonanza, and the behavior is pretty much the same whether the ADF is a dial gauge on the panel (Cessna 152 and DH Beaver), or it's on the Garmin 1000 PFD (Cessna 208 and Bonanza). 

Edited January 6Jan 6 by Ray Proudfoot
Added some paragraphs to ease reading.