I just tested again in the LW arena with Delirium on another country.
He flew from a field adjacent the water to rule out terrain height.
He gradually gained altitude, pausing at increments to allow the radar refresh to cycle.
He was painted on bar dar above 250 feet.
He reduced altitude in increments until his bar dar disappeared under 65 feet.
He gradually gained altitude again and his bar dar never reappeared again even about 1,500 feet. He was able to fly all the way across the map undetected and his bar dar only reappeared after he entered a radar ring.
No one else on the same country as me could see his bar dar either, so it was not localized to me.
I upped and Delirium observed. I gained altitude in increments the same way as he did. He saw no bar dar until I was over 500 feet. My bar dar disappeared to him as I flew under 65'.
Delirium and I recorded the same inconsistencies as Lusche (Snailman) and I recorded months ago. Sector counter height is 250' or 500' AGL.
Good research.
I've seen enemy me163s show up at 40k feet without a dar bar showing until we entered a dar ring as well.
Here's some more information.....
Your plane will flash a field regardless of being airborne or landed when it is within the radius of the dar ring.....whether operational or not......this includes the city/strats and HQ.
Many trees make it near impossible to approach a field NOE below 65 feet AGL without the red dot showing and the field is flashing anyway.
If you want to approach NOE and can get below red dot height, you had better make sure the field has a friendly tank spawn nearby or the enemy will surely know there is a NOE plane inbound.
Sometimes, I land on mountaintops just out of dar range near the city or HQ and wait for B29s to up.
If I get bored waiting, I slowly taxi into the "flash proximity" from my 20k foot mountaintop perch and cause it to flash while I am away from keyboard and turn the sound up as well as zoom the clipboard showing my area large enough for me to see a dar bar show up from across the room.
Then I wait to pounce.