4 ms·
There is something weird going on at FAA / NTSB etc. In most radio applications a guard band of 220Mhz is absolutely unheard of. You would do a guard at 10% o
by onphonenow 5y ago
There is something weird going on at FAA / NTSB etc.
In most radio applications a guard band of 220Mhz is absolutely unheard of.
You would do a guard at 10% of bandwidth lets say. On one side you'd have 5%.
So we are talking 1-2 Mhz?
My understanding was planes already had 2-3 altimeters, with guard band spacing of maybe 5Mhz (ie, planes already have devices blasting signals at frequencies much closer than 200Mhz).
- p_l 5y agoThere will be usually only one active radio altimeter, with center frequency around 4.3GHz.
- onphonenow 5y agoSo a guard band of 300Mhz then? What's weird is that I'd expect an altimeter to be on the order of .1 to 2MHz bandwidth max. There's just something wrong in the math here.
- drmpeg 5y agoRadar altimeters use frequency modulated continuous wave (FMCW) and the bandwidth is 20 to 170 MHz (the larger the chirp, the more accurate it can be). It's extremely difficult to have a 170 MHz wide filter at 4.3 GHz with a brick wall response out of band. https://www.ntia.doc.gov/files/ntia/publications/compendium/4200.00-4400.00_01MAR14.pdf https://www.ntia.doc.gov/files/ntia/publications/compendium/...