UHF vs VHF
VHF (Hloov Siab Heev) thiab UHF (Ultra High Frequency) yog ob lub xov tooj cua zaus ntawm electromagnetic waves. Ob leeg ntawm cov qhab no tau siv dav hauv kev tshaj tawm hauv xov tooj cua wireless. Cov bands no tau muab faib ua me me sub-bands hu ua channels. Cov channel no yog siv rau ntau lub hom phiaj hauv ntau lub teb chaws.
VHF (Hloov Siab Heev)
Electromagnetic tsis muaj zaus ntawm 30MHz txog 300MHz hu ua VHF. VHF band yog sandwiched ntawm HF (High Frequency) thiab UHF (Ultra High Frequency) bands hauv spectrum. TV tshaj tawm thiab FM xov tooj cua tshaj tawm (feem ntau siv 88MHz - 108MHz ntau) yog ob qho kev siv loj ntawm VHF.
VHF band yog siv rau kev sib txuas lus hauv av, thiab 'kab pom' (qhov chaw xa xov tuaj yeem pom los ntawm kev txais xov tooj cua yam tsis muaj teeb meem) tsis tsim nyog.
UHF (Ultra High Frequency)
Ntau zaus ntawm 300MHz - 3000MHz (los yog 3GHz) hauv electromagnetic yoj spectrum hu ua UHF. Nws tseem hu ua 'decimeter range' raws li lub wavelength nyob rau hauv thaj tsam ntawm 1 mus rau 10 decimeters. UHF band yog sandwiched ntawm VHF thiab SHF (Super High Frequency) bands hauv spectrum.
UHF nthwv dej feem ntau yog siv rau kev tshaj tawm hauv TV thiab xov tooj ntawm tes. GSM tes hauj lwm feem ntau siv 900MHz - 1800 MHz band. 3G mobile networks siv ntau zaus ntawm UHF band. Txawm hais tias 'kab pom' tsis yog qhov tsim nyog UHF nthwv dej ntau dua li VHF nthwv dej.
Qhov txawv ntawm VHF thiab UHF yog dab tsi?
1. UHF siv ntau zaus dua VHF
2. VHF band (nrog qhov ntev ntawm 270MHz) yog qhov nqaim dua li UHF band (uas muaj ntau zaus ntawm 2700MHz)
3. Feem ntau cov channels ntawm UHF muaj bandwidths siab dua VHF, yog li ntawd, nqa cov ntaub ntawv ntau dua
4. UHF nthwv dej feem ntau cuam tshuam los ntawm attenuation dua VHF nthwv dej. Yog li, VHF nthwv dej tuaj yeem taug kev ntev dua li UHF.
5. UHF kav hlau txais xov me me dua VHF kav hlau txais xov raws li lawv lub wavelength tsawg dua VHF
