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preeste
preeste • Jan 8, 2008

a few questions...regarding radio and communication technology

hey there guys....i need some help with the following questions that have been bothering me...done a lot of research but did not find any satisfactory answers so this is my last line of hope.

1. why does H.F usually use A.M modulation?
2.why does V.H.F usually use F.M modulation?
3. what limits the range of VHF transmissions?
4. what limits the range of HF transmissions?

all help will be greatly appreciated. thanks a lot😉
MaRo
MaRo • Jan 10, 2008
- AM uses HF transmission not HF use AM
AM is better for small entities like amateur radios and cordless phones because its signal go far distances but bad fidelity. (not very sure)

- FM uses the range of VHF, not VHF do
VHF transmission is better for FM channels because can transmit high fidelity sound over a city or two with very minimal interference and minimal signal loss, because VHF doesn't effected so much from buildings or weather interferences.

3 & 4:
these are relative to the wavelength.

still new in this frequencies thing, you can see this link and collaborate to get to understand it.

Radio frequency spectrum
just2rock
just2rock • Jan 25, 2008
1>x(t)=a*cos(w*t+phi)--A.M
so H.F uses this to enhance sound fidelity and quality over wide bandwidth
2>vhf uses F.M to construct its carrier well enough to desired range ...without interference caused by Phase jitters,noise etc. and can reconstruct correctly boyh audio/video at reciever like TV reciever
3>VHF tuners limits freq range transmission ovr 54-216MHZ
4>any freq below 54 MHZ
just2rock
just2rock • Jan 25, 2008
for any furthur consults do mail me at: mail.for.soumik@gmail.com

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