wave help

[biferi]

If vhf and uhf are line of site waves they go in a straight line from the transmitter.

Then ground wave go along the Earth Serface I get this.

But is AM ground wave and FM line of site??

 

[Robb]

No; it's frequency dependent - not mode dependent. Shorter wavelengths are more easily absorbed and therefore more directional. Doesn't matter if its AM, FM, or SSB. Don't know of too many people that have talked skip on 440mhz unless they were using a satellite beam antenna. "Line of sight"...

 

[biferi]

thanks but

so if it is wave length depended then why is uhf and vhf line of site???
Thoso are bands????????????????

 

[Beetle]

Wavelength and frequency are inversely proportional; as one increases, the other decreases.

V/UHF are primarily line of sight, as was said. There's little or no atmospheric propagation up there.

HF can be line of sight; it can also propagate via the ionosphere. Depends on the condition of the ionosphere, the frequency in use, the antennas, and so forth.

 

[n9zas]

During a warm air temp inversion it is possible to talk for hundreds of miles on vhf and even uhf. Warm evenings then cooling down enough at night to create fog in the morning is an ideal time for this to happen.
n9zas

 

[biferi]

thanks but

Well what I meen is Ground Waves move along the Earth serface they do not go into the Ionosphere right?????

so sertan FREQ are just shortwave they will never be groundwave they just go to the Ionoshpere.

Line Of site waves will never be ground waves they just go straight line.

AM I right or what am I missing

 

[kd-5-bgt]

HF or low frequency waves will "bend" so to say or are more prone to follow the earths surface when the ionsphere will not reflect the singal

HF waves are longer than VHF is so HF waves are more prone to fill in the area that is beyond the line of sight


kind of like shooting a gun over a small rise out in front of you,VHF being a rifle bullet and HF being shotgun shot,the rifle bullet will go right over the rise and the shotgun pellets will spread out and drop on the other side of the rise after a certain distance


did that make sence?

 

[Simon004]

Well what I meen is Ground Waves move along the Earth serface they do not go into the Ionosphere right?????

so sertan FREQ are just shortwave they will never be groundwave they just go to the Ionoshpere.

Line Of site waves will never be ground waves they just go straight line.

AM I right or what am I missing

biferi,

I'm no expert in propagation, but I think your getting confused with terminology.

HF is High frequency, Shortwave band, or whatever you want to call it.

HF signals can get from one antenna to another by different methods.

Groundwave is where the signal kind of hugs the curvature of the earth, making a contact over the horizon possible that would not be possible by line of sight, because at the distance involved, a line of sight signal would have headed off up into space by then.

Skywave or tropospheric/ionospheric propagation is where the signal leaves the antenna and goes skyward, it reflects/refracts in the atmosphere and returns to earth somewhere else, again making contacts over the horizon possible.

Line of sight contacts are direct from antenna to antenna. Could be talking to your next door neighbour, a guy across town or even across the state. The signal goes from antenna A to antenna B in a straight line.

All 3 of these types of propagation can occur on HF (0-30MHz), it doesn't matter what mode (AM, FM or SSB) that you are using. Deciding which type of propagation is happening to your transmission is really just down to experience, the more time you spend using the radio, the more instances of propagation you come across and the better guess you can make as to what is happening.

I don't really use VHF or UHF, but I do know that groundwave prop only occurs on HF, and not above. I'll leave it to somebody else to explain propagation above HF if they wish.

 

[Captain Kilowatt]

Just a guess here but I think he is confusing the terms AM and FM with the broadcast bands. AM of course is about 530 KHz to 1.7 MHz which is medium wave while the FM band is a VHF band at 88-108 MHz.

 

[Nursecosmo]

AM and FM are not related to frequency or how the propagation occurs. They refer to the way in which the radio signal is produced and decoded by the transmitter and receiver. The most common mode used on VHF(30Mhz-300Mhz) and UHF(300MHz-3GHz) frequencies, which are both generally considered line of sight, is FM, therefore VHF radio is sometimes referred to as "FM" radio. SSB and AM are the most common modes used on HF (3MHz-30MHz) and so AM radio is generally associated with HF and it's peculiar varieties of propagation. In reality, AM may be used on VHF, UHF, SHF and EHF. FM may be used on LF, MF, HF etc.

 

[biferi]

thanks but

so would I be right that sertaine FREQ. are for line of site and the same goes for Groundwave to?????????????????

 

[Nursecosmo]

so would I be right that sertaine FREQ. are for line of site and the same goes for Groundwave to?????????????????

Yes.