What is line of site? Like in property line? How does the wifi signal know where the line of the site is? Or is it line of sight, as in eye-sight? Sorry too many "native speakers" slipping in their pride.

Rafael

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You've been doing pretty good with informative posts that suggest you aren't a sophomore when it come to things RF, so I think you probably transposed AM and FM in the last sentence. FM broadcast band is at higher frequencies than AM, and higher frequency generally infers more line-of-sight. Also, 'bounce off the atmosphere' occurs at ionizing layers, which makes for one heck of long path for our R/C signals. My bet is that we rely about 99.9999999...% on direct path propagation for our R/C signaling, AM or FM (which modulation modes are used interchangeably on the same frequency band for R/C use).

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You are very right about line of sight in RC, regardless of RF theory.
If you can't see it, you should not be flying it. Think that is in the safety rules (video flyers excepted).

Are you sure about that, Mr. dbcisco? [sm=confused.gif]

Maybe I am wrong, however many years in using certain radios and wave lengths I think it is the wave length that determines the ability to follow the earth. Finding an airport using aural-null or radio-ranging on a low freq. radio made one glad that low freq. radio could follow the earth's curvatures.

OTOH, VOR (Very high frequency, Omnidirectional Radio) had limitations at higher altirudes on distances between using stations due to the line-of-sight transmissions. (Back before dirt I had to teach this stuff, but that was some 45+ years ago and I have not paid much attention to these facts so there are missing points in the old top side) The limitations were because of interference between station line-of-sight that would be blacked out at a lower altitude.

Line-of-sight begins with the shorter wave length of the higher freqs. I seem to recall that ground following was OK with the HF band, thus better for overwater while over land civil aircraft used VHF and military used UHF for communications. All Line of sight.

http://www.jneuhaus.com/fccindex/spectrum.html

Frequency Band 10 kHz to 30 kHz Very Low Frequency (VLF)
30 kHz to 300 kHz Low Frequency (LF)
300 kHz to 3 MHz Medium Frequency (MF)
3 MHz to 30 MHz High Frequency (HF)
30 MHz to 144 MHz 144 MHz to 174 MHz 174 MHz to 328.6 MHz Very High Frequency (VHF)
328.6 MHz to 450 MHz 450 MHz to 470 MHz 470 MHz to 806 MHz 806 MHz to 960 MHz 960 MHz to 2.3 GHz 2.3 GHz to 2.9 GHz Ultra High Frequency (UHF)
2.9 GHz to 30 GHz Super High Frequency (SHF) 30 GHz and above Extremely High Frequency (EHF)

I stand corrected. you are right, the higher the frequency the more likely require line of site. I was thinking back to the days I worked at an underground radio station (yes I am that old and was a hippie). I thought the station was FM (inner city) but it was an AM station precisely as you said, it could get around the buildings better than FM without a huge tower. My apologies, my grave mistake.

Wow!

What a refreshing post.

Normally in this forum people will twist their words to fit whatever was previously stated. Yes, you do indeed stand corrected and garner much respect IMO.

Actually, the recent series of posts seem to be very conducive to exchanging info.

I hope you stick around dbcisco.

I think it was Dostoevsky who said,"These things I beleive to be truths, I beleive with all my heart. However, when given evidence to the contrary I will abandon those beleifs immediately."

Fixed!

Microwaves cause incredible interference. While shielded, its imperfect. Had a set of 2.4Ghz phones that would pop, snap, hiss, etc when the microwave was activated, you could watch the signal level drop on a wireless card. multiple micros had the problem (one died from age, replaced it)

Note that I didn't say microwaves don't cause interference. I said that microwave ovens don't generally cause interference outside the house.

2.4 ghz is already pretty crowded, but because it tends to be a very short range signal in most applications, its not a problem for us. I don't think we're going to see large, high power transmitters being setup to blanket huge areas to provide free wi-fi because the small devices used won't have the power to transmit back over long distances. What we're more likely to see is lots of lower power wi-fi hotspots like those that are already provided commercially.

And large open fields won't be a target market.

Brad

It won't be free and it will sell new computers and PCMCIA cards with the long range transceivers as well.
The major ISPs and manufacturers have already brought this up in congressional hearings on the Spectrum Inventory bills.
I recall when people said cell phones would never become a reality, too. Free phone service with towers every where? Nope, pay to play phones with towers everywhere.