Line of Sight vs Power.

[LeoG]

You always here that UHF is line of sight.  If you can't see it, you can't talk to it.  My experience has been otherwise.  Granted if you have a 1000' mountain between you and the person you want to talk to it ain't happening simplex.  I just upgraded my repeaters power.  Same antenna at about 40' off the ground and surrounded by trees 270º around me.  Today I took a ride with my 20 watt Wouxun KG-XS20G+ with an MXTA26 Midland magnetically mounted, basically straight north.  I had my phone at my repeater as I called out to it recording with a voice activated app.  My truck was moving on all of these, probably around 40mph +/-

 

3.85 miles out with Line Of Site

Going farther out, on a hill but behind one also  6.54 mi

And then down that hill 75 feet below the other peak and still in the shadow of the hill   7.0 mi

Getting worse but still very readable  7.2 mi

Unreadable at Shoemaker Ln  7.9 mi

Sounded much worse on my end and I figured I was done but really it wasn't that bad  9.25 mi

 

Cute little experiment.  Shows line of sight doesn't mean you can't be heard.  Obviously you lose quieting and sometime you lose readability.  It was nice to find out I could insert audio.

 

 

 

 

[OffRoaderX]

There are a few places that I can hit on my base-station that defy all the laws of line-of-sight and I still can't figure out how I can talk to them.. One being on the other side of a 5,000ft mounting.  But the other 99.8% is def. line of sight.

[BoxCar]

The terrain has a lot to do with contacts beyond the line of sight. UHF bounces off hard surfaces such as concrete and granite. Its very possible your signal was reflecting through canyons. Digital signals don't do well as the bit stream becomes jumbled through the multipath hops.

[LeoG]

4 minutes ago, BoxCar said:

The terrain has a lot to do with contacts beyond the line of sight. UHF bounces off hard surfaces such as concrete and granite. Its very possible your signal was reflecting through canyons. Digital signals don't do well as the bit stream becomes jumbled through the multipath hops.

Not many hills on either side of me to bounce off of.  Mostly just hills in the way.  I do live in the valley, but I doubt they are bouncing anything beneficial to me in those cases.  I just think it's propagation from above and leaking down.

But at my house I think there's signal bouncing off a large building and then back to me.  The signal at my house varies a lot during the day.  Sometimes it at 1/2 scale and other times barely gets over a 2 squelch.  Now with more power my lows are what my highs used to be for the most part and I can get 3/4 scale on the meter.

[LeoG]

27 minutes ago, OffRoaderX said:

There are a few places that I can hit on my base-station that defy all the laws of line-of-sight and I still can't figure out how I can talk to them.. One being on the other side of a 5,000ft mounting.  But the other 99.8% is def. line of sight.

On occasion I can talk with LI NY which the signal has to go through a 750 ft mountain.  But it's tropospheric ducting so an entirely different phenomenon.

[Guest]

It’s still science. 460mhz does not do well bouncing off much its just a fact. Just because you found places that it works for you does not mean that’s the rule.   99% of this is line of sight.   Other bands do a MUCH better job of bouncing around.  That’s why a 5w hand held will do 50plus miles but a 50w may not do 1/2 a mile in the city.  After line of sight is radiated power.   It’s not just about the radios wattage but the actual power leaving the antenna.  

[WRUU653]

I have had a similar experience. Near me is a lake and at the far end is a canyon that I should not be able to hit a repeater over the mountain and yet I can just break the squelch on it in a particular spot. It has been suggested I might be bouncing the signal. I’ve just accepted it’s PFM (pure fn magic)

[LeoG]

46 minutes ago, WRXP381 said:

It’s still science. 460mhz does not do well bouncing off much its just a fact. Just because you found places that it works for you does not mean that’s the rule.   99% of this is line of sight.   Other bands do a MUCH better job of bouncing around.  That’s why a 5w hand held will do 50plus miles but a 50w may not do 1/2 a mile in the city.  After line of sight is radiated power.   It’s not just about the radios wattage but the actual power leaving the antenna.  

Pretty sure I mentioned it was my same antenna system I've been using with the RT97S, just not the same repeater.  My farz O meter says 40 watts out the back, 1.4dB loss in cable 7.2dBi gain antenna 40' off the ground 92 watts ERP

[AdmiralCochrane]

There is also knife edge refraction.

[marcspaz]

Yeah, I was thinking about knife edge refraction as well as troposcatter.

[LeoG]

I would think atmospheric scatter would be a normal propagation factor as the signal dissipates power into the atmosphere.

[marcspaz]

Yeah... refraction and scatter are why the RF horizon is further than the visual horizon. Once the photons overcome refraction and start to leave the atmosphere, a very small percentage of the signal is scattered, while most keeps traveling in a straight line.  The more power you put out, the more the parts per million the scatter is and the more easily the signal can be pulled out of the atmosphere beyond the line of sight.

 

Using troposcatter with a stacked beam antenna array and 1,500w, I have been able to talk to people in Texas from VA on 146.520 during contests and Field Day. UHF performs the same way. It's been awhile... so I don't remember the max distance we got on 446.000, but it was more than 300 miles. 

[MidnightMan]

The whole "UHF is LOS Only" is a cope by some really ignorant fellows that think they know everything, and it's a myth thats been spread to no end. UHF will absolutely go over, around, and even through all kinds of stuff including mountains and hills. Power also makes all the difference! Congrats on the upgrade!

[marcspaz]

1 hour ago, MidnightMan said:

The whole "UHF is LOS Only" is a cope by some really ignorant fellows that think they know everything, and it's a myth thats been spread to no end. UHF will absolutely go over, around, and even through all kinds of stuff including mountains and hills. Power also makes all the difference! Congrats on the upgrade!

 

I know you are new, and I want to cut you some slack, but your post is so incredibly wrong that I can't let it go.  We are talking about physics, not opinions.  Radio waves generally do not travel far through the ground.  A few meters at best, and it doesn't matter how much power you throw at it.  Soil, rock, and other dense materials will either reflect (most common) or absorb radio waves. The distance the waves travel through ground depends on several factors, including the frequency of the waves, the conductivity and composition of the ground, and the moisture content.

Absolute best case, low-frequency radio waves (e.g., Very Low Frequency, or VLF, 3–30 kHz) can penetrate several meters into the ground through materials like dry sand or soil.  As the moisture level increases, the distance decreases.  High-frequency waves (e.g., Medium to High Frequency, MF to HF, 300 kHz–30 MHz) penetrate the ground poorly and are mostly reflected at the surface or absorbed with penetration being 3 meters or less.  Going to VHF or higher, we start measuring the penetration in fractions of a meter.

 

Now, when it comes to radio waves flowing around objects (for lack of a better expression), there is a little bit of truth to that.  Think of it like a shadow.  When the sun is blocked by and object, there is not absolute darkness in the shadow.  There are photons scattering all through the atmosphere, illuminating the blind side of an obstacle. However, there are no radios that have the power of the sun behind them.  The energy that scatters around objects like buildings or hills is extremely minimal, and the closer to the blind side of the object, the less the saturation is.  Kind of like a shadow being the darkest at the base crease of the object blocking the light.

[LeeBo]

I don't even attempt to figure out physics or logic.

For example, Lake Lure NC.  I can walk out on the deck, look to my left, and there's Bearwallow Mountain with all its repeaters. I literally have line of sight.  Can't hit them even with a 50watt mobile and a 6' antenna.

However, I can hit a repeater on the other side of the mountain with a 10watt HT with Nagoya 771 antenna.

Maybe I need to cut back on the bourbon.  LOL

[marcspaz]

@LeeBo  I found some genuine humor in that last line.  It definitely had me chuckling. 

You are experiencing an odd situation with that mountain, for sure.

[LeeBo]

[mention=19521]LeeBo[/mention]  I found some genuine humor in that last line.  It definitely had me chuckling. 
You are experiencing an odd situation with that mountain, for sure.

Said mountain hates me.


Sent from my iPhone using Tapatalk

[SteveShannon]

3 hours ago, LeeBo said:

Bearwallow Mountain with all its repeaters. I literally have line of sight.  Can't hit them even with a 50watt mobile and a 6' antenna.

If you can see them but cannot contact them there’s something wrong. Try just listening on the right frequencies with no tones/no tone squelch. Once you have listening figured out then work on transmission.

[LeeBo]

4 minutes ago, SteveShannon said:

If you can see them but cannot contact them there’s something wrong. 

Obviously.  Said mountain hates me.  

I probably should have added that I can hit the repeaters on said mountain from Chimney Rock and Bat Cave (no line of sight but I assume signal is bouncing off the mountainsides). Just not from the western part of Lake Lure.

I'll ask my aunt if she'll let me install a tower.  She'll say no but I'll ask anyway.  

[WRUQ357]

3 hours ago, LeeBo said:

I don't even attempt to figure out physics or logic.

For example, Lake Lure NC.  I can walk out on the deck, look to my left, and there's Bearwallow Mountain with all its repeaters. I literally have line of sight.  Can't hit them even with a 50watt mobile and a 6' antenna.

However, I can hit a repeater on the other side of the mountain with a 10watt HT with Nagoya 771 antenna.

Maybe I need to cut back on the bourbon.  LOL

Less bourbon is never the answer

[SteveShannon]

17 minutes ago, LeeBo said:

Obviously.  Said mountain hates me.  

I probably should have added that I can hit the repeaters on said mountain from Chimney Rock and Bat Cave (no line of sight but I assume signal is bouncing off the mountainsides). Just not from the western part of Lake Lure.

I'll ask my aunt if she'll let me install a tower.  She'll say no but I'll ask anyway.  

Maybe you’re not really seeing the repeaters that you think you’re seeing.

[WRXR255]

34 minutes ago, SteveShannon said:

Maybe you’re not really seeing the repeaters that you think you’re seeing.

Obi Wan Steve: "These are not the towers your looking for, move along"

[MidnightMan]

11 hours ago, marcspaz said:

 

I know you are new, and I want to cut you some slack, but your post is so incredibly wrong that I can't let it go.  We are talking about physics, not opinions.  Radio waves generally do not travel far through the ground.  A few meters at best, and it doesn't matter how much power you throw at it.  Soil, rock, and other dense materials will either reflect (most common) or absorb radio waves. The distance the waves travel through ground depends on several factors, including the frequency of the waves, the conductivity and composition of the ground, and the moisture content.

Absolute best case, low-frequency radio waves (e.g., Very Low Frequency, or VLF, 3–30 kHz) can penetrate several meters into the ground through materials like dry sand or soil.  As the moisture level increases, the distance decreases.  High-frequency waves (e.g., Medium to High Frequency, MF to HF, 300 kHz–30 MHz) penetrate the ground poorly and are mostly reflected at the surface or absorbed with penetration being 3 meters or less.  Going to VHF or higher, we start measuring the penetration in fractions of a meter.

 

Now, when it comes to radio waves flowing around objects (for lack of a better expression), there is a little bit of truth to that.  Think of it like a shadow.  When the sun is blocked by and object, there is not absolute darkness in the shadow.  There are photons scattering all through the atmosphere, illuminating the blind side of an obstacle. However, there are no radios that have the power of the sun behind them.  The energy that scatters around objects like buildings or hills is extremely minimal, and the closer to the blind side of the object, the less the saturation is.  Kind of like a shadow being the darkest at the base crease of the object blocking the light.

Well I guess I should stop believing my lying eyes and ears then because my experience proves you wrooooonggggg  

[WRXR255]

I know little on the subject of RF propagation, but could there be a perfect placement of a tower structure or something like it on the antenna farm where the antenna has a narrow slice in a direction that is dead?

 

Just spitballing here.

[marcspaz]

32 minutes ago, MidnightMan said:

Well I guess I should stop believing my lying eyes and ears then because my experience proves you wrooooonggggg  

 

Do you have a single technical point supported by repeatable recorded data that disproves the fundamentals of physics as we understand them today, which were largely established in the 17th century and agreed upon by physicists worldwide for 300+ years? Or do you "just know" the earth is flat and we should take your word for it?