We had a light rain here yesterday evening. When I turned on my digital tuner (which is connected to roof antenna) I was getting all kinds of stations that don't normally come in, and the ones that did come in were much stronger. Some of the signals were twice their normal strength.

QUESTION: What causes this, and is there any way to harness this phenomenon to improve reception permanently?

I'm not sure whether it was from the antenna and/or connector balun being wet or whether it was from the atmospheric conditions (cleaner air maybe?)

Anyone have any thoughts on this?

I'd venture to guess it was due to the cloud coverage. Broadcasts will "bounce" off clouds, extending their range significantly sometimes.

Could be, but there have been lots of cloudy days without that kind of reception. Maybe I'll try hosing down the roof antenna on a day when it's not raining and see what that does.

Water does conduct electricity, maybe it conducts TV too

What you need is a really big Sprinkler system ;-}

The water droplets scatter the signal. If you don't have line-of-sight to the transmitter, more scattering can mean more signal reaching your antenna. I also get this effect on foggy or misty nights or mornings.

I have the same effect here. I live in a difficult OTA area as I am directly behind a 2700' hill. When it rains I believe the cloud cover guides the signal to my antenna better as I never get breakups then.

It also has a similar effect on FM radio signals. I can receive my favorite station at home but I can not get it normally when I go to work (on the other side of the 2700' peak). When it rains I can get this station fine at work.

Rick R

"QUESTION: What causes this, and is there any way to harness this phenomenon to improve reception permanently?"

Certain weather conditions,water vapor being one of them, have an effect on the K-factor. As radio waves journey into space they travel through the troposhere which "bends" the waves back to earth past the visual horizon to what is called the radio horizon. During certain weather conditions the K-factor is increased accordingly. Just Google K-factor to learn more.

I've had similar "improved" reception on some stations during rain, and speculated that it was attenuating some of the multipath signals to below detection threshold, allowing the main signal to be locked onto better.

The boundaries between cold and warm air masses pushing up over them that create rain also can reflect television signals. In other words it is not the rain but what created it.

Rory is correct - temperature inversion

The proper name for this condition is "ducting". An inversion layer at some height traps a tv or radio signal between the earth and the bottom of the cloud layer and "bends it". Hams experience this all the time ( My ham callsign is N6UZD)

Geez, so I guess I should tell the landscaping crew that I won't need that sprinkler system installed on the roof after all.

Geez, so I guess I should tell the landscaping crew that I won't need that sprinkler system installed on the roof after all.

However if you install many ducts on your roof to reproduce ducting that might help... :D

Here in Phoenix, one of the reasons that a light rain helps our reception is because the ground around here so is so dry that it is a very poor conductor. The ground is also fairly salty, so when it rains and the ground get wet, it becomes a much better conductor. So we get the same kind of improvemnt that you get when you transmitter over sea water.

Another interesting thing I've noticed on my NTSC reception, is that one of my neighbors is generating some noise that appears on Ch5 as a horizontal band that looks like a celtic braid. I think the noise must be on his ground line, because when it rains (and the thus the grounding rod and the ground get wet and conduct better) then the noise goes away until the ground dries out again (which happens pretty fast around here).

Here in Phoenix, one of the reasons that a light rain helps our reception is because the ground around here so is so dry that it is a very poor conductor. The ground is also fairly salty, so when it rains and the ground get wet, it becomes a much better conductor. So we get the same kind of improvemnt that you get when you transmitter over sea water.



AM has a groundwave - TV doesn't.

I used to experience this kind of stuff when I was more active on the Ham bands. BTW my Ham call sign is WA6QGG (Ex WA0BKY).

Rick R

Here in Phoenix, one of the reasons that a light rain helps our reception is because the ground around here so is so dry that it is a very poor conductor. The ground is also fairly salty, so when it rains and the ground get wet, it becomes a much better conductor. So we get the same kind of improvemnt that you get when you transmitter over sea water.

Another interesting thing I've noticed on my NTSC reception, is that one of my neighbors is generating some noise that appears on Ch5 as a horizontal band that looks like a celtic braid. I think the noise must be on his ground line, because when it rains (and the thus the grounding rod and the ground get wet and conduct better) then the noise goes away until the ground dries out again (which happens pretty fast around here).

With Phoenix having so many low band VHF channels, i'm not surprised. These frequencies are low enough, not only to benefit from ground-wave propagation, but can also be enfluenced by Sporadic-E. Just ask any Ham operator who talks on 6 meters.

Ground-wave propagation ceases above a few megahertz or the MF band. Even the low-band VHF is too high in frequency for any real propagation distances by ground-wave. Additionally, ground waves must be vertically polarized or the electric field component shorts circuits to earth. The TV transmitters are all horizontially polarized. HDTVFanatic has it right. TV is not propagated by ground-waves.

Ground-wave propagation ceases above a few megahertz or the MF band. Even the low-band VHF is too high in frequency for any real propagation distances by ground-wave. Additionally, ground waves must be vertically polarized or the electric field component shorts circuits to earth. The TV transmitters are all horizontially polarized. HDTVFanatic has it right. TV is not propagated by ground-waves.

I was not implying that any one was wrong relative to any post made on this topic. I was merely responding to the post made by Mack the Knife regarding signal reception and soil conditions. Yes ground -wave is not the preferred method for the distribution of TV transmissions. However, it is my opinion that low band VHF stations have useful ground-wave up to 15 miles from the transmitter and that enhanced propagation is possible with varying soil conditions. I fully understand that a horizontally polarized signal realizes much greater attenuation than one that is vertically polarized, but that factor does not cancel out 100% of the ground-wave propagation. BTW, AM is both ground-wave and sky-wave and all TV stations are NOT horizontally polarized. Before Hurricane Charley took down my low band VHF antenna, i received channels 2, 4, and 6 out of Miami and they all
use circular polarization.

it is my opinion that low band VHF stations have useful ground-wave up to 15 miles from the transmitter and that enhanced propagation is possible with varying soil conditions.

How did you determine this?


I also realize that a few stations use circular or even eliptical polarization. I was making a generalization.

However, it is my opinion that low band VHF stations have useful ground-wave up to 15 miles from the transmitter and that enhanced propagation is possible with varying soil conditions.


Again, there are no ground waves for FM or TV. If they were, you would literally be killed by electrocution if you walked up to a FM or TV antenna and touched the tower - as will happen with AM. In fact, an AM tower has to be insulated from the ground.

With FM or TV, the antenna has to be insulated from the tower - thus no connection - though grabbing a bay on top of a FM or TV tower will give you quite a burn.

How did you determine this?


I also realize that a few stations use circular or even eliptical polarization. I was making a generalization.

For one thing, by brother and i were in Lakeland the other day and he was on his Icom 706 MKII G mobile talking to a buddy of his in New Port Richey. The frequency
he was talking on was 144.225 MHz SSB with no LOS.

Again, there are no ground waves for FM or TV. If they were, you would literally be killed by electrocution if you walked up to a FM or TV antenna and touched the tower - as will happen with AM. In fact, an AM tower has to be insulated from the ground.

With FM or TV, the antenna has to be insulated from the tower - thus no connection - though grabbing a bay on top of a FM or TV tower will give you quite a burn.

Of course an AM tower has to be isolated from ground it is the antenna/radiating element. To better understand ground-wave propagation, read up on diffraction.
Have a nice day!

Clearly you have no idea what you are talking about as again, FM and TV have no ground wave.

You cannot find any reliable piece of science to say it does and any RF engineer that works with FM and TV will laugh in your face.

Clearly you have no idea what you are talking about as again, FM and TV have no ground wave.

You cannot find any reliable piece of science to say it does and any RF engineer that works with FM and TV will laugh in your face.

Your the one who needs a better undersatnding of how signals propagate via ground wave, it certainly has nothing to do with an antenna being attached to a tower as you have stated. And find any RF engineer, and he will tell you how my brother was able to talk from Lakeland to New Port Richey on 144.225MHz. Of course, you are welcome to enlighten us if you like.

For one thing, by brother and i were in Lakeland the other day and he was on his Icom 706 MKII G mobile talking to a buddy of his in New Port Richey. The frequency
he was talking on was 144.225 MHz SSB with no LOS.

OK, but that dosen't mean it's due to ground-wave propagation. What's technically known as space-waves can travel near the earths surface but because they do not follow the curature of the earth they are not ground-waves. At 144 MHz there are several propagation models but none include ground-wave propagation. A real ground-wave that depends on actual surface conductivity rapidly attenuates over a frequency of a few MHz. The basic propagation loss for a vertically polarized ground wave at 100 kHz is 30 dB at 10 miles and increases at the fourth power of distance rather than the normal square. At just 3 MHz the 10 mile loss is over 90 dB! ( reference data for radio engineers, 5th edition, 1956 ). That's where the charts end and there is no data available at 144 MHz because ground-wave propagation doesn't exist at those frequencies. I will cease to beat this dead horse now.
http://www.fas.org/man/dod-101/navy/docs/es310/propagat/Propagat.htm

OK, but that dosen't mean it's due to ground-wave propagation. What's technically known as space-waves can travel near the earths surface but because they do not follow the curature of the earth they are not ground-waves. At 144 MHz there are several propagation models but none include ground-wave propagation. A real ground-wave that depends on actual surface conductivity rapidly attenuates over a frequency of a few MHz. The basic propagation loss for a vertically polarized ground wave at 100 kHz is 30 dB at 10 miles and increases at the fourth power of distance rather than the normal square. At just 3 MHz the 10 mile loss is over 90 dB! ( reference data for radio engineers, 5th edition, 1956 ). That's where the charts end and there is no data available at 144 MHz because ground-wave propagation doesn't exist at those frequencies. I will cease to beat this dead horse now.
http://www.fas.org/man/dod-101/navy/docs/es310/propagat/Propagat.htm

Yes it does, ground wave = space wave + surface wave.

Yes it does, ground wave = space wave + surface wave.

No it doesn't. Did you even glance at the link I provided? Obviously not. What can easily be gleaned from that simple explanation is that ground waves and surface waves are the same thing and either one is different from space waves. They behave differently, propagate differently, calculated differently and they do not depend one one another. I have provided external references and real-world numbers saying your wrong. You can't just stomp your foot and say your right without something to back you up!

The amazing thing is that as all RF enginneers know, even if there was a ground wave for FM and TV as you speak of, which there is not, the less minerals in the soil, the worse it conducts a ground wave.

Sand is one of the worst conductors - along with Clay (found in most of Georgia) and Granite (which again, blows your theory as many FM and TV stations co-locate on top of Mountains).

AM stations in Florida because of the poor soil conductivity try to build as close to the water as possible because the salt water will act as a wonderful conductor - as compared with the sand in the soil. If one looks at signal maps for a Florida AM station, they will find that the signal explodes once it hits the coast with the salt water.

But again, this isn't for you, as you have shown that you don't care about reality - and live in some alternative universe which defies physics - but others reading this who do care about how things work will find it of interest.

Bottom line, as explained by Nighthawk, the groundwave doesn't exist on any TV or Commercial FM Broadcast Frequencies. Next you'll try and tell us that groundwaves exist on the higher frequency satellite broadcasts :rolleyes:

No it doesn't. Did you even glance at the link I provided? Obviously not. What can easily be gleaned from that simple explanation is that ground waves and surface waves are the same thing and either one is different from space waves. They behave differently, propagate differently, calculated differently and they do not depend one one another. I have provided external references and real-world numbers saying your wrong. You can't just stomp your foot and say your right without something to back you up!

I most certainly did read it and the information it provided was conflictory with the attenuation data you provided earlier for LF and MF frequencies. With respect to your definition of ground-waves i have provided a link for you.

http://tpub.com/content/neets/14182/css/14182_76.htm

The amazing thing is that as all RF enginneers know, even if there was a ground wave for FM and TV as you speak of, which there is not, the less minerals in the soil, the worse it conducts a ground wave.

Sand is one of the worst conductors - along with Clay (found in most of Georgia) and Granite (which again, blows your theory as many FM and TV stations co-locate on top of Mountains).

AM stations in Florida because of the poor soil conductivity try to build as close to the water as possible because the salt water will act as a wonderful conductor - as compared with the sand in the soil. If one looks at signal maps for a Florida AM station, they will find that the signal explodes once it hits the coast with the salt water.

But again, this isn't for you, as you have shown that you don't care about reality - and live in some alternative universe which defies physics - but others reading this who do care about how things work will find it of interest.

Bottom line, as explained by Nighthawk, the groundwave doesn't exist on any TV or Commercial FM Broadcast Frequencies. Next you'll try and tell us that groundwaves exist on the higher frequency satellite broadcasts :rolleyes:

With your earlier explanation of an AM radio tower being insulated from the ground just to keep people from getting burned, i don't feel that you are qualified to discuss this subject intelligently. As i stated earlier, the AM tower is the antenna and if it were not insulated/isolated it would result in an RF short. It is a groung plane antenna which are widely used for CB as well as the 2 and 6 meter bands.

No it doesn't. Did you even glance at the link I provided? Obviously not. What can easily be gleaned from that simple explanation is that ground waves and surface waves are the same thing and either one is different from space waves. They behave differently, propagate differently, calculated differently and they do not depend one one another. I have provided external references and real-world numbers saying your wrong. You can't just stomp your foot and say your right without something to back you up!

Thank for the link and yes i did read the article. However when you read under the topic of "Skywaves" you will see it is conflctory with the LF and MF attenuation data you provided earlier. With regard to your definition of ground-wave, i have provided a link.
http://tpub.com/content/neets/14182/css/14182_76.htm

I most certainly did read it and the information it provided was conflictory with the attenuation data you provided earlier for LF and MF frequencies.

In what way?

Thank for the link and yes i did read the article. However when you read under the topic of "Skywaves" you will see it is conflctory with the LF and MF attenuation data you provided earlier. With regard to your definition of ground-wave, i have provided a link.
http://tpub.com/content/neets/14182/css/14182_76.htm

Wonderful definition - however, it still does not reference anything about FM or TV producing a usable groundwave - which they don't.

I can give you the definition of a unicorn - that doesn't mean one exists.

The higher frequencies of FM and TV produce what is shown on your link as a "space-wave", unlike the lower AM frequencies.

Thus, you have again failed to show any legitimate scientific source that will mistakenly state that FM and TV even produce an usable groundwave.

http://www.qsl.net/g3cwi/Downloads/Propagation%201.doc

The range for surface waves is approximately described by:



Range(km) = 200/frequency (Mhz)



As AVSers know, less than 25 stations will operate nationwide ATSC on Channel 2-6 - and you can calculate the "usable groundwave" on these.



Channel 2 55.25Mhz
3.62km = 200/55.25Mhz
3.62km = 2.25 Miles

Channel 6 83.25Mhz
2.40km = 200/83.25
2.40km = 1.49 Miles


More stations will operate in the VHF High Band of Channel 7 to Channel 13:


Channel 7 175.25Mhz
1.14km = 200/175.25Mhz
1.14km = 0.7 Miles

Channel 13 211.25Mhz
0.94km = 200/211.25Mhz
0.94km = 0.5 Miles


But by in large, the majority of ATSC stations will operate in the UHF band:


Channel 14 475.75Mhz
0.42km = 200/475.75
0.42km = 0.26 Miles

Channel 51 693.25
0.29km = 200/693.75
0.29km = 0.18 Miles

So, again, to the original question and topic title, Groundwave has no effect - in rain or without rain - on TV reception.

Your the one who needs a better undersatnding of how signals propagate via ground wave, it certainly has nothing to do with an antenna being attached to a tower as you have stated. And find any RF engineer, and he will tell you how my brother was able to talk from Lakeland to New Port Richey on 144.225MHz. Of course, you are welcome to enlighten us if you like.

1.38 km = 200/144.225Mhz
1.38 km = 0.8616674633315304 Miles

Enjoy eating your crow.

In what way?

The data you provided from the RF handbook claimed attenuation of greater than 90dB at 10 miles for a 3MHz ground-wave signal, where the link you provided acknowleged ground-wave propagation for LF and MF frequencies.

The equation in the link:

http://www.qsl.net/g3cwi/Downloads/Propagation%201.doc

is 200/sqrt(freq MHz).

So the groundwave distance for a vertically polarized channel 2 signal (54 MHz) is about 17 miles. At that distance, the groundwave signal will be most likely be overwhelmed by the LOS signal.

Ron

Attached are the appropriate pages from the NAB Engineering Handbook on Radio Wave Propagation (for those wonder, yes TV is broadcast on a Radio Wave).

It was split into 2 parts to meet the size requirements of AVS Attachments.

Page 1 - 6 has some underlying principles, but the section referring to frequencies in the commercial broadcast band (noted in the tv channels listing above) start on Page 6. Note Figure 5 at the top of the page of attenuation of Ground Wave across the frequency across the bottom.

The reading on Ground Wave starts at the bottom of page 6 in the section "Propagation over 30Mhz".

As noted "At frequencies above about 30Mhz, the principal propagation mode is the troposhere. The ground surface wave is ATTENUATED TOO SEVERELY TO BE OF ANY PRACTICAL LONG DISTANCE USE.....

Furthermore the next paragraph states For waves that propagate close to the the earth's surface the curvature of the earth will introduce additional effects that must be included in the plane earth model (which is discussed in the first 6 pages).

For the very technically minded, there are complete scientific formulas of all kinds of conditions that follow.

The equation in the link:

http://www.qsl.net/g3cwi/Downloads/Propagation%201.doc

is 200/sqrt(freq MHz).

So the groundwave distance for a vertically polarized channel 2 signal (54 MHz) is about 17 miles. At that distance, the groundwave signal will be most likely be overwhelmed by the LOS signal.

Ron

Thank you Ron. For those who don't want to be bored to tears reading all the previous posts on this subject, it all got started with my stating that i felt that the low band VHF channels 2-6 had a useful ground-wave signal up to 15 miles and that they could be affected by varying soil conditions.

Thank you Ron. For those who don't want to be bored to tears reading all the previous posts on this subject, it all got started with my stating that i felt that the low band VHF channels 2-6 had a useful ground-wave signal up to 15 miles and that they could be affected by varying soil conditions.

And again you are wrong because you clearly don't understand the design.

Yes, transmission at those frequencies can have a groundwave.

However, again, back to the subject at hand, FM AND TV HAS NO GROUNDWAVE.

Because unlike AM, where 1/2 of the antenna system is underground and the tower is hot, in FM And TV, the bays are insulated from the tower. THE TOWER DOES NOT RADIATE.

Also remember the BASE OF THE AM TOWERS ARE HOT because, again, 50% of the AM signal is put into the ground for the groundwave. The RF Radiation Point on FM and TV is only at the elements (or panel if a panel antenna) which are up to 2,000 ft in the air - not at the base of the antenna.

The only neutral connected to the radiating bays (or panel) on the tower is in the transmission line which is specifically constructed and designed to make sure the signal goes into the air and is not wasted into the ground where there are NO RADIATING ELEMENTS LIKE AM.

So while could get in theory 17 Miles of groundwave radiation on Channel 2 and much less as the frequencies increase, a technical design would have to be made to take "advantage" of that possibility.

Thus, as stated, FM and TV has no usable Groundwave.

While it could if someone wanted to build a radiating system into the ground, because of the small distance it can travel, specific designs are take to make sure the power goes out the bays into the air - not back down the tower and wasted to ground as there is no radiation system in place - as no one wants to pay the electric bill to put out groundwave that travels 15 miles or less on channel 2-6 - they would rather it go into the air.

The equation in the link:

http://www.qsl.net/g3cwi/Downloads/Propagation%201.doc

is 200/sqrt(freq MHz).

So the groundwave distance for a vertically polarized channel 2 signal (54 MHz) is about 17 miles. At that distance, the groundwave signal will be most likely be overwhelmed by the LOS signal.

Ron

Let's not forget the polarization problem. Any TV channel 2 will most likely be H-pol.

The data you provided from the RF handbook claimed attenuation of greater than 90dB at 10 miles for a 3MHz ground-wave signal, where the link you provided acknowleged ground-wave propagation for LF and MF frequencies.

I see no contridiction. I tried to let this die but you kept telling me I was wrong. Don't try to claim everyone is bored now when you started this pissing contest. I made the simple statemant the TV transmissions don't propagate by ground waves by virtue of frequency and polarization and I'm right. Let it go.

I see no contridiction. I tried to let this die but you kept telling me I was wrong. Don't try to claim everyone is bored now when you started this pissing contest. I made the simple statemant the TV transmissions don't propagate by ground waves by virtue of frequency and polarization and I'm right. Let it go.

Go back and read the posts, you and your buddy started the pissing contest. I merely responded to the OP and the one by Mack the Knife.

Go back and read the posts, you and your buddy started the pissing contest. I merely responded to the OP and the one by Mack the Knife.

No, the original poster asked about Light Rain Improving OTA Reception - nothing about ground wave.

And again, FM and TV facilities go out of their way to make sure the signal goes out into the air and not to the ground as that would become a major waste of transmitter output power.