Television reception when windy...

[Externet]

Hello.
It always happens, from pixelation to full loss of signal from an antenna that otherwise works very well. It is mounted higher than trees, 30m distant from the nearest ones, which have no leaves this season.
What is the explanation beyond 'trees block signal when move in front of the propagation path' ? What moves are small bare branches. Happens to most channels received from 360 degrees azimuth, happens to different style antennas, happens with antennas in the attic, or long wires, to solidly mounted antennas, directional and omnis. Cannot discern a believable explanaton...

 

[BigBoss]

Have you ever measured the signal strength in normal case ? It may give you an insight about the problem.
I believe the signal strength is poor and there are some connection problems such as moving connectors, poor coaxial junctions, hidden cracks in coaxial cable etc.
If the whole patch is robust, the signal strength shouldn't be deviated from a average level.

 

[barry]

Are you saying you’ve used different antennas in different locations with the same results? And wind affects your signal? I would suspect cable or connector. you might be able to test this simply by wiggling the cables.

 

[betwixt]

I have a similar problem here, I can see the TV mast about 20Km away across a river estuary. At certain tide heights the TV picture pixelates. It isn't an issue of signal strength, it is caused by the signal taking more than one path from transmitter to your antenna, the different distances result in phase differences in the signal and as they meet together and add or cancel each other. It can be worse in winter when trees are bare because they make better reflectors, the foliage tends to 'blur' the reflection so it has less effect. Trees swaying in wind will change the strength and delay in the reflection.

You may find a more directional antenna make things better by reducing indirect signals but it depends on actual terrain and obstructions.

Brian.

 

[Externet]

Thanks. I will measure the signal strength while windy and when not, I have the equipment. Two things can happen: A varying signal strength reading (highly likely) corresponding to good and poor reception. Or, steady signal strength (which would be very unlikely)
In any of the cases will not explain how an attic antenna or a very solid mounted roof antenna and cabling drastically fades reception by wind.
Temperature, humidity and sunny or not also affects certain channels. But I can understand the changes as fresnel, refraction, temperature tunneling... But wind cannot comprehend.

First check, looked at air signal at the analyzer, the heavily pixelating channel, mostly no reception. It is TV channel 65 WLJC supposed to be 177MHz. There is nothing relevant showing. Nearby, at 173.310 there is an intermittent spiking signal. Posting its video .MOV, rejected by the forum. Message is " the uploaded file was not a video as expected" I cannot guess why cannot attach it.

--- Updated Feb 10, 2023 ---

Trying now to attach a picture instead of the short video, Air reception at the analyzer location, indoor 1m vertical antenna. Will move the instrument to the antenna termination in other moment. Nothing on 177MHz. Centered display to 173.310MHz that has the intermittent spike.

 

[albbg]

As already pointed out by betwixt your problem could be the multipath. Even if the signal strength doesn't change significantly, however many "copies" of the signal will reach the receiver with different phases, depending from the followed path; this could cause the channel estimator failure, increasing the BER, that is seen as pixelation.

 

[dick_freebird]

Directionality might be a problem, if the wind makes the
antenna wobble then there is a time-variable attenuation
w/ off-axis position.

RX may have an AGC which has trouble tracking a constantly
changing envelope, may over / undercorrect. Marginal signal
can go as far as dropping packets or just pick up higher BER,
which is where pixellation comes in.

 

[vfone]

I think is about Fresnel zone clearance:

Fresnel zone - Wikipedia

en.wikipedia.org

IW Academy | Wireless Networking Fundamentals | Radio signal propagation fundamentals

Radio signal propagation fundamentals Wireless Networking Fundamentals

academy.infinetwireless.com

There are equations to estimate this clearance.

 

[SWRmeter]

Hello.
It always happens, from pixelation to full loss of signal from an antenna that otherwise works very well. It is mounted higher than trees, 30m distant from the nearest ones, which have no leaves this season.
What is the explanation beyond 'trees block signal when move in front of the propagation path' ? What moves are small bare branches. Happens to most channels received from 360 degrees azimuth, happens to different style antennas, happens with antennas in the attic, or long wires, to solidly mounted antennas, directional and omnis. Cannot discern a believable explanaton...

Here are some other suspects to check out :

What time of day does this happen ? Full sunlight day / Dusk-Dawn/ night-time ?
Are you near a body of water in the direction of signal reception ?

Do co-relate these with the frequency bands you are observing, assuming other than TV bands.