Inside Wireless: Fresnel Zones

[@Rfelements]

How do you go about ensuring you link does not suffer from Fresnel zones reflection?

[@RomanLeBg]

Next time I need to do a wifi link I'll buy your stuff you're the best

[@Rfelements]

what kind of links do you work with?

[@DanielHamiltonWI]

You guys rock! Love these videos

[@Rfelements]

thanks, we try!

[@alessandrocorucci799]

The Fresnel Ellipsoid is indipendent of the radiation pattern of the antennas; so if the antenna is a parabolic dish of 1m diameter or a dish of 10m diameter the ellipsoid is the same. But for sure, at the same frequency, the main beam of the 10m diameter is more narrow than that of the 1m diameter paraboloid dish. So the reflections are more attenuated by the radiation pattern of the 10m dish... In same way, in an actual scenario, we have to take into account the influence of the radiation pattern.... In other words, we can have the first fresnel ellipsoid obstructed by a tree or intersecated by the terrain, but it could be no effect on the link performance (i.e. no further loss...) due to the very narrow radiation pattern... Do you agree with me ?

[@Rcschim]

That's a super good explanation of fresnel zones. While generally knowing about them I only now understood that it's related to multipathing. Does this mean that circular polarized antennas (as used on drones) the fresnel zones impact is less than with linear polarized antennas? (since circ pol antennas reduce multipathing problem), thanks, greets, RCSchim

[@Rfelements]

Exactly, sine the field vector constantly rotates transversally to the direction of propagation, it is very unlikely that the direct and reflected waves add up destructively, or constructively resulting into decreased Fresnel zone influence with circularly polarized antennas.

[@mobmic90]

Really nice content here! I have a question... How does that apply to home routers with omnidirectional antennas inside customer houses?

[@Rfelements]

It doesn't - the coverage inside houses is a lot more complex because there are so many reflecting surfaces, so Fresnel zones are not a useful concept for indoor..

[@alessandrocorucci799]

in this case, there is a lot of multipath and walls attenuation...

[@CraigMullins1]

How do actually verify this is happening? like partial Fresnel zone loss due to a building or tree or Fresnel zones cancelling each other out?

[@Rfelements]

It is not simple in real life because of the terrain complexity, but some of the RF link planners do show the 1st Fresnel zone in their results, so at the very least you can rule that out. Nevertheless, the fastest/easiest way to optimize the link performance in terms of the Fresnel zones is to sweep the antenna position on the order of a few wavelengths (6 cm @ 5 GHz) and see where you have the best signal

[@himanshujaiswal5923]

Thanks sir

[@lacyrjoao2553]

I would like to know if I can use your videos in my telecommunications classes. I am a teacher at a public technical school.

[@Rfelements]

Of course, feel free to use them in your classes, that is what the videos are for ;) what school are you at and where?

[@Rfelements]

Cool, hope the videos will help with your work!

[@lacyrjoao2553]

Thank you!!!!

[@migallocarolis6672]

¿Disculpe cómo puedo calcular la zona de fresnel si no se donde está la antena emisora? Me interesa conectarme a varios puntos de acceso situados a 1Km, 500m y 200m con visión directa, pero el problema es que dichas conexiones sólo funcionan de madrugada y lo hacen lento y durante el día es imposible conectarse a ellas, podría ser la interferencia de tantas redes wifi, me llegan unas 70 redes aproximadamente. Tengo la antena pegada al punto más alto de la ventana un poco abajo del marco de aluminio para evitar interferencias en un tercer piso y la altura desde la calle hasta dónde está la antena es de 9m, no puedo mover la antena, si la muevo milimétricamente se desconecta con facilidad. Anteriormente tuve una antena de exteriores supuestamente más potente que mi TP-LINK 7200ND en mi azotea que está a 12m de altura desde el suelo sin ningún obstáculo pero empeoró la situación dichas redes dejaron de llegar. ¿Qué solución me recomienda para hacer funcionar el enlace a tales distancias?

[@Rfelements]

La solución es realizar enlaces con suficiente altura, línea de vista y antenas en puntos de acceso eficientes, así como en CPEs. Así puede garantizar una conectividad a cualquier hora del día. Un saludo

[@leonardduzon1708]

can dual polarization of a given antenna work? or does it exist? thank you

[@Rfelements]

What exactly is your question? This one is very unclear...

[@jcchern3801]

@@Rfelements He offers a good question here. What happens when you use a dual polarization yagi? Example, an "X" polarization, to "X" polarization (or linear or horizontal antenna, at the other end). Or... a "+" polarization yagi to a "+" polarization yagi? Lots of variable here, but a good question on "what would happen?" Case examples of how obstruction into certain Fresnel zones - relative to data losses observed... would be GREAT to see! This issue is rarely addressed by many in the field.

[@Rfelements]

if the polarizations of antennas on both sides of a link are matching, the reception works optimally - no polarization mismatch loss is introduced. The Fresnel zones influence (and all the other reflections in the propagation channel) is not straight forward thing to model. This is why there is a lot of effort in scientific circles developing statistical models of the propagation channels, because statistics is what all the reflections melt down to in the end, since no scenario is the same.

[@Rfelements]

What is your language? If it's Spanish, we have a native speaker working for us..

[@rajanyadav8149]

Bro plz slow down

[@Rfelements]

YT now has a feature that allows you slow down the video (in the past it only did speed up) ;)