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Please excuse my lack of proficiency in this subject. I am just begining my understanding of antennas, bridges, repeaters and the like.

I have a somewhat standard situation of two buildings separated by about 1km, with the one caveat being a hill between the two.

Would it be possible to take the signal from a passive parabolic/helical WiFi antenna (2.4g) on the hill between to the two buildings, amplify it if needed, and send it with a directional antenna to the other building, which would also have an outdoor directional antenna?

Additionally, if this is possible, could it be done with a passive configuration, or would a repeater and possibly some type of filter be needed at the mid-point?

Please let me know if there are any details I can (hopefully) clarify.

Thanks, Zane

  • To amplify a radio signal is not passive, and it requires power. You also seem to think that this is a one-way proposition, but Wi-Fi is bidirectional, so using a parabolic antenna to a directional antenna in one direction would be wrong in the first place. In any case, you want to hire a consultant who can look at the situation and come up with a solution, There are a lot of variables in microwave transmission that need to be taken into account. – Ron Maupin Dec 19 '19 at 1:47
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Would it be possible to take the signal from a passive parabolic/helical WiFi antenna (2.4g) on the hill between to the two buildings, amplify it if needed, and send it with a directional antenna to the other building, which would also have an outdoor directional antenna?

To clarify, parabolic antennas and many helical antennas are directional in nature.

Is it possible? Certainly, many things are possible. Odds are that Wi-Fi will not have the power to provide good service within legal limits and you should look at dedicated point-to-point wireless solutions.

Additionally, if this is possible, could it be done with a passive configuration, or would a repeater and possibly some type of filter be needed at the mid-point?

Again this is possible, at least from what I know of RF theory. You could connect two antennas directly together, and this could work in both directions. However, the realities of the situation are that it is likely not to work as well as you might hope.

In the first place, you would need a signal strength that was powerful enough to travel the distance (>1km if your two buildings are 1km apart). This is to account the distance added by the elevation changes as well as the signal loss you will experience without amplification.

Second, you would have to properly align (and keep in alignment) all four antennas used for this purpose. Having any of them out of alignment will further reduce the signal between the two end points. Getting highly directional passive antennas into proper alignment will be a challenge.

Third, any such solution will also pass noise/interference between the endpoints that would otherwise be blocked by the hill. This point would be even more applicable using any sort of amplification without correct/adequate filters.

If you do amplify the signal, this would have to be bi-directional amplification and the amplification would have to be filtered to not amplify noise/interference as well. This also means that you need power at the midpoint. If you are already putting power at the midpoint, then you are probably far better setting up two separate point-to-point wireless links and bridging them together.

Alternatively and possibly best (depending on the size of the hill) would be setting up antenna masts on each end and elevating the antennas to a point where the two end points can directly connect to each other. Antenna masts for point-to-point directional antennas is preferable in any case as it helps to avoid obstructions and RF noise.

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    It should also be mentioned that an RF beam is not a laser-like, straight beam but it requires that the ellipsoidal Fresnel zone in between is free of obstacles. Any obstacle will (more or less severely) dampen the signal. This will be more a problem with a direct link using masts than with using a relay. – Zac67 Dec 19 '19 at 9:06
  • Thank you so much for the detailed response. I am clear on the fact that WiFi is bidirectional. The amplifier would help with the tx, the dish with the rx, but again passive would be best. Alignment is another good point, and probably a lot more of a real world challenge than I am accounting for. – ztrain727 Dec 19 '19 at 18:03
  • @Zac67, I thought about adding Fresnel zones into the discussion, but thought that may be too much of a deep dive. As to the masts, masts almost always help the Fresnel zone as it helps get you free of ground clutter and the earth's curve, whether that is direct link or relay. As to which one (direct vs. relay) is more affected by obstruction in the Fresnel zone, that would highly depend on quite a few factors that are not include din the OP. – YLearn Dec 19 '19 at 19:30
  • @ztrain727, antenna gains help with both the Tx and Rx. Amplifiers can also help with both. When I was mentioning bidirectional, I am talking about the capabilities of the equipment at the relay. – YLearn Dec 19 '19 at 19:31
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    @YLearn Exactly my thoughts, but with a hill in the middle, a direct line of sight won't really cut it. One km isn't that far though with a parabolic dish (@ztrain727 which are the best directional antennas you can get). – Zac67 Dec 19 '19 at 20:24

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