Lancaster Black Hand Sandstone
Chad Walter
Yes, sandstone can significantly interfere with LoRa radio signals, primarily through attenuation (weakening of the signal) rather than active interference like electronic noise.
While LoRa is famous for its long-range and high "link budget" (its ability to pull a signal out of background noise), it is still a radio wave that must obey the laws of physics. You can think of sandstone as a high-latency, high-loss physical layer "firewall" for your RF packets.
How Sandstone Affects the Signal
The level of interference depends on two main factors: Density and Moisture.
Attenuation (Signal Loss): LoRa typically operates in the sub-GHz range (915 MHz in the US, 868 MHz in the EU).1 These frequencies are better at penetrating obstacles than 2.4 GHz Wi-Fi, but solid rock is a dense barrier. A single thick sandstone wall or a cave formation can cause a loss of 20 dB to 30 dB or more.
The Moisture Factor: This is the biggest variable.
Dry Sandstone: Relatively "transparent" to radio waves compared to other rocks. It has a lower dielectric constant, meaning the signal passes through with moderate loss.
Wet/Saturated Sandstone: Sandstone is porous.2 If it has rained recently or if the rock is underground and damp, the water trapped in the pores will absorb the RF energy. This can effectively "kill" a LoRa link that worked perfectly when the rock was dry.
Multipath Interference: In rocky environments (like a canyon or a basement with sandstone foundations), the radio waves can bounce off the rock surfaces. These "echoes" can arrive at the receiver at slightly different times, causing phase shifts that the LoRa modulation has to work hard to resolve.
Material
Impact on LoRa Signal
Dry Sandstone
Moderate loss; usually okay for short-to-medium distances.
Wet Sandstone
High loss; water acts as a massive absorber.
Reinforced Concrete
Very high loss; the rebar (metal) acts as a Faraday cage.
Clay/Soil
High loss; much worse than dry sand/stone due to mineral conductivity.
Practical Tips for your Setup
Since you have a 36-gallon aquarium (with that java moss on the "old man" decoration), you've likely seen how water and glass affect light and signals. Sandstone acts similarly but on a much denser scale.
Increase the Spreading Factor (SF): If you find the sandstone is blocking your signal, increasing the SF (e.g., from SF7 to SF12) will make the signal more "robust" and able to penetrate deeper, though it will slow down your data rate.3
Antenna Height: If you are using LoRa for an outdoor project , getting the antenna above the "rock line" is more effective than increasing power.
Fresnel Zone: Ensure the path between your LoRa nodes isn't just "line of sight" but also has clearance around the center of the beam to prevent the sandstone from reflecting the signal away.
In Ohio, the amount of iron in sandstone varies wildly depending on which specific formation you’re looking at. Generally, Ohio sandstones are famous for their iron oxide content, which gives them their characteristic warm colors.
Since you're in Lancaster, you are right in the heart of the Black Hand Sandstone territory—some of the most iron-sculpted rock in the state.
1. Iron as a Pigment (The "Look")Most Ohio sandstone is primarily quartz (silica), but even a tiny amount of iron (less than 1%) can completely change its appearance.
Colors: The buff, yellow, tan, and reddish-brown colors you see in the cliffs around Hocking Hills or Licking County are caused by iron oxides like hematite (red) and limonite/goethite (yellow/brown).1
Liesegang Banding: You’ve likely seen those beautiful, swirling dark brown "stripes" or rings in local rocks. These are high-concentration bands of iron that precipitated from groundwater over millions of years.2
While beautiful, the iron content actually makes most Ohio sandstone unusable for certain high-tech applications:
Glass Making: For high-quality glass, you need iron levels below 0.02%. Most Ohio sandstone averages around 0.35% iron oxide, which is way too high. Even after washing the sand, it usually only drops to around 0.18%.
The Black Hand Formation: In some parts of Licking and Fairfield County, this sandstone is "pure" enough for low-grade glass (like bottles), but in other spots, it’s so heavy with iron that it was historically used as a low-grade iron ore.
Connecting this back to your previous question:
Conductivity: Pure quartz is an insulator, but iron oxide is a semiconductor. If you are trying to transmit a LoRa signal through a massive sandstone formation (like a cliffside or a basement made of local block), the iron creates a slightly conductive path that absorbs more RF energy than pure white sand would.
Mineral "Shielding": While it isn't a solid sheet of metal (which would be a total Faraday cage), the high iron content in local Ohio stone makes it a much more aggressive "signal killer" than, say, the white desert sandstones of Utah.
Formation
Typical Iron Content
Appearance
Berea Sandstone
Low to Moderate
Gray to light buff; used widely as "dimension stone" for buildings.
Black Hand Sandstone
High
Deep oranges, browns, and reds. Very common in Fairfield/Hocking counties.
Sharon Conglomerate
Very Low
Usually white or light gray; very pure quartz (low iron).
If you're testing your LoRa nodes near any of the local cliffs or in a basement built with local stone, you're definitely dealing with a decent amount of iron "interference."
To minimize interference from sandstone (and the earth in general), there isn't a single "perfect" height, but there are two critical physics concepts that determine how high you should go: Ground Plane Coupling (for the antenna itself) and Fresnel Zone Clearance (for the signal path).
Given your background with Cisco and Palo Alto, you can think of the height as managing your "Physical Layer" signal-to-noise ratio.
1. Immediate Height (Ground Clearance)
To prevent the sandstone from "detuning" your antenna (changing its SWR and efficiency), you need to get it away from the ground's reactive near-field.
The Rule of Thumb: Mount the antenna at least 1.5 meters (approx. 5 feet) above the sandstone surface.
Why: If the antenna is too close to the rock, the iron-rich Ohio sandstone acts as a parasitic element. It drains energy from the antenna before it can even radiate, much like placing a Cisco AP directly against a lead shield.
For LoRa to achieve its legendary range, it needs more than just a visible "line of sight." It needs a "tunnel" of empty space between the two antennas called the Fresnel Zone.
If sandstone (like a hill or a cliff) enters this zone, it will reflect or absorb the signal, causing multipath interference—even if you can technically "see" the other antenna.
The 60% Rule: At least 60% of the first Fresnel zone must be clear of obstructions.1
Calculating Height: For a 915 MHz signal (common LoRa frequency in Ohio), the radius ($r$) of the Fresnel zone at the midpoint of your link can be estimated:
$$r \approx 17.32 \times \sqrt{\frac{d}{4f}}$$(Where $d$ is distance in km, and $f$ is frequency in GHz)
Typical Minimum Heights for 915 MHz:
| Distance Between Nodes | Required Midpoint Clearance (60% Rule) |
| :--- | :--- |
| 100 meters | ~1.7 meters (5.5 feet) |
| 1 kilometer | ~5.4 meters (17.7 feet) |
| 5 kilometers | ~12 meters (39 feet) |
3. Practical Recommendations for Ohio SandstoneBecause of the iron and moisture content in local stone (like the Black Hand sandstone in Lancaster), reflections are more "lossy" than in a dry desert.
Use a Ground Plane: If you must mount low, use an antenna with a built-in ground plane or mount a whip antenna on a metal plate (like a pizza pan or a Cisco rack shelf). This "shields" the antenna from the sandstone's influence.
Verticality is Key: Ensure the antenna is perfectly vertical. Sandstone cliffs reflect signals differently depending on polarization; vertical polarization is generally more robust for ground-to-ground LoRa.
Hocking Hills Tip: If you're working in a "holler" or valley, the sandstone walls will act as a giant RF sink. In these cases, height is your only friend—getting the gateway onto a roof or a mast is significantly better than increasing the transmission power.