Hello,
I recently installed a Procaster on a ground post over approximately 30 radials each about 20 feet length and buried. Nearby I have a receive antenna used for LF to HF monitoring and the 1630 kHz signal usually comes in about -25 dBm. Drive around signal check confirmed about 1/2 to 3/4 mile range before signal drops into the noise. Overall the system works reasonably well.
We've had rain the last couple days. While driving around this morning, the acceptable listening range increased to 3/4 to 1.25 miles. The signal strength into the nearby antenna increased to -16 dBm... a significant increase.
Question:
Has anyone else noticed a significant range change vs. ground moisture content?
Ground conductivity is everything with a AM broadcast. So if the ground is saturated with water after a good rain your ground conductivity is higher than usual, therefore increasing your range.
http://part15lab.blogspot.com/2014/04/click-to-enlarge-ground-conductivity.html
That's a very useful link @richpowers. @jsh4 - I noticed only a slight increase in range when the soil was wet, but that's most likely because I don't think my ground connection was a very good RF ground. I'll spare you the details. I am now operating without a ground connection. My coverage is not that good as a result, unfortunately.
I have a feeling that if I had a good RF ground, I would notice the difference in coverage between the wet and the dry seasons. I'll be interested to see if anyone else with an outdoor installation has noticed anything.
Back when I operated a carrier current system there was a definite increase in range when the ground moisture was high. Dry ground reduced the range. So I tried a slow trickle from a water hose during dry periods and it worked! The range went up.
I was using the neutral loading way of feeding RF into the power lines with an 8-foot ground rod driven into the earth.
Back when I operated a carrier current system there was a definite increase in range when the ground moisture was high. Dry ground reduced the range.
This reminds me of a late 1940s college thesis about college carrier current stations where it talked about how identical installations at different colleges acheived different results and at the time they couldn't understand why.
I just googled "how dies rain affect am radio propagation" and noted the top result which is this AI summary:
"Rain can significantly impact propagation, particularly in the context of radio waves, by causing attenuation, meaning the signal weakens as it travels through the rain droplets, which absorb some of the signal's energy, leading to reduced signal quality and potential disruptions, especially at higher frequencies; heavy rainfall can cause significant signal degradation in certain communication systems."
Which at first glance seems to counter the idea that rain can increase range. But note that its talking in regard to the effects of raindrops decreases AM range, but it's just the opposite when it comes to the rain that has already fell, as that causes the range to increase.
That's how I deduce it.. Am I correct??
On a side related note, this is interesting too;
I asked ChatGPT what treatments could be added to the ground to improve AM radio signal propagation. The reply...
>To improve AM radio signal propagation, adding treatments to the ground can help enhance the effectiveness of the transmission by lowering ground resistance and improving the conductivity of the soil. Here are some approaches:
1. Salts or Saltwater Treatment
- How it works: Salt (especially sodium chloride or other conductive salts) can be added to the soil to increase its conductivity. A higher conductivity helps the radio waves travel further by reducing ground resistance.
- Application: A mixture of water and salt can be sprayed or applied directly to the ground around the AM antenna or transmitter. The area where the antenna base connects to the ground is especially important.
- Benefits: This treatment is commonly used at AM transmitter sites, particularly in areas where the soil has low conductivity (such as dry, sandy, or rocky areas).
2. Improved Grounding Systems
- How it works: A better grounding system can reduce signal losses due to high resistance. The more effective the ground system, the better the radio waves will propagate.
- Application: Ground rods, copper wire, or even copper mesh can be buried around the antenna to improve its grounding. Multiple grounding points can be established to create a more uniform and effective grounding system.
- Benefits: A proper grounding system reduces interference and improves the efficiency of the signal. This is especially effective when combined with other treatments like saltwater.
3. Adding Conductive Material
- How it works: Adding conductive materials like copper or aluminum to the ground can improve the transmission characteristics. Some AM stations use a layer of metal to enhance signal propagation.
- Application: Conductive materials can be buried around the antenna base or around the transmitter site to help create a more uniform electromagnetic field.
- Benefits: This method can enhance signal strength in areas with poor soil conductivity.
4. Moisture Content Management
- How it works: Soil moisture affects conductivity. Wet soil is typically more conductive than dry soil, so maintaining optimal moisture content is important.
- Application: In dry areas, irrigation systems or artificial watering techniques can be used to keep the ground moist. Avoid over-watering, as this can lead to soil erosion and other issues.
- Benefits: Moist soil helps the signal travel more efficiently, especially for shorter-distance AM transmissions.
5. Using a Radial Ground System
- How it works: A radial ground system is a configuration of conductors (usually copper or other conductive metal) arranged in a radial pattern around the base of an AM antenna. This system helps to spread the radio waves more evenly and reduces interference.
- Application: Radial wires should be placed underground in a spoke-like pattern, extending from the antenna base. The more radials, the better the signal propagation.
- Benefits: This method can improve the efficiency of signal radiation and reduce ground losses, especially in areas with poor conductivity.
6. Soil Conditioning with Minerals
- How it works: Some minerals, like gypsum (calcium sulfate), can improve the conductivity of certain types of soil. This can be especially helpful for soils that are low in natural salts.
- Application: Applying gypsum or other conductive minerals to the soil can improve its conductivity without affecting its pH or fertility.
- Benefits: This method can be particularly useful in alkaline or highly saline environments.
7. Antenna Impedance Matching
- How it works: Although not directly a treatment for the ground, ensuring the antenna's impedance is properly matched with the ground system can improve signal propagation. Proper matching helps maximize energy transfer and reduces losses.
- Application: Impedance matching devices like transformers or matching networks can be used to ensure that the antenna and the ground system work together effectively.
- Benefits: Optimizes the overall transmission and reception of signals, leading to better range and clearer signals.
8. Use of Artificial Ground Enhancement
- How it works: Special products known as "ground enhancement materials" (GEMs) are designed to be used around antennas to reduce ground resistance. These materials often contain mixtures of conductive polymers, metals, and other compounds that help improve ground conductivity.
- Application: GEMs are usually mixed with the soil or placed around the antenna to create an artificial "super ground."
- Benefits: Provides a significant improvement in signal strength and propagation, especially in areas with poor natural soil conductivity.
Summary
Improving the ground around AM radio antennas by increasing conductivity and optimizing grounding systems is essential for better signal propagation. These treatments help to reduce signal loss, interference, and resistance, thereby allowing AM signals to travel further and clearer. Combining several of these techniques—like saltwater treatment, a good grounding system, and the use of conductive materials—can have a synergistic effect on AM radio signal strength and coverage.<