My county recently got roughly 13 inches of rain here in Texoma. While the ground has dried and my signal has returned to regular coverage, what happened while the antenna system was water logged has me curious.
What would cause Antenna System loss while the grounding system is either underwater or on water logged soil? As long as some of my radials were under water I was unable to peak my tuning on the transmitter to normal levels. In fact, it completely threw my tuning out of whack.
My backyard can be both a creek and pond when the rains come down hard, this naturally makes for a great ground until it floods.
On the other side, The full power AM's site is in a swamp and rain does nothing to it.
In the case of a similar experience with my station the drop in output observed was due to water on the tuning coil. This both detunes the circuit and dissipates some of the power.
Water on the antenna components and insulators can also cause loss.
Things returned to normal when dried.
I've worked for the same AM 5,000 watt station for 28 years. I take the monitor points regularly -- field strength readings at various points during our nightime directional operation. Field strength always increases in the spring when the antenna ground radials are in wet ground caused by many feet of melting springtime snow. The affect goes away by late spring.
I don't notice this from just plain rain. I don't think a typical summer rain, even a heavy rain, has the longevity to saturate the ground enough to make any difference. But the snow melt creates a good long soaking.
TIB
That is exactly why I am stumped here Tim, rain should have little to no impact on the tuning. Especially with all the tuning equipment and transmitter indoors.
What percentage of an increase Tim? And what would you guess the increased range to be? TNX.
What are the effects of the environment over antenna performance?
How much the performance decreases in the rainy and the hot conditions?
What happened in the cold conditions?
Also how it could be avoided while desiging the antenna?
A few years ago I did a study of weather and seasonal effects on transmitted signal strength spanning about a year. Link is here: http://www.part15.us/blogs/radio8z/weather-effects-antenna-performance
Neil
For some perspective ...
The FCC propagation chart for 1650 kHz shows about a 2X increase in groundwave field at 1 mile when earth conductivity changes from 2 mS/m to 8 mS/m, and the same field as produced at 1 mile for 2 mS/m is produced at about 1.7 miles for 8 mS/m (other things equal).
Unknown in all this is what those seasonal earth conductivities really are for any given transmit site and propagation path.
@Rich said "Unknown in all this is what those seasonal earth conductivities really are for any given transmit site and propagation path."
hence the need for regular monitoring of your points