Electric Fences and the Observatory

Over the past few years, the Observatory has made significant strides in suppressing harmful on-site and community interference, including electric fence RFI. We receive gracious cooperation in solving RFI problems, but this reactive approach results in a substantial amount of Green Bank Telescope (GBT) and other telescope observing time being lost or damaged. As GBT time is very expensive, eliminating electric fence RFI is highly desirable.

It has been our experience that the vast majority of electric fences do not cause harmful interference, so we firmly believe some reasonable measures will be successful in preventing problems.

Scientific observations are conducted each summer at very low frequencies. Since harmful interference from electric fences is strongest at lower frequencies, our success in this area will be more crucial than ever. If you would like to see an example of electric fence RFI, click here.

Electric Fence Do’s and Don’ts:

  • Use Solid Wire – Although it requires a little more effort to install, it is less expensive and less likely to break.
  • Make Good Connections – For maximum effectiveness, make sure all connections are clean and tight.
  • Install Good Earth Grounding – Use grounding rods that are 6 to 8 feet long, either copper or galvanized, with good ground clamps or a ground return wire if you have dry, stony soil.
  • Use Good Quality Insulators – such as porcelain or glass reinforced plastic.
  • Run electric fence wire parallel to telephone or power lines.
  • Improperly splice broken fencing – Use a secure figure 8 knot, western union knot, or joint clamp to splice solid wire fencing.
  • Let wet vegetation contact the wires - this will decrease the effectiveness of your fence and increase the possibility of RFI.


  • Extends the life of your charger
  • Increases the effectiveness of your fence
  • Decreases power consumption
  • Improves community phone communications and internet connections
  • Improves community basic TV service
  • Improves community basic radio service
  • Eliminates harmful RFI, improving scientific observations
  • Since polywire fences are highly susceptible to breakage, the use of real wire should increase the reliability of your fence and reduce need for repairs
  • Soft galvanized wire is the least expensive fencing wire, and provides a cost effective solution for garden protection and containment fencing. High tensile wire is the best choice for heavy duty permanent fencing

Links for more information:

Modified on Wednesday, 02-Jun-2004 10:15:35 EDT