Pasture Creek Station is on an eight acre site located on the western shore of Chesapeake Bay, twenty miles south of Annapolis, MD. This is where the Potomac Valley Radio Club annual August picnic, the Fowlfest, is held and attended by an average of 75 PVRC and NCDXA club members and guests. The picture is from the 2008 Fowlfest.

Following a couple of casual field days in the early 90s, a station building was completed in 1995. The station focus is the low bands, 160 primarily. A radial field of 240 radials, 37,000 feet altogether, is used in conjunction with a balloon vertical antenna. All overhead electrical wires entering the site were replaced with a buried service. The station building is on nine eleven-foot stilts, with the underneath containing a hangar for a seven-foot diameter advertizing balloon. This size helium filled balloon permits a payload of just over five pounds.

A teather cord and number 18 antenna wire are connected to the balloon and raised from the top of a 30 foot tower supporting additional elevated radials. Open wire feeders descend to a large tuner box containing the matching network. A coax run of 300 plus feet goes to the station building. The radial field extends to the waters edge. Bay water is tidal, brackish, fifteen parts per thousand salt content, about 50% dilution from bay water at the confluence with the Atlantic Ocean. About a third of the site is a tidal marsh providing an ideal location for vertical antenna experimentation and use. Three beverage antennas are also used for receiving.

Early usage has revealed the following: Vertical heights of 1/4 wavelength compare with good permanent antennas of the same height, wheras a height of 3/8 wavelength already produces exceptional results. The antenna should be completely vertical because leaning even as little as twenty degrees greatly destroys performance. VSWR does not vary significantly as the balloon wanders. Signals increase in strength much faster than any increase in noise with increase in vertical height. A substantial ground wave signal extends out to at least a 50 mile radius.

Radial field construction was done by placing 2500 foot spools of no. 12 solid THHN insulated wire on pipes. These were carried by teams of two people each outward from a central point to the furtherest practical extent, a quarter wave or greater, while simultaneously pinning the wire on top of the grass surface with sod spikes placed every few feet. Then, at the perimeter, continuing around eighteen degrees, and then returning to the center, obtaining two radials from a single unbroken wire.

This was continued until 120 radials were laid. The wire color was then changed from black to red and the process repeated, interpolating between the original 120 resulting in a total of 240 radials, 37,000 feet of wire held by 13,500 sod spikes.

This was done in four days in a narrow window in early April. The radials were completely covered by grass by mid May. It required an eight hour day to strip the 240 wire ends, bundle them into eight groups of 30 wires each fastened by hose clamps to eight no. 8 wires. These were then clamped to three parallel no. 8 wires which lead a short distance to the tuner box.

Helium at 2500 psi is held in two large steel cylinders used alternately. A blimp inflator is used to transfer the gas to the balloon, which is filled until it is plump. Exhausted cylinders at zero psi are not empty but full of air. Recharged cylinders comingle this residual air with the new helium. A full balloon is stored in the hangar. Helium leaks steadily through the balloon skin; the air does not. Every use requires the balloon to be topped off. In time the ratio of air to helium in the balloon reaches the point where no payload lift results. The balloon must then be completely flattened and filled anew.

The antenna wire and teather are fastened every several feet. One end is connected to the balloon, the other to the elevated feed point. The antenna is arranged on the ground in a serpentine pattern in preparation for elevation. Once the balloon is set aloft one must move rapidly to compensate for wind currents, avoiding surrounding trees, while raising the balloon to its final elevation. The 30 foot tower keeps the antenna bottom end stationary reducing greatly the chance of perimeter tree entanglement. The tower was placed in the center of a field and adjacent tree branches were trimmed. Launching and retrieveng the balloon has not been a problem.

PVC tubes are suspended from and parallel to the ceiling of the hangar to prevent puncture. The path outside is also constructed to eliminate anything that could tear the balloon skin. A hand truck with a fibreglass pole extension is used to transport the balloon to and from the open field, frequently through snow cover.

The "dead balloon" test is performed by connecting the balloon to the end of the pole of the transport vehicle. The height the pole is raised serves as a good indication of payload lift.

The tuner box contains a large coil -- 33 turns of 1/4 inch diameter refrigeration tubing with an outside diameter of 3 1/2 inches. There is no coil form. The coil is suspended vertically and is in parallel with a variable capacitor tuned to resonance. The antenna is connected to the top, the ground lead to the bottom, the coax braid to the bottom, and the center conducter is tapped up from the bottom resulting in an autotransformer and perfect match.

W3YOZ, trustee of W3OSO. Also see W3SO biography.