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Going Full Circle – Trap Dipoles Ageeeeeeen.Ageeeeeeen.Ageeeeeeen….Part 4

After a detour to building the 2 band trap dipoles using rg-316 type coax, the worm turned. The failure of a couple of the coax trap antennas due to incomplete sealing and weather proofing the coax became a problem. The antenna at home failed. Two of them. Then the antenna being used for portable ops failed during the 2024 NC QSO party. In the meantime, the home antennas built from coils and capacitors for 40m/20m are still in use 4 years later with no change in resonance points.

Rather than continue with a seemingly fragile system it was time to revert to the coil-and-cap design. Avoiding the cap failures previously experienced on the 10m/15m antenna is addressed by using caps with low enough values to be appropriate for the 10/15 version. So a supply of the TDK ceramic caps was laid in. These caps have 3KV and 6KV ratings. Parts#810-CC45SL3JD080DYGN (example is 8pf SL 6kv) from mouser. TDK Data Sheet for Sl ceramic capacitors.

For the 10m trap a value of 10pf was used, with 16 turns of 18ga stranded wire tightly wound on a 1 inch diameter piece of fiberglass tube. (calculated inductance is about 3.25uh) This originally resonated about 27500, but crept up after taping and sealing to 28000. Decided to roll with them as constructed. These may be fragile, too fragile for portable use, as 18ga wire was also used for the connections. NOTE: USE LARGER GA WIRE FOR CONNECTIONS.

The “tricksey” part discovered previously is that […]

Continue reading Going Full Circle – Trap Dipoles Ageeeeeeen.Ageeeeeeen.Ageeeeeeen….Part 4