Crystal Radios Of The 2007 Contest Entrants
Antenna is 60 foot vertical with base 20 feet above ground level. Alternate antenna is 60 foot horizontal wire mounted 23 feet above ground level.
Antenna coil is contrawound 660/46 Litz on 4.5" dia styrene form. Tank coil is on 6" ferrite rod.
Instead of 8 ohm speaker, I'm using 32 ohm HiFi headphones, adjusting taps on a 70v line transformer. Regeneration/selectivity is controlled by positioning hand wound RF transformer relative to ferrite tank coil.
Reflex ckt is Robert Bazian's design with minor modifications. Bazian did not intend this design for DX or selectivity, just loud local reception. Although his latest design discourages regeneration, I find that encouraging controlled regeneration and using heterodynes to be more effective for DX work.
See more of Gil's superhet on his other page.
For this year’s 1 active device contest I used the same rig as the crystal contest just using a switch to select either the diode or the tube. I used my usual construction techniques by scrounging whatever I can find.
For a tube I used a 1N5GT battery pentode with 90V of B+ and using a variable coupling ticker coil. I liked the selectivity of a double tuned set so I used it for a one tube regenerative radio. I put the tickler coil between the Tuggle tuned antenna coil and the detector coil. For the spider web coil forms I used ¾” pvc couplers and round toothpicks.