Category Archives: Antennas

New 630M Tuner

A new matching network has been installed at the base of the 630M antenna.  A 410 uH coil (6 in. diameter, #12 copper) in series with a 1000 pF vacuum variable tune the vertical to resonance.  A 10uH roller inductor is configured as an autotransformer for impedance matching, one end grounded, the other end connected to the vacuum variable, and the roller connected to the coax center conductor.

630m-tuner(click to enlarge)

The current controller in the shack (Arduino based) reads data from the LP-100A wattmeter and adjusts the remote tuner accordingly.  Currently only the SWR is monitored and one motor driven (resonance tuning).  However, the plan is to re-implement the controller to use the impedance and phase measurements from the LP-100A and adjust both the series and shunt elements in the tuner to obtain the proper matching.

80M Bobtail Curtain installed

The new 80M Bobtail curtain is installed and on the air.  Dimensions are 220 ft top wire, 50 ft outer vertical sections, and 60 ft center section (to reach ground).  Tuning is accomplished through an L-network of approx. 8.5uH and 310 pF.

80M-bobtail-swr

Network passed the smoke test at 1.3kW.  Below is the modeled azimuthal and elevation plots per MMANA-GAL:

80M-bobtail-plot