The antenna is oriented north and south, axially.  Here's a crude diagram indicating relative height and orientation.  My wooden towers determine where I can play out 500 feet of copper wire.


L-Network matching circuit, in the testing state.  590 uH tapped coil, 400 mmf capacitor.



Block diagram



Fixed signal local oscillator, an HP-3586B Selective Voltmeter.  There is a 1V PP output available on the back panel
and the signal is quite stable.



IC-706MKII set to the operating frequency, USB, lowest output level.  With WSPR the transmit frequency is 1.5 Khz higher than the 'dial' frequency.



Tee and Homebrew pad to drop IC-706 output down to safe mixer level.



HP-10514A Double Balanced Mixer L,R input, X output



Southern Avionics Corp SS-250C NDB transmitter.  This unit came from a nearby municipal airport and had been struck by lightning or a power surge.  It was headed to the salvage yard when rescued.  The driver board was rebuilt, output transistors replaced and  it was retuned from 208 Khz to 500 khz.  The local oscillator, tone modulator, NDB keyer, and  timer circuits were disabled. A relay was added for A1 keying in CW mode.  This transmitter is built inside a weather proof enclosure.  The enclosure is removed for pictures and tweaking.



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