[Hallicrafters] Re: RMA Dummy Antennas

[Wormchile at aol.com]

Hi to the group,

A couple of years ago I did an Excel  spreadsheet study of the impedance vs. 
frequency properties of the RMA (later  EIA) dummy antenna. All of my Halli 
service brochures describe it as consisting  of: a 200 pF cap in series with 20 
microH inductor; a 400 pF capacitor in series  with a 400 ohm carbon (i.e., 
non-inductive) resistor is then connected across  the inductor. My study showed 
the impedance of this circuit to be around 337  ohms at 1.5 MHz, dropping to 
around 232 ohms at 2.5 MHz and finally leveling off  to a constant 300 to 400 
ohm range above 3.5 MHz. Apparently, most receivers of  the 50's (radio and TV) 
were designed to accept good old 300 ohm transmission  line. I hope this has 
been helpul.

73
Jim Mandelik,  KD8AKJ




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