[Hallicrafters] Re: Hallicrafters Digest, Vol 9, Issue 26 (Dummy Antenna)

[Wormchile at aol.com]

The following discussion should answer some of the recent questions  
concerning dummy antennas. In my library is a copy of Sams Postwar  Communications 
Receiver Manual, CR1, publication date unknown but approximately  around 1950. 
Included are Photofact sheets, containing schematics, parts  lists and alignment 
instructions, for the following Hallicrafters models: S-38,  S-40, S-40A, 
S-41G, S-41W, S-47, S-51, S-52, S-53, SX-42 and SX-43.
 
 The RF and IF alignment instructions all contain a column describing  the 
dummy antenna to be used during alignment. In most cases none is used for IF  
alignment. However, in many cases a dummy antenna is required to properly align  
the RF sections. The exact configuration of the dummy antenna varies across 
the  product line. In many cases it takes the form of a 300, 330 or 390 Ohm 
carbon  resistor connected between the signal generator and the antenna input. At 
other  times an RMA dummy antenna is specified, described as: a 200 pF 
capacitor in  series with a 20 microH choke, with the choke shunted with a 400 pF 
capacitor in  series with a 400 Ohm carbon resistor. Above 2 MHz this antenna 
has a fairly  constant impedance of  390- 400 Ohms.
 
If anyone is interested, I will be happy to make Xerox copies of  any of the 
above mentioned Photofact sets. The finished product should  be far superior 
to anything downloaded from BAMA. I also used Excel to do an  impedance vs. 
frequency analysis for the RMA dummy antenna. I will be happy to  email a copy to 
anyone who is interested.
 
Hope this clears up some of the fog.
 
73
 
Jim Mandelik, KD8AKJ