Modern Radio Labs®
MRL® Handbook No. 2
MRL® #2
and 2-A Long Distance Crystal Sets
Many
have acclaimed this as the "World's Best DX Crystal Set." This
handbook shows all the details for building this wonderful set.
HB-2
shows how to build both the #2 2-dial set and the #2-A single dial set. They
are the same circuit but the different types of condensers make a different
panel and wiring layout.
The MRL® No. 2/2A is a two circuit
(“dual tuned”) design, with a series tuned primary (“antenna ground circuit”),
and a parallel tuned secondary (“tank” or detector circuit), in a single
autotransformer coil. In tandem with the separate control of the variable
capacitor connected to ground, the detector is tapped at the top of the coil, and near
the bottom (closer to ground), to impedance match the detector for varied
selectivity and sensitivity.
The series-parallel variable capacitor arrangement
and the detector tap in this circuit is
historically significant. Elmer Osterhoudt is one of the very first, if not the
first writer/designer ("guru of the past") to experimentally
impedance match the detector in a crystal set circuit.
In actuality, the design of variable
detector tap is present in a couple of early circuits originating back to the
turn of the century (1900), but in the very early days of radio, as one editor
wrote in 1927: “...little attention, if any, was paid to the subject of
matching impedance”.
The MRL® 2/2A is the very first
professionally developed “High-performance Crystal
Set” of the 20th Century, in the 1930's, during a period of commercial
emphasis and development of tube technology for radio.
Copyright Paul L. Nelson 2015
Contents:
1. Introduction
2. Building the set
3. The Antenna System
4. Operations and Testing
5. Theory of Circuit
6. Records by Location
$7.80 postage paid U.S.
Please write for shipping outside the US
This MRL® Handbook is included with our MRL® No 2 Crysyal Radio Kit