Both the HT-37 transmitter and SX-111 receiver were produced by Hallicrafters in the early to mid 1960s. I acquired both of my current units in the late 1980's while residing in Fort Wayne IN. My novice receiver, circa 1973, was also an SX-111. I use my combo several times during the year. The photo below was taken while using the radios for the Fall 2008 Classic Exchange.
The SX-111 is a CW/SSB/AM 10M through 80M receiver employing dual conversion on all bands. There are two variants; the original and the MK 1. The MK 1 employs a 6BY6 product decector for CW/SSB reception. Both variants allow reception of 10 Mc. WWV and have a built in 100 Kc. crystal calibrator.
A common quesiton is how to tell the difference between the SX-111 and the SX-111 Mk 1.
Well, it's pretty simple. The Mk 1 version has a productor detector and hense an additional
tube. The Mk 1 version has 14 tubes, while the original version has only 13 tubes.
A simpler way is to look at the rear of the chassis. If there is a tube directly above the Mute Terminal strip, the radio is Mk 1. If there is a can capacitor there, it's the original!
The SX-111 MK 1 power transformer has three windings: 460V CT, 5V and 6.3V. The output of the 5Y3GT Rectifier is 220V DC.
The HT-37 transmitter provides about 100W output on CW and SSB, and 25W of low level AM. The phasing method is used for SSB generation and gives the HT-37 it's reputation for nice sounding audio. This transmitter provides complete 80M through 15M band coverage, and a 500 Kc section of 10M. The 10M section is determined by a crystal inside the unit. The default crystal provides 28.5 to 29.0 Mc, and the user may replace it with other crystals for different 10M band coverage.
Copyright (c) Mark S. Bell 2008 - 2010