Hallicrafters HT-37 & SX-111 Mk 1

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.

HT-37 Under Chassis Photos

Here's some photos of the "Warning Notice" that came with the transmitter:

Remember when, back in "the day", as a kid you'd light up the filaments on a cold winter's eve, when there were no such things as cell phones or the internet, and DX Summit was decades into the future; when working across the pond into England on 40 CW was a big deal....remember the smell of the radios as they warmed up, the hum of the transformers.... remember sticking a towel under the crack of your bedroom door so your parents wouldn't know you were out of bed and on the radio, hoping they wouldn't hear the kerchunk of the relay as you hit the B+, or the clicks of the trusty J-38 in the middle of a contact.... remember what your shack looked like in the dark.....


HT-37, SX-111 MK 1, and R-48A !!

Photo's showing power output on all bands

HT-37 Interior Photo's

SX-111 MK 1 Interior Photo's

Here are some videos of the HT-37 on AM and SSB being received on the SX-111

HT-37 on 75M AM

HT-37 on 75M LSB

HT-37 on 20M USB

Copyright (c) Mark S. Bell 2008 - 2018