Hallicrafters HT-46 Manual
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Hallicrafters HT-46 Manual

Hallicrafters HT-46 Manual

Communications transmitter
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5/15/2021 WDØGOF Walt Cates
1

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  • Page 1 5/15/2021 WDØGOF Walt Cates...
  • Page 3 INTRODUCTION The HT-46 was and is a very well designed transmitter. At the time of its design, it featured the latest innovations such as; it used a balanced mixer for carrier suppression, utilized a 6 pole lattice filter for unwanted sideband rejection, AALC, metered plate current, metered RF output and with the addition of the HA-16, Vox operation.
  • Page 4 TEST EQUIPMENT REQUIREMENT; What is the minimum test equipment needed to super tune the HT-46? 1, Frequency counter: In the 21 century you can get a very good HF counter for less than $100. You need 5 significant digits from 1 to 10MHz and 4 significant digits from 10 to 35MHz.

  • Page 5: Bias Adjustment

    WARNING!!! AS WITH ALL TUBE TYPE RADIO EQUIPMENT ONCE THE COVERS ARE REMOVED YOU ARE EXPOSED TO VOLTAGES THAT WILL KILL YOU. OBSERVE THE FREE HAND RULE. THAT IS, IF YOU ARE RIGHT HANDED KEEP YOUR LEFT HAND IN YOUR HIP POCKET. IF YOU ARE LEFT HANDED KEEP YOUR RIGHT HAND IN YOUR HIP POCKET.
  • Page 6 OSCILLATORS HETERODYNE OSCILLATOR TEST: We will start with the Heterodyne oscillator. The triode section of a 6EA8 is used for the het oscillator. There is no direct connection from the het osc to the het mixer. The designers used the interelectrode capacitance of the tube to couple the het osc signal to the mixer.
  • Page 7 Turn the function switch to LSB and allow 15 minutes warm up. Extreme precision is required if the HT-46 is going to be slaved to the SX-146. A, Connect the scope using a 10X probe, to test point A (pin 3 of T1). Key the mic and you should observe a minimum of 3.5vpp signal.
  • Page 8 Knifing should only be done by an experienced technician. Knifing done improperly will destroy C83. Extreme precision is required if the HT-46 is going to be slaved to the SX-146. This completes the OSC tests and alignments. BE AWARE: In the next section we will be aligning and tracking the mixers, driver and PA.
  • Page 9 The minimum signal level accepted is 0.85vpp. Any signal level above 4.0vpp will generate spurs in the output RF. Extreme precision is required if the HT-46 is going to be slaved to the SX-146. PROCEDURE: Pull V2, this will leave only the het mixer signal at the grid of the V4 mixer and prevent any signal from reaching the driver.

  • Page 10: Microphone Amp

    LATTICE FILTER ALIGNMENT: L1 & L2 ALIGNMENT: The input and output terminals of the lattice filter FL1 are tuned by L1 and L2. A, Tune up on the 40 meter band in the CW-TUNE mode. B, Switch to LSB mode. Using the microphone audio patch cable connect the audio oscillator to the radio. Set the audio oscillator for 20mvpp output at 1000Hz.
  • Page 11 R38 is 6.8K 1w MIXER/DRIVER TEST AND ALIGNMENT: At the time this document was written the HT-46 was 56 years old. Over the years small errors in alignment have been compounding. In this next process, we will attempt to correct these errors.

  • Page 12: Alignment Process

    ALIGNMENT PROCESS: Preset C40-C approximately ½ turn from tight. Connect a 50 ohm load to the ANTENNA jack, J4. Plug a telegraph key into the KEY jack J2. Set the MIC GAIN and CARRIER LEVEL controls to max counter clockwise. Set the METER switch to MA.
  • Page 13 If you have a large error recheck the 10 meter alignment before making any change. This completes the optimizing process. Good luck with your HT-46. ACKNOWLEDGMENT: Thanks to Mike/K5MGR for the loan of an HT-46 for test and analysis in the development of this document. 73, WDØGOF...
  • Page 15 APPENDIX 1 PA NEUTRALIZATION The following process was developed in the 1940’s. It is a bit labor intensive, but the most precise method of neutralization. In this process the high voltage and screen voltage is removed from the PA tube in such a way that the RF energy path is not broken.
  • Page 16 APPENDIX 2...

  • Page 17: Frequency Synthesis

    APPENDIX 3 HT-46 FREQUENCY SYNTHESIS BAND ALGORITHM OUTPUT 80 meters CARRIER OSC - VFO 4.O MHz to 3.5 MHz (HET – VFO) – CARRIER OSC 7.5 to 7.0 CARRIER OSC + VFO 14 to 14.5 (HET OSC + VFO) – CARRIER OSC 21 to 21.5...

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