Hallicrafters Alignment Pages

If your radio doesn't pick up at least one station, you should go to the CPR page. You are not ready for this.

As of 24 July 2026, some parts of the procedures are complete and some are still under development.
Please explore and comment but don't get upset if you run across something stupid or just plain wrong1.
Please see footnotes for status comments.

This is the top-level page for everything alignment related.
The pages are in multiple levels and categorized by functional blocks:

  1. Measure - A procedure or page to determine a value
  2. Test - A procedure or page to verify that something is working correctly
  3. Adjust - A procedure or page check an operation and what to do if it isn't right
  4. Theory - Notes on how it is supposed to work

Early Radios (SX-28)

Measure Crystal Frequency

The crystal is supposed to resonante at 455 KHz but like all components, it varies.
Knowing the exact resonant frequency of your crystal is critical to making the radio work as it's supposed to.

Follow the instructions here2.

Adjust the IF chain

The IF chain, which consists of transformers T1, T2 & T3 and tubes V5 and V6, has four inputs:
    The cathode return voltage via R16 and R21.
    The screen voltage via R17 and R22.
    B+ via V18, R23, and R30.
    The output of the mixer V3 pin 3 via T1.

   Adjust2    Theory6

Adjust the Local Oscillator

The only inputs to the oscillator are the tuning capacitors and the band switch position.
There are two parts to this section: the 6 feedback capacitors C7‐C12 and the 12 frequency adjustments.

Feedback
   Adjust5    Theory6
Frequency

The adjust procedure is a cgi script that takes the crystal frequency determined above as an input and adjusts all the expected values for the different bands accordingly.

The IF chain must be adjusted to the same frequency as the crystal. If the crystal is way off frequency, this isn't going to work.

   Adjust3    Theory6

Test the AVC2

The AVC is used in the procedures below as a measuring device. It uses two of the fifteen tubes in the radio. It's probably a good idea to see if it works properly.

   Test

Mixer

   Adjust4    Theory4

2nd RF

   Adjust4    Theory4

1st RF

There are no knobs to twiddle in the 1st RF section.

   Theory

BFO

The BFO is independant of everything except power.

   Adjust    Theory

Late Radios (SX-28A)

This section won't be started until the early radio section above is working. There's a lot of cut-n-paste and hopefully, it only gets done once.

Footnotes:

  1. The reason these pages are even made available is because people other than myself are trying to help figure out what's right
  2. Works
  3. Has worked successfully on the lower frequency bands. No known issues with the upper bands
  4. Worked OK in experiments but the pages have not been properly put together yet. Not expected to be complicated
  5. In progress
  6. OK for now

Page: /Alignment/Alignment_root.shtml

Last modified: Friday, 24 Jul 2026