[Hallicrafters] Chirping HT-40 Quiery

[Wj5mh at aol.com]

In a message dated 6/22/2003 6:00:35 PM Eastern Standard Time, dfischer at usol.com writes:

> Why does my HT-40 make a chirping sound on CW?

There were a few changes between the HT-40 and the HT-40 Mark II (the one with the clear neon lamp indicator).  The HT-40 Mk II oscillator cathode is always grounded when a jumper is across pins 3 & 4, or when an auxiliary switch shorts these two contacts.  Pins 3 and 4 MUST be short together, either way.  The key only keys the buffer and final.  In addition, during CW, the modulator is used as a series voltage regulator.

I suspect these changes were made to clean the keying characteristics of the radio.

I have had some newer crystals react strangely.  (A slight jump in frequency.)  Placing a 100 ohm (I think that's the value I used) in series with the crystal fixed the problem.  I suspect the feedback was a bit much for the newer crystals.  The old FT-243's still work, too.

Joe