Reference original thread:
http://amfone.net/Amforum/index.php?topic=44455.0;topicseenOlder thread. Replace C78, C82 and C83 .001uF bad sounding ceramic capacitors with polypropylene .02uF @ 450V. One cap is located at the front panel mic jack, others at the tube socket. Remove C81 cathode capacitor on first 12AX7 section for better high frequency audio. Change 12AX7 first section cathode resistor R57 to 3.6meg ohm for an unamplified Astatic D-104 as the mic will not produce 100 Hz into a lower value resistor. You will now have low 100Hz transmit audio vs 400Hz from factory, but is limited to about 2.5 kHz high frequency. The HT-44 has a low pass filter installed for SSB and stays in circuit on AM. To achieve about 6 kHz audio remove the low pass filter. It is located by the power socket at the rear panel and has an inductor with a .1uF capacitor connected on each side. Some have a .22uF or .47uF and .1uF cap installed. Remove C108 and C109. Remove inductor L101 and replace with a wire. The transmitter now transmits 100 Hz to 6 kHz audio. It would be wide on SSB. One could place a DPDT switch on rear panel with just one .47uF cap replacing the two .1uF and with the switch removing inductor shorting wire and adding the .47uF cap to select SSB or AM and providing about 3kHz audio in SSB.
The HT-44 transmits AM in DSB, not just one sideband. The HT-44 also transmits a healthy 25-30 watts AM carrier. IMO the HT-44 needs nothing else and is about as good as it gets for a vintage SSB/AM tube transmitter. Bama does have the schematic in PDF now.
