|
Title: Hallicrafters HT-40 Post by: DMOD on July 22, 2013, 06:43:11 PM Updated: 9/2021 With Text, Schematics, and Theory of Operation:
Phil - AC0OB Title: Re: Hallicrafters HT-40 Post by: KK4RF on October 09, 2013, 05:28:55 PM Phil,
Thanks for the message on the HT-40. I'm running mine stock and for the most part have been getting fairly good audio reports. Your mods do look pretty interesting, however, and I may look into them again at a later date. Working on another ScreenModulated/controlled Carrier rig, the KnightKit T150-A. It does not get very good audio reports, however. I plan to read up on as many mods for that radio as possible.I'd like it to sound as good as the HT-40. Thanks again, Phil.---Marty, KK4RF--- Title: Re: Hallicrafters HT-40 Post by: DMOD on October 22, 2013, 12:14:12 PM Quote Thanks for the message on the HT-40. I'm running mine stock and for the most part have been getting fairly good audio reports. Your mods do look pretty interesting, however, and I may look into them again at a later date. I am glad to hear your audio is acceptable, but I would bet if you looked at the modulation with a scope, it probably has no more than 75% modulation unless it has been modified. And having the Red Led modulation indicator is a lot of fun. :D If you are working on the T-150, check out these mods here as well: http://amfone.net/Amforum/index.php?topic=34680.0 I have another update coming with actual operating parameters noted during operation. Phil - AC0OB Title: Re: Hallicrafters HT-40 Post by: n4joy on February 02, 2014, 10:11:43 AM This is a good write-up. I firmly believe the HT-40 is perhaps one of the best carrier controlled transmitters for AM beginners. I use mine on 10 meters and always receive good audio reports with its stock configuration.
Title: Re: Hallicrafters HT-40 Post by: DMOD on February 02, 2014, 05:06:47 PM Thanks. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
I also get good audio reports as well. With a few component changes and additions the audio and modulation can be improved. The R-C feedback circuit from the Modulator cathode back to the speech amp really helps to reduce distortion. And the 6DQ5 final is both low cost ($7.50 to $10.00) each and pretty darn rugged. Phil - AC0OB |