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Title: Controlled carrier and audio mod for the Heathkit DX-40 Post by: n1uvi on January 26, 2012, 02:54:35 PM I recently began restoring a Heathkit DX-40 and put it back on the air, a very fun project indeed. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
Details are available on my QRZ page, please feel free to check it out. Anyhow, not finding any reference to any DX-40 mods, after trying several of the DX-60 mods on the DX-40 and not having any joy I managed to come up with a mod that works quite well on the DX-40. Much like the DX-60 mods that are out there, however this mod uses a 6DR7 tube in place of the 6DE7 modulator. The 6DR7 is a dissimilar double triode like the 6DE7, the second triode is identical but the first triode has a much higher amplification factor than the 6DE7. This mod provides 100% modulation with very good audio frequency response. The resting carrier is 12 to 15 watts, and carrier shift is eliminated. The negative 120 volt DC supply is obtained by using a 6.3 volt power transformer in reverse, that is as a step-up transformer, using the filament voltage available in the DX-40 |