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Title: Running audio to class AB1 modulator Post by: WB6VHE on August 31, 2005, 12:17:06 PM Greetings to All:
I am planning to use the output of the modulator in my B&W 5100B to drive a large class AB1 modulator. My question is this: should I dump the power into a 500 ohm resistor located at the B&W and then run the audio voltage across the shack to the big modulator, or should I locate the 500 ohm load at the big modulator? What is the best cable to use for this? Thanks for your support! 73, Title: Re: Running audio to class AB1 modulator Post by: WA1HZK on September 01, 2005, 06:12:48 PM Does this rigs mod iron have a CT secondary? Rigs like the Ranger & Valiant have a tap so the Mod. bias can be fed to your AB1 stage. How are you going to get the audio power & bias to your mod tubes? What are you going to use for Glass Fets in the big modulator?
Keith WA1HZK Title: Re: Running audio to class AB1 modulator Post by: Bacon, WA3WDR on September 01, 2005, 08:32:28 PM Assuming tap(s) on the mod secondary in the 5100, I would put the resistor (500 ohms?) in the 5100, so in case the wire gets disconnected unexpectedly, the amp has a load. Remember that you could dissipate a lot of power in the resistor, so it needs room and power capacity. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
Maybe you have a 500 ohm link between the output xfrmr in the 5100 and the big modulator? Does the 5100 have a 500 ohm tap? That would involve another piece of iron in the path, but it would be safer for the big modulator in case a cable got pulled or broken by mistake. I don't think you want its grids floating with B+ on, and I don't think you want the 5100 modulator to have no load. If the big modulator is AB1, you don't need much power, you just need voltage swing. All in all, it might be easier to build up a dedicated driver amp for it. A small hi-fi amp with a backward-connected audio output transformer to the grids? |