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Radio Wrangler · 17th Dec 2019, 7:43 pm

Interesting! and good work.

I assume the AR88 slug is a grade of carbonyl iron. It relies on oxide coating the iron particles to prevent eddy currents reducing the Q. I wonder if there's been some degradation? Modern material may have better binder agents.

Your results show the Q has fallen significantly and it looks enough to stop the LO running. Probably the same effects are spoiling the sharpness and gain of the RF stages, but that won't be as dramatic as no oscillation.

I wonder if there are some possible slugs in the Micrometals catalogue which could be glued onto the brass rod to replace the originals?

David

17th Dec 2019, 7:43 pm	#78
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: RCA AR88D Comms Receiver. Interesting! and good work. I assume the AR88 slug is a grade of carbonyl iron. It relies on oxide coating the iron particles to prevent eddy currents reducing the Q. I wonder if there's been some degradation? Modern material may have better binder agents. Your results show the Q has fallen significantly and it looks enough to stop the LO running. Probably the same effects are spoiling the sharpness and gain of the RF stages, but that won't be as dramatic as no oscillation. I wonder if there are some possible slugs in the Micrometals catalogue which could be glued onto the brass rod to replace the originals? David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done