Re: RCA AR88D Comms Receiver.
With the coil in circuit, I connected the gen across the ends via a 150 ohm res. With the scale set to 21.9 the coil tuned to peak, the amplitude using the ferrite rod, 5", is double that using the dust iron core.
Using the ferrite rod I can track the osc from the HF end to the LF end at 455 + the scale reading. The coil and trimmer tuning perfect. To achieve this I had to replace the 82pf grid coupling with a 5000pf disc.
Somewhere I have a loss that is damping the osc at LF on ranges 4 5 & 6.
It's looking me in the face and I can't see it.
Interestingly, Alan's morton Cheyney coil formers are all the same material.
My new valve bases are on their way to me, as are a set of coils on a scrap sig gen chassis that look good.
John
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