Of course one could use a larger box or switch to tiny poly-variables that would provide sufficient space for Tuggle style antenna tuning. PS. Heres a link you may find interesting.
Heathkit Cr 1 Series Tuningcoupling WrotaryThe series tuningcoupling wrotary switch to gnd seems a bit odd and overdone,but may be OK.IHMO you should be able to swap between series or parallel tuning on the primary, but maybe its to complex or there isnt enough room (etc). Anyone else care to critique this circuit-pros AND OR cons Again, I love the ruggedness of this rig and the fact that it is BY far the best bomb shelter class xtal set Ive seen so far. I always wondered how many AM stations will still be on the air after the Soviets dropped 600 or 800 Hydrogen bombs on the lower 48 states. The CR-1 would be no exception. J.W. Miller introduced their crystal tuner, on which the CR-1 was based, as a hi-fi tuner. Hi-fi was a big deal in the 1950s, and AM broadcasters played classical and jazz music, as FM was still in its infancy. The idea was to have limited selectivity, allowing full fidelity, and no distortion-adding active circuits ahead of the detector. No image rejection necessary, either Dave made a nice clone of the Miller set using toroids: As Dave notes, The results Well it sure looks great, but it is low on performance compared to my other sets. But I wonder if the set was kept in a UNDERGROUND shelter (Faraday shield ) andor in a metal box ( an ungrounded box better ). Completely OT while Ive got you: could you check my type 30 triode post in the tube section,especially re plate voltage implications. K. My friend, who was an expert on this stuff, unfortunately passed away last year. I cant say my calculations are even close, but I believe a 5-megaton blast would release about 3 x 1015 watts of EMP. On July 8, 1962, the EMP from the high altitude (250 miles above Johnston Island) Starfish Prime test (1.4 Mt) turned off 300 streetlights in Oahu, Hawaii (740 miles away). OTOH, if you were that close, getting news from the radio would be the least of your problems 73. As KR1S has said, getting news from the radio would be the least of your problems I agree. Anyone else care to critique this circuit-pros AND OR cons Ill, take a stab at it. For starters, its a decent set but a compromised design which could be improved with the addition of variable coupling between circuits. To accomplish this Id wind two medium strand count litz coils on 2 long ferrite rods and locate them at the bottom of the case, away from the caps and on opposite sides of the box. The detector coil would be mounted at one end of the box and the antenna coil mounted on a slide to vary the coupling by translating the antenna coil along the side of the box for maxmin coupling. Id also use J.B. ceramic variable capacitors and include a tiny Ocean State type transformer for SP phones, along with an FO-215 diode. Series tuning isnt my favorite since it requires a wide range of capacitance andor inductance (preferably both) to adequately tune the MW band. However, in this size housing, retaining the switchable fixed caps to tune the band is probably the easiest option. Of course one could use a larger box or switch to tiny poly-variables that would provide sufficient space for Tuggle style antenna tuning. PS. Heres a link you may find interesting.
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