Let's see, I just put in a few hours in a major contest (the IARU HF Championship) and Field Day was a couple of weeks ago. Why would I be thinking about filters? Radio would be a lot more difficult, maybe impossible, without filters - they're everywhere, including the theme of this week's crossword!

Across

1. Work all fifty to get this award
4. Parallel tuned circuit
8. Stop
10. Wheel used for lifting
11. Number of filter sections
12. Another term for broadcast band (abbr.)
13. Filter made from inductors & capacitors (abbr.)
14. Capacitor-and-clock filter
19. From (CW abbr.)
20. Correct
21. Variations in a filter's passband
23. The type of -pass for removing low frequencies
25. No good (abbr.)
26. Rotate opposite to 58 Across
27. Medical technique using RF to form pictures of the body
28. British term for high voltage (abbr.)
29. A filter with a large bandwidth
30. What 23 Across removes from a television
31. Change or correct
33. KP4's section abbreviation
34. Frequencies below RF (abbr.)
36. Adjust for maximum output
37. A filter that dissipates a lot of signal
39. Can-and-coil filter
43. Transfer of signal from filter section to section
46. Between a second and a microsecond (abbr.)
47. CW chuckle
48. You're (CW abbr.)
49. Light (abbr.)
50. Filter that requires power
52. Twin filter circuit
54. Tool for holding
56. Rotate opposite to 26 Across
57. Attach a load
58. Old abbreviation for a unit of frequency

Down

1. CW speed (abbr.)
2. Chemical symbol for element used to plate connector surfaces
3. Reduce speed
4. Measure to evaluate performance
5. RTTY tuning signal
6. The rating of a filter's ability to handle large signals
7. Document interchange format (abbr.)
8. Filters are used to reduce this (Q-signal)
9. Not used or busy
12. Unit of inductance common in audio filters
14. Term for filter's shape
15. Suffix meaning "like"
16. The frequency of a narrow filter's maximum response
17. Filtering with software
18. Counterpart to a filter's lower 3 dB frequency
19. Logarithmic ratio used to evaluate filters
20. Discoverer of fundamental electrical law
22. Small adjustments
24. A formula ..... an answer
29. State of a famous college fight song (postal code)
32. Treatment filters deserve
33. Host country for WRTC-2006 (prefix)
35. Repair
36. Filter that works without power
38. Transmission line filter
40. Long period of time
41. Filter that passes everything
42. Confirm presence or operation
43. Team that operates a ship or craft
44. One component of a list
45. Amplification
46. Empty (abbr.)
48. World time (abbr.)
51. Neighbor possession to 33 Across
53. Semiconductor similar to Silicon (chemical symbol)
55. Local ARES leader (abbr.)