During the 2001 AWA OT CW Contest Niel, W0VLZ, used a homebrew three tube superhet (plus external power supply and AF amp/speaker) with a 6L6 transmitter running approximately 7 watts. New York, Indianna, Illinois, Louisanna, Oklahoma, Georgia and Texas were all worked on 80 meters from southeast Minnesota using just a 100' end fed wire antenna.
The receiver is an improved version of the 1941 Beginner's Receiver. A major improvement was the addition of a crystal filter. It gives this simple receiver single signal selectivity. At 6dB down, the bandwidth is only 250Hz. Inserting the crystal into the middle of the regenerative IF stage allowed regeneration to make up for crystal insertion loss without adding an extra tube. Also modified from the original was changing the regenerative detector from 1/2 of a 6C8 to a 6J7, adding better bandspread, capacitively coupled headphone output and a front panel BFO adjustment. The attenuator on the antenna input was added following the contest after experiencing problems from strong signals overloading the receiver.
Left to right, top: Input tuning, Bandspread, Bandset
Left to Right, bottom: Ant. Attenuator, Regeneration, BFO Tuning, BFO On/Off
Left to right, Back: 6C8G, AF Choke, 6J7
Left to right, Middle: Osc Coil, 6K8, Input Coil
Left to Right, Front: Bandset Cap, Bandspread Cap, Crystal, Input Cap
Bottom View
| C1, C3 | 100 uufd. variable (Hammarlund SM-100) |
| C2 | .1 ufd. |
| C4 | 15 uufd. variable (Hammarlund SM-15) |
| C5 | 220 uufd. silvered mica + 3-30 uufd trimmer |
| C6, C9 | 0.01 ufd. |
| C7 | 0.005 ufd. mica |
| C8, C10 | 100 uufd. mica |
| C11 | 200 pf. (approximately) to set center BFO frequency |
| C12 | 10-90pf. (approximately) trimmer/variable |
| C13 | 10pf. (approximately) to set BFO range |
| C14 | 1.0 ufd |
| C15, C16 | 100 uufd. mica |
| R1 | 47K ohms, 1/2 watt |
| R2 | 47K, 1/2 watt |
| R3 | 1M, 1/2 watt |
| R4 | 10K potentiometer |
| R5 | 10K , 1 watt |
| R6 | 470K 1/2 watt |
| R7 | 33K 1/2 watt |
| R8 | 10K potentiometer |
| RFC | 2.5 mh. r.f. choke |
| L1 | Audio transformer, interstage type, 3:1 ratio, with windings in series |
| L1-L4 | See 1941 Beginner's Receiver coil description/table |
| L5 | 55 turns No. 30 d.s.c., close-wound on 3/4 inch diameter form (National PRF-2); inductance 40 microhenrys |
| L6 | 18 turns No. 30 d.s.c., close-wound on ground end of L5 form |
| X1 | Crystal at IF frequency |
| S | S.p.s.t. toggle switch |
| R3 | 47K ohms, 1/2 watt |
| L7 | 55 turns No. 30 d.s.c., close-wound on 3/4 inch diameter form (National PRF-2) |
| L8 | 18 turns No. 30 d.s.c., close-wound on ground end of L7 form |
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