K5AM       Boatanchor collection       Collins 51J-4 receiver • Serial number 1938. • Three original Collins mechanical filters, 1.4, 3.1, 6.0. • Matching cabinet. History. • 1957-1963. Approximate date of manufacture. • Manufacturer: Collins Radio Company, Cedar Rapids, Iowa. • Original cost: $1200.00 .. $10,300.00 in 2016 dollars. Cabinet was an optional extra. Three mechanical filters were optional extras. • December, 1996. Purchased by K5AM. • January, 1997. Complete check-out, alignment, and lube. • 1997-2016. Installed on boatanchor bench in shack. Modification. • Replaced 2 conductor line cord by IEC AC receptacle, 3c, including ground. (Line cord included.) This is safer, and an excellent improvement, not to have a dangling line cord to deal with when moving the receiver. Test results; November, 2016. HP 8640B, HP 3400A(true RMS). • Sensitivity test A, each band. Results well within specifications, without taking time to measure exact MDS on each of 30 bands. Specifications, for 10 dB S+N/N, conditions not stated: Band 1, 15 µV; Bands 2-30, 5 µV.       Measurements, SSB/CW, 1 kc filter:            Band 1 (0.5-1.5 mc): MDS -121 dBm (0.2 µV).            Bands 2-30: better than MDS -130 dBm on each band.       Results: excellent. • Sensitivity test B, exact measurement for each filter, SSB/CW. Frequency(mc), Bandwidth(kc), MDS(dBm).      28.050, 1, -133.      28.050, 3, -131.      28.050, 6, -128. Results: excellent. • Sensitivity test C, AM. Test conditions: 3880 kc, BW 6 kc, 60% modulation, 10 dB S+N/N.      Measurements:           400 cps, 0.45 µV           1000 cps, 0.50 µV      Results: excellent. • AM THD test; HP 8640B, HP 334A. Specs: less than 10% distortion at 0.5 watt output (conditions not specified). Test conditions: 0.5 watt into 8 ohms, 10 mc, BW 6 kc, 50 µV, 60% modulation.      Measurements:           400 cps, 5.4%           1000 cps, 4.2%      Results: excellent. • By-ear test, in speaker. Sounds great, SSB, CW, AM. Summary. An exceptionally fine specimen of a classic receiver. Mark, K5AM. www.zianet.com/k5am   home page     boatanchor page