• Country
• United States of America (USA)

• Manufacturer / Brand
• National Company; Cambridge & Malden (MA)

• Year
• 1944/1945

• Category
• Commercial Receiver (may include amateur bands)

• Radiomuseum.org ID
• 49575

• • alternative name: National Toy Co.
  • Brand: Thrillbox

Click on the schematic thumbnail to request the schematic as a free document.

• Number of Tubes
• 9

• Valves / Tubes
• 6D6 6D6 6C6 6C6 6D6 6D6 6B7 42 6C6

• Main principle
• Superhet with RF-stage; ZF/IF 456 kHz; 2 AF stage(s)

• Tuned circuits
• 11 AM circuit(s)

• Wave bands
• Broadcast, Long Wave and more than two Short Wave bands.

• Power type and voltage
• Powered by external power supply or a main unit. / AC 6.3 & DC 240 Volt

• Loudspeaker
• - This model requires external speaker(s).

• Power out
• 1.5 W (unknown quality)

• Material
• Metal case

• from Radiomuseum.org
• Model: HRO-M - National Company; Cambridge &

• Shape
• Boatanchor (heavy military or commercial set >20 kg).

• Dimensions (WHD)
• 440 x 220 x 300 mm / 17.3 x 8.7 x 11.8 inch

• Notes

• Coverage: 50 kHz - 30 MHz (9 ganged coil sets 50-100 / 100-200 / 180-430 / 480-960 / 900-2050 kHz / 1,7-4 / 3,5-7,3 / 7-14,4 / 14-30 MHz, no bandspread in these coils available).

  Modes AM / CW/SSB (BFO).

  The 0 – 500 epicyclic readout dial allows for continuous analog tuning while digitally indicating incremental progress over a range of ten full turns of the large tuning knob that tunes with velvet smoothness. Ten times the circumference of the dial is nearly 4 meters on a normal dial scale, which delivers great frequency resolution. The dial is not calibrated to directly indicate a frequency but a frequency calibration chart is necessary to determine the correct operation frequency.

  HRO model Var. 5 with all wave coil sets without bandspread (only one printed calibration chart on coil sets), knobs with metal skirts (selectivity control in right upper corner also with metal skirt), black laquered micrometer dial and round S-meter.

  External "dog house" type power supply : PSU 697 (filaments 6.3 V AC, B+ 240 V DC) used as standard.

• Net weight (2.2 lb = 1 kg)
• 14.5 kg / 31 lb 15 oz (31.938 lb)

• External source of data
• Ernst Erb

• Source of data
• Communications Receivers

• Circuit diagram reference
• Rider's Perpetual, Volume 17 = 1948 and before

• Other Models

• Here you find 446 models, 285 with images and 189 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
  All listed radios etc. from National Company; Cambridge & Malden (MA)