• Country
• United States of America (USA)

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

• Year
• 1938–1943 ?

• Category
• Commercial Receiver (may include amateur bands)

• Radiomuseum.org ID
• 86415

• • 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 180-240 Volt

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

• Power out
• 1.5 W (unknown quality)

• Material
• Metal case

• from Radiomuseum.org
• Model: HRO [Var.4 ] - 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 :

  1.7 – 30 MHz ( 4 standard ganged coil sets for 1.7 – 4, 3.5 – 7.3, 7 – 14.4, 14 – 30 MHz included, 2 coil sets for broadcast immediately available at extra cost, 7 more coil sets Additional coils (50-100, 100-200, 180-430, 480-960 and 900-2050 kHz) sold later including long waves and up to VHF ( total spectrum covered from 50 kHz to 54 MHz ).

  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.

  Bar knobs with metal skirts, S-meter toggle switch, red pilot light left of selectivity control, black bakelite epicyclic dial, usually rectangular IF filter shielding cans.

  External "dog house" type power supply : PSU 697 (filaments 6.3 V AC, B+ 240 V DC) für best performance when mains operated,  5886 (filaments 6,3 V AC, B+ 180 V DC).

  The HRO-B (battery model) is identical, adjusted for maximum performance with a plate voltage (B+) of 180 V. 6,3 Volt D.C. operation with 686S table model of battery power supply with vibrator.

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

• Price in first year of sale
• 329.00 $

• Source of data
• Communications Receivers

• Mentioned in
• - - Manufacturers Literature

• Literature/Schematics (1)
• Electronics Australia November 1990, Page 110

• Author
• Model page created by Martin Bösch. See "Data change" for further contributors.

• 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)