• Country
• United States of America (USA)

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

• Year
• 1936–1943 ?

• Category
• Amateur-Receiver (amateur bands, may include broadcast bands)

• Radiomuseum.org ID
• 86424

• • 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
• 58 or 6D6 58 or 6D6 57 or 6C6 58 or 6D6 58 or 6D6 2B7 or 6B7 2A5 or 42 57 or 6C6 57 or 6C6

• Main principle
• Superheterodyne (common); ZF/IF 456 kHz; 2 AF stage(s)

• Tuned circuits
• 11 AM circuit(s)

• Wave bands
• Broadcast plus more than 2 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 Junior HRO-JR - 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

• Low budget version of the HRO Senior withoud bandspread, only one calibration chart in the center of coil set, no S meter, no crystal filter or selectivity control.

  After WWII a kit was available to install an S meter and to upgrade the set to a HRO Senior, it's coil sets were compatible.

  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 sold later including long waves ( 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, so more used as logging dial, the frequency is determined used printed calibration charts on coil sets.

  External "dog house" power supplies used : 5886 (B+ 180V), PSU 697 (B+ 240V) or 5897 (filaments 2,5V AC, B+ 230V DC) for sets equipped with battery valves set.

• Net weight (2.2 lb = 1 kg)
• 12.5 kg / 27 lb 8.5 oz (27.533 lb)

• Price in first year of sale
• 99.00 USD

• Source of data
• Communications Receivers

• Mentioned in
• Shortwave Receivers - Past & Present (3rd ed.)

• Literature/Schematics (1)
• Short Wave Craft March 1936 page 666.

• 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)