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HRO Var.4 (according to Moore)

HRO; National Company; (ID = 1130554) Commercial Re
HRO; National Company; (ID = 1166033) Commercial Re
HRO; National Company; (ID = 471878) Commercial Re HRO; National Company; (ID = 471879) Commercial Re
HRO; National Company; (ID = 471880) Commercial Re HRO; National Company; (ID = 1132755) Commercial Re
HRO; National Company; (ID = 1132757) Commercial Re HRO; National Company; (ID = 1132758) Commercial Re
HRO; National Company; (ID = 1132759) Commercial Re HRO; National Company; (ID = 1132760) Commercial Re
HRO; National Company; (ID = 1165928) Commercial Re HRO; National Company; (ID = 1764494) Commercial Re
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HRO; National Company; (ID = 471878) Commercial Re
National Company;: HRO [Commercial Re] ID = 471878 933x571
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For model HRO Var.4 (according to Moore), National Company; Cambridge & Malden (MA):
Var. 4 table model, with black bakelite dial, toggle switch for S-meter, bar type selectivity control. Table model without engraved markings for AVC and B .
Country:  United States of America (USA)
Manufacturer / Brand:  National Company; Cambridge & Malden (MA)
alternative name
National Toy Co.
Year: 1938–1943 ? Category: Commercial Receiver (may include amateur bands)
Valves / Tubes 9: 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)
from Model: HRO [Var.4 ] - National Company; Cambridge &
Material Metal case
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

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

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

All listed radios etc. from National Company; Cambridge & Malden (MA)
Here you find 430 models, 275 with images and 162 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.