HRO Receiver Models

HRO Receiver Models

While the National HRO is easily recognized by a common style, the models are also easily confused. There are many cosmetic and design differences between the various models of the HRO. The National Company was continually refining the design. Besides the common "street" versions, many variations also exist only to fill specific commercial or military requirements. This will be a summary of the more common versions of the HRO.

HRO Receiver Tube Lineups

  Sr Sr/Jr/MRAS HRO-5 HRO-5AHRO-7 HRO-50 HRO-50-1 HRO-60
  2.5V 6.3V
1st RF 58 6D6 6D6 6K7 6K7 6K7 6BA6 6BA6 6BA6
2nd RF 58 6D6 6D6 6K7 6K7 6K7 6BA6 6BA6 6BA6
Mixer 57 6C6 6C6 6J7 6J7 6J7 6BE6 6BE6 6BE6
HF Osc 57 6C6 6C6 6J7 6J7 6C4 6C4 6C4 6C4
2nd HF Conv                 6BE6


1st IF	       58   6D6   6D6	6K7   6K7    6K7    6K7       6K7	6SG7
2nd IF	       58   6D6   6D6	6K7   6K7    6K7    6K7       6SG7	6SG7
3rd IF							      6SG7	6SG7
Det,AVC,(AF)   2B7  6B7   6F8G	6SQ7  6H6    6H6    6H6       6H6	6H6
BFO	       57   6C6   6C6	6J7   6J7    6J7    6J7       6J7	6SJ7
AF Output      2A5  42	  6V6G	6V6G  6V6GT  6V6GT  6V6GT(2)  6V6GT(2)	6V6GT(2)
AF				      6J5    6SJ7   6SJ7      6SJ7	6SJ7
Noise Limiter			      6H6    6H6    6H6       6H6	6H6
AF Inv/S-Mtr					    6SN7GT    6SN7GT	6SN7GT
Volt Reg				     0A2    0B2       0B2	0B2
Rectifier					    5V4G      5V4G	5V4G
Current Reg								4H-4C

HRO Receiver Designs

HRO Sr The HRO Senior series (sometimes known as the HRO-series) embodies an S-Meter, crystal filter circuit with phasing and selectivity controls, and coils sets A, B, C and D which have a bandspread feature. It was availablewith either 2.5 or 6.3 volt tubes.

HRO-C HRO Sr combined with SPC unit (power supply, coil container and loud speaker) in a MRR table rack (24.5" high).

HRO Jr The HRO-Junior series is similar to the HRO-series but does not have the S-Meter or the crystal filter and associated controls. It was shipped with only one general coverage coil set. The Jr was available with either 2.5 or 6.3 volt tubes. (This model must not be confused with the Navy/WWII RAS receiver below.)

RAS The RAS was designed/built for the Navy beginning in 1939 and through WWII. It is basically a HRO Jr with changes required by the Navy. The most significant difference is the 175KC IF that allowed the receiver to be used on 500KC. All of the RAS coil sets are general coverage only.

HRO-M Basically the same as the HRO Sr series except the standard coils were general coverage only. It used glass tubes and a plug-in crystal.

HRO-MX The same as the HRO-M except the crystal is inside the crystal unit housing.

HRO-M-RR The HRO-M supplied for mounting in a relay rack.

HRO-M-TM The HRO-M equipped with a cabinet for tabletop use.

HRO-5 The HRO-5 series is similar to the MX series accept it used metal tubes.

HRO-5T This is the same as the HRO-5 and is equipped with a cabinet for tabletop use.

HRO-5R This is the same as the HRO-5 but is supplied for rack mounting.

R-140/FSM-1 This is the same as the HRO-5R or HRO-MX (rack mount) except for the rewiring of the breakin switch and speaker connections.

HRO-5A1 The HRO-5A1 series is similar to the HRO-5 series accept an extra stage of audio and a noise limiter were added.

HRO-5TA1 The HRO-5A1 supplied with a cabinet for tabletop use.

HRO-7 This is an HRO-5A1 with improved HF osc and regulation.

HRO-7T This is the same as the HRO-7 and is equipped with a cabinet for tabletop use.

HRO-7R This is the same as the HRO-7 but is supplied for rack mounting.

HRO-50 Added push-pull audio output, internal P/S and direct freq readout.

HRO-50-1 Added 3rd IF stage

HRO-60 Added dual conversion for bands A and B (20 mtrs and above)

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