RA37A LF Converter

November 2015: The RA37A preceded the RA137A just as the RA17 was the precursor to the RA17L. The differences between the two are electrical as well as physical. The RA37A is only 1U high as opposed to the 137A which is 2U high. Just as the preselector in the RA17 is simpler than that in the 17L, the preslector in the 37A is far simpler than that in the 137A.

RA37A preselector

RA137A preselector

As well as the obviously far simpler circuitry and the lack of a tuning scale, the RA37A preselector ranges differ significantly thus …


RA37A                                                                                  RA137A

1. Wideband                                                                          1. Wideband

2. 12KHz - 37KHz                                                                  2. Wideband with filter

3. 37KHz - 110KHz                                                                3. 10KHz - 20KHz

4. 110KHz - 330KHz                                                              4. 20KHz - 40KHz

5. 330KHz - 980KHz                                                              5. 40KHz - 90KHz                                                                                                6. 90KHz - 210KHz

                                                                                               7. 210KHz - 300KHz

                                                                                               8. 300KHz - 980KHz


As well as have only 5 ranges as opposed to the 137A’s 8, the RA37A also tunes ‘backwards’ … i.e. turning the preselector knob clockwise actually decreases the tuned frequency.    

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Mail: ian@chavfreezone.me.uk?subject=RA37A LF Converter