Sommerkamp FR-50B

by Cor van Rij

The Sommerkamp FR-50B is a Double Conversion Superheterodyne General Amateur Band Communivations Receiver employing a variable oscillator for the first mixer stage, and a crystal controlled oscillator for the second mixer stage. 8 tubes. For use in conjunction with the FL-50B Ranges: 3.5-3.8 MHz, 7-7.5MHz, 14-14.5MHz, 21-21.5MHz, 28-29.2MHz.

Type:HF receiver
Frequency range: 10-80 m
Sensitivity:0.5 uV (10 dB S/N)
Selectivity:5 KHz (-50 dB), 1.8 KHz (-6 dB)
Image rejection:>50 dB
Audio:1.5 W 4/600 Ohm
IF:5.173,9; 455 kHz
Voltages:110-235 VAC, 50/60 Hz
Current drain: ?
Impedance:50-75 ohms
Dimensions (W*H*D):13 x 6 x 10.25"
Weight:17.5 lbs
Manufactured:Japan, 196x-19xx
Other:8 tubes

I bought this receiver in May 2004. It was and it is not working. In the beginning I couldn't figure out why for all seemed to be OK. After some begging and pleading the lady from Yasy was so kind to make a photocopy of the circuit and send to my land-mail. After this I spend a short-time to come to the conclusion what the problem was. The crystal (5628.9 kHz) that is used to convert from the first IF (5.173,9 kHz) to the second IF (455 kHz) was missing. I am now looking for a replacement.

Then other day I got a request from a fellow to send me the schematic. After some more requests I've decided to put it online. You can download it in three seperate parts or in one large file.

In three seperate parts: Part1 (154 kB); Part2 (156 kB); Part3 (148 kB).

Or in one large file (633kB).