Solid state BFO in tube receiver
Noone answered this question in the Collins newsgroup, so I try it here.
I recently inspected a Collins 75S-3B receiver, and I found that someone had modified the BFO circuit with the addition of a transistor (I have not determined whether the transistor actually replaces the BFO oscillator tube, or it instead just amplifies the BFO signal).
The receiver works fine, but I cannot figure out the reason for the modification.
I would tend to believe that:
- either it is a well known modification (but for which purpose?)
- or it was just a way to circumvent the problem of a weak BFO crystal that does not start oscillating with the BFO tube alone. As BFO crystals are not easy to find, that could be a possible justification.
Thanks in advance for any suggestion.
73
Tony I0JX
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