Very nice Charles! The BC-348 and BC-455 radios I transistorized based on your manuals function better then what I had expected. Also, my Cessna has a NDB (non-directional beacon) receiver that tunes 200 Khz to 1.6 Mhz. There are no longer any more NDB transmitters at our airports or harbors but I least I can home-in on AM broadcast stations.
There is a cb? radio on ebay right now with like 20 or 30 tubes, has the microphone and everything, but the seller says it has a crystal oscillator on 49.66 mc. Any idea what this would be? I'm pretty sure that's not in the cb band. Did it used to be? It is made by link. I thought about getting it but it would probably arrive in a thousand pieces.
It is likely an early police radio. Fred Link won a contract with the CT state police in 1940 before Motorola became the dominant manufacturer of public service radios. While it is rare, I doubt it is worth a lot since it is in rough shape and there aren't too many collectors for that type of radio.
Here's a list of NDB's - they are very apt to be abandoned rather than repaired if they give trouble but many are still working: www.dxinfocentre.com/ndb.htm Very interesting design and video!
Thanks for that link. It is perfect for what I need to identify those mystery signals on the BC453. It took 16 pages printed on both sides but it was worth it. The 453 turned out much better than expected but I had to fight with it all the way because of the low frequency IF transformers. The converted IF circuits in the 454, 455 will work in the 453 but with much reduced signal because the chokes would need to be much larger to accommodate the lower frequency. In that case you might as well just use the transformer itself with only some resistance added to the drain. My final method worked just fine and I don't have to use any chokes at all. In the 454, 455 radios the chokes actually work best. It took a lot of experimentation to find that out. Going from tubes to transistors presented a number of problems but the solutions I used in all my conversions actually worked OK. A lot of people have tried conversions over the years but got stuck on how to interface the drain or collector to the coil it served. The impedance difference increases drastically as the frequency increases and has to be addressed correctly or else signal transfer is compromised severely. Now we know.
