Total posts : 45366
I turned on my th5 by mistake with the antenna disconnected for about 10 minutes. The out put transistors TR306 printed on the circuit board is a NPN C547B and TR305 is a PNP C557B. They are complimentary or matched output transistors running push pull. I had no output and ordered them from Mouser Electronics. They where cheap at about 2.09 for 10 of them and about 4.99 for shipping LOL. There is a patent schematic of the Th 5 but hardly readable as they really dont want people to know much about it. I want to design a output lowpass filter for it like the one on the ramsey am25 transmitter and take a better look at the final output and make a lc network tank circuit to match a 1/2 wave antenna to it better with out that expensive whip tuner they sell. Also this transmitter needs an adjustable input level control badly like on the ramsey am25. Anyway we now have full output again judge by the recieving range i am getting while driving around and listening. With a 1/2 wave inverted vee at 67 feet was able to cover a 3 plus mile range beaming in 2 directions giving a S4 signal at the fringe. Not bad for a untuned output. The auto antenna tune looks like one is for the high end of the band and the other for the low end. Could have some fun with that and replace it with a manual tapped tank circuit and tuning capacitor. Just some ideas.
