Saturday, June 27, 2009

New airband input filter

New problems....

Built the filter in this schematic:

"My" filter stops after C8 and without R6 and C9, basically everything that is connected until the 2SC transistor.

After making the coils and soldering everything.... power to the circuit. Input connected to my airband antenna and output (right end of C8) connected to my TM-D700.... it went from an amplifier to and attenuator... before the filter insertion I had S2 on a continuous transmission frequency, now I barely can hear the transmission.....could be the coils... made a new set and solder them.... a litle beter but no increase in signal, only S0! Tryed some varicaps in paralel with the 82p capacitors some triming and nothing.... could be the transistor..but it's brand new and was tested in my multimeter....
Next time i will probably test every tuned circuit agains the antenna analyser, that way will have a beter idea of how far I am from expected ressonance frequency.

RF is fun.... the emiter terminal of the 2sc transistor is about 1cm long, is connected to the ground but if I placed an trimer capacitor bettwen ground and 3mm of the lenght of the terminal (from ground) there is some notiçable change in sound from the receiver......oh well, giving up for the weekend...probably not.

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