Rahul
Has anybody drawn up an updated schematic to show the changes from Farhan's original circuit? If available, this might help others upgrade their older BITX20 units, and could help new builders focus on the newer design.
Thanks,
Arv K7HKL
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On Fri, 22 Apr 2005 22:08:57 -0700 (PDT), Rahul Srivastava <vu3wjm@...> wrote:
Hi!
Many BITX are on air on 20 now in VU. In my city we have made 4 nos. 2 sets were made using the Ver 2 PCB I posted in group earlier.
We faced a minor problem as the local BC547s were not giving sufficient gain on 20 so we modified the IF amp Q3 stage by adding one more transistor to make it a shunt feedback amp. Now the rig is real hot and audio level more than enough even on inefficient antennas.
Incorporating these changes I have made Ver3 PCB. The front end device Q1 is 2SC2570A a 5Ghz low noise cheap CATV transistor. The mixer has now been made doubly balanced. IF amp slightly modified.
PA board has been also done it includes PSU as well. A portable BW TV transformer is used AC 18V. Unreg DC is given to IRF PA. LM317 regulates to 13.6V for operation of rest of the rig . 2 Small on board cube relays do the necessary changeover. Unfortunately C-E leads of driver 2N3866 had been swapped in layout. We noticed it too late 10nos board had already been made.
Will try posting some of the ver3 board pic. Ver2 is already there in archives.
73
Rahul VU3WJM
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