Friday, March 20, 2015

BITX20 - 24. PA part 2... the story continues....

Well, it has been a long while since the 2 criteria to work on the bitx20 both were valid....
A) I have to feel like it....
B) I need time...

But as i have the week off.... i picked up the project box where the Bitx20 is in and opened it up.....
I took out the PA and started to look what was needed.....

I left off here.....





So i grabbed the manual and started to work with the dreaded coils i had to make......
Fortunately I did not have to make trifilar's, just bifilar and singles, which is a lot better.

So after a bit the board looked like this.......

According to the manual you are done at this point.... but i already stated that  the manual is a bit quirky and not 100% correct due to Indian>English>"Dutch understanding" translations.
If you look closely you will see that a 220pF capacitor, 0.55uH coil and a 1N4001 are missing...
Also a 100pF, but you cant see that due to the heat sink being in front of it.
On the top part you see some missing components as well, but that is only if you wanna use a higher voltage on the PA (or actually on the IRF510) then the standard 12 volts. As I intend to use this with standard 12v (or actually 13.8), I choose the other build method described in the manual. few less components.. (diode's resistors and an lm317)

Now getting back to the non explained missing components.........
This is a mod that was allready added to the PCB and also to the parts.... but not so good in the build manual....
In the mod section you find something , but not how to make this L2....
this is the mod:  Bitx20 Linear AMP mod
As it was still not clear what and how to do with L2 (found out later that it was named L2) i downloaded the build manuals of the Bitx20 ver 3b/c.
In there i found exactly what was needed....... 14 turns on a T50-6.
The diode is used in the version 3b/c as well , so i put it in and i have no idea if i should or not.....
I still need to do some testing and do the measuring to see if all is ok....
At least the PA/PSU looks finished now :)





Onto the next part !!! This will be a rebuild of the VFO from test version to something a bit more neat (Has to be done as well as 1 of my cats decide to chew on all the wires.... grrr)  and i will put the VFO and Counter in HF tin enclosures (or whatever they are called in proper English :) .....
Something like this :)


We're getting near something that will actually work!
Untill the next time!

73's
Alex
PA1SBM

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