Re: Help Needed Bitx ver3.0 Lineal amplifier


Thank you Jonh
I did one a year ago with the PCB came with the driver with no tuning and
work ok using exactly 3 bifilar turns on the FT37043 following the Leornard
tutorial, after that the PCB came with the driver tuning and i found a
diagram with the t2 trifilar, I did too but this was a little less stable,
some oscilation arise and the number of turns change, it's was a new desing
and Leornad there nothing about this.
All the value were changed to 40 meter with no problem.
In Cuba 40 meter is the most popular and the band I use to get all my
friends daily.
If someone has exactly any paramenter to work in 40 meter using the
trifilar winding will be appreciate to send the information to my friends
Now I am completing the DDS with the ATMEL and the AD9850, all the
programming are OK but the DDS is give me no RF, I think the chips are FAKE
from China.
The project about the DDS are very interesting becuase use two AD9850 at
the same time.
Thank you for your time


El 7 de marzo de 2012 01:30, iam74@...


-- In BITX20@..., Juan Carlos Berberena Glez <jcberberena@...>

Hi Fellows
I need help to complete the lineal amplifier Bitx-40 ver 3.0.
What is the best way to load the IRF510? bifilar or trifilar winding in
Please any suggestion will be welcome
We have several Bitx-40 working in Cuba, but with different lineal system
and they want to use the Sunil lineal PCB.
Try first to build it according to Leonard's manual except that the LPF
must be changed. Probably you can just double the values and it will work
on 40m.

Adjust the gate by slowly increasing the voltage while observing the
output. No matter what the current draw, the voltage should not exceed 3-4v.

Then experiment with matching the gate to the driver output transformer.
Start by trying a different capacitor to see if you can get a better
impedance match. Then maybe a pi filter.

It is likely that you will get much more power out of the linear on 40m.
than on 20m., even with no changes. Watch out for VHF oscillations. You may
get away with just using a ferrite bead on the gate to suppress them. You
may have to load the drain with some capacitance also; that will help with
suppressing oscillation and with matching output. With the right cap
(200-400 pf?), power output should be increased.

If there is instability, try dampening the coupling transformers with a
small resistor across the windings. See the mods to the BITX20A for
information about this.

Let us know what you find out!



Lic.Juan Carlos Berberena Gonzalez

[Non-text portions of this message have been removed]

Join to automatically receive all group messages.