On Tue, 7 Jan 2025, 19:55 Joe Subich, W4TV, <lists@subich.com> wrote:
>
>
> On 1/7/2025 11:17 AM, Lukasz wrote:
>
> > This will be difficult . I can pull at most 4mA at 3.3V on the
> > control lines out of the uC board. That is not a lot of power....
> > I'm already at over half of that, so realistically ... I can't pull
> > more than 3mA with a bit of safety factor.
> Then don't drive the base of the transistors directly. Use a
> buffer/line driver between the controller and the transistors.
>
> Alternatively, you may want to look at a voltage drive switching
> device (FET) instead of the current controlled NPN transistor.
Thank you for replying , but I don't see what the benefit would be. Quite
the contrary the way I think about it. With BJT at least the signal has to
drive enough current to open the transistor. With FET all it takes is
voltage. Much easier for RF to mess things up IMO. Unless I'm missing
something .
Initial testing is very promisings after:
- adding 100nF smd cap between each base and emitter and another one before
the base resistors to ground. (these are 0408 parts, impossible to solder
without a microscope).
- connecting shields on both ends to cases
- drilling the steel frame and cast aluminum cases, connecting them
together with thick copper braid and crimped ring terminals
So far I sent 1800W into my dummy load at 28.7MHz and it seemed fine. The
uC keeps blinking its led as it should too so it's not getting disturbed. I
had time for just one test tonight, but considering it did click all the
relays before at 200W on that frequency before it may be solved....although
I'll keep tmy cheers for once I had time to test it properly(on all bands).
73,
Łukasz - SP4IT (also SQ4KW)
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|