On Mon, Mar 5, 2018 at 07:46 pm, Jerry Gaffke wrote:
Set bias for 100ma of drain current on each IRF510 using RV2 and RV3 and then leave it be.
That 100ma shouldn't change much even if you were to go from a 12v PA-PWR to 24v.
Adjust power level using RV1 on the uBitx. (RV1 sets IRF510 drain current on the Bitx40)
For SSB, could also vary power level by adjusting the mike gain at Q6 somehow.
I assume the smoked U1 was marked "WX". Can you verify?
The WX clones blow for no particular reason.
The WX probably works reliably if the supply voltage is reduced to 5v or so, down from 12v.
Search for "TDA2822" in this forum to see some nice long discussions
The NTE7155 will probably work fine, perhaps you could report back on that too.
> The first signal reports were the audio was poor with too much high frequencies and no mid to low.
Sounds like the 12mhz bfo is positioned incorrectly relative to the passband of the crystal filter.
Should be able adjust your audio (both transmit and receive, affects both equally)
by using the calibration routine in the Raduino for the bfo frequency adjust.
On Mon, Mar 5, 2018 at 07:23 pm, Bob wrote:
My question is how to set the maximum power? Use Rv2 and Rv3 to set the bias or use Rv1 to back off the drive after the bias has been set using Rv2 and Rv3.
Hi Jerry I have an FCI/FOI TDA in my ubitx batch 2. It is very hot indeed after rig on for an hour.is there an over voltage issue to the chip?
Thank you again for all your help getting it going again with the RF510.
GQRP - #15057