To get a higher PA voltage using a DC booster what sort of power supply do you use?

Can you use an AC to DC plug pack? ?Say 16VDC at 3A or whatever?

Thanks - Noel

I tried this thing:

Connect the 12V from the power input to the module input, adjust the pot for 20V to 24V at the output and connect your PA power connector to the output of the module.

There is an "Enable" pin which I did not use. The data sheet says it should be connected to GND in order to shut down the converter:

Did not measure the volatge drop when disabled, or if the module passes the input voltage to the output when disabled.

You will need about 1A at output so almost 2A at the input, which adds to your regular 0.5A currect draw of the rest of the board, so a 12V/3A power supply is required.

Good luck,

--

Ion

VA3NOI

Ion,

did you experience any RF noise when connected? ?I used a DC DC buck step down to power the QRP Labs DDS VFO (need 5v) from the 12v supply of the bitx40. ?I ended up building a 7805 circuit that cut the noise, but less efficient as well.?

Thanks

Robert/KD0YMC

Hi Robert!

I don't think you will get much more noise as the DC/DC converter is only supplying power to the Power amplifier.

I did not use it myself as I am not finished with the other tweaks I want to implement.

If it will not work for me is not a big issue as I plan to stay QRP only.

I might try something later today, or tomorrow, using the same converter I have posted above. Set he converter at 13V and use a 3Ah LiPO pack that is built with 3 cells, so when fully charged only has 12.2V.

If it works I'll let the group know.

Take care,

--
Ion

VA3NOI

VA3NOI

I managed to connect the DC/DC converter and do a test in receive mode.

The noise increases significantly when the converter is powered.

It might be possible to reduce it by adding extra bypass caps and serial chokes, but I wouldn't go for this solution.
--
Ion

VA3NOI

At the moment I'm using my 13.8 V 40A ?main rig PSU to power my two BITX40s. ?Can I take another line?

from that, run it through a DC/DC buck converter and use it to power the PA ?separately at the higher voltage?

Sorry for such a dumb question but I'm not planning on mobile operation - just desktop stuff and I'm learning

stuff as I play around. ?

Thanks - Noel

开云体育

Hi Noel!

You can sure try. Depending on the DC/DC converter you have it might work.

In my case the model I had on hand (for which I've posted the link in my previous post) generates a lot of switching noise on the 12V power line. That increases the receiver noise which is quite high from the start.

For the PA the current requirements are only 1.5A to 2 A. If it is for desk use I would use a second linear power supply for PA. If you have a 120V to 24V transformer that can deliver 2A I would make a power supply just for that.

A good option is this:

or this:

Second option has higher output current capability but you cannot adjust the current limit and the voltage is set using a multi turn trim pot.

You need to find a good heat sink for the power transistor.

--
Ion

VA3NOI