What is the PA port and How Do I use it?

[busysteve]

Please forgive my ignorance but PA could mean PreAmp or Power Amplifier... etc. What does it mean for the truSDX and how do I use it and set it? I noticed that it's voltage drops when I hit PTT. Can I you it to switch an amplifier's PTT?

Many thanks for your feedback and understanding,

Steve
K4SDM

[dl6sez]

Hello OM,

please read it at the manual at:
dl2man.de
it is normally a pull down at the tip to ground (outermost contact of 3.5mm connector=tip), but be aware
it can only switch very low current no relay.
If you look here in the forum you will find a discussion on howto amplify it and invert it if you need.
I will not discuss it again here
See an example here:

viewtopic.php?p=4058&hilit=pa+connection#p4058

73 de Chris

[busysteve]

Thank you. This is great info! I did read the manual but still don't understand to PA bias min/max. I've searched the forum and not getting clarity where I am looking. However, my searching is not great or I would have found the post you so kindly supplied.

Thank you again!

Steve
K4SDM

[dl6sez]

You are welcome OM Steve

Maybe a simplified expression of PA bias:
The PA Fets are switched on and off with the frequency you are tx-ing. It is a square wave signal, simply because it is a simple class E-PA. So you can change the amount of how long it is switched on in one period of the square signal. Eg. you are controlling the pulse width of the on switching pulse part of the square wave.... You should adjust this in CW, start with lower values maybe <100 and increase slowly and watch your output power and monitor your DC current. Stop when the output power does not increase any more, otherwise you will heat up the PA FETs because you are adding more than necessary DC power to them, because they are switched on to long unnecessarily than
Normally you don't really have to change the default value very much.

73 de Chris

[DL2MAN]

Thank you. This is great info! I did read the manual but still don't understand to PA bias min/max. I've searched the forum and not getting clarity where I am looking. However, my searching is not great or I would have found the post you so kindly supplied.

Thank you again!

Steve
K4SDM

Please don't mix up PA Bias with external PA Port ! Pa Bias settings im menu are only for internal fets "working point". Pa Bias min is best at 0 and pa Bias max is optimal for 3xbs170@128 and for fdt86256@160

73 Manuel; DL2MAN