[hpsdr] ALEX SETUP

[Marc OLANIE]

Hi Tony
This answer could include real pieces of stupidity and 100% natural human errors... but

- in the first column of the HPF/LPF filter config, checking this check box will bypass the filter as advertised. In other words, suppress the resulting BPF when receiving. The only remaining filter will be the 60 MHz lpf (antialiasing)
 
If you are located in a quite area, you probably won't notice anything. If you are in a heavy RF polluted urban area, receiving without filter will drastically increase the noise floor and the QRM level.

- TX Inhibit is a logical level present on the external connector of your rig (pin 9 on angelia boards) which is use to mute an external separated transmitter. The "rev input logic" reverse the "mute" level to low or high depending on the logic of the "inhibit" input logic of the external transmitter.

- The ATT level sets the input RX input attenuator to protect the input level of the receiver when transmitting. Keep in mind that your receiver is always "on", and you always can receive your own transmission when TXing (monitoring) . Your RX input could also be used to sample the "pure signal" feedback signal... both must be stongly attenuated to avoid saturate or destroy your ADC input. 

Once again, this answer probably contains a appreciable level of human error or language approximations... 
VY 73
Marc
(ps : may I suggest you to read the Alex documentation https://openhpsdr.org/alex.php . This is an important document describing exactly the way this frontend works)