Step attenuator on Thetis setup

User avatar
I2NOY
Posts: 48
Joined: Thu Mar 25, 2021 10:44 am
Location: Milano - Italy

Step attenuator on Thetis setup

Postby I2NOY » Wed Jun 16, 2021 1:48 pm

Hi, someone can explain briefly what is the step attenuator voice in Thetis setup?
Many thanks.
User avatar
w-u-2-o
Posts: 3079
Joined: Fri Mar 10, 2017 1:47 pm

Re: Step attenuator on Thetis setup

Postby w-u-2-o » Wed Jun 16, 2021 2:26 pm

Stuck in meetings today but will reply later...
User avatar
w-u-2-o
Posts: 3079
Joined: Fri Mar 10, 2017 1:47 pm

Re: Step attenuator on Thetis setup

Postby w-u-2-o » Thu Jun 17, 2021 2:21 pm

In the openHPSDR hardware architecture, in the receive path there are two switched attenuators in series on the PA/RF board, 10 and 20dB, and a 31dB step attenuator on the actual SDR board.

In Thetis (and it is similar in PowerSDR), when the ATT button is shown on the main console UI, you have access to the following settings: 0, 10, 20 and 30dB of attenuation. This is accomplished by switching in one or both of the attenuators on the PA/RF board.

If you double click the "ATT" label above the attenuator setting drop-down control, it will change to "S-ATT". In this mode the switched attenuators are turned off and control is given to the step attenuator integrated circuit on the SDR board. The control is changed to spinner type control and it offers between 0 and 31dB of attenuation in 1dB steps.

I prefer the step attenuator mode. It more allows more precise settings. I recommend that you add attenuation until you just start to detect a drop in the SNR of the largest signals on the panadapter. This optimizes the dynamic range for existing band conditions.
User avatar
KA5KKT
Posts: 45
Joined: Thu Aug 06, 2020 6:51 pm

Re: Step attenuator on Thetis setup

Postby KA5KKT » Thu Jun 17, 2021 9:17 pm

w-u-2-o wrote:In the openHPSDR hardware architecture, in the receive path there are two switched attenuators in series on the PA/RF board, 10 and 20dB, and a 31dB step attenuator on the actual SDR board.

In Thetis (and it is similar in PowerSDR), when the ATT button is shown on the main console UI, you have access to the following settings: 0, 10, 20 and 30dB of attenuation. This is accomplished by switching in one or both of the attenuators on the PA/RF board.

If you double click the "ATT" label above the attenuator setting drop-down control, it will change to "S-ATT". In this mode the switched attenuators are turned off and control is given to the step attenuator integrated circuit on the SDR board. The control is changed to spinner type control and it offers between 0 and 31dB of attenuation in 1dB steps.

I prefer the step attenuator mode. It more allows more precise settings. I recommend that you add attenuation until you just start to detect a drop in the SNR of the largest signals on the panadapter. This optimizes the dynamic range for existing band conditions.



Thanks, Scott.
Dick - KA5KKT
User avatar
I2NOY
Posts: 48
Joined: Thu Mar 25, 2021 10:44 am
Location: Milano - Italy

Re: Step attenuator on Thetis setup

Postby I2NOY » Fri Jun 18, 2021 8:42 am

Many thanks!
Cristal clear. :)

Return to “Everything Else: Antennas, Relays, Switches, Power, Grounding, Cooling, etc.”