Output power indication with external PA and remote operation monitoring in Thetis

[Martin S.]

Hello everyone,

I am currently using a Hermes Lite 2 together with a Micro PA 100 amplifier. Between the PA and the antenna I have installed an RF sampler, and I am also using PureSignal for predistortion.

I have two questions related to this setup.

First, I would like to have Thetis show the actual transmit power after the PA, not only the RF output power of the Hermes Lite 2 itself. Is there any way to achieve this? I understand that PA output power does not depend only on the drive level and that it varies with operating mode, bias, frequency, etc. However, in principle one could make some measurements, derive a transfer curve, and obtain at least an approximate estimation of PA output power that could even be logged automatically (for example in Log4OM). I am interested to know whether anybody has implemented something like this or whether Thetis already has provisions for it.

Second, I am operating the HL2 and the Micro PA 100 remotely. I currently do not receive any direct status feedback from the PA. If it trips due to high SWR, overdrive, or another protection condition, I do not immediately know about it. I would be very interested in ideas or practical solutions that others use for monitoring PA status during remote operation.

A related thought: since I know the attenuation value of my RF sampler (−46 dB), would it be theoretically feasible to evaluate the sampled signal used by PureSignal and derive the approximate PA output power from that? In principle, one could even detect a PA fault if no sampled RF is present anymore. These are just ideas at this stage, so I would appreciate any comments on feasibility and possible implementations.

I am very interested in your experiences and recommendations on both topics.

Thank you in advance for your input.

Best regards,

Martin
DB3MAR