Sure thing, Chris.
Simulation at 25 ohms (2:1 SWR) shows each BS170 dissipating about
half a watt, so there is some margin.
JZ
On Thu, Sep 14, 2023 at 9:26?AM Chris KB1NLW via groups.io
<chrisrey1@...> wrote:
John Z
Thanks for your response. Looks like steady state SWR of 3 will heat the BS170s to their PD limit, so I assume SWR <2 is OK.
Transients from an auto tuner that can be as high as SWR of 10 will cause transient power dissipation significantly higher than the allowable dissipation. Unfortunately we don't have sufficient thermal data on the BS170 to understand transient thermal response at the silicon chip in order to determine allowable SWR Transient time product.
Bottom line is Don't Use an Auto Tuner without reducing the transient at the QMX. Reduced power or attenuation between QMX and tuner.
