SPA Firmware V2.0.1 available! See links below.
The SPA is meant to go between a QRP transceiver (of your choice) output and an amplifier (which may or may not then drive a larger, linear amplifier).
Here is how the Smart Power Attenuator (SPA) came to be, what it is, and how it is used.
I
have an HL2+ which makes around 5W driving a Hardrock-50. Even with the
HL2+ output backed down to it's minimum (which is about 1W), the HR-50
makes about 29W (for example on 40m where I spend most of my time). 29W
is way too much input power for my RF2K-S LDMOS amplifier.
To
solve that problem, I designed the SPA. The SPA is a 20W input capable power attenuator
which provides 0-15 dB in 1 dB steps. It has COR, a PTT IN RCA jack, 2)
programmable delay/sequenced PTT OUT RCA jacks and measures frequency so it changes
selected attenuation automatically when it detects RF. The SPA uses an
ESP32 processor with 2.4 GHz WiFi and a web-based control interface.
You store the value of attenuation you want for each band (160m-6m) on
the web page and the SPA will automatically change to that attenuation upon
frequency determination. The PTT outputs are also programmable for
desired delay (if needed). Using the SPA, I can provide the exact
amount of power needed for each band to my RF2K-S to generate the power
level I desire.
The SPA has a number of web GUI screens designed for setting up, using, and reconfiguring the unit as desired. A login screen is provided to provide some measure of security. The SPA automatically logs out and returns to the login screen after 5 minutes of inactivity. The SPA main page provides the ability to set the desired attenuation by band, PTT OUT 1 and 2 Delay as desired, and a bypass mode checkbox which uses the SPA RX path during TX when checked. A SPA Reset WiFi Settings page is provided in the event that the user wants to change what WiFi network the SPA connects to and utilizes. A SPA Over The Air (OTA) Firmware Update page is provided so that the SPA can be easily updated with new firmware as it becomes available.
Here is the latest firmware for the SPA and a Changelog describing what has been changed. Use the SPA Setup document Over The Air (OTA) SPA Firmware Update instructions to update the firmware.
SPA Firmware V2.0 New Features and Enhancements
