Initiating AT sequence by serial command
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Author:  KB8CR [ Sun Jan 27, 2019 12:58 pm ]
Post subject:  Initiating AT sequence by serial command

I am considering a HardRock50 with the ATU. I understand that there is no auto-initiation of a tune sequence without pushing the button, but I see in the instruction manual commands to initiate a tuning sequence, as well as commands to read the SWR and FWD Power. Has anyone written a program to use this ability on Windows?

I have a Flex 1500 I'd like to use with the amp, and if I can figure a way to send those commands and display SWR on a computer (the Flex 1500 does not have a SWR bridge to read it itself), this would be a great amp for me. The reason for wanting to use a computer to display this is that the amp will reside in a rack cabinet, away from the operating position.


Charlie KB8CR

Author:  jimveatch [ Mon Jan 28, 2019 6:34 am ]
Post subject:  Re: Initiating AT sequence by serial command

Hi Charlie,

The main reason you can't get data while the amp is transmitting is that in some circumstances, especially with the ATU, RF gets into the serial line a fills the buffers with garbage which can cause the microprocessor to respond erratically and/or completely lock-up. As a result the microprocessor completely disables serial communications during TX.

I have looked at making a "tune the ATU the next time the amp is keyed" command so you can remotely issue a ATU tune. And I can add this to the ATU firmware pretty easily. It will be a bit more complicated to extract power and SWR info during TX. The ATU is continuously reading FWD and RFL power so it could record peak and average power for the last transmission and allow you to query it after the transmission is over.

You could also add an external computer based wattmeter like our RS-WM1 and an Arduino to provide real-time monitoring of the RF output.


Author:  KB8CR [ Thu Feb 28, 2019 8:13 pm ]
Post subject:  Re: Initiating AT sequence by serial command

Thanks for the quick reply. I see the problem. FoxDelta makes a SWR bridge that outputs real time readings to a serial or USB line, and has a program to run at the operating position to display a "meter" on the screen. I think the Hardrock50 looks like the perfect match for my little Flex 1500. Now the only question will be whether to find a used one, or try to find someone to build one for me. (My only successful build was a Norcal 40A several years ago when my hands were steadier).

Thanks again,

Charlie KB8CR

Author:  jimveatch [ Fri Mar 01, 2019 8:04 am ]
Post subject:  Re: Initiating AT sequence by serial command

Hi Charlie,

Depending on how much of a 'hands-on' project you are looking for, the HobbyPCB RS-WM1 wattmeter might be a solution.


For your application you'll need a 20 dB directional coupler (1 binocular core or 2 toroids, I can help with the design) then the RS-WM1 will read 0-200W forward and reflected power.

There are a couple of examples of wattmeters based on the RS-WM1 on its site:


It seems like you don't need a display so you could modify the code to simple respond to serial requests. If you get a RS-WM1 and the Uno on our website it's about $65 plus the core and wire for the directional coupler.

I'll be happy to work with you on the project if you are interested.


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