Amplifier and AH-2 Interface to HL2

[Ken]

Noobie to HL2, sorry.

New HL2, Filter Board and I/O Board. I have a AK 4951 companion board on the way. Learning Thetis. 

I have an Icom AH-2 I wish to use with my HL2. I have seen that other people are using the HL2 to control external tuners. I also have an MFJ that uses the same interface as the Icom. 

I have seen posts about the external tuner control but I have not found any detail on hoe they made it work. 

I understand that there are a few ways to make this work. Currently I have the I/O board installed. From reading that is a preferred way to interface an external tuner and amp. Not sure why but it may have something to do with the audio path. 

I have the AK4951 companion board on the way but I have read that some prefer not to use it. Not sure why. 

Anyway can someone point me in the direction of getting the Icom external tuner connected? I will need to connect the 100w amp when I decide on which one. 

Thank you

WB8VTW

[Heath Petty]

I'm sure others will chime in as well, but I would skip the companion board. It requires a 3rd party gateware, which is not supported by the hermes lite 2 project. If you have issues with it, you'll have to contact the person that produces that board. For audio, the companion board is basically a network attached sound card. The I/Q signals are still sent to the computer to be processed, then the audio is sent back over the network to the companion board. The latency isn't noticeable, but why the extra steps when about everyone has a sound card in their computer already? I use my HL2 remotely. It sits in my garage near my antenna feed point, and I access it from my second floor office. In this setup, I don't need an audio port on the radio. 

For the I/O board, all the instructions for it are located here: https://github.com/jimahlstrom/HL2IOBoard. It is a pico based device that you load firmware on to control what you want. There is a library in that github repo for the icom AH tuners. You can control that and whatever amp you get at the same time with the I/O board, but it will probably take some customization. One of my HL2s has an I/O board and its all setup to control the hardrock 50+ amp (which I also own). I have not had time to work on getting it all setup and verified, but it seems straight forward. My tuner is an LDG pro II, so that just works automatically. 

I hope this helps,

Heath

NQ7T

[Dalton Williams]

I agree with Heath.

If you need help with programming the pico on the I/O board I and others can help and Jamison who designed the board is a great help and responds quickly to questions.

Dalton 

W5EIM 

Dalton Williams

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[Ken]

Thank you for the reply. I see in the n2adr_lib a reference to the AH4 but I am not sure what to do with that icom_ah4.c file. I looked at other files and see pictures of what jumpers need to go to the DB9 connector. I believe it was for the 50+ amplifier. I am sorry I am not up to speed on software creation. Seems like I am missing something in the documentation on how to load the required software as well as the jumpers to the DB9 connector. 

Thank you for your patients. 

[Ken]

Follow-up. I realize the interface from the DB9 to the AH2 is dependent in how I create the cable. There are 2 signal and 2 power leads. I need to know where to get those signal leads. 

[Ken]

Thank you for the replies. Writing the code for the AH4 tuner on the I/O board is out of my abilities for now as I am more hardware oriented. I am not looking for hand-holding but I need to get a handle on the basic concepts of creating the program for the AH4. From reading other posts it appears that others are having the same issue. As I stated I do have the + companion board but it would be nice to use the I/O board. 

On Wednesday, September 10, 2025 at 2:21:39 PM UTC-4 Dalton Williams wrote:

[Steve Haynal]

Hi,

I use a AH-4 and AH-705 on my 3 HL2 setups. I use the non-I/O board method which requires some installation and wiring of the rear endplate on the HL2.

 https://github.com/softerhardware/Hermes-Lite2/tree/master/hardware/enclosure/endcaps/kf7o/hl2_40b#atu

73,

Steve

kf7o