My goal is to capture some of my adventures with my Hermes Lite 2.0 SDR Transceiver. The project is well documented and there is a Google Group dedicated to all things HL2. My objective is to document what I have done with my HL2 which has been airborne as of about October 23, 2020. It has been a journey filled with challenges mostly caused by my lack of computer networking skills. The HL2 and your computer MUST be on a network!

Who works QRP? Well I am a member of the QRPARCI Hall Of Fame; but because I ask questions like that --they have threatened to revoke my award. But I still ask and for those who want a bit more fire in the wire my 1st project is a Linear Amplifier Interface Control

The HL2 does indeed have a port on the rear apron (RCA Jack) connected to an Open Drain switching FET. The limitation is no higher than 28 VDC switching voltage. If you connect the HL2 to an unmodified Heathkit SB-200 -- you will smoke that Open Drain FET as the voltage on the SB-200 linear pin is > -100 VDC.

The theory of operation is that the HL2 causes the Opto Isolator to engage thereby triggering the Gates in the 7400 and essentially powering "on" the SPST relay to operate the Relay control in any linear. There is electrical isolation between the HL2 and amplifier units. Just make sure the relay contacts can switch up to 160 Volts and that wiil take care of the SB-200.

This circuit has been in operation for several days and has worked well.

NOW a disclaimer for the CW nut jobs who operate high spped CW. You will need a fast acting reed relay so that you can do the 120 WPM in your head thing. For SSB a standard small relay works well with VOX. Now for those who always have to pick things apart. The ciruit was developed about 8 years ago for use in my KWM-4 SSB transceiver. It worked well for that application and the same here. Keep in mind I also IUWIH ( I used what I had in the junk box). Don't ask me about substitutes -- build as is or you get a chance to experiment by developing your own circuit. Just sharing info here.

 

Coming soon to a Theater or Drive In near you. Sending CW on the HL2 using a homebrew keyboard sender controlled by an Arduino.

 

Keyboard Sender Article

Keyboard Sender Sketch