N2ADR HL2 IO Board jumpers to key an amplifier

[d b]

Greetings!

Thanks to all the designers and folks assisting on this project. I recently received an HL2 with IO and filter board and am a newbie. Starting off with Thetis for HL2 on a Windoze 10 machine. 

I wish to key an amplifier using an external opto-isolator via the IO board. 

Looking at the IO board schematic, it seems that one can jump from a pin at either J4 or J6 to the D9 connector. I would like 5V to appear at the D9 connector when in transmit, so maybe a pin on J4 could do it. Is there any convention that I should follow keeping in mind Thetis? 

How does the IO board receive and pass the PTT output-do we need to do any programming in the Pico?

Thank you!

Dan

W1DAN

[Mike Lewis]

If you are just looking for PTT between the amp and the PA, you can just use the EXTTR RCA jack on the back panel of your HL2.  It closes to GND on TX, open on RX.   It can handle decent voltage and current, check the specs.  The HL2 will operate EXTTR anything any SDR app puts the HL2 into transmit.   Not Thetis specific.  You may not need an optocoupler there.

 

You can also jumper EXTTR from the HL2 header directly onto the DB9 bypassing the IO board for the purpose of landing the EXTTR signal on the DB9 to make a connection to your amp in a common cable, useful if you are doing band decoding or serial control for it.

 

If you want the IO Board CPU to pass through the PTT instead of use EXTTR jack directly, firmware can monitor EXTTR (PTT) and operate the output driver of your choice – J4 or J6 as needed.   YOU will need to code that firmware to choose a pin on J4/J6 and then install the jumper for that pin to the DB9.  I am not aware of any general standards for pin assignments on the DB9, probably influenced most by the way your PA is wired for simplicity.   You did not specify what amplifier you want to connect.  Some amps and tuners are supported by available firmware, and you want to look at the specific amp firmware to see what signals they send out and there may be a suggested DB 9 wiring for it.  Again, it is amp specific.

 

Let’s assume you still want to drive an opto-coupler with the IO Board sending out 5V from J4.   Ensure you have the correct current limit series resistor somewhere in that line, in or outside the HL2 case.  You could also supply that voltage externally and use J6 for closure to GND.   Per the above I think you can pick any pin your firmware will support, or that you program yourself.   I drive a multiband transverter with PTT on the same band decoder cable, so I monitor TX frequency and EXTTR in custom firmware and send out a GND for PTT and Band from J6 pins I arbitrarily chose.

 

• Mike K7MDL

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[d b]

Hi Mike:

Yoi have opened my tired eyes as I overlooked the EXTTR RCA jack! I will just use that to feed an external opto-isolator (yes with current limiting resistor external to the radio). The external LDMOS amp is homebrew, and to key it, the amplifier has internal 5V logic that one pulls to ground to enable amplification.

Once I get the radio and amp working for about 100w, then possibly feed a Heath SB200 (will build another opto and relay drive circuit), I will build an RF sample and get Pure Signal to pre-correct the amplitude nonlinearity on the amp (s). If I get stuck on Pure Signal I'll look around here for possible answers. Will do this in stages and test.

So far the radio receives and transmits 5 watts into an RF load. Happy so far and I am being slow and careful.

Thanks again!!

Dan

W1DAN