Hello all, HL2, PTT and Xiegu X125b

[Kevin Polston]

Hello all,

I received my HL2 just last week.  I must have been one of the last recipients in this batch.  So saying "Hello all”.

However, I do have some questions:-

Q1) I bought a Xiegu XPA125b amplifier and I am trying to use this with my HL2.  I'm assuming that I need PTT from the HL2 EXTTR RCA socket to connect with the X125b to get the amplifier to work?

Q2) The XPA125b socket pinouts are given as pin6 is GND and and pin2 is PTT.   I guess I must “mirror” this socket on my plug, that is plug pin1 is PTT and plug pin5 is GND?

Q3) The XIEGU manual says “If you want to start the XPA125b and put it into transmit mode you must set the PTT port to a low level (<= 0.1V).  If the PTT signal is at a high level then this must be converted into a low level and then input into the XPA125b ACC port”.   The voltage I measure across the HL2 EXTTR PCA socket (across a 500 ohm resistor) is 1.9V.  On transmit I measure the voltage as 2.7V.   Are these voltages to be expected? 

Q4) How would I convert this (high) 2.7V to a low (<= 0.1V) that the XP125b is expecting?  

Q5) The operating current on the XPA125b front panel is displayed as 0.0A (the voltage is displayed as 13.6V).  I would have thought that the amplifier would be reading something above 0.0A even when not amplifying? 

To be frank, I was just hoping to connect the HL2 EXTTR socket directly to the XP125b.  I have watched a YT video describing such a connection but I guess it’s not that simple.

If I have got my knickers in a twist then I’d appreciate some gentle guidance.  Please note I have only had my licence a couple of years and am a ‘know nothing” electronics person…

73, Kevin, M0XYM

[DL1YCF]

Q1 yes the PA RCA jack is needed to „key“ the PA

Q2 do not understand the question

Q3 the RCA jack should switch the center to ground. If you connect +12V through a 4k7 resistor to

the center of the RCA jack, you should measure +12 V there upon RX, and close to zero upon TX

Isn’t this compatible with your PA?

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[Reid Campbell]

Hi Kevin,

On 18/09/2022 13:48, Kevin Polston wrote:

Hello all,

I received my HL2 just last week.  I must have been one of the last recipients in this batch.  So saying "Hello all”.

However, I do have some questions:-

Q1) I bought a Xiegu XPA125b amplifier and I am trying to use this with my HL2.  I'm assuming that I need PTT from the HL2 EXTTR RCA socket to connect with the X125b to get the amplifier to work?

So did I and made some mods to the Gateware to support band selection to control the XPA125B. See https://github.com/softerhardware/Hermes-Lite2/wiki/Band-Volts 

Q2) The XPA125b socket pinouts are given as pin6 is GND and and pin2 is PTT.   I guess I must “mirror” this socket on my plug, that is plug pin1 is PTT and plug pin5 is GND?

Not sure what you are getting at here, as Pin2 on the 6 pin mini DIN goes to the centre pin of the RCA. I did make a separate connection on a 9 pin DIN connector on the back end plate. If you have any old wired computer mice, you might be lucky to find one which has all six pins wired. I found the majority only have minimal wiring and pin 2 in not used in the mouse connection.

Q3) The XIEGU manual says “If you want to start the XPA125b and put it into transmit mode you must set the PTT port to a low level (<= 0.1V).  If the PTT signal is at a high level then this must be converted into a low level and then input into the XPA125b ACC port”.   The voltage I measure across the HL2 EXTTR PCA socket (across a 500 ohm resistor) is 1.9V.  On transmit I measure the voltage as 2.7V.   Are these voltages to be expected?

I'm not sure how you are measuring these voltages as the RCA PTT will be pulled to ground. This can be a direct connection and doesn't require any special interface.

Q4) How would I convert this (high) 2.7V to a low (<= 0.1V) that the XP125b is expecting? 

Not needed.

Q5) The operating current on the XPA125b front panel is displayed as 0.0A (the voltage is displayed as 13.6V).  I would have thought that the amplifier would be reading something above 0.0A even when not amplifying?

The current shown is the current drawn by the PA finals on Tx. It doesn't show the supply current for the rest of the amp.

 

To be frank, I was just hoping to connect the HL2 EXTTR socket directly to the XP125b.  I have watched a YT video describing such a connection but I guess it’s not that simple.

It is.

If I have got my knickers in a twist then I’d appreciate some gentle guidance.  Please note I have only had my licence a couple of years and am a ‘know nothing” electronics person…

I have been running this amp for about 1.5 years with no problems. On some bands I can't get the drive low enough (0.5w gives 120W) but I mainly run FT8, so can control the drive level through the WSJT sliders.

Cheers

Reid
Gi8TME/Mi0BOT

[Heath Petty]

I also have an XPA125B. I have not built an auto band-switching interface, but the PTT hook up is dead simple. One big word of warning, do not get the pins wrong in the mini-din 6 plug for the PTT. The manual has the pins listed as you are looking at the port in the back of the radio, not looking straight at a male mini-din 6 plug. If you hook up to pins 1 and 5, you'll probably blow a tiny mosfet in the radio, and it will stop working. Ask me how I know ...  IIRC if you put a multi-meter across pin 2 and pin 6, you'll see about 9VDC. I don't know what you'll see across pins 1 and 5, but its better to be safe than not.

I have used the HL2 connected directly to the XPA125B, but now-a-days I use a radiodan PTT box, because I use my IC-705 with the xpa125b as well, and its just simpler to leave all that hooked up.

Hope this helps.

Heath

KL0PC

[Kevin Polston]

Thanks to all those who replied.

I have been lucky enough to have a member of my club who also has a HL2.  I temporarily substituted his HL2 for mine, with all cabling in-situ, and the amplifier worked perfectly.   So, now I'm certain that my cabling and my amplifier are ok. 

 When I measure the resistance between the EXTTR center pin and outer shield it is high on both receive AND transmit so I think my HL2 isn't grounding the EXTTR.  I wonder if anybody could guide me from here?   Now, although my cabling is fine now it is quite possible that I initially had pins 5 and 1 connected rather than 6 and 2 (i.e. I had the mirror image).

Kevin M0XYM 

PS apart from the EXTTR not working on TX my HL2 is working really well on receive (I'm using SDR Console).  I'm also measuring up to 5W on TX - so it appears that only my EXTTR is playing-up.