Amplifier band switching - How?

[radi...@mail.com]

Sorry for a basic question, but I've tried to decode the Wiki and also trawled this group for answers but I'm not much the wiser.

Could someone please explain in very simple layman's terms how HL2 sends band switching signals to a linear amplifier? Is there a recognised standard or standards for this, perhaps manufacturer related? Is it serial data, or is it simple voltage levels that are decoded by the linear or some intermediate interface board? What does HL2 generate? I'm not using Hardrock as I already have a 100W+ linear which has auto-sense bandswitching. Not sure which linear yet, could be self-build LDMOS or from pre-assembled boards.

Thanks for looking. 

Max

[Kristofer Danner]

2 ways are built in. One is sending out the VFO frequency in hertz via the DB9, appropriate for Hardrock. The Hardrock then switches to the correct band based on the frequency, or disables itself if the frequency is out of band. The other way is repurposing the fan output to provide voltages appropriate for the Xiegu XPA125B. Anything different from those 2 you're looking at doing something like using an Arduino to convert one of those 2 into whatever your PA needs.

KD

[Reid Campbell]

Hi Max,

There are two methods to determine the band select information. One is via the serial data sent in a format which the Hardrock understands. I'm not well up on that one, so I'll let someone else give their real world experience.

The other method is a voltage level per band. The Gateware has been set-up to provide PWM levels which can be translated to a voltage via a simple capacitor/resistor filter. The details on the filter can be found at:

https://github.com/softerhardware/Hermes-Lite2/wiki/Band-Volts

Note, this is a re-purpose of the fan PWM and it's mode is selected via address 0x00[11] of the protocol.

The current Gateware is setup for the Xiegu XPA125B (which I have) but the levels could be easily changed if you are comfortable with rebuilding the FPGA Gateware. 

Cheers

Reid
Gi8TME/Mi0BOT

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[radi...@mail.com]

Many thanks to both KD and Reid for your responses. Ah, this probably explains my confusion as I had not realised there were the two different methods. Looking at the PDF in the github section for HR50 I could see only mention of some sort of data, but then I also kept seeing people refer to voltage levels so I was trying to make sense of the conflicting information. Now all becomes clear.

So as I have no fan and seemingly no need for one, I will most likely use the band volts method and some sort of level translator or band decoder.

Many thanks

Max

On Monday, 18 April 2022 at 07:50:36 UTC+1 scumballc...@gmail.com wrote:

Hi Max,

There are two methods to determine the band select information. One is via the serial data sent in a format which the Hardrock understands.

 

The other method is a voltage level per band. The Gateware has been set-up to provide PWM levels which can be translated to a voltage via a simple capacitor/resistor filter. The details on the filter can be found at:

https://github.com/softerhardware/Hermes-Lite2/wiki/Band-Volts

[Robert Dale]

I use the info from the I2C outputs fed into an Arduino Nano. The Nano is programmed to select the appropriate band on the LPF board and displays the band (and other info) on an OLED display. Pretty easy to do.

73, 

Robert VE7ZN

[Vince Vielhaber]

Another option is this:

https://github.com/michvhf/Hermes-Lite-2-Xiegu-interface

It gives both voltage and port switching.

Vince - K8ZW.

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[radi...@mail.com]

Thank you Vince. I will take a look at that.

73

Max

[Ivan Medvedev]

A very interesting option for connecting Xiegu XPA125B to HL2. What I don't understand is where the arduino input D12 is connected to HL2?  I can't find Connector P2 in the schematics?

https://github.com/michvhf/Hermes-Lite-2-Xiegu-interface/blob/main/HL2_CI-V_band_voltage_interface-1.pdf

73 Jonas LY1O

[Steve Haynal]

See this thread:

https://groups.google.com/g/hermes-lite/c/gBU_Wjh-5Uk/m/RR_O87_ZAgAJ

[G4ZAL]

Jonas, the P2 connector you reference is the same as the db9 companion board (the serial band data and PTT from the HL2)

https://github.com/softerhardware/Hermes-Lite2/tree/master/hardware/companions/db9

Nigel, G4ZAL

[Ivan Medvedev]

Thanks, I read the thread. It talks about PTT controle. I have no problem with PTT. I am looking for a VFO signal that can be connected (perhaps through a buffer) to the arduino input D12 for frequency reading. See the schematic in my link.

Jonas LY1O

[Reid Campbell]

Hi Jonas,

Have you looked at

 https://github.com/softerhardware/Hermes-Lite2/wiki/Band-Volts

It was developed specifically for the  XPA125B .

Cheers 

Reid
Gi8TME/Mi0BOT

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[Ivan Medvedev]

Thanks Reid, using the arduino PA control voltages are more accurate. They do not depend on the transistor type and specifications.

73 Jonas LY1O

[Mark Herbert]

I am using the bandvolts feature with the XPA125b and it works flawlessly. I did the work myself to install the SMD components as per the article.

It usea the "Dither"setting available on most of the SDR software except SDR Console.

Mark

G1LRO 

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From: herme...@googlegroups.com <herme...@googlegroups.com> on behalf of Reid Campbell <scumballc...@gmail.com>
Sent: Wednesday, June 28, 2023 2:12:12 PM
To: herme...@googlegroups.com <herme...@googlegroups.com>
Subject: Re: Amplifier band switching - How?

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[Ivan Medvedev]

Thank you very much Mark, the option of reading the frequency and making the PA control voltage with arduino looks nicer. SDRConsole is a big loss for me because it is able to adjust the output power of HL2 nicely, but it does not support PureSignal :(. FT8's soft output power setting is more important and PureSignal is not needed. You have to accept the compromises. If I understand correctly, HL2 does not have an output with frequency information, do you need a companion?

Jonas LY1O

[Ron Lewkowicz]

If you look at the manual for XPA125b you will see that the ACC input for band switching actually uses voltage from 230mV to 2530mV to determine the band to switch to. This exactly what the band volts mod for the HL2 provides.  The circuit you build for the end panel adds a 9 pin connector which you then adapt to the 6 pin connector on the XPA125b amp.

I have a Micro PA50 amp connected to my HL2. It uses an RF sense circuit for both PTT and band switching. You connect one coax patch cable through the amp and that is it.  No other ACC cable needed to switch band or activate PTT.  It's slick as snail snot.  If you were to build any circuit for amp control that is what I would look at.  The Aliexpress sellers will send you a schematic of the amp if you ask.

I'm doing pretty well with the extra 50 watts. I'm not sure if 100 watts would amount to enough difference to worry about.  XPA125b ATU is rumored

to be quite good though if you also need a tuner.

[Mark Herbert]

Hi Jonas, drop me an email on my qrz email address, I would be interested in jointly trying this out to see if it can get SDR Console to work. I did contact the author of SDR Console to add the Dither setting but nothing received back, so this may be a work around for me.

Mark

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[Ivan Medvedev]

Mark, I think the HL2 capabilities will increase a lot when the HL2IOBoard is available, but it won't be soon. So I'll install Band Volts for now. 

By the way, I offer XPA125B "modification". Rotating the front panel 180 degrees and removing the bottom cover provides better cooling. The monitor ribbon cable is long enough. In addition, a low-speed fan can be applied.

73, Jonas LY1O

[Barry Bahrami]

Just started following this thread about controlling the Xiegu XPA 125B from the HL2.  The IO board is out now.  Is there an out of the box solution to do this that I can pickup somewhere?  Or simple instructions?

thank you so much

73

[KP4RX - Ramon]

Barry, I've compiled a firmware for the IO Board which provides both alternatives, serial and Xiegu Band Voltage, you can find the details here: https://groups.google.com/g/hermes-lite/c/yD7bFNAgULw/m/DyHda1gQCAAJ

73 de KP4RX - Ramon