PURE SIGNAL - HERMES LITE 2

HOW DO I  BECOME PURE?

People email me saying they've read my blog-posts about the wonderful Hermes Lite 2 but point out that I don't provide instructions on how to use Pure Signal, so let's fix that right now!  It's a very simple process and can be achieved quickly. Using PS is detailed in the manual, but it seems some people don’t read them, lol. Bear in mind though, I'm a simple M7 license holder, so everything written below is based purely on experimentations. 

There's actually a couple of ways of doing it - internally or externally. I have only used the HL2's internal method, but that might change as I go along.  Anyway, let's start with the easiest way first of all. Anyone can use this method and there's no extra parts to pay for it you already have a Pure Signal output.

Pure Signal (an advanced, adaptive predistortion technique) is used to significantly clean up your transmitted signals by reducing distortion, IMD (Intermodulation Distortion), and harmonics. By sampling a portion of the output and correcting for nonlinearities, it improves transmission quality, reduces splatter and enhances efficiency.

In order for Pure Signal to function on your Hermes Lite, you must start by switching on PS-A (which is the Pure Signal Auto calibration) and DUPLEX (meaning that the radio receives even when transmitting). This is so that the transmitted signal can be monitored, measured and subsequently adjusted. So go to your Thetis software and switch it on (by the way, I'm using V2.10.3.12)...

Then you need to switch on AGC AUTO by double-clicking the text above the AGC until it switches from S-ATT  to  A-ATT. If you forget to do this, Pure Signal will not work properly.

Then go to the menus at the top of the screen and click on LINEARITY. A screen will appear - make sure you have all these settings...

Now find a clear spot on your preferred band and transmit. You will notice that the green   Feedback/Pure Signal 2  markers will change to indicate that your transmission is being examined, measured and adjusted...

That's it! You have PURE SIGNAL! 

 

WHAT ABOUT CONNECTING AN AMP?

So when you use the internal method, everything leaving your HL2 antenna port will be pure as the driven snow. But what if your pure signal goes out to an amplifier? That amplifier could undo all your good work!

Up to now, I've not seen a single post on the internet about this. There's little bits here and a few hints there, but no simple, straightforward guide on how to use Pure Signal with a HL2 and an Amp. So let's hope this post fixes that situation.

In this case, you want to monitor the signal leaving the amp instead of the radio. To do that you need a special splitter which is actually an RF SAMPLER. There are a few samplers available on the market and in the example below, I've shown an Australian sampler from VK3AMP in the illustration...

You will note from my diagram that the Pure Signal connector on the radio is actually an INPUT and not an output as some mistakenly believe. It's very important that the RF Sampler output to this connector is -50dB or greater to avoid overload. Ideally, you should connect the sampler directly to the amplifier's output connector. In the above case, it would mean using an PL239-PL239 Male pass-thru. 

😂 A pretty diagram versus reality 😂

If you are going to insert an ATU in the circuit, it's going to be between the RF Sampler and the Antenna. You should (in this example) put the amplifier into BYPASS mode during tuning.

Note that I have included an RF Choke in the mix too - that's only because I often use a ground mounted vertical which generates problematic common mode currents. If you have no need for one (or for an ATU) then ignore. In this case, the layout would be simpler still...

So there you have it! Pretty straightforward huh? But what if you don't yet have a Pure Signal connector on the rear panel of your transceiver? Don't worry, it's a very simple and cheap mod - all you have to do is buy an RG-178 pigtail from Amazon (other stores are available lol) and solder one end to the connector block which connects the HL2 PCB and the Filter Board.

Note that the center-conductor goes to pin-6 and the shield (twist it all together) goes to both pins 3 and 4.

HL2 Internals

Close-Up

I hope this post proved to be useful to you.

73, Tom, M7MCQ.

 

UPDATE : 24 FEB 2026

Found a competitively priced RF SAMPLER here in the UK - just ordered one for £44. It gets good reviews, so happy days. Also ordered a couple of inline SMA-SMA attenuators in case I need more attenuation than the sampler provides.

The sampler arrived very promptly from the supplier, well packaged and the whole thing looked to be constructed to a very high standard. Excellent value for money!!

If you wish to purchase the VK3AMP sampler, click here. ($150) 😵

 

If you are from the STATES, perhaps this sampler would be a better option....

73, Tom, M7MCQ.

Q: Explain Pure Signal on the Hermes Lite 2 HL2 + Plus

Q: How do I use Pure Signal on my Hermes Lite 2?

Q: How do I use Pure Signal on my Hermes Lite 2 with an AMPlifier?

Q: How do I connect my amplifier to Pure Signal on the Hermes Lite 2 HL2 Plus?