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.

There's actually a couple of ways of doing it - internally or externally. I have only used the HL2's internal method, but I might change that soon.  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 (assuming that you have a Pure Signal connector on the rear panel of your transceiver (if you don't then see the information at the end)).

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! 

So that's the internal method and everything leaving your HL2 antenna port will be pure as the driven snow. But what if your pure signal goes to an amplifier? That amplifier could undo all your good work!

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 used an Australian sampler from VK3AMP for the illustration...

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.