There’s a lot of misinformation out there on this topic, but even more misunderstanding and a general perception that is simply not based on facts. In this blog entry, we’ll explore, in-depth, the differences between the two technologies and why they’re more alike than not.
The first thing to know is that “GEN2+” is sort of a misleading term, and can lead one to believe that GEN2+ is “old technology” compared to the “new” GEN3, and that’s simply not the case. GEN2+ is actually NEWER than GEN3, as far as that goes. To add yet another layer of confusion, the difference between the two TODAY is by no means the same as it was 7 or even 4 years ago.
The last 5 years have seen continual improvement in Gen2+ technology, especially in Autogating performance, Low-Light Sensitivity, Luminance Gain, etc. In contrast, the only notable improvement to GEN3 in the past ten years or more has been the “Supergain” from L3Harris.
So where did the term “GEN2+” come from? In essence, the term was formed around a complex of scientific, political, & international trade influences pushing for a completely different TRADE NAME for a product which differed slightly from GEN3 in materials and technical construction. Indeed, “Gen2+” has more to do with the chemicals and assembly inside the tube than any inherent difference in performance apples-to-apples.
As a result, people often confuse GEN2 with GEN2+, which is entirely incorrect. Combine that with our good old American mistrust of foreign-made products (except, of course, our clothes, our computers, our mobile devices, appliances, televisions, cars, vacuum cleaners, and just about everything else we use on a daily basis) and we end up with the general idea that any GEN3 tube, or at least just about any GEN3 tube, is going to perform better in the real world than any GEN2+ tube. Like most things we learn about on the internet, this is just plain wrong.
😉
The truth is, all other things being equal, GEN2+ is MUCH closer to GEN3 than the older GEN2 technology, in just about every way. One way to think about this, and this paints a pretty accurate picture, is to make the following analogy;
If GEN3 is the iPhone 17, then GEN2+ is the Samsung Galaxy 22+, and GEN2 is something like the Motorola Flip Phone from 2010.
But we’re getting ahead of ourselves. Let’s start at the beginning. What is the technical difference between modern GEN2+ tubes and GEN3?
The actual TERM “GEN2+” came about from a complex array of scientific, corporate, and also political pressures inside and outside of NATO, to come up with a trade name which would distinguish AMERICAN tubes from all others. Think stuffy rooms filled with L3Harris lawyers and their Good Friends in the DOD. But there ARE mechanical differences.
So what ARE the mechanical differences? Well, the TLDNR version is that they use different materials to achieve certain trade-offs in how they perform their task. The largest difference is that GEN3 tubes use a MCP (Microchannel Plate) barrier, or ION BARRIER FILM, which protects the MCP from ionized particles (stuff you don’t want), which are created as a byproduct within the tube. GEN2+ tubes do not have a MCP Barrier, but more on that later. The trade-off with this barrier film is that it can also block photons (stuff you DO want) and reduce overall gain and brightness. (NOTE: This is the “FILM” you hear about when GEN3 tube makers like L3Harris and ELBIT say “Thin-Film” or “Unfilmed”).
GEN2+ tubes require NO Ion Barrier Film, because their Photocathode or “PC” (the section just in front of the MCP) is made of an entirely different material, which does not produce significant ion particles, so the barrier is not needed. The trade-off here is that the GEN2+ PC is fractionally less sensitive to incoming light than the GEN3 type, and therefore overall sensitivity & system gain in extremely low ambient light conditions can be slightly less than GEN3, all other things being equal. This doesn’t make either type inferior or superior in this respect; it merely makes them DIFFERENT, and the 2 construction types result in different TRADE-OFFS.
How is the Photocathode different? In GEN2+ tubes, generally a Multialkali (S-25) material is used, and in GEN3, Gallium Arsenide (GaAs) is used. The development of Gallium Arsenide (GaAs) Photocathodes was largely driven by the complex relationship between the US Military and its private defense contractors, like L3Harris. These developments are proprietary, fiercely guarded by domestic and international laws, and most of all, extremely expensive. When the US military-industrial complex developed GEN3, it was absolutely superior to GEN2 in just about every way, but GEN2+ technology was developed in the years after, not by trying to make GEN2 tubes better, but simply by choosing a different, more affordable material for the PC construction, which also allows for a less complex design overall. A DIFFERENT way to achieve virtually the same results, not an “older” or “inferior” one.
While GaAs offers superior performance in extremely low-light conditions by having higher quantum efficiency in the near-infrared spectrum (around 800-900 nm), and can also allow for overall higher average Luminance Gain, modern high-end Gen 2+ (like NNVT and Photonis 4G) use advanced multi-alkali hybrid Photocathodes that are sensitive over a broader range, including deeper blue/UV light and slightly longer near-infrared wavelengths that GaAs Gen 3 cannot detect at all. This is why many people say that the contrast in GEN2+ I2 tubes can be more “vibrant” to the human eye. Again, as with anything mechanical, these are all trade-offs in taking different approaches to different parts of the tube’s function.
So, summed up, using GaAs GEN3 is not inherently an UPGRADE to GEN2+, or “NEWER” technology, but rather a different technology used for legal, political, and especially cost considerations, with different performance trade-offs to those in GEN3. That’s it!
Taking all this in, it’s important to understand that the most modern, super high-performance NVT or Photonis GEN2+ tubes are equal in every way of super high-performance GEN3 tubes. GEN3 tubes can achieve much higher gain levels, as well as higher sensitivity to ambient light in certain parts of the spectrum, than ANY GEN2+ tube. GEN3 tubes can also achieve overall higher signal-to-noise ratios (“SNR”) than even the best GEN2+ tubes. But the point here is not to compare the average NVT tube to the absolute highest spec L3H or Elbit tube. It’s about comparing apples to apples; the real-world difference in performance one can expect between each type during normal use, and is that difference worth the 100%, 150% or even 200% higher cost you can expect to pay for GEN3. Only YOU can answer that question, and we want you to have all the FACTS.
