What use is an F-call? When I was a lad, which for me was in the 1970's, I had a big tub of LEGO. I used it to learn about the mechanics of things. I built a diff with Yellow, Blue and Red cogs - long before LEGO Technic came along with a pre-made diff. I built trucks and steering linkages, suspension arms and when I had the opportunity to build a V8 engine with several kits from friends, I did that. My electronics building followed a similar path. I had a Commodore VIC-20 - which reminds me, Jack Tramiel, the founder of Commodore Business Machines passed away aged 83 - read up on his story when you have a moment. Anyway, I had a Commodore VIC-20. My experimentation with that was at a TTL level, rather than at a component level. I plugged in switches and connectors, made a serial port between an Apple ][ and my VIC-20 and did all manner of software and hardware experiments. Other amateurs I have spoken with have experienced a similar journey, some with LEGO, others with Meccano, or Valves, Leiden Jars or a kite with a piece of string in a thunderstorm - hi hi. What I'm getting at is that even though I have limited experience with resistors, capacitors, tuned circuits, transistors and diodes, let alone designing and building circuit boards, I have the pre-requisites to start, that is, a thirst for understanding, a joy with experimentation and a steady enough hand to solder. While there is no way I would consider myself at any level other than beginner in this field of circuits, I know enough to start to read diagrams and when another amateur turns up for lunch showing off a frequency divider, I can follow what it's doing and how. Why does this matter? I've heard plenty of people tell me that they are not smart enough to know about electronics, and that they don't have enough physics, or maths, or what ever excuse they come up with. What I'm trying to say is if you think of yourself as not capable of doing something, you'll be right almost every time. However, if you think about how the skills that allowed you to survive until now might apply to what you're looking at, you might be surprised. I'm Onno VK6FLAB