Showing posts from April, 2012

8640jr First 3 Stages

  8640jr First 3 Stages Filed in homebrew on Apr.22, 2012 I finally got some time to work on the 8640jr Signal Generator Project. I decided to put the VFO and the first two amplifiers inside an aluminum box. Why? I’m hoping it will help the frequency circuits temperature-stabilize, and provide a way to isolate the sensitive frequency determining components from the effects of a hand getting near them and shifting the frequency while operating it. I started by mounting the blank pc board in the enclosure. This gave me a guide as to the height and position of the main and bandspread tuning caps:    The main tuning cap was one I picked up from Antique Radio Supply, in Tempe, AZ. Their website lets you order for the will-call window, if you are local. The bandspread cap was a hamfest special.  Once the caps were mounted, I now had a guide as to where to place the pads for the various components. I knew I had to avoid the areas directly under the tuning caps. I drew up the com

LTSpice Simulation of 8640Jr Q1 Hartley Oscillator

  LTSpice Simulation of 8640Jr Q1 Hartley Oscillator Filed in homebrew on Apr.08, 2012 Continuing on with our LTSpice Tutorial, here is a segment for analyzing the 8640Jr Signal Generator Hartley Oscillator, Q1. It’s a little tricky to get oscillators to start in Spice programs. They need something to kick them off. This video shows how to do that. It also discusses some more of the mechanics of LTSpice, along with using the FFT Spectrum Analysis function. I also show how to add new components to the component library.    

LTSpice Simulation of Q4 in 8640Jr Signal Generator

  LTSpice Simulation of Q4 in 8640Jr Signal Generator Filed in homebrew on Apr.08, 2012 Here is a video demonstrating the building and simulation of the buffer amplifier preceding the divider chain in the 8640Jr Signal Generator. It is a simple emitter follower stage, but is useful for showing how to place components and run the simulation in LTSpice. The Group build can be followed at the QRP-Tech Yahoogroup. The circuit description can be found on Wes Hayward site: 8640Jr Signal Generator    Migrated Comments: One Response to “LTSpice Simulation of Q4 in 8640Jr Signal Generator” David Davidson Says: September 14th, 2012 at 1:19 pm Trying to find the 8640jr pdf.seems wes took all his info down off his you know of a place to download it.would love to build this signal generator.. Thanks David Grover,north carolina

Downloading and Installing LTSpice

  Downloading and Installing LTSpice Filed in homebrew on Apr.08, 2012 We’ve started a new group build project on the QRP-Tech Yahoogroup: QRP-Tech This one is to build a stable, usable signal generator to cover 80 – 10 meters. I may try to take it down lower, we’ll see as I move along. Anyway, part of the “Homework” was to load and use the (free) circuit simulator, LTSpice to simulate various parts of the circuit. So I created a video walking through the download and installation of LTSpice on a Windows XP machine. There is no audio on this one, as I was having microphone problems when I made this, but I added text annotations.   I will follow up with walkthroughs of simulating some of the stages of the 8640Jr project. And hopefully, the actual build of the project, as well.