HF Transmitter: RF Preamp version 4C

OK, here are the files that I mentioned in the YouTube episode.  The PowerPoint should be straight-forward to follow, as it essentially is in narrative format.  The spreadsheet, however, will require you to examine the formulas, but hopefully you can deduce how the calcuations work.  Having a copy of Experimental Methods in RF Design (EMRFD) will help, too.  Enjoy!

Excel Spreadsheet

PPT file

Schematic

Comments

Post a Comment

Popular posts from this blog

SMD Transistors for RF use

Image
I've decided to experiment with modern SMD transistors, to see if I can find a few that will work at least as well up to 30MHz as the old TO-39 2N2218 and 2N2219.  You can see the first episode on YouTube here: Link to Video I've attached below a link to a ZIP archive containing the three KiCAD files that I created for the simple amplifier circuit for evaluating various part numbers.  As I covered in the video, I had to create custom footprints for the SMDs to get better heat dissipation.  I am not including the KiCAD design for the TO-39 circuit. Also included are the LTSpice simulations, minus several of the .lib files - the ones that specifically say that redistribution is not allowed are not included.  You'll have to go get them yourself. For the input impedance model, I use an AC current source at 1A. Then measuring the output voltage is directly equivalent to the impedance (the units still say Volts but it also equals Ohms). Enjoy! Download File
Read more

Two Tone Audio Generator

Image
This is a device that generates two stable audio tones.  It is handy for testing the intermodulation of a SSB transmitter.  YouTube episodes can be found at these links: Episode #1 Episode #2 Before building your version of this project, you need to download the ARRL test procedures manual from the ARRL website.   This project starts on page 140.    There’s some technical information in their writeup that I am not repeating here. See below for my version of the schematic.  All symbol references made below refer to it. The ARRL design specified using polystyrene or mylar caps in the filter networks, likely for temperature stability.  This would be for capacitors C1 through C14.  I used C0G/NP0 grade MLCC’s instead.  The C0G material is plenty stable in this application. I could not find the 25ma 12V lamps they specify, so I went with 40mA 12V lamps.   I added spots for series resistors R1 and R2.   As it turned out, they we...
Read more

Active Probes

Image
An active probe is a useful piece of test equipment that lets you use a low input impedance piece of test equipment, such as a spectrum analyzer, to examine a high impedance circuit without loading the circuit with the test equipment's impedance. I built and tested three different designs that I found on the internet. YouTube episodes can be found at these links: Episode #1 Episode #2 The three probe designs that I built and tested are: The "High Input Z 'scope Probe" by Bob Pease The "Poor Man's 1GHz Probe" by David Jewsbury The "High Impedance Op Amp FET Probe" by Steve Hageman None of these three are my own design creation, all that I did was re-package the information on the internet into a very small form factor.  Plus I designed and 3D printed my own probe plastic parts.  So the stuff that I created, I am making available below.  You will need to do your own internet searching to find the source materials. Bob said you can use the 2N5485 ...
Read more