Just setting up

 I'll write about some of my radio experiments once & a while.

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Even a Blind Pig finds an acorn once and a while (35 watt push-pull RD30HVF1 amp for HF)

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     I spend (waste?) significant time looking for RF bargains on the auction site that you all know and love.  Recently, I found a US-based listing for Mitsubishi RD30HVF1 MOSFETs at a very reasonable price (<$12/piece for 4).  So I bought 4 and thought I'd put together a 35 - 50 watt HF amp for my Hermes Lite 2 that would perform a bit better than the typical IRF510/IRF530 designs that abound on the net.  A cursory search didn't reveal any examples to use for guidance.  So I looked at several RD15HVF1/RD16HHF1 designs that served as a starting point:  1.  A couple of examples from 60dbm.com 2. KK4DAS's design that had evolved from Skelton's (EI9GQ) design. I had actually built an example of Dean's design, and while it worked as advertised, I never quite got the input match a good as I wanted.  I figured that another try, using the RD30HVF1's, was in order.  The circuit I came up with lies below: A photo of the test build f...
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Playing with Phasing - part 1

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      Every so often it seems that some folks are lured into the less-populated territory of SSB reception and transmission using the phasing method.  Maybe it's the promise of simpler (?) circuitry, eliminating the need for crystal/mechanical filters, or perhaps as a gateway drug into SDR-land.   Rick Campbell's (KK7B) articles describing a single-signal direct conversion receiver (QST - Jan 1993), followed by a phasing transmitter (QST - April 1993) are seminal works that detail the implementation of the phasing method with modern (for the 1990's, at least) circuitry.  These papers also discuss design tradeoffs in terms that are easily understood.  Quite a few years ago, I actually built a R2/T2 transceiver, shamelessly copying those designs and adding a Si5351 quadrature LO along the lines of that described by ZL2CTM in his blog.  It worked OK, but the opamp-based, all-pass phase shifters required hand matching of the RC components fo...
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Playing with Phasing - part 2b - audio processing code

Target is Teensy 4.0 + SGTL5000 audio shield.  Mostly ZL2CTM's code again - he's done some good stuff (IMO)!  Filter coefficients were generated using Oak Hills filter design program.  Oak Hills site is gone, but the GUI filter design program (Windows only, unfortunately) can be found by searching the interweb.  Same disclaimer as part 2a. _______________________________________________________________________________________________  #include <_Teensy.h> #include <Wire.h>                           #include <Audio.h>  // Teensy audio library // Number of Filter Coefficients #define NO_HILBERT_COEFFS 200   #define SSB_SWITCH 3 #define FILTER_SWITCH 4 // Iowa Hills Hilbert transform filter coefficients const short Hilbert_Plus_45_Coeffs[NO_HILBERT_COEFFS] = { (short)(32768 *  0.00000187995362921356), (short)(...
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