Tuesday, September 6, 2016

Steve's Eclectic Radio Blog


For years, I've enjoyed reading the blogs of other radio and electronic hobbiests and following the blogger's progress as he (she) converts an idea, first into a seemingly random pile of parts, and then into some sort of useful or superfluous (but nontheless fascinating) device.  

This got me to thinking:  I make some pretty cool and weird stuff, and I'm semi-literate, maybe someone might be interested in following along on some of my techno-adventures?  So, here we are!

To introduce myself:  I'm Steve Murphy, N8NM.  I've been a licensed amateur for over 30 years, extra class for 28 of those, but my fascination with making things out of junk started long before I was ever granted any sort of license, other than, perhaps, a library card.  As far back as I can remember, I was lugging home the carcasses of discarded TVs and radios, where I'd carefully dismantle them and sort and catalog all of the various bits.  God, I wish I were as organized today as I was at six or seven!

Since then, I'd built numerous small "homebrew" accessories, some of which worked as desired, and quite a few kits (most of which worked as designed), but it wasn't until about 20 years ago when I jumped in with both feet, designing and building my first homebrew receiver.  It was a relatively simple affair: 20 meter band only, using a FET VFO, MC1350P IF amplifiers, SBL-1 Mixer and product detector and LM-380 audio. It worked well enough to receive signals and I even used it for a few QSOs, but the VFO drifted horribly.   

Career and changes kept my homebrewing on the back burner for the next several years, when I again decided to jump in and build a "modern" version of the 6AG7/6L6 MOPA transmitter - covering 80-10m using Xtal or VFO control and with a regulations-compliant PI-L filter on the output.  This one worked much better, and I still occasionally use it today..

Then, a couple of years ago, I came across Ashhar Farhan's discussion of his new Minima transceiver.  I was already aware of his famous BITX rigs, but the Minima intrigued me because it was an "All band" transceiver.  So, I started analyzing Farhan's design, changing things here and there, mainly just because I could, and about six months later had my version of an 80-10m SSB/CW transceiver with general coverage receiver.  Though still unfinished, this is my current "main" rig.

This little rig uses two bilateral, termination sensitive amplifier blocks for the IF stages, homebrew diode-ring mixers for the mixer and product detector, and an LM380 driven by a 2N3904 for the audio.  Mic amp is a pair of J310s.  VFO and BFO are provided by the wonderful little Si5351, which is controlled by an arduino Nano, and the RF PA is currently a switching MOSFET, providing about 15 W on 80 down to about 2 W on 10.  Made hundreds of QSOs on this rig - having so much fun that I haven't been able to bring myself to tear it down for paint!

Another rig that I've been working on (and is setting on the back-burner at present) is my "Thermatron" receiver.  This is a general coverage SW receiver that uses tubes in the signal path, but is controlled by an Arduino Uno and uses another Si5351 for frequency/bfo.
It's really a cool little rig - it works, but needs a lot of refinement.  I plan on finishing this one up over the winter months.

So, what's in the works now? Well, a couple of things!  About a month ago, after some email exchanges with Pete Juliano, N6QW, I got the bug to build a 60m rig.  Since, in all of my prior efforts, I've started by having a chassis footprint and panel layout in mind, which never leaves quite enough room for all of the circuitry, I decided to build this one on a simple chunk of scrap board and figure out how to package it afterwards.  On seeing pics, Pete bestowed a rather brilliant name apon it: The Planker!  
So, here's the planker in it's current state - AF/IF/Mixer/BFO and low-level transmit stages are operational, next step is to complete the PA and band-pass filters.  Since 60m is channelized, I opted to use a single 7 segment LED (left over from an abandoned project) to indicate channels 1 - 5, with 6 being WWV at 5.000 MHz.  The receiver works great, and the low-level transmit signal sounds good and the IF bandwidth is within the FCC requirements, so I just have to give it some suitable "snot" to drive the antenna.  Looking forwared to that - 60m is the only HF band where I've never made a single QSO!

Meanwhile, I have several antique radio restorations in the works, including an Atwater Kent 20C, ERLA "Sky Rover" console, and a recently acquired NC-109 that - hopefully - won't require much more than a simple "recap".  Fortunately, I have enough bench space to support going back and forth between all of these active projects, which suits my short attention span perfectly.

So - this is me and what I do... From here forward, I'm going to share some of my fun with you, in much the same disorganized and unorthodox manner that I work in.  One day, I may document progress on some cool HB transceiver, then the next, write about replacing the mica wafer capacitors in the IF cans of a 50s GE or Zenith.  

Sounds like fun?  If so, please feel free to check back often!

73 - Steve N8NM