Monday, September 16, 2013


     "Big Nick," KC9KEP, does amazing work.  He's been building classic late-1930s/early-'40s ARRL Handbook receivers (plus some others) and good-looking as the League originals were, his are even better.  If you like building your own ham gear, he's a inspiration.

     On the other side of the Atlantic and a generation or two more recent in technology, the clever Tim Walford (Walford Electronics) has been turning out very nice kits for some time.  I've built one, a nice 80-meter QRP transceiver, and it was fun to build and fun to use on the air.  He's added an antenna tuner and his answer to the problem of providing a variable inductance is one of the best ideas I've seen.  Go to this page and scroll down to Antenna Matching Unit.  Yes, he's using a short piece of ribbon cable and a set of short traces on the PC board to make a coil!  His notes say that particular solid-wire jumper went unavailable, so he's redesigning it for an alternative coil and I'll be interested to learn what that will be. Good equipment from a good guy.

Friday, September 6, 2013


     At the WARMfest last weekend, I met a fellow riding a Coker Wheelman pennyfarthing, with the same wheel size as my QU-AX.

     Both have similar rake angles, pneumatic tires and the main wheel is a yard across -- but that's about it for similarities:
Coker at left, QU-AX at right
     They're both nice-looking ordinaries and attract a lot of interest.  While the Coker does have a brake on the main wheel, the rider I met admitted he doesn't use it much.  Meeting him made me wish I'd've ridden mine to the event; there aren't so many of us on pennyfarthings, still less the modern versions.

Sunday, September 1, 2013


     What's a transmatch?  It's a device for matching a transmitter (or a receiver) to an antenna, or perhaps the other way around.  It's an impedance-transforming network.  They're pretty common in amateur radio and you can even find high-power versions at some MF AM and SW stations.

     This one was made by the perfectionist James Millen Corporation, their "Junior" model (manual for 92201 here), rated at 150W continuous, 300W peak:

     Internal construction is as clever as most Millen devices.  The split-stator input variable condenser sits on top of a little copper-plated box and the input connector is at the rear-wall end of the box.  What's in the box?  A standing-wave bridge, a pair of directional couplers for providing equal-amplitude coupling-value samples of forward and reflected power.  They go to a front-panel selector switch. Set the front-panel meter to full-scale in "Forward," flip it to "Reverse" and adjust the tuning controls for the lowest reading.  Voila, matched!
     (I removed the cover for these photographs.  It matches the front panel.)

     The output capacitor stands on ceramic pillars: both sides are at an RF potential above ground.

     On the back panel, an extra connector!  It connects to a one-turn loop coupled to the main coil (see the manual), and provides a sample of the signal for an oscilloscope or keying/modulation monitor.

     Found on an auction site for a remarkably low price, this example is unrestored.  Typical of Millen products, it is overbuilt and will only need attention if the meter movement or passive components in the SWR bridge (two diodes, two resistors, a fixed condenser or two) are damaged.