KX3 and a Boat Anchor Amp

A year ago, in a rare foreshadowing of radios to come, I acquired a linear amplifier built around a single 572B running grounded grid. It matched my Central Electronics 20A and the seller
had done really nice job of replacing the four original/modified 1625s in the P&H Electronics LA-400B with a 572B.

Now, seeing it in my shack, I realize that I have a potential May-December wedding here. Sure enough, my KX3 with KXAT3 easily drives the 572B to 100 watts out. The next step is to build a relay box that bypasses the amplifier and delivers -100VDC cutoff bias on receive. It can be controlled via the KX3 Keyline Out signal and a "Keyall" board from Jackson Harbor Press/WB9KZY.

At 35 pounds this one will be a heavy weight. I doubt it will see any picnic table operating but it will certainly help warm up the shack next winter.

The Mitey Mite Beginner Transceiver

Last weekend I attended the TwinsLAN/3M swapmeet in St Paul, MN. This is always one of my favorite swapmeets of the year. It is open-air in a large parking lot so all of the boatanchors show up that we don't want to lug inside to a table...just throw open the van doors or uncover the pickup bed and sell.This year I saw many more boat Nationals, Hallicrafters, Johnsons and Heathkits than I've seen in the past...it was a great meet.

One item caught my attention, a late 40's United Surplus Materials "Mity Mite" HF radio. It is a three tube regenerative receiver/transmitter. The audio stage of the two tube receiver doubles as a single tube crystal controlled oscillator/transmitter. The third tube is a rectifier. I bought it from KB0DVM. He built and used this little rig while he was an Ag student at U of Wisconsin/Madison in 1948.

This is a great example of a minimal design making use of available WWII surplus parts. The first steps in the instruction manual explain how the disassemble the included BC-745 pogo stick transceiver tuning unit to get the crystal, two sockets, a tuning coil and the bandset capacitor. The design itself would not make it off of today's drawing boards. First it is an AC-DC set with one side of the AC line connected directly to the metal chassis/cabinet...what a shocker! A safer (and more expensive) AC-DC design has circuit ground isolated from the chassis but not this one. A quick look at the operating instructions shows a note about not connecting an antenna ground but nothing about the shock hazard. Next there is no tuned circuit in the transmitter output. Any harmonics generated by the crystal oscillator are passed unattenuated to the antenna. Again not a good design but it works, though on several bands at the same time.

The Mity Mite is a pretty neat little radio that reflects the time and market it was designed for. It is a keeper. I'll probably figure out a way to put it on the air (while staying on one band and not killing myself).

Another Swapmeet Find

Here's something that I keep around to show visitors that hams really did build the transmitters described in QST. Take a look at my version of George Grammer's push-pull TNT transmitter. This one here is a lot worse for wear but it is recognizable.

Swapmeet Find

Every once and a while over the years I've picked an item at a swapmeet just because it was interesting and if it could talk would have a story to share.

Here's one. I don't remember when or where I got it but probably at a central Texas swapmeet a few years ago. Some one on a budget wanted to get into ham radio. The local trash heap contributed an old crystal set complete with loose coupler. The tuning coil was rewound as the antenna transformer primary. Some tuning was allowed by striping off insulation in a few places. The loose coupler became the antenna coil and allowed variable coupling. I found a section of the Sunday comics shoved into the loose coupler to keep it in place..date1930. Two of the holes on the board next to the spark coil match the mounting holes for a Bunnell telegraph key.