Real radio engineering

[Andre' Kesteloot]

Subject:
Diet Coke can tuner in an 80 m. xmtr [Yahoo! Clubs: The
Crystal Set Radio Club]
Date: Wed, 24 Jan 2001 08:15:09 PST
From: rick_weber <clubs-mail@yahoo-inc.com>
To: roneill@clark.net



I was intrigued with Larry Pizzella’s (Loose-Coupler) Diet
Coke Can tuner when he first posted the photo on this web
site.. This
past weekend, I set up my own personal challenge to build a
QRP CW transmitter for 80 meters that used only ONE
commercial electronic component -- a vacuum tube -- and
other NON-electronic junk commonly found around the house
including several Diet Coke cans.
This is not a crystal radio, of course, but
is in the crystal radio enthusiasts’ spirit of “minimal”
design and constructtion.

I started with a very old ‘27 tetrode vacuum tube made in
the late 1920’s. No commercial resistors, capacitors,
chokes, or variable tuners were used.
Capacitors were made from Diet Coke cans
and clear packing tape -- two .002 mF and one 250 pF. Made
the 500 pF variable condenser from one diet coke telescoping

over another one with packing tape insulation. RF choke is
160 turns of wire on a ball point pen body.
The 10 KOhm grid resistor was made using the old science
fair trick of a soft graphite pencil rubbed on carboard.
Two paper clips provided the resistor leads.
Twelve turns of wire on a plastic pill bottle for the
tank coil.

Swing link loosely coupled to the tank coil via an LDG QRP
tuner/4:1 balun to a center-fed Zepp ant. Used the rcvr part

of a Sierra as my receiver. Powered the xmtr with an old
1929
‘80-based power supply.

The crazy thing worked!

Had a QSO Tuesday night with Bob Howard K0RDF about 350
miles away. My RST -- 239. The best I could tell, this thing

was putting a little under a Watt to the antenna. Here’s a
photo:

 http://www.vintagehamradio.com/junkbox-xmtr

Here’s the total parts list for the xmtr:

1 ‘27 tetrode vacuum tube
5 Diet Coke cans (capacitors)
1 Plastic pill bottle (tank coil form)
2 Ballpoint pens (one for RF choke and one for tank coil
form support)
1 Roll of packing tape (insulation for caps and general)
2 paper clips (resistor leads)
1 HB pencil (resistor)
Wire, epoxy, nails, cardboard, wood, solder

Why use a vacuum tube instead of a transistor? I’m an OT
radio nut. (The best QRP radios glow in the dark!)

A lot of you rockheads out there who are also hams have a
whole lot more ingenuity and skill than this old coot. Why
not try your luck at a building something similar and let us

know how it worked.

Rick Weber
W9QZ