Well, Serge,

It consists of 5 major parts. A piece of 300 ohm twinlead, a coil, some
wire, a copper disk plus a length of PVC pipe and cap on top. The twinlead
matches 50 ohm input to the radiator, which consists of two half waves on 2M
separated by a phasing coil. On 70 CM, the radiator will be two full
wavelength radiators in phase.

Matching section:
Start with a piece of 300 ohm twinlead about 50 cm long. Strip and short
one end. 3.8 cm from the short, remove a few mm of insulation from both
conductors, and connect a 50 ohm coax to it, center conductor to one side
(call it A) and shield to the other side. Now, trim the twinlead to exactly
42.4 CM long, leaving this end open. Remove 1.3 cm of insulation from the
conductor on the A side. This is where the radiator will attach.

Phasing coil:
Dry wood dowel (or Plexiglas or polystyrene, but not PVC) 1.3 cm diameter
(actually 1/2") and 3.8 cm (1.5") long. Drill a 2.5 or 3 mm hole through
each end to hold the ends of a coil. You need about 55 cm of solid 20 gage
(0.889 mm dia.) insulated wire. Wind 13 equally spaced turns of this 20
gage wire on the dowel and pass the ends through the holes. Cut the ends
leaving a couple of cm on each end. Strip a cm of insulation off each end.
These dimensions are likely to be fairly critical.

Radiator:
Made from straight pieces of 12 gage (2.053 mm) insulated solid wire.
(Typical house wiring material in the US.) Cut one piece 97.8 cm long,
strip a few mm of insulation from each end, and connect (solder) from A of
the twin lead to one end of the coil. Cut a second piece the same (97.8 cm)
length, and solder to the other end of the coil. The wire diameter is not
critical, but the lengths are.

Pipe and top disk:
The author used a 10 foot (3.1 M) piece of 3/4" (nominal OD ~ 27 cm) PVC
pipe to support this assembly. He cut a piece of copper clad material just
larger than the ID of the pipe, drilled a hole in the center and passed the
end of the second piece of 12 gage wire through it and soldered it. Then he
dropped the antenna in the pipe, and put a PVC pipe cap over the end.

The author recommends adjusting the lengths of the twin lead and the
radiator wires to achieve best SWR.
--
Crazy George
Remove NO and SPAM from return address
"Serge Stroobandt, ON4BAA" wrote in message
...
Dear OMs,

Via this newsgroup I learned that last September the following article
appeared in QST:

p.28: An Easy to Build, Dual-Band Collinear Antenna by Dan Friedrichs,
K0IPG

I am particularly interested in this article, because at this very moment
I
am designing myself a 70cm colinear.
Unfortunately, I do not have access here to this article.

Before I contact the ARRL's reprint service, I was wondering if somebody
of
this newsgroup who has read this article,
could brievely describe the basis principle of this antenna (coils?,
phased
line?, electrical length?).

Many thanks!

73 de Serge ON4BAA / HB9DWU
http://salsawaves.com/propagation/