[amsat-bb] Re: 70cm Antenna Ident

i8cvs domenico.i8cvs at tin.it
Wed Aug 29 12:01:51 PDT 2007

Hi David, W0DF

It is a very old model of a 2 x 19 element yagi made by TONNA for 435 MHz
more than 20 years ago.
I have the original manual but I have never used this type of antenna.
The computed gain claimed by Tonna at 432.0 MHz both for the E plain and the
H plain is 16.20 dBi and the front-to-back ratio is -23.56 dB while the -3
dB beamwidth is 2 x 14.76 dB
The distance between each first director and the respective folded dipole is
such that the feed impedance is 50 ohm.
This antenna do not make use of any 1/1 balun so that the inner conductor of
the 50 ohm coax cable is directly connected to one side of the folded dipole
and the braid is directly connected to the other side and this is bad to
supply a balaced folded dipole to an unbalance feed line like a coax cable.
The manual do not supply any information on how connect both coax cables
to the folded dipoles for circular polarization RHCP or LHCP but you can get
the necessay schematic diagram from any antenna-book.

73" de

i8CVS Domenico

----- Original Message -----
From: "David Fine" <dfine100 at sbcglobal.net>
To: <amsat-bb at amsat.org>
Sent: Wednesday, August 29, 2007 2:47 AM
Subject: [amsat-bb] 70cm Antenna Ident

> Can anyone help me identify the manufacturer of a used 70cm crossed yagi
that I picked up along with a Yaesu 5400B rotator system at a local hamfest.
The antenna has a  12 foot 5/8 inch square boom (in two pieces), 19 elements
horizontal, 19 vertical uninsulated through the boom, and folded dipole
driven elements.  There are two things that I believe make this antenna
unique.  The coax attaches to the driven element with push-on crimp
terminals (UGH), and the directors and reflectors are held in place on the
boom with "W" shaped stainless steel spring clamps that are pressed over the
boom.  The elements then pass through the clamps and the spring tension
holds the elements in place.  Does this sound familiar to anyone?  Thanks
for the help.  W0DF
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