The T2FD (Terminated Tilted Folded Dipole) was developed by the US Navy
after carrying out experiments using terminating resistors. Numerous
variations have appeared over the years, usually accompanied by warnings
that as a transmitting aperiodic multiband antenna, its performance may
leave something to be desired. This is because the transmitting power may be
wasted in the terminating resistor.

As mentioned previously the antenna developed from US Naval experiments to
broaden the bandwidth of a folded dipole to a reasonable degree. The was
first described publicly in 1949, after Navy Captain C.L. Countryman tested
it for long periods in California during WWII. The T2FD (also known as a
tilted, centre fed, terminated, folded dipole) can offer claimed gains of
4-6dB over a dipole, depending on the frequency, although 1-3dB is nearer
the mark with some frequencies exhibiting 1dB, as the resistor absorbs the
RF power in transmission. The main attraction of the T2FD is not its gain
however; it's its broadbandedness. It was, and still is, being publicized
in journals as a broadband aerial suitable for use between 3.5 and 28 Mhz.
In addition the T2FD has some attractive properties in terms of noise
reduction, which some long wires / dipoles and ATU combinations are
susceptible too.

In addition the T2FD can be used at higher frequencies than its design
frequency. Some sources claim that it can be used over a range of 5 or even
6:1, although my own observations indicate 4:1. None the less a 40-meter
version will cover 7Mhz to 25 Mhz, with some useful performance up into the
27 Mhz CB band.

See http://www.gb4iom.co.uk/new_page_4.htm for more information.

73



Adrian

M1LCR

"Kees" wrote in message
...
Hello fellow shortwave listeners !

More info to make a T2FD yourself, like I did mine, please have a
look at:

http://members.home.nl/rita.kees/t2fdmake.html


I hope you can appreciate it and use it for your practice.


I will be glad to answer your questions.

73/cheers

Kees

= = = "Tam/WB2TT" wrote in message
= = = ...
"Kees" wrote in message
...
Hello fellow shortwave listeners !

More info to make a T2FD yourself, like I did mine, please have a
look at:

http://members.home.nl/rita.kees/t2fdmake.html


I hope you can appreciate it and use it for your practice.


I will be glad to answer your questions.

73/cheers

Kees


I have no idea how well the antenna works, but the method of connecting the
reisistor is very complicated. May I suggest:

Connect the two wires to a normal dog-bone insulator, and solder the
resistor across the insulator to the two wires. Insulate if you wish. For
receive only, a 1/2 W resistor is as good, or better.

Tam/WB2TT

WB2TT - Simplier is better ~ RHF

..

On Tue, 22 Jun 2004 00:56:48 +0000, M1LCR wrote:

between 3.5 and 28 Mhz. In addition the T2FD has some attractive
properties in terms of noise reduction, which some long wires / dipoles
and ATU combinations are susceptible too.


I live in a suburb. My dipoles and long wires had so much noise that I
hardly ever would listen to HF. Once I read about the noise immunity
provided by a T2FD antenna, I constructed one to try. It was the best
thing I could have done! It made HF livable in my high noise urban
environment. I almost don't notice the noise I had before. I am able to
pick up signals that my neighbor with a tri-band 3 element yagi is unable
to hear due to his noise.

I would recommend this design to anyone combating local QRM.

On Tue, 22 Jun 2004 05:45:27 GMT, yea right wrote:

On Tue, 22 Jun 2004 00:56:48 +0000, M1LCR wrote:

between 3.5 and 28 Mhz. In addition the T2FD has some attractive
properties in terms of noise reduction, which some long wires / dipoles
and ATU combinations are susceptible too.


I live in a suburb. My dipoles and long wires had so much noise that I
hardly ever would listen to HF. Once I read about the noise immunity
provided by a T2FD antenna, I constructed one to try. It was the best
thing I could have done! It made HF livable in my high noise urban
environment. I almost don't notice the noise I had before. I am able to
pick up signals that my neighbor with a tri-band 3 element yagi is unable
to hear due to his noise.

I would recommend this design to anyone combating local QRM.


That's indeed what it is:
a very low-noise antenna.

Look at : http://members.home.nl/rita.kees/t2fdmake.html

for my "version ".

On Tue, 22 Jun 2004 05:45:27 GMT, yea right wrote:

On Tue, 22 Jun 2004 00:56:48 +0000, M1LCR wrote:

between 3.5 and 28 Mhz. In addition the T2FD has some attractive
properties in terms of noise reduction, which some long wires / dipoles
and ATU combinations are susceptible too.


I live in a suburb. My dipoles and long wires had so much noise that I
hardly ever would listen to HF. Once I read about the noise immunity
provided by a T2FD antenna, I constructed one to try. It was the best
thing I could have done! It made HF livable in my high noise urban
environment. I almost don't notice the noise I had before. I am able to
pick up signals that my neighbor with a tri-band 3 element yagi is unable
to hear due to his noise.

I would recommend this design to anyone combating local QRM.


That's indeed what it is:
a very low-noise antenna.

Look at : http://members.home.nl/rita.kees/t2fdmake.html

for my "version ".

Yes, that is an advantage. Everytime someone asks a question about a receive
only antenna on this newsgroup, there are always many responses saying to
just put up a piece of wire and run it strait to your radio. That will work,
assuming that you live out in the middle of nowhere, have no neighbors and
have no electrical appliances. For the rest of us, noise is a consideration
and more thought needs to be put into an antenna system.

"Kees" wrote in message
...

That's indeed what it is:
a very low-noise antenna.

Look at : http://members.home.nl/rita.kees/t2fdmake.html

for my "version ".

Yes, that is an advantage. Everytime someone asks a question about a receive
only antenna on this newsgroup, there are always many responses saying to
just put up a piece of wire and run it strait to your radio. That will work,
assuming that you live out in the middle of nowhere, have no neighbors and
have no electrical appliances. For the rest of us, noise is a consideration
and more thought needs to be put into an antenna system.

"Kees" wrote in message
...

That's indeed what it is:
a very low-noise antenna.

Look at : http://members.home.nl/rita.kees/t2fdmake.html

for my "version ".

"CW" no adddress@spam free.com wrote in message
...
Yes, that is an advantage. Everytime someone asks a question about a
receive
only antenna on this newsgroup, there are always many responses saying to
just put up a piece of wire and run it strait to your radio. That will
work,
assuming that you live out in the middle of nowhere, have no neighbors and
have no electrical appliances. For the rest of us, noise is a
consideration
and more thought needs to be put into an antenna system.



How does the antenna differentiate between "noise" and a valid signal?

(Perhaps these are going to be the solution to BPL.)

Pete

"CW" no adddress@spam free.com wrote in message
...
Yes, that is an advantage. Everytime someone asks a question about a
receive
only antenna on this newsgroup, there are always many responses saying to
just put up a piece of wire and run it strait to your radio. That will
work,
assuming that you live out in the middle of nowhere, have no neighbors and
have no electrical appliances. For the rest of us, noise is a
consideration
and more thought needs to be put into an antenna system.



How does the antenna differentiate between "noise" and a valid signal?

(Perhaps these are going to be the solution to BPL.)

Pete

In article sBEDc.1168$Rr2.4@lakeread03,
" Uncle Peter" wrote:

"CW" no adddress@spam free.com wrote in message
...
Yes, that is an advantage. Everytime someone asks a question about
a receive only antenna on this newsgroup, there are always many
responses saying to just put up a piece of wire and run it strait
to your radio. That will work, assuming that you live out in the
middle of nowhere, have no neighbors and have no electrical
appliances. For the rest of us, noise is a consideration and more
thought needs to be put into an antenna system.

How does the antenna differentiate between "noise" and a valid
signal?

Antennas are not intelligent agents able to differentiate between noise
and a broadcast signal. If the noise signal is generated a long
distance from the antenna it will be received right along with
broadcast signals. The only advantage some antennas would have here is
its reception pattern where the antenna could be orientated to be
relatively insensitive in the direction of the noise signal. This
generally is not helpful for short wave signals though because they are
generally too spread out directionally instead of looking like a point
source to take advantage of antenna nulls. Another problem for most
people is the fact that they cannot get the antenna up high enough for
it to exhibit its directional characteristics to a great degree.

A local noise is another matter greatly affecting many peoples
reception of short wave signals since many electronic devices around
the home and neighbor¹s homes generate noise. Here the type of antenna,
how it is connected to the receiver, and where it is located on the
user¹s property makes a huge difference on what may be heard.

Fundamentally, you want the entire antenna system to reject common mode
noise since to a local antenna this is the mode in which, the local
noise will couple to the antenna. You will want to use an antenna that
is balanced (Hertzian) instead of unbalanced (Marconi). You might also
want to consider using an antenna type that responds more to the
magnetic field component of the radio wave instead of the electric.
These two suggestions encompass the fact that most of the local noise
energy reaching and coupling to the antenna is a common mode electric
field and since the far field broadcast signals you want to receive is
composed of both electric and magnetic the later will be enhanced at
the expense of the former.

The connection from radio to antenna is best shielded so you would use
coax. You could use a balance line but they are harder to acquire, use,
and still will not work as well as coax shielding against local noise.

The antenna would be located as far from the majority of local noise
sources as possible on the property. Distance reduces the coupling to
local noise sources.

--
Telamon
Ventura, California