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.

I see... thanks for the reply.

I was confused by the toroid in transmission. When transmitting, the
ferrite toroid is usually near the transceiver, but for other reason: to
avoid the RF catch by the coax shield or reflected due to a mismatched
antenna to reach the transceiver (it can cause RF shock to people and
interferences). In reception, yes, you're right, but I think that only
if the coax shield is correctly grounded.

The signal at the received is not the one coming through the line, but
the difference between the signal coming through the line and the signal
coming though the shield, so grounding the shield puts the shield signal
to zero, and then only the line signal is considered. If the radio is
operated from batteries or ungrounded, both signals will count and the
noise will be noticed, whether it comes through the line or through the
coax.

Maybe I'm wrong. RF is a very empirical "science" and experiencie is
more valuable than books ;). I have little experiencie and few books ;)

I spent great moments with a long wire (30 meters or 100 feet) coupled
with a MFJ antenna tunner with long wire coupler (MFJ-941E) in the
country. Now I have a constant electrical noise in the city in all the
band, about S7-S9, 24h... I'm limited to strong signals.

Best regards.


Kees wrote:
Hi

Well, the coax receives it on the outer side.
It would travel up to the balun and goes from there into the coax
inside back to the receiver.
That's why I put it up there.

Kees


On Mon, 21 Jun 2004 12:53:59 +0200, Nacho
wrote:


Hello.

Just a question.

Why is the ferrite toroid near the antenna instead of near the receiver?
It is used to supress the waves received by the coax, but at the far
side from the transceiver, the supress will be minimum...

Best regards.


Kees wrote:

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

"Kees" wrote in message
...
Hi

Well, the coax receives it on the outer side.
It would travel up to the balun and goes from there into the coax
inside back to the receiver.
That's why I put it up there.

Kees


If you really want to keep house noise from entering the antenna, there
should be an isolation transformer at the RX end. Your choke at the antenna
end will indeed reduce conducted noise from getting into the antenna but not
radiated noise. Think of the outer shield of the coax as an antenna in close
proximity to the T2FD. Perhaps running the coax at right angles to the T2FD
would help some if an isolation transformer is not used in the shack.

Dale W4OP

N8KDV,

Fritzel "FD4" Multiband Antenna 80M-10M / 3.5 to 30 MHZ 2kw Dipole
eHAM-REVIEWS= http://www.eham.net/reviews/detail/1055
http://www.eham.net/reviews/detail/1055?page=2

Fritzel "FD3" Tri-Band 'Dipole' Antenna 40M/20M/10M
eHAM-REVIEWS= http://www.eham.net/reviews/detail/3497

History of the Windom Antenna
http://www.scotham.net/modules.php?n...rticle&sid=218
"What became perhaps the most popular multiband Windom design
of all, was the German-made Fritzel 'FD4' Antenna"

The "No Tuner, Multi-Band, Off-Center-Fed (OCF) Dipole"
at 135 Feet long with a 6:1 Voltage Balun
OCFD= http://hamcall.net/6bandmegpole.html
Description - Pictures - Graph - Table
NOTE: Some features of this Off-Center-Fed Dipole Antenna
{Windom} are similar to the no longer available and once
popular German Fritzel FD-4 Antenna.

iane ~ RHF
..
..
= = = dxAce wrote in message
= = = ...
Kees wrote:

Hi

What are the odds ? :-)

Well I hear some successtories and non-successtories.

Mine is very low-noise; signals are low too, but I think S/N here is
very very good.

Mine was low noise too..., low noise, low signal... always had much, much
better results with a transformer matched wire.

When I use a FD4 or FD3 (Fritzel) or a (long)wire, the RX is much more
"nervous". Very unpleasant listening.

What exactly do you mean by 'nervous'?

Steve
Holland, MI
Drake R7, R8 and R8B

http://www.iserv.net/~n8kdv/dxpage.htm

NACHO,

IMHO: Your T2FD could also use a "Feed-Line-Isolator" at the
'junction' of the Receiver and Coax Cable.

Take a look at the Wellbrook "Low Noise Antenna" 'design concept'
using two components they manufactu the Universal Magnetic
Balun (UMB) and the Antenna Feed Isolator (Feed-Line-Isolator).

GoTo= http://www.wellbrook.uk.com/longwire.html

FWIW: This webpage has two Drawings/Diagrams "The Wrong Way"
and "The Correct Way" plus a brief description of the 'Whys'
and 'Hows' of this "Low Noise Antenna" design concept.

NOTE: These are labled as "Longwire" Antenna Baluns, but
in reality they are mostly used on the more common
"Random Wire" Antennas that the majority of SWL are able to
build and use in their backyards or outside/inside the house.


iane ~ RHF
..
..
= = = Nacho wrote in message
= = = ...
I see... thanks for the reply.

I was confused by the toroid in transmission. When transmitting, the
ferrite toroid is usually near the transceiver, but for other reason: to
avoid the RF catch by the coax shield or reflected due to a mismatched
antenna to reach the transceiver (it can cause RF shock to people and
interferences). In reception, yes, you're right, but I think that only
if the coax shield is correctly grounded.

The signal at the received is not the one coming through the line, but
the difference between the signal coming through the line and the signal
coming though the shield, so grounding the shield puts the shield signal
to zero, and then only the line signal is considered. If the radio is
operated from batteries or ungrounded, both signals will count and the
noise will be noticed, whether it comes through the line or through the
coax.

Maybe I'm wrong. RF is a very empirical "science" and experiencie is
more valuable than books ;). I have little experiencie and few books ;)

I spent great moments with a long wire (30 meters or 100 feet) coupled
with a MFJ antenna tunner with long wire coupler (MFJ-941E) in the
country. Now I have a constant electrical noise in the city in all the
band, about S7-S9, 24h... I'm limited to strong signals.

Best regards.

..

= = = "Dale Parfitt" wrote in message
= = = .. .
"Kees" wrote in message
...
Hi

Well, the coax receives it on the outer side.
It would travel up to the balun and goes from there into
the coax inside back to the receiver.
That's why I put it up there.

Kees


If you really want to keep house noise from entering the antenna,
there should be an isolation transformer at the RX end. Your choke
at the antenna end will indeed reduce conducted noise from getting
into the antenna but not radiated noise. Think of the outer shield
of the coax as an antenna in close proximity to the T2FD. Perhaps
running the coax at right angles to the T2FD would help some if
an isolation transformer is not used in the shack.

Dale W4OP

DP / W4OP,

Are you referring to a 1:1 Matching Transformer that is used as
"Feed-Line-Isolator" at the 'junction' of the Receiver and Coax
Cable that feeds the T2FD Antenna.

Wellbrook "Low Noise Antenna" 'design concept' using two
components they manufactu the Universal Magnetic Balun (UMB)
and the Antenna Feed Isolator (Feed-Line-Isolator).

GoTo= http://www.wellbrook.uk.com/longwire.html

FWIW: This webpage has two Drawings/Diagrams "The Wrong Way"
and "The Correct Way" plus a brief description of the 'Whys'
and 'Hows' of this "Low Noise Antenna" design concept.

NOTE: These are labled as "Longwire" Antenna Baluns, but
in reality they are mostly used on the more common
"Random Wire" Antennas that the majority of SWL are able to
build and use in their backyards or outside/inside the house.

iane ~ RHF
..
Some Say: On A Clear Day You Can See Forever.
http://groups.yahoo.com/group/Shortw...na/message/502
I BELIEVE: On A Clear Night...
You Can Hear Forever and Beyond - The Beyond !

..

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 ".