A Radio forum. RadioBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » RadioBanter forum » rec.radio » Shortwave
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

T2FD antenna opinions solicited



 
 
Thread Tools Display Modes
  #1  
Old March 15th 06, 02:54 AM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default T2FD antenna opinions solicited

I will hang T2FD in attic this weekend and have question about slope vs
bandwith. Well here is same post I just made to yahoo group. I have
some big dipoles for 75m and 160m, but I don't think they work so good
for SWL. I also have a very difficult time to climb up on roof
especially when cold. I'm a fraidy cat with heights( but no prob to
jump with a chute). This may be just an interm antenna till WX gets
better.

"Last time I was up in the attic about a year ago it looked like I
had about 12 foot of headroom. I was figuring I would put up a T2FD
about the full length 45 feet of attic and I could get a decent
slope. I was up there Saturday and now it looks like it's about 8
foot of headroom. I figure at the rate it's shrinking I better
hurry up and get the thing up while I can still stand up in the
attic.

So dilemma is length of antenna vs the slope. I can get a 20 degree
slope with a 23 foot antenna for about 14mc bottom end or a 30
degree slope with a 16 foot antenna for a 20mc bottom end. I am more
interested in SWL than ham bands. Antenna/attic is orientated along
a line parallel to 135/315 degrees."

I am looking for a comparison of the two potential installations.

Thanks & regards,
Bob
N9NEO

  #2  
Old March 15th 06, 04:04 AM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default T2FD antenna opinions solicited

N9NEO wrote:
I will hang T2FD in attic this weekend and have question about slope vs
bandwith. Well here is same post I just made to yahoo group. I have
some big dipoles for 75m and 160m, but I don't think they work so good
for SWL. I also have a very difficult time to climb up on roof
especially when cold. I'm a fraidy cat with heights( but no prob to
jump with a chute). This may be just an interm antenna till WX gets
better.

"Last time I was up in the attic about a year ago it looked like I
had about 12 foot of headroom. I was figuring I would put up a T2FD
about the full length 45 feet of attic and I could get a decent
slope. I was up there Saturday and now it looks like it's about 8
foot of headroom. I figure at the rate it's shrinking I better
hurry up and get the thing up while I can still stand up in the
attic.

So dilemma is length of antenna vs the slope. I can get a 20 degree
slope with a 23 foot antenna for about 14mc bottom end or a 30
degree slope with a 16 foot antenna for a 20mc bottom end. I am more
interested in SWL than ham bands. Antenna/attic is orientated along
a line parallel to 135/315 degrees."

I am looking for a comparison of the two potential installations.

Thanks & regards,
Bob
N9NEO


Is this a T2FD which you made (or are making) yourself, or is it from
RF Systems or B&W? I'm guessing home made since you talk about
changing the length.

I've used an RF Systems 45 foot T2FD at two different location with two
different angles because of the supports I had to work with, one maybe
20 degrees and the other at only 10 degrees!

Can't say that I noticed a difference. If anything, I'd say that I
pulled in more of the really low-power stations from Africa, South
America, Asia and the Pacific (omnidirectional) with it sloped at only
10 degrees all over the frequency range, from 60 meters to 19 meters
(never got anything that I'd consider low-power in the 16 meter band).
I did notice that I was able to DX in the 90 meter band only when the
angle was 20 degrees. Propogation always plays a huge part in whether
or not you receive a signal, but these results were pretty consistant.


I also believe that a big part in the exceptional signal-to-noise ratio
was the use of a Transi-Trap and a ground rod, even though the set-up
at 10 degrees had a pretty poor excuse for a rod (2 foot brass tube I
found at some hardware store, don't even know what it was supposed to
be used for).

I'd say use the full 45 feet with no slope.

BTW, where do you live? Its getting close to Spring everywhere here in
the States. Maybe six more weeks and you could set up your antenna
outside in relative warmth, if you're a Yankee like me :-)

  #3  
Old March 15th 06, 06:56 AM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default T2FD antenna opinions solicited

In article . com,
wrote:

N9NEO wrote:
I will hang T2FD in attic this weekend and have question about slope vs
bandwith. Well here is same post I just made to yahoo group. I have
some big dipoles for 75m and 160m, but I don't think they work so good
for SWL. I also have a very difficult time to climb up on roof
especially when cold. I'm a fraidy cat with heights( but no prob to
jump with a chute). This may be just an interm antenna till WX gets
better.

"Last time I was up in the attic about a year ago it looked like I
had about 12 foot of headroom. I was figuring I would put up a T2FD
about the full length 45 feet of attic and I could get a decent
slope. I was up there Saturday and now it looks like it's about 8
foot of headroom. I figure at the rate it's shrinking I better
hurry up and get the thing up while I can still stand up in the
attic.

So dilemma is length of antenna vs the slope. I can get a 20 degree
slope with a 23 foot antenna for about 14mc bottom end or a 30
degree slope with a 16 foot antenna for a 20mc bottom end. I am more
interested in SWL than ham bands. Antenna/attic is orientated along
a line parallel to 135/315 degrees."

I am looking for a comparison of the two potential installations.

Thanks & regards,
Bob
N9NEO


Is this a T2FD which you made (or are making) yourself, or is it from
RF Systems or B&W? I'm guessing home made since you talk about
changing the length.

I've used an RF Systems 45 foot T2FD at two different location with two
different angles because of the supports I had to work with, one maybe
20 degrees and the other at only 10 degrees!

Can't say that I noticed a difference. If anything, I'd say that I
pulled in more of the really low-power stations from Africa, South
America, Asia and the Pacific (omnidirectional) with it sloped at only
10 degrees all over the frequency range, from 60 meters to 19 meters
(never got anything that I'd consider low-power in the 16 meter band).
I did notice that I was able to DX in the 90 meter band only when the
angle was 20 degrees. Propogation always plays a huge part in whether
or not you receive a signal, but these results were pretty consistant.


I also believe that a big part in the exceptional signal-to-noise ratio
was the use of a Transi-Trap and a ground rod, even though the set-up
at 10 degrees had a pretty poor excuse for a rod (2 foot brass tube I
found at some hardware store, don't even know what it was supposed to
be used for).

I'd say use the full 45 feet with no slope.


Good advice.

BTW, where do you live? Its getting close to Spring everywhere here in
the States. Maybe six more weeks and you could set up your antenna
outside in relative warmth, if you're a Yankee like me :-)


Put up the attic antenna anyway. It would not be much trouble to put it
up and you might like the way it works. More antennas means more options.

--
Telamon
Ventura, California
  #4  
Old March 15th 06, 07:22 PM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default T2FD antenna opinions solicited

Ok then it will be about 45 feet at whatever dangle it ends up at.

And yes, I am born and raised Connecticut Yankee. QTH here now is
Uxbridge, Ma. Gateway to the beautiful Blackstone valley.

And yes, more antenna options are good.

regards,
Bob
N9NEO

  #5  
Old March 15th 06, 07:35 PM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default T2FD antenna opinions solicited

On 14 Mar 2006 18:54:34 -0800, "N9NEO"
wrote:



So dilemma is length of antenna vs the slope. I can get a 20 degree
slope with a 23 foot antenna for about 14mc bottom end or a 30
degree slope with a 16 foot antenna for a 20mc bottom end. I am more
interested in SWL than ham bands. Antenna/attic is orientated along
a line parallel to 135/315 degrees."

I am looking for a comparison of the two potential installations.

Thanks & regards,
Bob
N9NEO


Since we're at the bottom of the sun spot cycle I'd guess an antenna
with a 14 mc bottom end would be better than 20 mc. If anything, I'd
extend it a bit to get it even lower, but you know what frequencies
you like listening to better than I do.

bob
k5qwg
  #6  
Old March 16th 06, 01:43 AM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default T2FD antenna opinions solicited

Actually Bob that is part of the problem. I am total newbie to SWL and
so I don't know which frequencies I would prefer the best. I'm usually
all over the place in any band I happen to find myself in. I seem to
have the most difficulty down in the shack with the higher
frequencies. Antenna situations for swl is not too good here. I have
160m inverted V, 75m dipole, and 5btv verticle. I'll stick the T2FD in
the attic for now and that should help near upper bands. Then I'll try
a long wire when WX gets better. Part of problem here I'm sure is bad
ground too, so lots of work needs to be done still.

regards to all,
Bob

  #7  
Old March 16th 06, 11:56 AM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default In-the-Attic : Terminated "Twisted" Folded Dipole (T2FD) - Think Twisted -not- Tilted !

N9NEO,

MY IDEAS ON AN IN-THE-ATTIC T2FD ANTENNA :
Old Idea - Terminated 'Tilted' Folded Dipole (T2FD)
[ Twisted -Not- Tilted ]
New Idea - Terminated "Twisted" Folded Dipole (T2FD)
[ Twisted / Flat-not-Tilted / In-the-Attic ]

First Build the Terminated Tilted Folded Dipole (T2FD)
as Big as you Can to get down to your "Lowest Desired
Operating Frequency" per the design Formulas.

Second the In-the-Attic T2FD is after all In-the-Attic and so . . .
It Ain't Gone-Ah-Be Tilted - It's Gone-Ah-Be FLAT [.]

QUESTION - What Did the Tilting Do For the T2FD ?
1 - Added to the Broadbanded Frequency Characteristics
of the T2FD Antenna.
2. Added to the Omni-Directional (All-Around 360 Degrees)
Characteristics of the T2FD Antenna.
Note - The TILT of the T2FD Antenna was usually about
30 Degrees and that would mean that the Height of the
Antenna "Vertical Dimension" was 50% of the Length of
the T2FD Antenna plus the Elevation at the Lower Base
(Bottom) Support.

Doing the Math - Your 45 Foot Long T2FD Antenna would
have to have a "Vertical Dimension" Drop of 22.5 Feet and
to keep the Wires overhead a minimum Lower Support
Height of 7.5 Feet for a Top Mounting Support Height of
at least 30 Feet. All sort of hard-to-do in most Attics.

ALTERATIVE - Omni-Directional Antenna Trick :
Build a T2FD Antenna In-the-Attic with a TWIST
Terminated "Twisted" Folded Dipole (T2FD)
- - - Instead of a Tilt )

The Ends would both have "Vertical" Spacers / Spreaders
and the Center Spacer / Spreader would be "Horizontal".

The Left-Top-Wire would become the Center-Near-Wire
and then the Right-Bottom-Wire -while- The Right-Top-Wire
would become the Center-Far-Wire and then become the
Left-Bottom-Wire.

If additional Mid-Point Spacers / Spreaders were used
then they would be set at 45*/225* and 135*/315* to
maintain the distance between the two Wires.

When building a T2FD Antenna In-the-Attic :
Think - Twisted -not- Tilted :
Terminated "Twisted" Folded Dipole (T2FD)


MORE GENERAL INFO ABOUT THE T2FD ANTENNA :

B&W makes two general statements about the
Terminated Tilted Folded Dipole (T2FD) Antenna :

* For example, an {T2FD} Antenna for the lower portion of
Shortwave (3 - 18 MHz) will be roughly 33m (110 feet) long,
with conductors spaced 1m (3.3 feet).
[With a Top End mounted about 60 Feet High at 30 Degrees.]

* In order to cover the higher portion of Shortwave (5 - 30 MHz),
this {T2FD} Antenna will be roughly 20m (66 feet) long,
with a spacing of 60 cm (24 inches).
[With a Top End mounted about 40 Feet High at 30 Degrees.]

Build one size or the other = No Formula Required.

READ : Terminated Tilted Folded Dipole (T2FD)
Antenna - WOW ! ! ! {One SWL's Experiance}
http://groups.yahoo.com/group/Shortw...na/message/293

Hard Core DX - "T2FD Antenna" - Info and Design Links
GoTo= http://www.hard-core-dx.com/nordicdx...ire/index.html
- - - The Terminated Tilted Folded Dipole (T2FD)
- - - The "T2FD" is a Broad All Band Antenna for SWL.
http://www.hard-core-dx.com/nordicdx...wire/t2fd.html
http://www.hard-core-dx.com/nordicdx.../t2design.html
http://www.hard-core-dx.com/nordicdx.../t2fdfeed.html
http://www.hard-core-dx.com/nordicdx.../t2fdcomp.html
http://www.hard-core-dx.com/nordicdx...re/t2fd_1.html

More About the Terminated Tilted Folded Dipole (T2FD)
* How To Build the TTFD : A Broadband Antenna for
Shortwave Reception - by Arnie Coro [RHC] Dxers Unlimited
http://www.radiohc.org/Distributions/Dxers/ttfd2.html
* Modeling the T2FD - by L.B. Cebik [W4RNL]
http://www.cebik.com/wire/t2fd.html

The Formulas for Calculating Terminated Tilted Folded
Dipole (T2FD) Dimensions are found at :
http://www.hard-core-dx.com/nordicdx.../t2design.html

TIP - Take a look at the Wellbrook Universal Magnetic Balun
UMB T2FD is a Receiving Antenna Balun designed to
simplify the construction of the Terminated Tilted
Folded Dipole (T2FD) Antenna.
http://www.wellbrook.uk.com/images/umbt2fd.gif
http://www.wellbrook.uk.com/images/umbt2fdc.gif
http://www.wellbrook.uk.com/images/umbt2fde.gif
(o: Construction Hints )

RF Systems - Terminated Tilted Folded Dipole (T2FD)
Receive Antenna - Coverage : 3 - 35 MHz
http://www.universal-radio.com/catalog/sw_ant/0562.html


hope this helps in a twisted sort of way - iane ~ RHF
  #8  
Old March 16th 06, 05:32 PM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default In-the-Attic : Terminated "Twisted" Folded Dipole (T2FD) - Think Twisted -not- Tilted !

Ok, Thanks for the good links.

If you explain the twist..... so I can understand. I don't think you
are telling me to just build a T2FD and make the feed point horizontal.
You are telling... Ok, I think I got it... So the loop will actually
go thru a 180 degree spin I think. is what you are telling me.

Yes, biggest problem was that roof wasn't high enough the last time I
was up there. I can stand up in it no prob and last weekend daughter's
BF and I laid a 24" wide path of plywood down the full 45 foot length.

Ok, I'll give this a try and see how it works out. I got some #43 ring
cores that I was going to build a 4:1 balun on. I may get bored one
day and fire up a transmitter into this setup, so I'll wind a few turns
on it so I don't smoke it.

thanks again
Bob

  #9  
Old March 16th 06, 07:20 PM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default In-the-Attic : Terminated "Twisted" Folded Dipole (T2FD) - Think Twisted -not- Tilted !

On 16 Mar 2006 09:32:42 -0800, "N9NEO"
wrote:

Ok, Thanks for the good links.

If you explain the twist..... so I can understand. I don't think you
are telling me to just build a T2FD and make the feed point horizontal.
You are telling... Ok, I think I got it... So the loop will actually
go thru a 180 degree spin I think. is what you are telling me.

Yes, biggest problem was that roof wasn't high enough the last time I
was up there. I can stand up in it no prob and last weekend daughter's
BF and I laid a 24" wide path of plywood down the full 45 foot length.

Ok, I'll give this a try and see how it works out. I got some #43 ring
cores that I was going to build a 4:1 balun on. I may get bored one
day and fire up a transmitter into this setup, so I'll wind a few turns
on it so I don't smoke it.

thanks again
Bob


One other idea -- since your attic will have plenty of connection
points -- a fanned dipole; one for 12 meters, another for 17 meters;
feed both with one length of coax, no balun needed. And the two
dipoles should be within yelling distance of most of the upper
frequency swl listening bands, when you're not using the antenna for
ham things.

bob
k5qwg
k5qwg
  #10  
Old March 17th 06, 07:26 AM posted to rec.radio.shortwave
Guest
 
Posts: n/a
Default In-the-Attic : Terminated "Twisted" Folded Dipole (T2FD) - ThinkTwisted -not- Tilted !

The T2FD style antennas are most popular for NVIS communication, where
the intent is to transmit and receive nearly straight up and back down
within a few hundred miles on freqs generally lower than 12MHz. The T2FD
does this best at lower elevations where itís less than .25 wavelength
above ground at highest operating frequency. Itís gained popularity with
military frequency hopping and ALE stations because of itís instant
broad band charm. With that said, one problem I see is placing the
antenna in the attic will put house wiring right underneath the antenna,
causing the pattern to point mostly up and not at a low angle to the
horizon where you want it for SWL DX (same for any horizontal ant in the
attic). It will also be more susceptible to RFI from stuff within the
house. The T2FD is generally a low noise antenna and it also requires
about a 16:1 balun, not a 4:1. You will seriously degrade the
performance if you try to feed it with anything less than the difficult
to obtain 16:1 flavor.
Bob


N9NEO wrote:
Ok, Thanks for the good links.

If you explain the twist..... so I can understand. I don't think you
are telling me to just build a T2FD and make the feed point horizontal.
You are telling... Ok, I think I got it... So the loop will actually
go thru a 180 degree spin I think. is what you are telling me.

Yes, biggest problem was that roof wasn't high enough the last time I
was up there. I can stand up in it no prob and last weekend daughter's
BF and I laid a 24" wide path of plywood down the full 45 foot length.

Ok, I'll give this a try and see how it works out. I got some #43 ring
cores that I was going to build a 4:1 balun on. I may get bored one
day and fire up a transmitter into this setup, so I'll wind a few turns
on it so I don't smoke it.

thanks again
Bob

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
I Want Another Antenna Lenny Shortwave 4 January 23rd 06 10:12 PM
No CounterPoise - Portable Antenna System RHF Shortwave 1 November 19th 05 06:18 PM
ABOUT - Making a SWL Antenna out of 300 Ohm Twin Lead and TV Coax Cable RHF Shortwave 0 October 28th 05 12:22 PM
Questions -?- Considering a 'small' Shortwave Listener's (SWLs) Antenna RHF Shortwave 1 January 24th 05 09:37 PM
Outdoor Antenna and lack of intermod Soliloquy Scanner 11 October 11th 03 01:36 AM


All times are GMT +1. The time now is 04:27 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ©2004-2014 RadioBanter.
The comments are property of their posters.