Broad band folded HF dipoles
 

Hi,
does any one have constructive comments about this type of
aerial?

http://www.bwantennas.com/ama/fdipole.ama.htm

How would it compare against a dipole dedicated to a specific frequency
for instance? I assume not as well, but how much less?

All sensible replies much appreciated, thank you.
--
Bill

Broad band folded HF dipoles
 

Bill wrote:
Hi,
does any one have constructive comments about this type of aerial?

http://www.bwantennas.com/ama/fdipole.ama.htm

How would it compare against a dipole dedicated to a specific frequency
for instance? I assume not as well, but how much less?

All sensible replies much appreciated, thank you.
I have used folded dipoles quite a bit in my QRP days. I used heavier
300 ohm TV twin-lead, and went through a 4-1 balun. The folded dipoles
have wider bandwidth. So you won't need to re-tune the antenna as often
if you are scanning from one side of the band to another.
I once had a 15 meter folded dipole that loaded up on all. 80-10 meter
bands. But the lose was too great on 40 and 80 meters. The long
feed-line is why it did load up on the bottom bands. Running QRP I did
work DX with it on 20 meters up to 10 meters.
The full wave loop, and the folded dipoles are my favorite antennas!
Jack
NZ9U

Broad band folded HF dipoles
 

On Thu, 13 Mar 2008 03:21:35 +0000, Bill wrote:

Hi,
does any one have constructive comments about this type of
aerial?

http://www.bwantennas.com/ama/fdipole.ama.htm

How would it compare against a dipole dedicated to a specific frequency
for instance? I assume not as well, but how much less?

All sensible replies much appreciated, thank you.

It's nice and quite. Great for urban hams. It matches very well on all
bands if you have a radio with a built in tuner. I would recommend this
antenna over anything else if you had but room for one antenna.

I use 1/4 fiberglass rods for the spreaders but the two end spreaders are
1/2 PVC. The flying terminating resistor was the hard part. I used 450ohm
feed line at the feed point instead of flying the balum to keep the
center of the antenna light as there was already too much weight in the
center from the flying load resistor. If your not running more than 100
watts, you can use a smaller resistor.

hope this helps!

Broad band folded HF dipoles
 

In article ,
Bill wrote:
does any one have constructive comments about this type of aerial?

http://www.bwantennas.com/ama/fdipole.ama.htm

You can find more than you want to know about this kind of antenna,
as well as comments about it good and evil, if you google for T2FD
which means tilted, terminated folded dipole.

I use one of the B&W 90-foot antennas, not as high as I wish I had it,
but we do what we can. I haven't compared it with a single band dipole,
but compared with a Carolina Windom the latter gives about 2 or 3 S
units stronger signal, pretty much on all bands. A recent posting
I read says that the 180 foot antenna is substantially better than
the 90 foot, as would be expected.

There are some similar antennas from some other manufacturers,
Bushcomm for instance.

If you need frequency agility without retuning that is where this kind
of antenna shines. You may have to fiddle with it to get the SWR as
low as they claim. Locally one was put up at the county emergency
operations center and at first the SWR was higher than advertised.
They eventually decided this was because of all the metal in the roof
and changed it from a sloper to a horizontal dipole and that made
things much better.

Frequency agility is mostly of interest to the ALE (Automatic Link
Establishment) folks, groups.yahoo.com/group/hflink where this
kind of thing gets discussed a lot.

Broad band folded HF dipoles
 

OK guys,
thanks for all the replies.

My main reason for asking about this type of aerial is that in a month
or so I have a job for a few days in the Highlands of Scotland, miles
from the nearest road and even further from habitation. This location
should be nice and quiet for HF and has a very wet ground surface so
should provide a reasonable earth. Also, and this is the good part, I
will have a 100' trailer mast with me that only has a VHF collinear on
top, this mast is just asking to have an HF aerial attached to it !!.
Unfortunately once it is up in the air I don't think my customer would
appreciate me raising and lowering it to tweak the HF aerial, hence
looking for something broad band and pretty much "plug and play".

My original intention had been to make something similar but thanks to
Chris G4BOH's offer I shall be using his aerial on the day.

http://www.cebik.com/
http://www.eham.net/reviews/?ehamsid...f1d9505a382115
http://www.arrl.org/members-only/prodrev/bymfg.html

all made for interesting reading. Ranging from "rubbish" to "
brilliant" so we shall see. :-)

W4RNL's site managed to use up quite a few hours of my day yesterday,
certainly made a good read, it is now well and truly book marked on my
PC, thank you.

--
Bill
G8IAY
Bedford
UK

Broad band folded HF dipoles
 

On Mar 12, 11:21*pm, Bill wrote:
Hi,
* * * * *does any one have constructive comments about this type of
aerial?

http://www.bwantennas.com/ama/fdipole.ama.htm

How would it compare against a dipole dedicated to a specific frequency
for instance? I assume not as well, *but how much less?

All sensible replies much appreciated, thank you.

Generically that antenna is a T2FD.

It has a power resistor in it. A certain amount of power (or, on
receiving, sensitivity) is lost in that resistor.

http://www.cebik.com/wire/t2fd.html has some detailed simulation
results for T2FD's, showing SWR vs frequency and power dissipated in
resistor for frequency.

Having tried some multi-band antennas in the past, I strongly feel
that what the vast majority of hams actually want is an all-band
doublet: http://www.cebik.com/wire/abd.html

I put an all-band doublet up a few months ago and am so, so, so happy
with it that there are no words. It loads up easily on 80M all the way
up to 10M and again I'm so so happy with how it works.

Tim.