Really Inefficient Antennas
 

Hi,
Since much has been made of the pros and cons of the B&W dipole or T2FD, I
thought it would be interesting to see if other amateurs have managed to
homebrew one of these. The B&W costs $200 USD. Seems like one could make
something that has the same amount of inefficiency for a lot less dollars.
Maybe use resistance wire (nichrome?), or connect a light bulb at the
feedpoint. The Isotron has been mentioned, but it costs too much. Any ideas?
73 Gary N4AST

Take a dummy load and attach a piece of wire on some kind of a windup
system. To increase the efficiency, let out more wire and vice versa.

Good Idea, and we want to decrease efficiency, so the wind-up system may just
may be what is needed. What I was looking for is antenna materials that
decrease efficiency.
If we could come up with something as bad as the B&W dipole for a lot less
money, then we may have something.
73 Gary N4AST

JGBOYLES wrote:

Take a dummy load and attach a piece of wire on some kind of a windup
system. To increase the efficiency, let out more wire and vice versa.

Good Idea, and we want to decrease efficiency, so the wind-up system may just
may be what is needed. What I was looking for is antenna materials that
decrease efficiency.
If we could come up with something as bad as the B&W dipole for a lot less
money, then we may have something.
73 Gary N4AST

Kite string and a lawn sprinkler? :-)

73, jk ac6xg

"JGBOYLES" wrote in message
...
Hi,
Since much has been made of the pros and cons of the B&W dipole or T2FD,
I
thought it would be interesting to see if other amateurs have managed to
homebrew one of these. The B&W costs $200 USD. Seems like one could make
something that has the same amount of inefficiency for a lot less dollars.
Maybe use resistance wire (nichrome?), or connect a light bulb at the
feedpoint. The Isotron has been mentioned, but it costs too much. Any
ideas?
73 Gary N4AST

Try this: a 16 Ohm resistor in series with each side of the dipole, and a
100 Ohm resistor across the feedpoint. Unless I messed up, this will give
you SWR = 2:1 for all conditions including shorted, and absent dipoles.
Tam/WB2TT

Tam/WB2TT wrote:
Try this: a 16 Ohm resistor in series with each side of the dipole, and a
100 Ohm resistor across the feedpoint. Unless I messed up, this will give
you SWR = 2:1 for all conditions including shorted, and absent dipoles.

Why stop there? A single Bird Termaline will guarantee a 1:1 SWR over a
1:100 frequency range.
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Tam/WB2TT wrote:
Try this: a 16 Ohm resistor in series with each side of the dipole, and
a
100 Ohm resistor across the feedpoint. Unless I messed up, this will
give
you SWR = 2:1 for all conditions including shorted, and absent dipoles.

Why stop there? A single Bird Termaline will guarantee a 1:1 SWR over a
1:100 frequency range.

But mine will actually radiate. Efficiency could easily be 33% for some
dipole lengths/frequency combinations.
Tam
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Tam/WB2TT wrote:
Try this: a 16 Ohm resistor in series with each side of the dipole, and
a
100 Ohm resistor across the feedpoint. Unless I messed up, this will
give
you SWR = 2:1 for all conditions including shorted, and absent dipoles.

Why stop there? A single Bird Termaline will guarantee a 1:1 SWR over a
1:100 frequency range.
--
73, Cecil http://www.qsl.net/w5dxp



I got a B & W Dummy Load/Wattmeter. Would that do? LOL?



Jerry





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Actually, at one time was a antenna_ shortened "Dipole", claimed worst match
was 3:1 literally from
dc to light! turned out, inside the center "insulator", was a 50 ohm
resistor! now, thats lousey effeciency! Jim


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"JGBOYLES" wrote in message
...
Take a dummy load and attach a piece of wire on some kind of a windup
system. To increase the efficiency, let out more wire and vice versa.

Good Idea, and we want to decrease efficiency, so the wind-up system may
just
may be what is needed. What I was looking for is antenna materials that
decrease efficiency.
If we could come up with something as bad as the B&W dipole for a lot
less
money, then we may have something.
73 Gary N4AST

Also remember that a terminated rhombic has 50% loss, about the same as the B&W.
Pat W0OPW

Also remember that a terminated rhombic has 50% loss, about the same as
the B&W.

==========================

A terminated rhombic does NOT have a loss in the forward direction.
Radiation in the forward direction remains the same as when unterminated.

When terminated it is radiation in the UNWANTED reverse direction which is
absorbed by the termination and suppressed.
---
Reg, G4FGQ

PatW wrote:
Also remember that a terminated rhombic has 50% loss, about the same as the B&W.

But, unlike the B&W, that loss is in only one direction
which turns the rhombic into an effective directional beam.
--
73, Cecil http://www.qsl.net/w5dxp



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"PatW" wrote in message
m...
Also remember that a terminated rhombic has 50% loss, about the same as
the B&W.
Pat W0OPW

If GAIN - LOSS 0 you still come out ahead.

Tam/WB2TT

Try this: a 16 Ohm resistor in series with each side of the dipole, and a
100 Ohm resistor across the feedpoint. Unless I messed up, this will give
you SWR = 2:1 for all conditions including shorted, and absent dipoles.

Thanks Tam, This is exactly what I was looking for. A dummy load is 0%
efficient. A B&W dipole is less than 20% on 80m and 160m. It costs a lot of
money. There are less expensive ways to achieve 20% efficiency on 160m and
80m. 0% does not radiate (dummy load), a good bad antenna in my opinion is one
that radiates, but not too much. And it can't cost too much.
73 Gary N4AST

Try this: a 16 Ohm resistor in series with each side of the dipole, and a
100 Ohm resistor across the feedpoint. Unless I messed up, this will give
you SWR = 2:1 for all conditions including shorted, and absent dipoles.
Tam/WB2TT

========================

There's no need to mess about with the antenna. Just connect a crude
attenuator at the transmitter end of the transmission line. This much
reduces the cost of the antenna. It's then just a length of wire.