Query..
 

Ted wrote:




I have about 40 feet of garden to erect an antenna....Could anyone
tell me if I took 2 20 feet length of twin ladder and shorted the
ends fed one side of the dipole with twin ladder and connected a 52
ohm resistor across the other side so the tx would see a match would
be better than feeding a 40 foot endfed through an atu...
My thinking is that most of the small antenna on the market are just
dummy loads with a small amount of wire attached and appear to work
so would my 40 feet work better.. ??

Many thanks to all who replied to my query...

--
Regards
Ted Wager
Using PCLinuxos

Query..
 

I have about 40 feet of garden to erect an antenna....Could anyone tell
me if I took 2 20 feet length of twin ladder and shorted the ends
fed one side of the dipole with twin ladder and connected a 52 ohm
resistor across the other side so the tx would see a match would be
better than feeding a 40 foot endfed through an atu...
My thinking is that most of the small antenna on the market are just
dummy loads with a small amount of wire attached and appear to work so
would my 40 feet work better.. ?? ......................................

If you are trying to avoid a dummy load, a resister is the last
thing you want. It should be illegal to add resisters to otherwise
perfectly good antennas.
It's hard to comment about the antenna, as I don't know what
bands, how much height, etc... Not enuff info...
MK

Query..
 

wrote:
It should be illegal to add resisters to otherwise
perfectly good antennas.

Except Rhombics, of course. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Query..
 

Cecil Moore wrote:
wrote:

It should be illegal to add resisters to otherwise
perfectly good antennas.


Except Rhombics, of course. :-)

And Beverages ...

Query..
 

"Cecil Moore" wrote -
Except Rhombics, of course. :-)
====================================

Cecil, get yourself up to date.

A terminated rhombic is only 50 percent (or even less) efficient.

It transmitts to, and receives from, only half of the available
directions. A wicked waste of power. I can't imagine why anybody
bothers to use one which is not rotateable.

Have you ever erected a 160-meter or 80-meter or even a 40-meter
rotateable rhombic? smiley
----
Reg, G4FGQ.

Query..
 

On Mon, 9 Jan 2006 20:55:39 +0000 (UTC), "Reg Edwards"
wrote:


"Cecil Moore" wrote -
Except Rhombics, of course. :-)
====================================

Cecil, get yourself up to date.

A terminated rhombic is only 50 percent (or even less) efficient.

Actually, that is not true.

A big enough rhombic is nearly self-terminating. The energy radiated
is not available to the terminating resistor and thus is not -lost-.

It transmitts to, and receives from, only half of the available
directions. A wicked waste of power. I can't imagine why anybody
bothers to use one which is not rotateable.

Have you ever erected a 160-meter or 80-meter or even a 40-meter
rotateable rhombic? smiley

I completed my 2-meter Worked All Continents award by working VK5MC,
who was using stacked rhombics (350 feet/leg), partially steerable by
a rope and pulley arrangement. Worked for me [g].

Query..
 

"Wes Stewart" wrote in message
...
On Mon, 9 Jan 2006 20:55:39 +0000 (UTC), "Reg Edwards"
wrote:


"Cecil Moore" wrote -
Except Rhombics, of course. :-)
====================================

Cecil, get yourself up to date.

A terminated rhombic is only 50 percent (or even less) efficient.

Actually, that is not true.

A big enough rhombic is nearly self-terminating. The energy
radiated
is not available to the terminating resistor and thus is not -lost-.

It transmitts to, and receives from, only half of the available
directions. A wicked waste of power. I can't imagine why anybody
bothers to use one which is not rotateable.

Have you ever erected a 160-meter or 80-meter or even a 40-meter
rotateable rhombic? smiley

I completed my 2-meter Worked All Continents award by working VK5MC,
who was using stacked rhombics (350 feet/leg), partially steerable
by
a rope and pulley arrangement. Worked for me [g].

===========================================
Wes, of course it worked. You would have done even better had it not
been terminated.
===========================================

Query..
 

Reg Edwards wrote:
"Cecil Moore" wrote -

Except Rhombics, of course. :-)

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

Cecil, get yourself up to date.

A terminated rhombic is only 50 percent (or even less) efficient.

It transmitts to, and receives from, only half of the available
directions. A wicked waste of power. I can't imagine why anybody
bothers to use one which is not rotateable.

Have you ever erected a 160-meter or 80-meter or even a 40-meter
rotateable rhombic? smiley
----
Reg, G4FGQ.


Reg, during the Vietnam War we used a terminated rhombic from the State
of Utah [USA desert area] to SEA [AKA Vietnam]as part of the antenna
farm at AGA5HI [USAF MARS Gateway Station] for phone patch traffic. It
would outperform the Yagi and the LP antenna.

I was AFF1C TDY at AGA5HI [Hill Air Force Base, Utah]

I don't believe there is a net loss of gain in the preferred direction.
If one loses -3 dB in the resistor, does one not waste -3 dB in the
non-preferred direction [180 degrees from the desired direction]?

Query..
 

Don't get too hung up on efficiency. What counts is signal strength.
Suppose you have a bidirectional antenna. Unless you're talking to two
people in opposite directions at the same time, it doesn't matter if the
antenna is 100% efficient and half the power goes into an unused reverse
lobe or whether it goes into a resistor which makes the antenna 50%
efficient. The result is exactly the same as far as the other station is
concerned. So to the extent that the rhombic isn't optimal, it's because
it's inherently bidirectional, not necessarily because it's inefficient.

A bidirectional antenna is usually not an optimum choice. For the same
number of elements or same amount of real estate, you can usually make a
unidirectional antenna which has a single main lobe of about the same
width but 3 dB greater gain. Or, you can have a main lobe of about the
same gain as before but greater width, which is an advantage when the
antenna can't be rotated. However, this doesn't say anything about
simplicity, which is the main attractiveness of a rhombic, along with
its bandwidth.

Roy Lewallen, W7EL

Query..
 

Reg Edwards wrote:
A terminated rhombic is only 50 percent (or even less) efficient.

But it's 50% in the bad direction, not the good direction. :-)
--
73, Cecil http://www.qsl.net/w5dxp