Trevor Day wrote:

In message , Reg
Edwards writes

Trev,
Performance is no better and no worse than what can be expected from
any other sort of antenna of about the same physical size and the same
length of feedline. Try it and see.

I once worked 3 miles on SSB, on 160m, in broad daylight, with about
10 milliwatts, on 8 feet of wire lying on the ground, thrown out of a
downstairs window. The ground connection was via 10 feet of wire from
a domestic gas pipe. But I don't brag about it. The credit all goes
to Clerk Maxwell.

As Clerk implied, any bloody thing works.
----
Reg.


Thanks Reg,

I expect you are quite right, but I am still puzzled about the bandwidth
aspect. Roy states that this is due to losses in the matching system,
in which case would it be possible to 'detune' a similar small antenna
and get similar results in that regard. If I can actually do that and
see the result, then I will be happy :-)

Trev

Try running it it parallel with a suitable resistive load. You will see
increased 'bandwidth', i.e. the SWR will be lower over a greater
frequency range. If you eliminate the aerial altogether then the 'bandwidth'
will cover frequencies up to several GHz with a good quality load ;-)

I have actually worked a local amateur dummy load to dummy load. Both
loads were good quality (one Bird, one Marconi) and all the cabling was
short and good quality coax. Leakage was probably less than a few milliwatts.
The rigs had different IFs so it probably was the signal frequency we were
hearing. Being able to work stations is no measure of antenna efficiency.

Heating is not a good way of determining efficiency unless you do real
calorimetry. I've tried 100W CW key down into a real 100W continuous load
(not one of the Made From Junk ones, which are grossly overrated), for
ten minutes and the temperature increase was just discernible, it
certainly didn't get hot.


vy 73

Andy, M1EBV




vy 73

Andy, M1EBV

Trevor Day wrote:

Roy,

I think you got as far as my first paragraph and didn't read any further.

I am not attempting to justify this antenna or the way it works, just
trying to get an explanation for one aspect of it. If you had read what
I had written you would have seen the answer to your questions above.

Is it possible to 'mismatch', for want of a better expression, a loop to
achieve an equivalent bandwidth?

Yes. Put a resistor in series or parallel with it, or put a pad
(attenuator) between it and your rig. When you find the value that gets
you the bandwidth of the CFA, you'll also have about the same
efficiency. The power will be going into the resistor instead of into
the "phasing" and/or matching networks.

I have constructed many short
verticals for portable and mobile use over the years, but have always
experienced narrow bandwidth. It is this aspect of the 'EH' that I
would like to understand.

It's loss, plain and simple.

btw, starting your answer with "Sigh" might be justified if I appeared
to be ignoring your continued advice but surely not at first meeting?

Sort of. You apparently didn't check groups.google.com to see the great
mass of postings I and others have made about those antennas, many times
before. A tremendous amount has been written and posted about the CFA
and EH antennas. But like astrology, homeopathy, and other hoaxes, no
amount of objective evidence keeps people from wanting to believe.
Either they don't search it out, they're not able to evaluate it when
they find it, or they choose to ignore it when it threatens their
beliefs. It's resigning myself to that sad certainty and the Sisyphusian
(Sisyphusan?) task of combatting it which makes me sigh.

Roy Lewallen, W7EL

Trev,

As Cecil says, a wider than expected bandwidth in an antenna of given
size, is an absolutely sure sign of greater loss somewhere in the
wideband antenna system.

Unless one knows how the thing is supposed to work, which with EH and
CFA is not very likely, there's no indication of where the loss may be
except from a visual examination. If there are any coils of
relatively thin wire, either in the antenna or tuner/phaser, then
that's a good pointer.

But experimenting to improve the bandwidth*efficiency product, one way
or the other, will not get you very far. As one goes up the other is
sure to go down. It's not difficult to guess which you would prefer.

A magloop. with a single turn coil of copper pipe at the lower
frequencies, is far and away the most narrow banded and therefore the
most efficient of all the small antennas. Furthermore it has a
built-in, equally very low loss tuner.
----
Reg.

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

"Trevor Day" wrote in message
...
In message , Reg
Edwards writes
Trev,
Performance is no better and no worse than what can be expected
from
any other sort of antenna of about the same physical size and the
same
length of feedline. Try it and see.

I once worked 3 miles on SSB, on 160m, in broad daylight, with
about
10 milliwatts, on 8 feet of wire lying on the ground, thrown out of
a
downstairs window. The ground connection was via 10 feet of wire
from
a domestic gas pipe. But I don't brag about it. The credit all
goes
to Clerk Maxwell.

As Clerk implied, any bloody thing works.
----
Reg.

Thanks Reg,

I expect you are quite right, but I am still puzzled about the
bandwidth
aspect. Roy states that this is due to losses in the matching
system,
in which case would it be possible to 'detune' a similar small
antenna
and get similar results in that regard. If I can actually do that
and
see the result, then I will be happy :-)

Trev
--
Trevor Day
UKSMG #217
www.uksmg.org

Being able to work stations is no measure of antenna efficiency.

What then, is the true relationship which affects the ability to work
stations.

Dear Roy:
I am in complete agreement. As an example, when dealing with antenna
tower evaluation I convert everything about the tower to SI (knowing the
approximate SI density of materials helps to ensure that the conversion was
done correctly), and then do the evaluation. When it comes to the design of
foundations, I need to convert the SI answer back into the other units so
that the skilled trades are able to do their thing.

How silly to have a system that depends on an assumed gravitational
system.

73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Roy Lewallen" wrote in message
...
Years ago I tracked down a constriction ("resistance") in my house's
water system with a bucket and stopwatch to measure flow ("current") and
a fuel pump pressure gauge to measure water pressure ("voltage") and a
schematic of the "circuit". I kind of chuckled thinking of all the
simplified explanations of electricity using water -- I found it much
easier to convert in the other direction.

As for "pounds", I was always off by the acceleration of gravity squared
in the only two one-semester courses I took which weren't metric,
Statics and Dynamics. I never could remember which of those units --
pounds mass, pounds force, poundals, slugs, aargh, had the acceleration
already built in and which didn't. I finally managed by first converting
each problem to metric, solving it, then converting the result back to
that God-awful system of units.

Roy Lewallen, W7EL

"Trevor Day" wrote in message
...
In message , Reg
Edwards writes
Trev,
Performance is no better and no worse than what can be expected from
any other sort of antenna of about the same physical size and the same
length of feedline. Try it and see.

I once worked 3 miles on SSB, on 160m, in broad daylight, with about
10 milliwatts, on 8 feet of wire lying on the ground, thrown out of a
downstairs window. The ground connection was via 10 feet of wire from
a domestic gas pipe. But I don't brag about it. The credit all goes
to Clerk Maxwell.

As Clerk implied, any bloody thing works.
----
Reg.
You want QRP, Trev, I'll give you QRP. The telemetry transmitters used on
the early TIROS weather satellites delivered only 10 milliwatts, yet they
produced an S9 signal at a 400 mile high orbit at maximum slant range of
1800 miles to the horizon.

I don't know about other TV satellites, but the RCA Satcoms of the late
70s and early 80s used transmitters that delivered only 5 watts at an
altitude of 23,000 miles. (I will have to admit, however, that 5 watts into
its 30 dB dish produced an EIRP of 5 kw.)

Walt, W2DU


----------------------------------------------------------------------------
----

"Spike" wrote in message
...
Frank wrote:

The spring and damper can be exactly model as an electrical analog;

I'm sure you're right.

However, a coil/capacitor is not a model or analogue of a
spring/damper system. It was discussed extensively at the time.

from
Aero Spike

I am not sure I understand your response. To be exact a "spring/damper" can
be modeled as a coil/resistor. For resonance to occur you need a
capacitor/inductor, or mass/spring. All components of either mechanical or
electrical circuits require the solution of the same simple differential
equation, such as i = C*dv/dt etc.

Regards,

Frank

On Sun, 10 Jul 2005 23:46:13 +0100, "Gerard Lynch"
wrote:


[snip]
Guns aren't an issue here. We're not allowed to have them. Nobody much (as
in about 90% of the population) cares. We care about things you folks have
never even heard about instead (fancy an ID card?)

Over here in 'Merica they're called "Social Security Cards." Every
newborn baby is required to have one.

"Reg Edwards"
As Cecil says, a wider than expected bandwidth in an antenna of given
size, is an absolutely sure sign of greater loss somewhere in the
wideband antenna system.
________________

I don't know your definition of an "expected bandwidth," but for a reality
check--many forms of panel antennas used in FM and TV broadcast transmission
have 20% or better SWR bandwidth, and radiate nearly every watt that can be
delivered by the feedline with almost NO "matching" losses. They have been
in routine use for decades at master antenna transmit sites all over the
world.

RF

Visit http://rfry.org for FM transmission system papers.

Wes Stewart wrote:
Over here in 'Merica they're called "Social Security Cards." Every
newborn baby is required to have one.

But the illegal aliens can get their GED without one.
They are issued a non-SS tracking number instead of SS#.
--
73, Cecil http://www.qsl.net/w5dxp


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