"Roy Lewallen" wrote in message
...
Oops, I stand corrected -- thanks, Frank. Once again I read too hastily. A
*mass*/spring combination mimics an inductor/capacitor, of course. A
damper adds resistance. So a spring/damper combination would act more like
an RC or RL circuit, but with a little stray L or C from the spring's
mass.

Hope I don't have to give up my new title. Titles really impress folks in
some parts of the world.

Roy Lewallen, W7EL, ROW, ASI, OFC


No problem Roy. To be exact a mass is equivalent to a capacitor.
As in Newton's 2nd law: f = m*dv/dt, and its electrical analog
i = c*dv/dt, where "v" refers to velocity in the mechanical case,
and voltage in the electrical. I think this qualifies me to place the
letters "ASI" after my name. Well; I must admit I took a quick
look at my physical systems text book, so hope it does not
disqualify me.

Frank Meredith ASI

My EE students, noting that the characteristic equations are the same,
regularly convert mechanical problems (of the mass-spring-damper type) into
electrical problems, solve, and then convert back to mechanical answers.
Some ME students catch on and some just do not get it. Of course, it helps
if one is using SI units all round. I continue to be in awe of MEs who
always seem to know whether the "pounds" they are talking of are
sort-of-like mass, or sort-of-like force, or money. I have even had it
suggested that energy and power are sort-of the same thing.


I am keen on Roy being the collector of titles. I have quite enough for
a lifetime. 73 Mac N8TT etc.

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Roy Lewallen" wrote in message
...
Oops, I stand corrected -- thanks, Frank. Once again I read too hastily.
A *mass*/spring combination mimics an inductor/capacitor, of course. A
damper adds resistance. So a spring/damper combination would act more
like an RC or RL circuit, but with a little stray L or C from the
spring's mass.

Hope I don't have to give up my new title. Titles really impress folks
in some parts of the world.

Roy Lewallen, W7EL, ROW, ASI, OFC

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 watter 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

J. Mc Laughlin wrote:
My EE students, noting that the characteristic equations are the same,
regularly convert mechanical problems (of the mass-spring-damper type) into
electrical problems, solve, and then convert back to mechanical answers.
Some ME students catch on and some just do not get it. Of course, it helps
if one is using SI units all round. I continue to be in awe of MEs who
always seem to know whether the "pounds" they are talking of are
sort-of-like mass, or sort-of-like force, or money. I have even had it
suggested that energy and power are sort-of the same thing.


I am keen on Roy being the collector of titles. I have quite enough for
a lifetime. 73 Mac N8TT etc.

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

Roy Lewallen wrote:

Spike wrote:

Can this be the same idiot who thought that a spring/damper
combination was the mechanical equivalent of a coil and capacitor, on
the grounds that they both exhibited resonance?

from
Aero Spike

I'm that idiot. Actually, one of the very many. The equations for the
two systems are identical.

Roy Lewallen, W7EL, ROW, ASI
(Reg's Old Wife and now Aero Spike's Idiot. The titles just keep
accumulating. Of course I'm also a proud member of the OFC.)

Posting under the sock-puppet "Airy R. Bean", he said the following
quoted below, and to which I was referring. I leave it to you to spot
the glaring error. I very much doubt you said anything like this.

The original message was posted in sci.physics at 9:53 am on 21st
January this year.

"Reactance is characterised by the storage of energy.

In the case of the capacitor, you might think that your
AC source is the only voltage source in your circuit, but
after the first 1/4 cycle, the capacitor acts as a voltage source
and starts to give back the energy that it has stored.

The combined result of the two voltage sources, your
AC excitation and the capacitor itself, accounts for
the out-of-phase current waveform.

(This bothered me for years! How could the current
be non-zero if the AC driving voltage was zero?!)

The same analogy applies to springs and to shock absorbers;
the spring stores energy when stretched; the shock-absorber
stores energy when compressed. Both the spring and shock
absorber will return energy at some time and this exhibit reactance!"


from
Aero Spike

In message , Walter Maxwell
writes
snip
Just try to imagine what you bloody 'ole Brits could have accomplished
around 1200 if you'd only had the tremendously high voltages achieved in the
near field of a CFA antenna to hurl at the enemy.

Walt

Excuse me for 'jumping in' here, it was difficult trying to locate a bit
of the thread that referred to the current title (CFA) I would like to
ask you learned chaps a question about the 'EH' antenna which I
appreciate is not the same as the CFA but its near enough for me:-)

I have built a couple of these and used them on 40m. Performance hasn't
been brilliant but they have worked and I was reasonably satisfied with
the contacts achieved considering the fact I used a barefoot K2 at
around 10 watts o/p and the antenna was sat on the shack bench connected
to the K2 by a 1 metre BNC to BNC cable laid across the bench. (I only
mention this last to try and forestall the inevitable comment that the
feeder does all the work)

All of this was done out of interest just to see if the antenna worked
at all, as my gut reaction was, and still is, sceptical regarding the
claims of its method of operation. I am not a mathematician, so the
various lengthy discussions regarding Maxwell's equations et al pass me
by; I am more interested in the practical aspects of this rather than
the theory. My question refers to the SWR bandwidth achieved using this
system. For an electrically very short antenna of this type I expected
something extremely sharp at resonance, perhaps in the order of 5 or 10
KHz between the 2:1 SWR points. In practice, the 2:1 SWR points are
some 100 KHz or so apart. When fed with 100 watts from an IC706, the
antenna itself does not get warm and neither does the short feeder so it
doesn't appear to be acting as a dummy load. Can someone satisfy my
curiosity and tell me (drawing comparisons with springs and dampers if
need be:-) how this is achieved.

Thanks,
Trev G3ZYY

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

Trevor Day wrote:

Excuse me for 'jumping in' here, it was difficult trying to locate a bit
of the thread that referred to the current title (CFA) I would like to
ask you learned chaps a question about the 'EH' antenna which I
appreciate is not the same as the CFA but its near enough for me:-)

I have built a couple of these and used them on 40m. Performance hasn't
been brilliant but they have worked and I was reasonably satisfied with
the contacts achieved considering the fact I used a barefoot K2 at
around 10 watts o/p and the antenna was sat on the shack bench connected
to the K2 by a 1 metre BNC to BNC cable laid across the bench. (I only
mention this last to try and forestall the inevitable comment that the
feeder does all the work)

All of this was done out of interest just to see if the antenna worked
at all, as my gut reaction was, and still is, sceptical regarding the
claims of its method of operation. I am not a mathematician, so the
various lengthy discussions regarding Maxwell's equations et al pass me
by; I am more interested in the practical aspects of this rather than
the theory. My question refers to the SWR bandwidth achieved using this
system. For an electrically very short antenna of this type I expected
something extremely sharp at resonance, perhaps in the order of 5 or 10
KHz between the 2:1 SWR points. In practice, the 2:1 SWR points are
some 100 KHz or so apart. When fed with 100 watts from an IC706, the
antenna itself does not get warm and neither does the short feeder so it
doesn't appear to be acting as a dummy load. Can someone satisfy my
curiosity and tell me (drawing comparisons with springs and dampers if
need be:-) how this is achieved.

Thanks,
Trev G3ZYY


Sigh.

A couple of questions:

1. Have you tried using something like a loop or other non-magical
antenna of similar physical size for comparison? Or putting a 20 dB pad
between your rig and a decent antenna? Most people are amazed at how
much they can do with 100 mW.
2. I assume you're using a "phasing network" or some similar device to
achieve whatever it is the antenna is supposed to accomplish. The wide
bandwidth is a sure sign of loss, and the majority of it is just about
surely in the "phasing network" and/or whatever matching network you're
using. Have you checked to see if either of them is getting warm after a
few minutes of key-down (with breaks to ID of course)?

But don't be surprised it they don't. If you're running 100 watts of CW,
your average power output is probably no more than 20 watts while
transmitting. If you're running SSB, it's considerably less than that
unless you're using serious compression. Try running your rig normally
(keying or talking) to a good-sized dummy load and see how long it takes
for it to get noticeably warm. Then imagine it to be the size of your
matching/"phasing" network and think about what you'd expect to happen
if it were absorbing *all* your transmitter's power. It is, after all,
absorbing most of it.

Roy Lewallen, W7EL

In message , Roy Lewallen
writes
Trevor Day wrote:

Excuse me for 'jumping in' here, it was difficult trying to locate a
bit of the thread that referred to the current title (CFA) I would
like to ask you learned chaps a question about the 'EH' antenna which
I appreciate is not the same as the CFA but its near enough for me:-)
I have built a couple of these and used them on 40m. Performance
hasn't been brilliant but they have worked and I was reasonably
satisfied with the contacts achieved considering the fact I used a
barefoot K2 at around 10 watts o/p and the antenna was sat on the
shack bench connected to the K2 by a 1 metre BNC to BNC cable laid
across the bench. (I only mention this last to try and forestall the
inevitable comment that the feeder does all the work)
All of this was done out of interest just to see if the antenna
worked at all, as my gut reaction was, and still is, sceptical
regarding the claims of its method of operation. I am not a
mathematician, so the various lengthy discussions regarding Maxwell's
equations et al pass me by; I am more interested in the practical
aspects of this rather than the theory. My question refers to the
SWR bandwidth achieved using this system. For an electrically very
short antenna of this type I expected something extremely sharp at
resonance, perhaps in the order of 5 or 10 KHz between the 2:1 SWR
points. In practice, the 2:1 SWR points are some 100 KHz or so
apart. When fed with 100 watts from an IC706, the antenna itself
does not get warm and neither does the short feeder so it doesn't
appear to be acting as a dummy load. Can someone satisfy my
curiosity and tell me (drawing comparisons with springs and dampers if
need be:-) how this is achieved.
Thanks,
Trev G3ZYY


Sigh.

A couple of questions:

1. Have you tried using something like a loop or other non-magical
antenna of similar physical size for comparison? Or putting a 20 dB pad
between your rig and a decent antenna? Most people are amazed at how
much they can do with 100 mW.
2. I assume you're using a "phasing network" or some similar device to
achieve whatever it is the antenna is supposed to accomplish. The wide
bandwidth is a sure sign of loss, and the majority of it is just about
surely in the "phasing network" and/or whatever matching network you're
using. Have you checked to see if either of them is getting warm after
a few minutes of key-down (with breaks to ID of course)?

But don't be surprised it they don't. If you're running 100 watts of
CW, your average power output is probably no more than 20 watts while
transmitting. If you're running SSB, it's considerably less than that
unless you're using serious compression. Try running your rig normally
(keying or talking) to a good-sized dummy load and see how long it
takes for it to get noticeably warm. Then imagine it to be the size of
your matching/"phasing" network and think about what you'd expect to
happen if it were absorbing *all* your transmitter's power. It is,
after all, absorbing most of it.

Roy Lewallen, W7EL

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? 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.

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

Trev G3ZYY
--
Trevor Day
UKSMG #217
www.uksmg.org

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.

====================================
..
"Trevor Day" wrote in message
...
In message , Walter Maxwell
writes
snip
Just try to imagine what you bloody 'ole Brits could have
accomplished
around 1200 if you'd only had the tremendously high voltages
achieved in the
near field of a CFA antenna to hurl at the enemy.

Walt

Excuse me for 'jumping in' here, it was difficult trying to locate a
bit
of the thread that referred to the current title (CFA) I would
like to
ask you learned chaps a question about the 'EH' antenna which I
appreciate is not the same as the CFA but its near enough for me:-)

I have built a couple of these and used them on 40m. Performance
hasn't
been brilliant but they have worked and I was reasonably satisfied
with
the contacts achieved considering the fact I used a barefoot K2 at
around 10 watts o/p and the antenna was sat on the shack bench
connected
to the K2 by a 1 metre BNC to BNC cable laid across the bench. (I
only
mention this last to try and forestall the inevitable comment that
the
feeder does all the work)

All of this was done out of interest just to see if the antenna
worked
at all, as my gut reaction was, and still is, sceptical regarding
the
claims of its method of operation. I am not a mathematician, so the
various lengthy discussions regarding Maxwell's equations et al pass
me
by; I am more interested in the practical aspects of this rather
than
the theory. My question refers to the SWR bandwidth achieved using
this
system. For an electrically very short antenna of this type I
expected
something extremely sharp at resonance, perhaps in the order of 5 or
10
KHz between the 2:1 SWR points. In practice, the 2:1 SWR points are
some 100 KHz or so apart. When fed with 100 watts from an IC706,
the
antenna itself does not get warm and neither does the short feeder
so it
doesn't appear to be acting as a dummy load. Can someone satisfy
my
curiosity and tell me (drawing comparisons with springs and dampers
if
need be:-) how this is achieved.

Thanks,
Trev G3ZYY

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

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