The CFA de-bagged (Was: Re: First "Del" and now "D'Alembertian"!)

Be sure to wash your hands after reading.

Roy Lewallen, W7EL

Reply to
Roy Lewallen
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The citizens in this country have never been armed, and in fact even hand-guns for sport use were recently outlawed.

73 de G3NYY
Reply to
Walt Davidson

That's why Cecil's ancestors left the British Isles, so they could have the freedom to shoot one another, a proposition to which my ancestors heartily gave support.

73, Tom Donaly, KA6RUH
Reply to
Tom Donaly

"... NEVER BEEN ARMED ..."! Is that REALLY TRUE ?

If I recall history lessons regarding ANGLO-SAXON conflicts over the past 1000 years, I seem to recall that many armies were 'raised' in the Isles and the people provided their own weapons.

Only after the establishment of a solid Monarchy were the citizens disarmed. [Power consolidating control of Power].

Is my understanding of history wrong ?

Reply to
Ham op

So what kind of handguns did King Alfred outlaw? Maybe that was why King Ethelred was so unready.

73, Tom Donaly, KA6RU
Reply to
Tom Donaly

Polly parrotted:

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

Reply to
Spike

Um, a little. There's been a solid monarchy in England, at least, for about

1200 years.

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?)

Here endeth the second lesson.

Reply to
Gerard Lynch

Yes, it is. The Anglo-Saxon period in England extended from 597 AD until the Norman Conquest of 1066 AD.

For the past 940 years, there has been "a solid Monarchy" in this country, apart from a short interlude between 1649 and 1660 AD.

In contrast, the history of the United States of America began only

229 years ago. :-)

73 de G3NYY

Reply to
Walt Davidson

The spring and damper can be exactly model as an electrical analog; as can virtually any physical system. As a reference refer to "Dynamics of Physical Circuits and Systems", by Lindsay and Katz at Concordia University, Montreal. ISBN 0-916460-21-5 published by Matrix of Beaverton OR.

Frank

Reply to
Frank

Wow! Check your history. Once it was a requirement for persons in England to be armed. Practice was also compulsory.

It is true, and always has been true, that only when the state is not afraid of its armed populous that you have citizens rather than mere subjects.

Respectfully, Mac N8TT

Reply to
J. Mc Laughlin

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.)

Reply to
Roy Lewallen

Of course, I should have mentioned a mass/spring/damper (equivalent to capacitor/inductor/resistor), not just spring/damper. I think the only physical system that can not be entirely modeled as an electrical analog is a thermal system; which has no inductor equivalent.

Frank

Reply to
Frank

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

Frank wrote:

Reply to
Roy Lewallen

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

Reply to
Walter Maxwell

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

Reply to
Frank

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.

Reply to
J. Mc Laughlin

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 Laughl> My EE students, noting that the characteristic equations are the same,

Reply to
Roy Lewallen

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

Reply to
Spike

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

Reply to
Spike

In message , Walter Maxwell writes snip

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

Reply to
Trevor Day

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