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

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

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.

In message , Reg Edwards writes

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

On Monday 11 Jul 2005 00:34, the world held its breath whilst J. Mc Laughlin delivered the following wit:

Believe it or not, it still is compulsory for an able-bodied male to practice his archery skills on the village green on a Sunday...

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

It's loss, plain and simple.

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.

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

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

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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

[snip]

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

"Reg Edwards"

________________

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

for FM transmission system papers.

But the illegal aliens can get their GED without one. They are issued a non-SS tracking number instead of SS#.

In message , Reg Edwards writes

Thanks for your time Reg, I drafted a lengthy response to your note above a little earlier but binned it in favour of this :-) I suppose my problem is that I would dearly like to believe the claims for the EH et al but my head tells me that it can't be so. I have had a lot of fun 'playing' with the idea and I suppose I should be happy with that.

Trev

And, for the record, it wasn't me who said that.

I refer you my other post on the subject, where I quote the OP in full.

No-one was arguing that that was not the case. A spring might have the mechanical equivalent of reactance, but a damper will most certainly not - hence the rubbish posted by the OP, where he believes that dampers store energy. They do not, and therefore cannot have the mechanical equivalence of a reactance. Therefore, resonance is not possible with such a system. In the extreme, the OP was reduced to likening dampers to bicycle pumps, a sure sign of a failure to grasp a fundamental point (and hence the error of his assertion).

from Aero Spike

Now shrink down those antennas by a factor of, say, 10 in size. Think they'd still do it? If so, you're the natural prey for the charlatans.

In product development, we say fast-cheap-good, pick any two. With antennas it's small-efficient-broadband, pick any two. "Small" is, of course, always in terms of wavelength when it comes to antennas.

Roy Lewallen, W7EL

transmission

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I've no reason to doubt it.

But this is a topic about the bandwidth of physically small HF antennas.

And as usual, when the slightest difference of opinion occurs, somebody invariably feels impelled to go off at a tangent and drag in something they feel more at home with, such as VHF and UHF TV transmitting antennas, and, very soon, if we are not careful, distractions such as scattering parameters, reflected power, etc.

On Mon, 11 Jul 2005 17:51:06 +0000 (UTC), "Reg Edwards" Gave us:

Do you even know how to make a proper Usenet post?

Oh... I see now... that's right... yet another dolt posting with Outhouse Express. Do a google on "Newsreader".

You'll see many out there. There is a reason for that.

Hell, even the one in Mozilla is better than Billy's utter crap.

Bone Up!