Gene Fuller wrote:
As you know, generating the helix coils and using them are two separate
things. I have only EZNEC version 3, which does not support automatic
helix generation. However, there does not appear to be any reason why
helices cannot be used in EZNEC version 3. That is what I did. I copied
your wires, edited them, and re-input into EZNEC.

That probably explains everything. Version 4, with the helix
generation option, does a geometry check. The geometry of your
coil is unacceptable to Version 4 of EZNEC.

As for the height, you asked for an 8 foot whip. I adjusted my model
until I got to a 10 foot whip.

Actually, you stopped at 11.775 ft., ~12 feet as I stated earlier.
It won't do any good to keep going. The coil you generated is
unacceptable to EZNEC 4.0.

But thanks for your effort. I learned something about EZNEC.
--
73, Cecil http://www.qsl.net/w5dxp

Gene Fuller wrote:
I did what you "challenged", with the exception of the exact whip
length. (And the version I sent had a total height of 11 feet 9 inches,
which is not absurdly unreasonable.)

I have to say I am surprised that it took you more than 24 hours to
misinterpret what I sent (10 turns per foot) and then to blame the tools.

I don't see any of the errors on my computer.

There is little point of carrying this any further. You already stated
that the results did not make technical sense to you and that perhaps
EZNEC cannot be used for this task. I cannot repair your "technical
sense", and I have no control over the capabilities of EZNEC.

Gene,

Send me the file please. Don't use my akorn newsgeroup addres. I do not
check it.

Use my callsign at contesting.com

73 Tom

wrote:
Send me the file please. Don't use my akorn newsgeroup addres. I do not
check it.

Here's just about all you need to know about Gene's EZNEC file:

http://www.qsl.net/w5dxp/ezerror.GIF

EZNEC doesn't like 4 TPI coils at 4 MHz.
--
73, Cecil http://www.qsl.net/w5dxp

John Popelish wrote:
"it seems that these references are not particularly concerned with
dimensions of the coil with respect to wavelength, or to the mode of
propagation within the coil.

OK. I gave an example of a traveling wave tube which uses a coil
specifically to retard wave progress ao that an electron beam could keep
up with a signal winding its way through the coil.Terman describes the
Traveling Wave Tube (TWT) starting on page 678 of his 1955 edition of
"Electronic and Radio Engineering".

Here is another version of how the TWT works. The TWT was developed to
provide wideband gain, about 10 to 60 dB over 10% of the operating
frequency or more, and produce a power output of one kilowatt, if
needed.

The TWT consists of an electron gun similar to those used in CRTs, a
wire helix, and a collector. The gun at one end of the helix produces a
focused beam of electrons directed through the center of the helix. The
helix is a uniform coil of wire used to slow down the forward progress
of an RF signal fed into the gun-end of the helix inside a glass vacuum
tube. Output is taken from the helix at the collector end of the helix.
The collector and the helix are positively charged. The collector is the
electrode which catches the spent electrons which have traveled through
the length of the tube.

A magnetic field distributed along the length of the TWT is used to keep
rhe electron beam from spreading during flight.

Transfer of power from the direct current of the electron beam to the RF
signal is by velocity modulation of the beam into periodic bunches of
electrons. these accelerating electron bunches generate a stronger
signal along its path. Interaction between the electron beam and the
helix is continuous and accumulative. Amplitude of the signal grows as
it travels down the helix.

The axial wave velocity is fixed by the helix while the initial
eleectron velocity (before modulation) is proportional to the positive
potential on the helix and collector.

The signal to be amplified is fed to the end of the helix nearer the
electron gun. This RF signal travels as a surface wave around the turns
of the helix, toward the collector, at about the velocity of light. The
forward or axial movement of the signal is slower, of course, because of
the pitch and diameter of the helix. This forward movement of the wave
is analogous to the travel of a finely threaded screw where many turns
are required to drive it into position. The signal wave generates an
axial electric field which travels with it along the longitudinal axis
of the helix. This velocity modulates (slows down and speeds up) the
electrons of the beam current.

So, the wave traveling from one end of the coil towards the other is a
"slow-wave" while the wave travelimg around the coil turns is only
slightly slowed below the speed of light. This is how a coil works.
Frequency and coil form matter but don`t change the basics.

Best regards, Richard Harrison, KB5WZI

Cecil Moore wrote:
wrote:
Send me the file please. Don't use my akorn newsgeroup addres. I do not
check it.

Here's just about all you need to know about Gene's EZNEC file:

http://www.qsl.net/w5dxp/ezerror.GIF

EZNEC doesn't like 4 TPI coils at 4 MHz.
--
73, Cecil http://www.qsl.net/w5dxp

Sorry Cecil, I was talking to John, and not you.

I prefer low distortion accurate information that has not been run
through a "Cecil Moore filter".

73 Tom

wrote:
Cecil Moore wrote:
EZNEC doesn't like 4 TPI coils at 4 MHz.

Sorry Cecil, I was talking to John, and not you.

If you were talking to John and not me, you should have
done it over private email and not in a public forum. My
technical information is free - everyone can take it or
leave it.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil,

I have no idea what you did, but you screwed something up quite royally.
There is no way that segment 3 is too close to segment 197.

I just ran a cut-down version in the EZNEC 4 demo, and I found no
geometry errors. Yes, each segment length is too short, about 80% of the
recommendation, but Roy indicated a couple of days ago that should not
present a big problem. I cannot say much more about EZNEC, except that I
did not see any problems.

The coil I modeled is very similar to the Texas Bugcatcher model 680
coil. ( http://www.texasbugcatcher.com )

I don't own a Texas Bugcatcher coil, but I suspect they actually work
more or less as advertised.

73,
Gene
W4SZ

Cecil Moore wrote:
wrote:

Send me the file please. Don't use my akorn newsgeroup addres. I do not
check it.


Here's just about all you need to know about Gene's EZNEC file:

http://www.qsl.net/w5dxp/ezerror.GIF

EZNEC doesn't like 4 TPI coils at 4 MHz.

On Thu, 30 Mar 2006 00:04:28 GMT, Gene Fuller
wrote:
The coil I modeled is very similar to the Texas Bugcatcher model 680
coil. ( http://www.texasbugcatcher.com )

Hi Gene,

Could you pass a copy my way too?

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Thu, 30 Mar 2006 00:04:28 GMT, Gene Fuller
wrote:
The coil I modeled is very similar to the Texas Bugcatcher model 680
coil. ( http://www.texasbugcatcher.com )

Hi Gene,

Could you pass a copy my way too?

73's
Richard Clark, KB7QHC

Be sure you get a copy that has not been edited in a DXP filter.
Although free, the corrupted or selectively filtered data is useless.

73 Tom

Cecil,

I forgot to say one thing.

It appears that the files I sent you got corrupted somehow. First there
was the problem of "10 turns per foot" and now all the geometry check
errors. (Did you drop the card deck on the floor?) 8-) 8-)

The original files are still good at my end. I will resend if that will
help.

73,
Gene
W4SZ

Cecil Moore wrote:


Here's just about all you need to know about Gene's EZNEC file:

http://www.qsl.net/w5dxp/ezerror.GIF

EZNEC doesn't like 4 TPI coils at 4 MHz.