Slow wave antenna design for top band
 

Gentlemen
In constructing "slow wave" antennas for top band I am finding that a
wavelength in equilibrium is a bit longer than expected.
As I am using large diameter formers for circular radiation I suspect
the reduction in number of turns is the reason.
Does anybody know of a turns versus length graph has been made for
this phenomina and where I could find it?
At present I start with scaling up a Tesla coil as a starting point
but that is becomming somewhat laborious after winding a few antennas.
( I will be placing a photo of my antenna on my page in a few days)
TIA
Regards
Art Unwin KB9MZ.........XG (uk)

Slow wave antenna design for top band
 

art wrote:
Gentlemen
In constructing "slow wave" antennas for top band I am finding that a
wavelength in equilibrium is a bit longer than expected.
As I am using large diameter formers for circular radiation I suspect
the reduction in number of turns is the reason.
Does anybody know of a turns versus length graph has been made for
this phenomina and where I could find it?
At present I start with scaling up a Tesla coil as a starting point
but that is becomming somewhat laborious after winding a few antennas.
( I will be placing a photo of my antenna on my page in a few days)

Here you go, Art. Equation 32 and Fig. 1 should be within
10% of what you need assuming your device meets the test
equation boundaries given between Equation 31 and Equation 32.

http://www.ttr.com/TELSIKS2001-MASTER-1.pdf
--
73, Cecil http://www.w5dxp.com

Slow wave antenna design for top band
 

On 25 Oct, 08:22, Cecil Moore wrote:
art wrote:
Gentlemen
In constructing "slow wave" antennas for top band I am finding that a
wavelength in equilibrium is a bit longer than expected.
As I am using large diameter formers for circular radiation I suspect
the reduction in number of turns is the reason.
Does anybody know of a turns versus length graph has been made for
this phenomina and where I could find it?
At present I start with scaling up a Tesla coil as a starting point
but that is becomming somewhat laborious after winding a few antennas.
( I will be placing a photo of my antenna on my page in a few days)

Here you go, Art. Equation 32 and Fig. 1 should be within
10% of what you need assuming your device meets the test
equation boundaries given between Equation 31 and Equation 32.

http://www.ttr.com/TELSIKS2001-MASTER-1.pdf
--
73, Cecil http://www.w5dxp.com

Thanks so much for that article by the most formost
scientists on this subject.
I have not made things easier on myself lately as I
have migrated to tinned
copper braid for extra gain which obviously increases
the slow wave length somewhat because of the added
indunctance which some would considered as being cancelled Hi.
At first I was considering the actual wire length
in the braiding b ut that influence became little
compared to the current pertabutations. Also have
found that the standing waves do not completely
disapear until the top band radiator is up at a
one wave height which was a bit of a dissapointment
but still acceptable at 850 feet.
Thanks again for what appears to be a jewel
Art Unwin KB9MZ....XG....(uk)
Can't wait to add a flyback transformer so I can
make a radio wave missile launcher.

Slow wave antenna design for top band
 

art wrote:
At first I was considering the actual wire length
in the braiding b ut that influence became little
compared to the current pertabutations.

Sounds like you are working on a self-resonant coil
and need to know the length of time for the current
to flow from end to end.

Both sides of the argument are wrong on that one.
The current does not jump from one end of a coil to
the other in a very small number of nanoseconds as
one "expert" has asserted which implies a VF close
to 1.0. Neither does the current follow the wires
directly round and round the coil as asserted by the
other side which would imply a VF around 0.01.

The actual measurable VF of a coil seems to be just
about double the round-and-round argument side as
there is indeed some coupling between adjacent coils.
A typical 75m Texas Bugcatcher 6" dia, 6.5" long,
4 tpi coil has a VF of around 0.02 making it about
40 degrees long at 3.8 MHz.
--
73, Cecil http://www.w5dxp.com

Slow wave antenna design for top band
 

On 25 Oct, 09:38, Cecil Moore wrote:
art wrote:
At first I was considering the actual wire length
in the braiding b ut that influence became little
compared to the current pertabutations.

Sounds like you are working on a self-resonant coil
and need to know the length of time for the current
to flow from end to end.

Both sides of the argument are wrong on that one.
The current does not jump from one end of a coil to
the other in a very small number of nanoseconds as
one "expert" has asserted which implies a VF close
to 1.0. Neither does the current follow the wires
directly round and round the coil as asserted by the
other side which would imply a VF around 0.01.

The actual measurable VF of a coil seems to be just
about double the round-and-round argument side as
there is indeed some coupling between adjacent coils.
A typical 75m Texas Bugcatcher 6" dia, 6.5" long,
4 tpi coil has a VF of around 0.02 making it about
40 degrees long at 3.8 MHz.
--
73, Cecil http://www.w5dxp.com

No Cecil you are following a fatal aproach by using
lumped loaded circuitry which is a no no when measuring current speed.
Especially when you are following a path of zero standing waves.
To obtain a voltage doubling you can only solve by using
distributed loading aproach where a single wire has approx length
when measured close to the ground short of two wavelengths .
Unfortunately by using braid to get extra current perbutatation
the length extends quite a bit longer even tho braiding electrical
length is longer that the physical measurement.
Ofcourse the introduction of a flyback transformer would be
exciting but we must not run before we walk
Regards
Art

Slow wave antenna design for top band
 

"art" wrote in message
ups.com...
On 25 Oct, 09:38, Cecil Moore wrote:
art wrote:
At first I was considering the actual wire length
in the braiding b ut that influence became little
compared to the current pertabutations.

Sounds like you are working on a self-resonant coil
and need to know the length of time for the current
to flow from end to end.

Both sides of the argument are wrong on that one.
The current does not jump from one end of a coil to
the other in a very small number of nanoseconds as
one "expert" has asserted which implies a VF close
to 1.0. Neither does the current follow the wires
directly round and round the coil as asserted by the
other side which would imply a VF around 0.01.

The actual measurable VF of a coil seems to be just
about double the round-and-round argument side as
there is indeed some coupling between adjacent coils.
A typical 75m Texas Bugcatcher 6" dia, 6.5" long,
4 tpi coil has a VF of around 0.02 making it about
40 degrees long at 3.8 MHz.
--
73, Cecil http://www.w5dxp.com

No Cecil you are following a fatal aproach by using
lumped loaded circuitry which is a no no when measuring current speed.
Especially when you are following a path of zero standing waves.
To obtain a voltage doubling you can only solve by using
distributed loading aproach where a single wire has approx length
when measured close to the ground short of two wavelengths .
Unfortunately by using braid to get extra current perbutatation
the length extends quite a bit longer even tho braiding electrical
length is longer that the physical measurement.
Ofcourse the introduction of a flyback transformer would be
exciting but we must not run before we walk
Regards
Art

Art
I think you cannot rely on calculating the braided length as being longer
than the physical length. While it is true that the braided wire if
unravelled would likely be considerably longer, RF waves propagate along the
surface of the wire. They will jump from one wire to the next where the
braids cross, following the path of least resistance. You would probably
need to use braided Litz wire, where each strand is individually enamelled
to achieve what you appear to be trying to do.
Regards
Mike G0ULI

Slow wave antenna design for top band
 

art wrote:
No Cecil you are following a fatal aproach by using
lumped loaded circuitry which is a no no when measuring current speed.

Nope, I'm arguing against that approach, Art. Some
"experts" seem to like lumped load concepts but not
I. Dr. Corum warns against using lumped load concepts
for large coils and I agree with him.
--
73, Cecil http://www.w5dxp.com

Slow wave antenna design for top band
 

On 25 Oct, 11:32, "Mike Kaliski" wrote:
"art" wrote in message

ups.com...



On 25 Oct, 09:38, Cecil Moore wrote:
art wrote:
At first I was considering the actual wire length
in the braiding b ut that influence became little
compared to the current pertabutations.

Sounds like you are working on a self-resonant coil
and need to know the length of time for the current
to flow from end to end.

Both sides of the argument are wrong on that one.
The current does not jump from one end of a coil to
the other in a very small number of nanoseconds as
one "expert" has asserted which implies a VF close
to 1.0. Neither does the current follow the wires
directly round and round the coil as asserted by the
other side which would imply a VF around 0.01.

The actual measurable VF of a coil seems to be just
about double the round-and-round argument side as
there is indeed some coupling between adjacent coils.
A typical 75m Texas Bugcatcher 6" dia, 6.5" long,
4 tpi coil has a VF of around 0.02 making it about
40 degrees long at 3.8 MHz.
--
73, Cecil http://www.w5dxp.com

No Cecil you are following a fatal aproach by using
lumped loaded circuitry which is a no no when measuring current speed.
Especially when you are following a path of zero standing waves.
To obtain a voltage doubling you can only solve by using
distributed loading aproach where a single wire has approx length
when measured close to the ground short of two wavelengths .
Unfortunately by using braid to get extra current perbutatation
the length extends quite a bit longer even tho braiding electrical
length is longer that the physical measurement.
Ofcourse the introduction of a flyback transformer would be
exciting but we must not run before we walk
Regards
Art

Art
I think you cannot rely on calculating the braided length as being longer
than the physical length. While it is true that the braided wire if
unravelled would likely be considerably longer, RF waves propagate along the
surface of the wire. They will jump from one wire to the next where the
braids cross, following the path of least resistance. You would probably
need to use braided Litz wire, where each strand is individually enamelled
to achieve what you appear to be trying to do.
Regards
Mike G0ULI- Hide quoted text -

- Show quoted text -

I see where you are coming from but braid wicks like mad so a good
dose of quick drying polythene varnish solves that problem IF it were
to
occur, tho the current will not jump but follow the path of resonance.
What I am doing now is a combination of insulated wire with doped
braiding
and it appears so far that the braid is required to be much longer.
When time permits I will make seperate models using wire and then with
braid
on a higher frequency where the single wire form is easily calculated
as a datum
As far as Litz wire goes there is a frequency transition line when you
use that
(skin factor) so I am not anxcious to introduce another variable or
spend
the required extra money.
Regarding travelling on the surface of the wire I have often pondered
that the use of braid for grounding wire is subject to question
compared
to a copper wire or ribbon. As I see it the braid is heavily inductive
even tho it has the appearance of the field balancing out since the
current must still traverse the windings, but that is another subject
all together
deserving of its own topic title.
I know it may sound wierd but I am trying to slow down the current by
half so that
for the tank circuit I will have four pulses of energy release over
the existing
two.Single wire windings are just a hair to fast to accomplish that
In other words double the power of a particle generator which is
what
radiation is all about, at least in my mind, since I see the
attributed gain of a helix
being controlled by the voltage increase in sync with the current flow
which I see as
not quite correct when using single wire since. I am still seeing
standing vaves which are small
but does not prevent full traverse of all amateur frequencies using a
single antenna with a
variometer for use when resistance levels drop below 20 ohms.
It just blows my mind how just applying a time varying field to a
static
field is providing so much more info with respect to radiation
assuming
one has a true understanding of what equilibrium is really all about
and which the majority deride
Cheers
Art. KB9mz

Slow wave antenna design for top band
 

On 25 Oct, 12:45, Cecil Moore wrote:
art wrote:
No Cecil you are following a fatal aproach by using
lumped loaded circuitry which is a no no when measuring current speed.

Nope, I'm arguing against that approach, Art. Some
"experts" seem to like lumped load concepts but not
I. Dr. Corum warns against using lumped load concepts
for large coils and I agree with him.
--
73, Cecil http://www.w5dxp.com

Good for him. It appears that constant use of lumped circuit analysis
is gaining more votes against true science of today especially in
amateur
radio. Soon it will be promoted to a Law disregarding that it is
only theory based. Something akin to a poll
Regards
Art.

Slow wave antenna design for top band
 

Umm a velocity factor of .50 might be attainable with a variation on
leaky coax... Some of the cheap stuff is already as slow as .66...
Off the top of my pointy head braided wires wrapped on your form (same
as you are currently doing) then potted in an appropriate dielectric
material for filling the braid interstices should slow things down
some more... The question extant is what material for potting (or for
adding to your potting resin) will further slow progression of the
wave front along the braid...
We know that solid polyethylene dielectric on coax results in a lower
vf than the foamed materials.. So it appears that denser material
results in slower wave progression... Perhaps UHMW, or similar might
suffice...
Other thoughts come along, such as a flat ribbon with a deeply
embossed pattern then filled with dielectric might be slower than
braided wire... Or even a ribbon of screening material similarily
filled...
Dunno... Interesting problem...

denny / k8do