Jimmie D wrote:

...
I thought the base coil would be for impedance matching, maybe he is tapping
up on the coil to find a 50 ohm point.

That is exactly the way I interpreted his description/pics; and, it's
exactly the way I implemented it (a modified gamma match--implemented in
helix form?) The wire-length/inductance is a 1:1.4 ratio between bottom
helix and upper loading coil--with the 1.4 of the length in the upper
loading coil. An adjustable 20" length of conductor is used between
lower and upper coils. Top whip is a 20" length also. (10 meter design)

From what I estimate, it ended up using, VERY CLOSE! TO, a computed
half-wavelength of wire at 28.050! And, I mean within' 1-3 inches! I
honestly did not expect that ...

Tap ended up almost dead center in the bottom helix turns for a 50 ohm
match; a variable capacitor is in series with this tap point on the
bottom helix and used to tune out the inductance of the tap wire.

I kludged a var/cap together using two small sheets of light aluminum.
These sheets are rolled into tubes and made so one is a smaller dia and
slips very loosely into the one of a larger dia. I then cut some clear
plastic from a drink container, rolled it and use it as the dielectric
(withstands the 1-100 watts test signal) between the inner/outer tubes.
This makes a serviceable/usable var. concentric cap. Inner tube is
roughly the dia of a bic pen (~1/4 inch.)

#8 copper is used, except for the upper loading coil which is #10 copper.

Try one; prove me wrong; I dare ya!

Regards,
JS

Try one; prove me wrong; I dare ya!

Regards,
JS



I don't see where the "inventor" of the DLM style antenna has violated
any laws of physics... He has simply found the sweet spot of mixed C &
L and short straight radiating sections along a shortened antenna to
pull it into resonance while maintaining a a flatter SWR curve...
With the helical lower section if that is how it is actually
functioning also acting as an auto transformer he simplifies the
matching of the feed point to coax...
Sevick proved that shortened antennas can work well...
If you look at the Fisher Island data for the DLM it shows that the
gain of the antenna improves considerably with top loading - a finding
we would definitely expect in a shortened monopole... Authors from
Sevick, to Cebik, to W8JK, to W8JI, have championed the benefits of
top hats for short antennas...

BTW, we have the oposite end of the spectrum in the distributed
capacity antenna with multiple caps along the length to redistribute
current peaks... So using capacitive reactance to redistribute
current along the antenna is well known and documented...

All in all, it sounds like a fun antenna, John... The guys really
ought to be looking at this as a method of trimming 160 and 80
verticals to a more manageable size while retaining some bandwidth and
having easy matching... If I didn't already have full size antenna
arrays for these bands I would be out there building one to see how it
performs...

I would hope that all those posting on the topic have read all the
URL's provided - and also noted the point that the antenna benefits
from being elevated and having elevated radials to work against , even
whilst mounted over the excellent ground plane of the Navy's test
range - a major piece of information......

denny / k8do

Denny wrote:

...
All in all, it sounds like a fun antenna, John... The guys really
ought to be looking at this as a method of trimming 160 and 80
...
denny / k8do


Denny:

I already like 'ya more than I did yesterday; This is why we got into
amateur radio, isn't it?; How come so many seem to have forgotten?

Warm regards,
JS

"Denny" wrote in message
oups.com...


Try one; prove me wrong; I dare ya!

Regards,
JS



I don't see where the "inventor" of the DLM style antenna has violated
any laws of physics... He has simply found the sweet spot of mixed C &
L and short straight radiating sections along a shortened antenna to
pull it into resonance while maintaining a a flatter SWR curve...
With the helical lower section if that is how it is actually
functioning also acting as an auto transformer he simplifies the
matching of the feed point to coax...
Sevick proved that shortened antennas can work well...
If you look at the Fisher Island data for the DLM it shows that the
gain of the antenna improves considerably with top loading - a finding
we would definitely expect in a shortened monopole... Authors from
Sevick, to Cebik, to W8JK, to W8JI, have championed the benefits of
top hats for short antennas...

BTW, we have the oposite end of the spectrum in the distributed
capacity antenna with multiple caps along the length to redistribute
current peaks... So using capacitive reactance to redistribute
current along the antenna is well known and documented...

All in all, it sounds like a fun antenna, John... The guys really
ought to be looking at this as a method of trimming 160 and 80
verticals to a more manageable size while retaining some bandwidth and
having easy matching... If I didn't already have full size antenna
arrays for these bands I would be out there building one to see how it
performs...

I would hope that all those posting on the topic have read all the
URL's provided - and also noted the point that the antenna benefits
from being elevated and having elevated radials to work against , even
whilst mounted over the excellent ground plane of the Navy's test
range - a major piece of information......

denny / k8do


I agree, this is just nothing new. As you say Jerry Sevick has already been
thier and done that. Jery already has established that making a short
antenna is no big deal as long as you have a good ground system and a low
loss matching network How well Vincents antenna performed has more to do the
the excellent ground system used in the test than anything special about the
antenna..



Jimie

Jimmie D wrote:

...
I agree, this is just nothing new. As you say Jerry Sevick has already been
thier and done that. Jery already has established that making a short
antenna is no big deal as long as you have a good ground system and a low
loss matching network How well Vincents antenna performed has more to do the
the excellent ground system used in the test than anything special about the
antenna..
Jimie

You must realize that you are either severely mentally disabled, of a
liar of monumental effort!

If not, don't worry, the rest of us do ...

JS