"Richard Clark" wrote in message
news
On Tue, 29 Aug 2006 11:27:10 GMT, "Lee"
wrote:

Yes, thanks for the info but i would like a little more gain than a
standard
discone gives...going to a parabolic discone would be the alternate
option
but a little too involved....

Parabolic discone??!!!?? Involved is not the word.

Hi Lee,

Everyone wants more gain. You don't say why and that may negate
wanting gain.

At the frequency you are desiring, performance is very much limited to
line of sight and even 2M handhelds with rubber duckies can work the
Space Shuttle an hundred miles up.

Consider the downside of gain: you are a tourist at the Grand Canyon
and you put a telephoto lens on your camera (high gain). When you get
home and show your pictures to friends, they might ask why you went to
the Grand Canyon but took pictures only of the river bed at the
bottom, or a cactus on the ridge. Too much gain for the intended use
which was to show the ENTIRE canyon in one shot. This would take a
wide-angle lens (very low gain).

I have a wide angle lens (low gain) it`s known as a discone !!!
freq range to 3000megs, supposedly 0db ref dipole that has heard one
or two weak signals just outside its range....now i need a telephoto lens
to make out what it is.......a wideband antenna with gain -- a log
periodic!!!!

With respect Richard, i have a scanning radio receiver that scans up to
2500megs
- that`s a lot of coverage which requires more gain the higher you go....a
discone
just doesn`t cut it gainwise so i need a wideband antenna with more
directional
gain to work alongside the discone...a yagi with one meg bandwidth isn`t
much use
either...imagine how many i would have lying around!!! besides, i know how
to
design those....... :-)


Anyway, simple scaling works. Just research the model of antenna that
gives you the gain characteristics you want, and scale to your band of
interest. The downside here is you may find that you have designed
yourself into a corner because you cannot find the right stock that
supports the dimensions. For a log periodic, this might not matter so
much, and especially for a receiver, but latitude is not generous.


If i knew how to scale or re-engineer an existing design, i wouldn`t be on
this NG
asking how to do it ...

Thanks for the advice Richard ......

73...

Lee......G6ZSG......

On Wed, 30 Aug 2006 06:19:09 GMT, "Lee"
wrote:

I have a wide angle lens (low gain) it`s known as a discone !!!
freq range to 3000megs,

Hi Lee,

Simply because it has a "frequency range to 3000megs" does not mean it
is usable to 3000megs - only that it matches to 3000megs. Matching
and usability are not strictly related.

supposedly 0db ref dipole that has heard one
or two weak signals just outside its range

Antennas don't have "ranges." You may experience poor performance due
to the combination of transmit power, path loss, and receiver
sensitivity, but none of this has anything to do with the antenna
(unless its poor construction adds loss). If you have too much path
loss, not enough transmit power, or poor receive sensitivity, then,
yes, a gain antenna will make up for those problems (as long as S+N/N
is sufficient in the end) - but this still does not confer a range
specification to an antenna.

This would be whole lot simpler if you simply told us the model number
of this discone.

If i knew how to scale or re-engineer an existing design, i wouldn`t be on
this NG
asking how to do it ...

You don't offer enough parameters like frequency span, gain, F/B, how
long a feedline, what kind of feedline (lot of potential loss there)
for someone to whip out a design here, and that wouldn't be a modest
enterprise if you did. Scaling is the easiest solution, perhaps you
should buy a log periodic. Google would be another solution, your
problem would not be unique - would it?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 30 Aug 2006 06:19:09 GMT, "Lee"
wrote:

SNIP!!!!

Richard, all i want is design software to build a LPA!!!! do you or
don`t you know of any?????

Lee.....G6ZSG.......

On Wed, 30 Aug 2006 07:04:08 GMT, "Lee"
wrote:
Richard, all i want is design software to build a LPA!!!! do you or
don`t you know of any?????

EZNEC

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 30 Aug 2006 07:04:08 GMT, "Lee"
wrote:
Richard, all i want is design software to build a LPA!!!! do you or
don`t you know of any?????

EZNEC

Why didn`t you say that in the first place??

Thankyou...

G6ZSG...


73's
Richard Clark, KB7QHC

On Wed, 30 Aug 2006 08:16:12 GMT, "Lee"
wrote:

EZNEC

Why didn`t you say that in the first place??

Hi Lee,

Because of various clues in your discussion, and your claim
If i knew how to scale or re-engineer an existing design, i wouldn`t be on
this NG
asking how to do it ...
Re-engineering goes to the heart of a successful outcome and is part
and parcel to modeling. On the other hand, the trivial work for
simple scaling will always give a solution.

EZNEC, although probably the best modeler for the occasion, is one
that does require deep knowledge of design elements and program
operation in this case. Modeling an LPDA is not trivial.

73's
Richard Clark, KB7QHC

ARRL Antenna Handbook gives all the LPDA design equations.

However, LPDAs do not have high gain!! They have typical gain of 6 to 8 [+/-]
dBd and broad bandwidth. They typically function as either a three or four
element driven array. They are driven arrays, not parasitic [i.e. Yagi
principle] designs.

Also, LPDAs for 3,000 MHz will have a L/D ratio issues with element geometry and
general construction will require fairly precise measurements.

Unlike a Yagi, a long boom length LPDA does not equate into higher gain.

/s/ DD

Lee wrote:

"Richard Clark" wrote in message
...

On Wed, 30 Aug 2006 06:19:09 GMT, "Lee"
wrote:


SNIP!!!!

Richard, all i want is design software to build a LPA!!!! do you or
don`t you know of any?????

Lee.....G6ZSG.......

"Dave" wrote in message
. ..
ARRL Antenna Handbook gives all the LPDA design equations.

However, LPDAs do not have high gain!! They have typical gain of 6 to 8
[+/-]
dBd and broad bandwidth. They typically function as either a three or four
element driven array. They are driven arrays, not parasitic [i.e. Yagi
principle] designs.

Also, LPDAs for 3,000 MHz will have a L/D ratio issues with element
geometry and
general construction will require fairly precise measurements.

Unlike a Yagi, a long boom length LPDA does not equate into higher gain.

/s/ DD

Yes thanks Dave i am aware of the functions of a LPA i just need a little
directivity
and a little more gain than a discone offers, plus design software!!...

Regards...

Lee....G6ZSG......

Lee wrote:

Yes thanks Dave i am aware of the functions of a LPA i just need a little
directivity
and a little more gain than a discone offers, plus design software!!...

If you're looking for software to design an antenna for you, EZNEC isn't
it. EZNEC will analyze an antenna you design, but it won't design it for
you.

Roy Lewallen, W7EL