Log Periodic ant
 

"Owen Duffy" wrote in message
...
On Tue, 29 Aug 2006 07:43:15 GMT, "Lee"
wrote:


I have just bought a Yaesu VR5000 receiver/scanner and while looking
round
for a wideband antenna
...

Scanners are notorious for a lack of front end selectivity and
resultant high intermodulation products / noise.

Yes i am taking a bit of a chance with a wideband antenna Owen but
if i can resolve a signal, it is a start.....i have built a bow tie
can-tenna
for 23cms which seems to work okay, now, i`ll build one for 13 cms
with a corner reflector, only because i know something is there!!!.


Sometimes they depend on narrow band antennas to supplement their
meagre front end selectivity.

Agreed!!.

In the absense of external front end selectivity, you may find that
the realisable sensitivity is quite a deal higher (tens of dB worse)
than specification, depending on your own RF environment.

That is where i will need a narrow filter pre-amp which will be bought (or
built)
when needed.....

Thanks for your input Owen, the Yaesu is certainly a great deal better than
the
AOR 2002 which is as wide as a barn door, but served its purpose!!!.....

Regards..

Lee....G6ZSG....

Log Periodic ant
 

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.......

Log Periodic ant
 

"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......

Log Periodic ant
 

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

Log Periodic ant
 

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

Log Periodic ant
 

On Tue, 29 Aug 2006 07:43:15 GMT, "Lee"
wrote:

Hi All.....

I have just bought a Yaesu VR5000 receiver/scanner and while looking round
for a wideband antenna
came across the good old log periodic but what a price!!!, circa £200+......

I have a discone but it`s not a lot of use up around the 2gig area (or
anywhere else!!) so i thought i
might have a go at making my own, the magloops are working great as is the
QFH 137megs
weathersat ant, thanks to everyones assistance!.....

Is there any software around to design a log periodic to around
2400megs??.....i`ve found some but is there any better?..

http://members.aon.at/hwabnig/
input your numbers....

Log Periodic ant
 

"Helmut Wabnig" *_.-_- wrote in
message ...
On Tue, 29 Aug 2006 07:43:15 GMT, "Lee"
wrote:


Is there any software around to design a log periodic to around
2400megs??.....i`ve found some but is there any better?..

http://members.aon.at/hwabnig/
input your numbers....

Thankyou Helmut, very much apreciated.......

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

Log Periodic ant
 

Why try to design and build one if you can get a 900 to 2600MHz version
for US$12 or a 2 to 11GHz version for US$6. See Ebay items 300021857426
and 300021856873. How about 400 to 900MHz for US$24, item 300021857046.
Cheers!
Bob

Lee wrote:
"Helmut Wabnig" *_.-_- wrote in
message ...
On Tue, 29 Aug 2006 07:43:15 GMT, "Lee"
wrote:

Is there any software around to design a log periodic to around
2400megs??.....i`ve found some but is there any better?..
http://members.aon.at/hwabnig/
input your numbers....

Thankyou Helmut, very much apreciated.......

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