Log-Periodic Antenna Design
 

christofire wrote:
"Rich Grise" wrote in message
...
My current UHF antenna is a 14" Radio Shack clip lead clipped from the
center of my coax to the venetian blind. I have to hand-adjust it
for the channel, weather conditions, phase of the moon, etc. I can
do this because I can _see_ an indication of signal strength.

Well, with this new Fascist "No More Free TV" crap, I'm gonna need
a real UHF antenna. My budget is exceedingly limited, but I have
a supply of materials (GTAW filler rod, with some coppery-colored
coating, so it solders like a dream, and is as stiff as piano wire)
to build an antenna with.

But I've been searching the web for some weeks now, and I can't
seem to find any kind of formula, except there was this program
I downloaded - LPDA.EXE, which runs on DOS. Unfortunately, it's
in Russian or Polish or Uzbekistani - one of those East Yurp
languages. Here's a screen snap:
http://mysite.verizon.net/richgrise/...rog-Output.gif

Which I went through pretty much by-guess-and-by-gosh - can
anybody read that stuff?

There are a lot of factors I don't know about, like "Tau", and
all of the specific designs on the web are flat - something is
telling me I want one of those pyramid-shaped ones, but I really
don't know the difference (between that and flat) - it's probably
something to do with bandwidth or F/B ratio or whatever.

My local library has no ARRL Antenna Book (!), and did I mention
I have a seriously limited budget?

So, how do I pursue this? It'd be nice to have a program that will
calculate the whole thing for me, but am I dreaming? If I want to
send myself to Log-Periodic School, where should I start?

Or, does anyone have a UHF-TV log-periodic design that they'd share? :-)

Thanks,
Rich


You probably don't need a program, just a decent text book that covers the
topic adequately, which, undoubtedly is what the program writers worked
from, and they might not have got it right! 'Antennas' by John Kraus
contains enough detail to make a start and it's probably more general than
someone's program which might involve specific choices of some parameter
values. So my recommendation would be to find a technical library that
offers access to non-members and send yourself to Log-Periodic School as you
put it. The IET library in London does this, for free. Do you have an
equivalent institution (e.g. IEEE), or a local university that covers
electronic engineering? You might be surprised how much access you can gain
to libraries to which you have contributed through taxes, or which need to
maintain an 'altruistic' public appearance.


Orfanidis's book on electromagnetic waves and antennas is online, and
covers LPDAs.. Kraus is better, but you'll have to fork out at least
$20+shipping for a used copy. Kraus *is* my recommendation if you have
to have a single antenna book, though.

Log-Periodic Antenna Design
 

"Rich Grise" wrote in message
...
I was doing a thought experiment with this and
when it's completely "flattened out", (180 degrees between the booms),
it looks like a drum roll please Bow Tie!

I think a bow tie's design is actually motivated more by one of the "standard"
ultra-wideband antenna designs, that of a pair of opposing cones touching each
other at their narrow ends, being translated down into 2D.

Log-Periodic Antenna Design
 

Jim Lux wrote:
Kraus is better, but you'll have to fork out at least
$20+shipping for a used copy. Kraus *is* my recommendation if you have
to have a single antenna book, though.

Here's a new international 3rd edition available for less
than $10 plus shipping.

http://www.abebooks.com/servlet/Sear...tennas&x=0&y=0
--
73, Cecil http://www.w5dxp.com

Log-Periodic Antenna Design
 

Rich Grise wrote:

...
Hey, "John Smith", why don't you go outside and play
hide-and-go-****-yourself?

Cheers!
Rich


LOL ...

Darn, you just can't get decent psychiatric help with your food stamps,
can you? :-(

Regards,
JS

Log-Periodic Antenna Design
 

GregS wrote:

Ever hear of the BOW TIE. Its a sort of Fractal antenna. Having a wide band.
It could be improved by making it a full fractal.

greg

That's interesting. In what way(s) is it improved by making it fractal?
How much is the improvement? Can you point me to a reference about this
which gives some quantitative data?

Roy Lewallen, W7EL

Log-Periodic Antenna Design
 

Rich Grise wrote:
On Wed, 19 Nov 2008 22:53:28 -0800, Richard Clark wrote:
. . .
73's

"Best Regardses"? ;-)

No, that's "Best Regards's". It's the possessive, not plural, form of
"Best Regards". I think the grammar is part of the same dialect as the
verb "destinate" (as in "I've just destinated"), but you'd have to ask
Richard about that -- he's the one with the English Lit degree.

Roy Lewallen, W7EL

Log-Periodic Antenna Design
 

"Rich Grise" wrote in message
...
My current UHF antenna is a 14" Radio Shack clip lead clipped from the
center of my coax to the venetian blind. I have to hand-adjust it
for the channel, weather conditions, phase of the moon, etc. I can
do this because I can _see_ an indication of signal strength.

Well, with this new Fascist "No More Free TV" crap, I'm gonna need
a real UHF antenna. My budget is exceedingly limited, but I have
a supply of materials (GTAW filler rod, with some coppery-colored
coating, so it solders like a dream, and is as stiff as piano wire)
to build an antenna with.

It may not take too much antenna. I picked up one of the converter boxes
and hooked it to a 432 mhz beam at 70 feet and got 21 stations on the auto
tune. Then to a 9 element M2 2 meter bem and it picked up 29 stations.
This was at the end of about 130 feet of low loss rg-8 size coax and then 25
feet of rg-6.
Several of the stations were the same transmitter,but differant chanels on
the TV.

Log-Periodic Antenna Design
 

"Joel Koltner" wrote in message
...
I think a bow tie's design is actually motivated more by one of the
"standard" ultra-wideband antenna designs, that of a pair of opposing
cones touching each other at their narrow ends, being translated down into
2D.

Standard, indeed; this antenna is known as a biconical. It has excellent
wideband response making it ideal for EMC testing. Most good antenna texts
such as that by Krauss give a detailed analysis of the biconical antenna. I
see no relationship between its design and a fractal design other than both
are wide bandwidth antennas.

The bowtie antenna which Rich and others have mentioned is a "flattened"
form of the biconical. If the bowtie is bent along its major axis, it makes
an excellent wideband driven element for a corner reflector antenna.

73, Barry WA4VZQ

Log-Periodic Antenna Design
 

Thanks for the details, Barry... tell me though, then, is a discone just a
biconical with a ground plane used to create the (image of the) missing cone?

Log-Periodic Antenna Design
 

"Joel Koltner" wrote in message
...
Thanks for the details, Barry... tell me though, then, is a discone just
a biconical with a ground plane used to create the (image of the) missing
cone?

Yes. It will have less gain than a biconical and the bandwidth is slightly
more restrictive too. But it is much easier to construct!

73, Barry WA4VZQ