On Wed, 19 Nov 2008 16:49:03 -0800, Jim Lux wrote:

Rich Grise wrote:
....
myself to Log-Periodic School, where should I start?

Looking for a cookbook design, or the theory to do it yourself?

Cookbook, if at all possible. Like, element lengths and spacing,
and the angle between the booms - which brings up a question - what
effect does it have when you take a flat L-P and "open it up", like
to a pyramid shape - 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!

Thanks,
Rich

"Rich Grise" wrote in message
news
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.

"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

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?

"Rich Grise" wrote in message
news
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.

The pyramidal form has greater aperture in the vertical plane for all but
the highest frequencies. It behaves like a vertically-stacked pair of
Log-Periodic Dipole Arrays and achieves a bit more gain. Its pattern in the
vertical plane is consistently sharper over a range of frequencies because
of the vertical taper, but it is a bit more difficult to design. Not all
'wideband' UHF antennas are based on the LPDA - some are Yagi-Uda arrays
designed using NEC and its derivatives, achieving a useful compromise
between bandwidth, gain, and pattern shapes. But if you want to include
channels below 21 as well as the UHF band, with consistent directivity, then
LPDA is probably the only way to go.

Chris

christofire wrote:
"Rich Grise" wrote in message
news
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.

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

Rich Grise wrote:
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.


LOL ... talk about trolls! That HAS TO BE THE BEST TROLL OPENING LINE I
HAVE EVER SEEN!

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.


Well, that is the second best ...

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


hmmm ....

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


Ever heard of amplifed rabbit ears?

Regards,
JS

Hi John.
On Nov 19, 6:31 pm, John Smith wrote:
Rich Grise wrote:
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.

LOL ... talk about trolls! That HAS TO BE THE BEST TROLL OPENING LINE I
HAVE EVER SEEN!

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.

Well, that is the second best ...

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

hmmm ....



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

Ever heard of amplifed rabbit ears?

Regards,
JS

It's not a troll. I bought a fair good UHF-VHF antenna,
assembled it and sat it on a saw horse in the driveway
for test, and it tested perfect for 3 channels + ch.34 .
So I set her up using a roof mount and LOST ch.34,
and no amount of rotating got it back.
(I was a pro antenna/tower installer as a kid).

Next I'm going to tape wire on 1/8" panelling and do
experiments ... ugh, I hate trial and error.
Ken

Ken S. Tucker wrote:

...
It's not a troll. I bought a fair good UHF-VHF antenna,
assembled it and sat it on a saw horse in the driveway
for test, and it tested perfect for 3 channels + ch.34 .
So I set her up using a roof mount and LOST ch.34,
and no amount of rotating got it back.
(I was a pro antenna/tower installer as a kid).

Next I'm going to tape wire on 1/8" panelling and do
experiments ... ugh, I hate trial and error.
Ken

OK brother, you may not be what I accuse you of ...

But darn, the antenna you bought was designed with certain parameters in
mind ... I would seriously doubt you are going to vastly increase
performance with the route(s) you have described here ...

Sorry if I made a joke. But, my advise to you would be, if you saved
your receipt, take it back! DON'T HACK THE ANTENNA!

Chat with buddies or someone who has had better experience(s) (or,
varied experiences) with a better antenna, one which would serve you better.

Without expensive instrumentation and experience of years of
experimenting, it is hard to accomplish what I perceive your goals to be ...

I would never say anything is impossible, just what I feel is the best
advise I can provide you with in hoping for your best success.

Wish you the best,
JS