Anyone have any practical LPY (log-periodic Yagi) antenna designs they
care to share? Something with about 4% or 5% bandwidth in the VHF/low
UHF range should do well--the element diameters should be appropriate
for scaling the design to my frequencies of interest. 10dBi or so
gain is probably fine.

Cheers,
Tom

"K7ITM" wrote in message
...
Anyone have any practical LPY (log-periodic Yagi) antenna designs they
care to share? Something with about 4% or 5% bandwidth in the VHF/low
UHF range should do well--the element diameters should be appropriate
for scaling the design to my frequencies of interest. 10dBi or so
gain is probably fine.

Cheers,
Tom

define "log period yagi"??? ramsey has a line of products that they call
'log periodic and yagi' pcb antennas that has apparently been smushed into
"LPY" as the prefix to their part numbers... but 'Yagi' antennas are one
thing, and 'Log Periodic Dipole Array' antennas are something else. The
only place they cross practically that i have seen is the use of a log
periodic section feed section in between yagi style tuned parasitic elements
to give a wider bandwidth feed point... in this case it is usually just 2 or
3 elements worth of lpda feeding the yagi which i have always considered
just a way to add buzzwords to your antenna design description.

On Feb 24, 4:37 am, "Dave" wrote:
"K7ITM" wrote in message

...

Anyone have any practical LPY (log-periodic Yagi) antenna designs they
care to share? Something with about 4% or 5% bandwidth in the VHF/low
UHF range should do well--the element diameters should be appropriate
for scaling the design to my frequencies of interest. 10dBi or so
gain is probably fine.

Cheers,
Tom

define "log period yagi"??? ramsey has a line of products that they call
'log periodic and yagi' pcb antennas that has apparently been smushed into
"LPY" as the prefix to their part numbers... but 'Yagi' antennas are one
thing, and 'Log Periodic Dipole Array' antennas are something else. The
only place they cross practically that i have seen is the use of a log
periodic section feed section in between yagi style tuned parasitic elements
to give a wider bandwidth feed point... in this case it is usually just 2 or
3 elements worth of lpda feeding the yagi which i have always considered
just a way to add buzzwords to your antenna design description.

Yes, that's the design. I have data on a couple that suggest a pretty
"flat" gain across a modest range of frequencies, with a relatively
abrupt drop in gain outside that range. Googling got me to the
printed circuit antennas (I guess for wireless networks and the like),
but they aren't suitable to scale for what I want to do--too many
things different about them (flat elements on a dielectric substrate,
versus round elements in air).

Cheers,
Tom

"K7ITM" wrote in message
...
On Feb 24, 4:37 am, "Dave" wrote:
"K7ITM" wrote in message

...

Anyone have any practical LPY (log-periodic Yagi) antenna designs they
care to share? Something with about 4% or 5% bandwidth in the VHF/low
UHF range should do well--the element diameters should be appropriate
for scaling the design to my frequencies of interest. 10dBi or so
gain is probably fine.

Cheers,
Tom

define "log period yagi"??? ramsey has a line of products that they call
'log periodic and yagi' pcb antennas that has apparently been smushed
into
"LPY" as the prefix to their part numbers... but 'Yagi' antennas are one
thing, and 'Log Periodic Dipole Array' antennas are something else. The
only place they cross practically that i have seen is the use of a log
periodic section feed section in between yagi style tuned parasitic
elements
to give a wider bandwidth feed point... in this case it is usually just 2
or
3 elements worth of lpda feeding the yagi which i have always considered
just a way to add buzzwords to your antenna design description.

Yes, that's the design. I have data on a couple that suggest a pretty
"flat" gain across a modest range of frequencies, with a relatively
abrupt drop in gain outside that range. Googling got me to the
printed circuit antennas (I guess for wireless networks and the like),
but they aren't suitable to scale for what I want to do--too many
things different about them (flat elements on a dielectric substrate,
versus round elements in air).

Cheers,
Tom

for hf you want to look for 'owa', "optimized wideband array" antennas, and
also for yagi designs with dual driven elements like the m-squared 40m4lldd.
The advantages are a wider swr bandwidth and perhaps an improvement in the
gain or f/b bandwidth. you may also find some info searching for
'lpda-yagi' hybrids, though probably most of those are more for vhf/uhf.

On Feb 25, 1:28 pm, "Dave" wrote:
"K7ITM" wrote in message

...



On Feb 24, 4:37 am, "Dave" wrote:
"K7ITM" wrote in message

...

Anyone have any practical LPY (log-periodic Yagi) antenna designs they
care to share? Something with about 4% or 5% bandwidth in the VHF/low
UHF range should do well--the element diameters should be appropriate
for scaling the design to my frequencies of interest. 10dBi or so
gain is probably fine.

Cheers,
Tom

define "log period yagi"??? ramsey has a line of products that they call
'log periodic and yagi' pcb antennas that has apparently been smushed
into
"LPY" as the prefix to their part numbers... but 'Yagi' antennas are one
thing, and 'Log Periodic Dipole Array' antennas are something else. The
only place they cross practically that i have seen is the use of a log
periodic section feed section in between yagi style tuned parasitic
elements
to give a wider bandwidth feed point... in this case it is usually just 2
or
3 elements worth of lpda feeding the yagi which i have always considered
just a way to add buzzwords to your antenna design description.

Yes, that's the design. I have data on a couple that suggest a pretty
"flat" gain across a modest range of frequencies, with a relatively
abrupt drop in gain outside that range. Googling got me to the
printed circuit antennas (I guess for wireless networks and the like),
but they aren't suitable to scale for what I want to do--too many
things different about them (flat elements on a dielectric substrate,
versus round elements in air).

Cheers,
Tom

for hf you want to look for 'owa', "optimized wideband array" antennas, and
also for yagi designs with dual driven elements like the m-squared 40m4lldd.
The advantages are a wider swr bandwidth and perhaps an improvement in the
gain or f/b bandwidth. you may also find some info searching for
'lpda-yagi' hybrids, though probably most of those are more for vhf/uhf.

Hi Dave, and thanks for the reply. I'll try some searches on those
keywords. Often, just finding the right keyword for a search is well
over half the battle.

I perhaps didn't make it clear that I'm interested in optimizing the
design for my particular application, which is up around 450MHz, so
designs already at VHF/low-UHF are probably going to have reasonable
element diameter-to-length ratios and may offer some ideas about good
mechanical design. I'll happily spend some time with simulations to
optimize the design for my application, but it helps a lot to start
with a design that's close to what I want in the final implementation
at least with respect to d/l ratios and percentage bandwidth.

Cheers,
Tom

what's the high and low frequency you want to cover and how long do
you want the boom to be?
me


On Sun, 24 Feb 2008 18:17:58 -0800 (PST), K7ITM wrote:

On Feb 24, 4:37 am, "Dave" wrote:
"K7ITM" wrote in message

...

Anyone have any practical LPY (log-periodic Yagi) antenna designs they
care to share? Something with about 4% or 5% bandwidth in the VHF/low
UHF range should do well--the element diameters should be appropriate
for scaling the design to my frequencies of interest. 10dBi or so
gain is probably fine.

Cheers,
Tom

On Feb 26, 7:07 pm, wrote:
what's the high and low frequency you want to cover and how long do
you want the boom to be?
me

On Sun, 24 Feb 2008 18:17:58 -0800 (PST), K7ITM wrote:
On Feb 24, 4:37 am, "Dave" wrote:
"K7ITM" wrote in message

...

Anyone have any practical LPY (log-periodic Yagi) antenna designs they
care to share? Something with about 4% or 5% bandwidth in the VHF/low
UHF range should do well--the element diameters should be appropriate
for scaling the design to my frequencies of interest. 10dBi or so
gain is probably fine.

Cheers,
Tom

Let's see...500MHz to 1.05*500MHz = 525MHz; boom long enough to get me
about 10dBi over that range. I'll scale it to my particular
frequencies of interest, so any other ~5% bandwidth in that general
vicinity of frequencies would be fine too.

Cheers,
Tom

On Tue, 26 Feb 2008 23:02:37 -0800 (PST), K7ITM wrote:
Let's see...500MHz to 1.05*500MHz = 525MHz; boom long enough to get me
about 10dBi over that range. I'll scale it to my particular
frequencies of interest, so any other ~5% bandwidth in that general
vicinity of frequencies would be fine too.

Cheers,
Tom

This is a Log Periodic design. Double booms, 1 inch square, spaced
1.4 inches c-c. Boom length ~55 inches.

Sweep for 500-525 MHz
Free Space Gain - 11.6 - 12.6 dBi
vswr 1.7:1.0

X is the position of the element along the boom.
Y is the length of each "half-element". With a double boom design,
one half of the dipole is mounted to one boom and the other half is
mounted to the other boom.

Coax attached to the front of the booms, shield to one, center to the
other. Do not run coax between the booms.

Booms can be electrically shorted to each other behind element # 1.


You don't have to be this accurate, my calculator defaults to 5
places. Simply convert lenghts to the nearest mm is the easiest.

x y
End 0
1 2, 5.78592,
2 6.16586, 5.61234,
3 10.2067, 5.44397,
4 14.1264, 5.28065,
5 17.9285, 5.12223,
6 21.6165, 4.96857,
7 25.1939, 4.81951,
8 28.6639, 4.67492,
9 32.0299, 4.53468,
10 35.2948 , 4.39864,
11 38.4618, 4.26668,
12 41.5338, 4.13868,
13 44.5137 ,4.01452
14 47.4041 , 3.89408,
15 50.2079, 3.77726,
16 52.9275, 3.66394,
End 54.9275

have fun