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The Lazy H does not seem to exhibit any gain over a dipole in thereal world



 
 
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  #1  
Old May 12th 11, 06:04 AM posted to rec.radio.amateur.antenna
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Posts: 650
Default The Lazy H does not seem to exhibit any gain over a dipole in thereal world

On Tuesday, May 10, 2011 8:13:36 AM UTC-5, Michael wrote:


Has anyone seen real world gain with the Lazy H on 10 meters verses a
dipole? My experience shows it consistently lags behind the 1/2 wave
dipole even through the Lazy H is 10+ feet higher than the dipole.

I also built an extended double zepp for 10 meters with a 450 matching
section to a 1:1 balun and then to coax, and the extended double zepp
consistently out performs the dipole in it's preferred direction.


I've never tried one, so can't say from experience.
But that you have to use extreme tuner settings to match
the system tells me you may be seeing a good amount of loss.
And then you have the issues Richard mentioned on top of that.
The coax fed dipole is very efficient. Very little system loss
involved. So even if it had less directional gain, it's possible
that gain could be offset by matching losses. Or even driven
negative if the loss was extreme.
Compare the two on a dead frequency just listening to noise.
If the H seems real quiet compared to the dipole, I would
suspect excess tuner loss. If they are about the same, may be
other issues.

The only phased dipoles I ever ran were parallel horizontal
dipoles. I would steer the pattern by changing the phasing.
Usually by adding lengths of feed line. It worked pretty well.
That was on 40m.. But as mentioned, there is only so much
blood that can be squeezed from two elements, even if configured
in an optimum manner, say as with a yagi or whatever. :/



  #2  
Old May 12th 11, 03:05 PM posted to rec.radio.amateur.antenna
Michael[_10_]
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Posts: 28
Default The Lazy H does not seem to exhibit any gain over a dipole in thereal world

On May 12, 1:04*am, wrote:
On Tuesday, May 10, 2011 8:13:36 AM UTC-5, Michael wrote:

Has anyone seen real world gain with the Lazy H on 10 meters verses a
dipole? My experience shows it consistently lags behind the 1/2 wave
dipole even through the Lazy H is 10+ feet higher than the dipole.


I also built an extended double zepp for 10 meters with a 450 matching
section to a 1:1 balun and then to coax, and the extended double zepp
consistently out performs the dipole in it's preferred direction.


I've never tried one, so can't say from experience.
But that you have to use extreme tuner settings to match
the system tells me you may be seeing a good amount of loss.
And then you have the issues Richard mentioned on top of that.
The coax fed dipole is very efficient. Very little system loss
involved. So even if it had less directional gain, it's possible
that gain could be offset by matching losses. Or even driven
negative if the loss was extreme.
Compare the two on a dead frequency just listening to noise.
If the H seems real quiet compared to the dipole, I would
suspect excess tuner loss. If they are about the same, may be
other issues.

The only phased dipoles I ever ran were parallel horizontal
dipoles. I would steer the pattern by changing the phasing.
Usually by adding lengths of feed line. It worked pretty well.
That was on 40m.. *But as mentioned, there is only so much
blood that can be squeezed from two elements, even if configured
in an optimum manner, say as with a yagi or whatever. *:/


I rebuilt the center fed Lazy H twice with different pieces of 450
ladder line, and I installed it in two different locations. I used two
different antenna tuners. I built it exactly as specified in the ARRL
antenna handbook. Both times the antenna exhibited a high SWR and
poor performance compared to a mono band dipole for the same frequency
and at about the same height. I suspect the underling problem may be
too many arm chair antenna experts plugging their designs in to
computer antenna modeling software, and not enough people actually
going out in the backyard and building the antenna and comparing it's
performance to a real world dipole for the same frequency. There are
many web pages touting the supposed gain of the Lazy H with EZNEC
plots posted as supporting evidence, but real world performance has
shown that it is consistently out performed by a plain old dipole.
I was able to make contacts with the Lazy H, and I did get some good
reports with it. However, when I switched to the plain old wire
dipole the dipole was consistently the stronger performer. I have not
tried the end fed Lazy H design with a 180 degree twist and the 1/4
wave matching stub yet.

Michael Rawls
KS4HY








  #3  
Old May 12th 11, 05:42 PM posted to rec.radio.amateur.antenna
Richard Clark
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Posts: 2,951
Default The Lazy H does not seem to exhibit any gain over a dipole in the real world

On Thu, 12 May 2011 07:05:36 -0700 (PDT), Michael
wrote:

I suspect the underling problem may be
too many arm chair antenna experts plugging their designs in to
computer antenna modeling software, and not enough people actually
going out in the backyard and building the antenna and comparing it's
performance to a real world dipole for the same frequency.


Hi Michael,

All very true, but be careful of the conclusions you thinks this leads
you to. For instance:

There are
many web pages touting the supposed gain of the Lazy H with EZNEC
plots posted as supporting evidence, but real world performance has
shown that it is consistently out performed by a plain old dipole.


The Lazy H, in professional installations known as Sterba Curtains,
are THE antenna of the big gun Shortwave Broadcasters. Engineers,
stations, and their backers looking at field data do not erect costly
antennas without good judgment. In the past, we have had contributors
here who have designed for these big guns.

Now, as to what you see as "evidence" on the Web in the form of EZNEC
software reports (something I've been using for nigh-on 20 years) has
to be looked at in the details, and the details that are significant:
1. The presence of ground
2. The quality of ground
3. The antenna elevation above ground
4. The presence of conductor loss
5. Transmission line specification
6. Transmission line drive
7. The load Z
8. The system gain (or loss)
at a minimum. That is a lot of detail to hold in the mind while
trying to compare two antennas, much less 3, 4, or 5.

One of the glaring mistakes between the outcome to this and "reality"
(and this undoubtedly conforms to your experience) is that the
placement of the source (transmitter) in software is vastly different
than the placement of the transmitter (source) in physical reality.

For instance, the twist in the line between elements is to enforce a
necessary phase relationship so that you can fee it at the bottom.
Otherwise you can go with a non-twist if you feed it in the middle.
The design varies in particulars there. So what? You can feed either
a twisted connection, or a non-twisted section in the middle; BUT for
the second version, the line back to the transmitter MUST BE dressed
AWAY from the middle of the interconnecting line. Proximity will
confound everything. Proximity for this second choice is almost
guaranteed in a casual installation where an EZNEC "schematic" of the
system offers only a blob called "source" in a spot of convenience
that does not exist in reality.

So, the long and short of it is:
Do not feed in the middle of the interconnecting line.
Observe proper phasing requirements.

You can perform your own EZNEC analysis using the free version. The
benefit of this is you can control all the variables, adjust items 1
through 6 in the list above, and you can replicate your experience.
Doing this will also reveal what you need to do to optimize your
antenna.

73's
Richard Clark, KB7QHC
  #4  
Old May 12th 11, 07:38 PM posted to rec.radio.amateur.antenna
Michael[_10_]
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Posts: 28
Default The Lazy H does not seem to exhibit any gain over a dipole in thereal world

On May 12, 12:42*pm, Richard Clark wrote:
So, the long and short of it is:
* * *Do not feed in the middle of the interconnecting line.
* * *Observe proper phasing requirements.

You can perform your own EZNEC analysis using the free version. *The
benefit of this is you can control all the variables, adjust items 1
through 6 in the list above, and you can replicate your experience.
Doing this will also reveal what you need to do to optimize your
antenna. *

73's
Richard Clark, KB7QHC



The W8JI web page goes to considerable length to bash the end fed Lazy
H with the twist, but since the real world performance of the center
fed Lazy H is less than stellar I'll have to give it a try.

There is one thing the center fed Lazy H did better than the dipole
and the extended double zepp. When I applied RF to the center fed
Lazy H four of my outside motion sensor flood lights would come on. I
guess if I wanted to go outside at night I could just switch to the
Lazy H, key the mic, and save myself a trip to the light switch. ha
ha

W8JI bashing the end fed Lazy H with the twist
http://www.w8ji.com/curtain%20sterba...Lazy_H_Antenna

-Michael

  #5  
Old May 12th 11, 09:29 PM posted to rec.radio.amateur.antenna
Richard Clark
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Posts: 2,951
Default The Lazy H does not seem to exhibit any gain over a dipole in the real world

On Thu, 12 May 2011 11:38:38 -0700 (PDT), Michael
wrote:

The W8JI web page goes to considerable length to bash the end fed Lazy
H with the twist, but since the real world performance of the center
fed Lazy H is less than stellar I'll have to give it a try.


Hi Michael,

As I offered, feed at the bottom, and observe proper phase
relationships. This page you reference also makes a note of those
relationships being improper will point your radiation straight up,
and straight down. Go figure - this is quickly revealed by EZNEC.

When I applied RF to the center fed
Lazy H four of my outside motion sensor flood lights would come on.


This is 100% rock-solid proof of Common Mode current on your
transmission line. This condition will cause extreme grief in trying
to match your transmitter to. It also skews the radiation/reception
lobes BIG-TIME.

Does this sound familiar?

The problem probably comes from your tuner's BalUn having a connection
to earth ground.

Solution to that (for all "balanced," horizontal antennas):
1. Use Coax.
2. Put a choke style (W2DU) BalUn at the antenna (ask about this).
3. Add a second choke a quarter wave away from the feed point.
OR
1. Fix the ground path inside your tuner (not as simple as it may
seem, unfortunately - in fact it can be an Herculean task - it may not
even be doable).
2. Obtain (purchase or build) the proper tuner.

Your antenna will then tune with vastly more grace, and you may even
find it performs much like common sense would expect. As I said
earlier, there is a world of experiential details that can kill an
EZNEC model's prediction - and it isn't the fault of EZNEC.

73's
Richard Clark, KB7QHC
 




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