Homebrew 222 Mhz Beam Antenna Project
 

I'm building a yagi from the measurement tables the ARRL Antenna Book. I
have the driven element finished and getting a good SWRs with a home-made
gamma match.

I'm going to mount it on a wood 2 X 2 with as many directors as will fit on
an 8 feet boom.

Any advice? (I've already read that a gamma match is a poor choice but it
did work, so we can skip that one. :-)

"Sal"
(KD6VKW)

If you delve deeper, you will read that each time you add directors - you have to recalculate the spacing between each director.
The length of each director and the spacing is very important.
Wood is a poor choice for anything more then a experiment - it is heavy, and not very strong.

If you are serious about building that antenna, you would want to look for a old UHF / VHF television antenna such as the Radio Shack VU 190.
Rob the elements off the antenna, cut them to length and mount your gamma match to it with a appropriate sized reflector.

There was a channel master VHF antenna that was made back in the 1970's that was about 24 feet long which also made a excellent donor antenna / platform for a home brew beam antenna.

Homebrew 222 Mhz Beam Antenna Project
 

Channel Jumper wrote:
If you are serious about building that antenna, you would want to look
for a old UHF / VHF television antenna such as the Radio Shack VU 190.
Rob the elements off the antenna, cut them to length and mount your
gamma match to it with a appropriate sized reflector.

There was a channel master VHF antenna that was made back in the 1970's
that was about 24 feet long which also made a excellent donor antenna /
platform for a home brew beam antenna.

In those days, we could buy raw stock from the bureau of the amateur
radio association, who obtained it from local antenna manufacturers that
we still had back then.

Dipoles already to size for VHF/UHF bands, and elements to the maximal
length required for each band, that you cut down to the correct length
for your design.

Those elements already had the mounting block and bolt just like the
commercial TV antennas. I made 2M and 70cm crossed yagis for satellite
operation out of those parts.

Homebrew 222 Mhz Beam Antenna Project
 

"Sal" salmonella@food poisoning.org wrote in message
...
I'm building a yagi from the measurement tables the ARRL Antenna Book. I
have the driven element finished and getting a good SWRs with a home-made
gamma match.

I'm going to mount it on a wood 2 X 2 with as many directors as will fit
on an 8 feet boom.

Any advice? (I've already read that a gamma match is a poor choice but it
did work, so we can skip that one. :-)


While not what you want to hear, scrap that idea. Look at the Quagi antenna
and a 10 foot piece of the grey plastic electrical conduit. I built one
from an old handbook design years ago and it worked great. Compaired it to
a comercial Crushcraft 11 element beam and also a 6 element home built one,
all at the top of a 40 foot push up pole, one at a time. I used some
stainless steel welding rods for the directors and some fiberglass sticks
about 1/4 inch in diameter for the quad spreaders from those bicycle flags.

Homebrew 222 Mhz Beam Antenna Project
 

On 2/16/2013 1:31 AM, Sal wrote:
I'm building a yagi from the measurement tables the ARRL Antenna Book. I
have the driven element finished and getting a good SWRs with a home-made
gamma match.

I'm going to mount it on a wood 2 X 2 with as many directors as will fit on
an 8 feet boom.

Any advice? (I've already read that a gamma match is a poor choice but it
did work, so we can skip that one. :-)

"Sal"
(KD6VKW)



A gamma match will skew the pattern a bit but that's really nothing to
worry about.

The worry on a gamma match (and most matches) is where the impedance of
the driven element is low, where low is less than 20 ohms.

20 ohms is a number I like, others may like a different number. For
sure if you are down in the 10 or 12 ohm range you are in trouble.

T matches are better, but are more and less complex at the same time.
Personally I use gamma at 6m, both at 2m and T at 70cm.

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

On Fri, 15 Feb 2013 23:31:52 -0800, "Sal" salmonella@food
poisoning.org wrote:

I'm building a yagi from the measurement tables the ARRL Antenna Book.

Which Antenna Book and which yagi?

I have the driven element finished and getting a good SWRs with a home-made
gamma match.

Think about using a T-match. Slightly better bandwidth and slightly
more symmetrical pattern. However, I will conceded that the Gamma
match (half a T-match) is simpler because it can be driven directly
without a balun.

I prefer a folded dipole driven element (200 ohms) and a 4:1 balun.
With 200 ohms.

I'm going to mount it on a wood 2 X 2 with as many directors as will fit on
an 8 feet boom.

The problem with wood is that it doesn't survive well on top of a
tower. You could paint and preserve it, but by the time you're done,
a metal pipe would probably have been easier. 2x2 also seems a bit
light to support its own weight (plus any birds that may want to
roost). I would suggest a 2x4. Wood is also hygroscopic (absorbs
water), which might have an effect depending on how the antenna is
built.

Drivel: About 15 years ago, I had the semi-bright idea of building an
all wood portable yagi for 440MHz. It was built as if it were a
carpentry project complete with mostly non-metallic joinery. To turn
it into a real antenna, I covered the wooden dowel elements with
aluminum duct tape.
http://www.homedepot.com/Paint-Adhesives-Tape/h_d1/N-5yc1vZ1xhmZarpz/R-100030120/h_d2/ProductDisplay?catalogId=10053#.USBOGfIrFR0
The T-match and balun were attached with U shape staples. Sorry, I
didn't take any photos. After about month of tinkering, I turned it
into firewood. The problem was that trimming this antenna was rather
difficult. As the wood in the elements dried out, the velocity factor
changed, causing the element tuning to change. Of course, I used the
cheapest green lumber I could find, resulting in a continuously
changing VSWR as the wood slowly dried out in the sun. You won't have
that problem if you make only the boom out of wood.

Any advice? (I've already read that a gamma match is a poor choice but it
did work, so we can skip that one. :-)

Measure the 2:1 VSWR bandwidth of the antenna. If it's too narrow to
cover the 220 band, think about using a T-match and balun.

With an 8 foot boom, you'll probably fit 9 elements:
http://www.vk5dj.com/yagi.html
13dBi gain, 44 degree beamwidth.

Idea: I was at the hardware store today and noticed some 2"x3"x10ft
rectangular cross section vinyl rain gutter downspouts. A downspout
might make a usable boom for a yagi.
http://www.lowes.com/pd_12493-322-AW200_4294806370__?productId=1007997
It's quite light, doesn't sag, UV proof, and cheap.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Homebrew 222 Mhz Beam Antenna Project
 

On 2/16/2013 9:57 PM, Jeff Liebermann wrote:
On Fri, 15 Feb 2013 23:31:52 -0800, "Sal" salmonella@food
poisoning.org wrote:

I'm building a yagi from the measurement tables the ARRL Antenna Book.

Which Antenna Book and which yagi?

I have the driven element finished and getting a good SWRs with a home-made
gamma match.

Think about using a T-match. Slightly better bandwidth and slightly
more symmetrical pattern. However, I will conceded that the Gamma
match (half a T-match) is simpler because it can be driven directly
without a balun.

I prefer a folded dipole driven element (200 ohms) and a 4:1 balun.
With 200 ohms.

I'm going to mount it on a wood 2 X 2 with as many directors as will fit on
an 8 feet boom.

The problem with wood is that it doesn't survive well on top of a
tower. You could paint and preserve it, but by the time you're done,
a metal pipe would probably have been easier. 2x2 also seems a bit
light to support its own weight (plus any birds that may want to
roost). I would suggest a 2x4. Wood is also hygroscopic (absorbs
water), which might have an effect depending on how the antenna is
built.

Drivel: About 15 years ago, I had the semi-bright idea of building an
all wood portable yagi for 440MHz. It was built as if it were a
carpentry project complete with mostly non-metallic joinery. To turn
it into a real antenna, I covered the wooden dowel elements with
aluminum duct tape.
http://www.homedepot.com/Paint-Adhesives-Tape/h_d1/N-5yc1vZ1xhmZarpz/R-100030120/h_d2/ProductDisplay?catalogId=10053#.USBOGfIrFR0
The T-match and balun were attached with U shape staples. Sorry, I
didn't take any photos. After about month of tinkering, I turned it
into firewood. The problem was that trimming this antenna was rather
difficult. As the wood in the elements dried out, the velocity factor
changed, causing the element tuning to change. Of course, I used the
cheapest green lumber I could find, resulting in a continuously
changing VSWR as the wood slowly dried out in the sun. You won't have
that problem if you make only the boom out of wood.

Any advice? (I've already read that a gamma match is a poor choice but it
did work, so we can skip that one. :-)

Measure the 2:1 VSWR bandwidth of the antenna. If it's too narrow to
cover the 220 band, think about using a T-match and balun.

With an 8 foot boom, you'll probably fit 9 elements:
http://www.vk5dj.com/yagi.html
13dBi gain, 44 degree beamwidth.

Idea: I was at the hardware store today and noticed some 2"x3"x10ft
rectangular cross section vinyl rain gutter downspouts. A downspout
might make a usable boom for a yagi.
http://www.lowes.com/pd_12493-322-AW200_4294806370__?productId=1007997
It's quite light, doesn't sag, UV proof, and cheap.


Nice response.

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

On Sat, 16 Feb 2013 19:57:44 -0800, Jeff Liebermann
wrote:

With an 8 foot boom, you'll probably fit 9 elements:
http://www.vk5dj.com/yagi.html
13dBi gain, 44 degree beamwidth.

Here's another yagi calculator program:
http://www.yagicad.com/YagiCAD/YagiCAD.htm
It will do a variety of driven elements and yagi styles. It also
exports results to 4NEC2.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Homebrew 222 Mhz Beam Antenna Project
 

On 2/16/2013 10:08 AM, Ralph Mowery wrote:
"Sal"salmonella@food poisoning.org wrote in message
...
I'm building a yagi from the measurement tables the ARRL Antenna Book. I
have the driven element finished and getting a good SWRs with a home-made
gamma match.

I'm going to mount it on a wood 2 X 2 with as many directors as will fit
on an 8 feet boom.

Any advice? (I've already read that a gamma match is a poor choice but it
did work, so we can skip that one. :-)


While not what you want to hear, scrap that idea. Look at the Quagi antenna
and a 10 foot piece of the grey plastic electrical conduit. I built one
from an old handbook design years ago and it worked great. Compaired it to
a comercial Crushcraft 11 element beam and also a 6 element home built one,
all at the top of a 40 foot push up pole, one at a time. I used some
stainless steel welding rods for the directors and some fiberglass sticks
about 1/4 inch in diameter for the quad spreaders from those bicycle flags.




I concur! I disassembled my 2 meter quagi antennas and an the process of
building a 222 MHz quagi from using the parts. I also use 1/8 inch
stainless steel welding rods, because I have a bunch of them!

The 2 meter quagi antennas worked great and I expect the 222 antenna to
work well, also.

Paul, KD7HB

Homebrew 222 Mhz Beam Antenna Project
 

On 2/17/2013 12:24 AM, Jeff Liebermann wrote:
On Sat, 16 Feb 2013 19:57:44 -0800, Jeff Liebermann
wrote:

With an 8 foot boom, you'll probably fit 9 elements:
http://www.vk5dj.com/yagi.html
13dBi gain, 44 degree beamwidth.

Here's another yagi calculator program:
http://www.yagicad.com/YagiCAD/YagiCAD.htm
It will do a variety of driven elements and yagi styles. It also
exports results to 4NEC2.



My calculation, based on a database of 100+ EME antennas predicts 13.6
dBi maximum reasonable gain. So that sounds about right.

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

On 2/17/2013 7:51 PM, tom wrote:

My calculation, based on a database of 100+ EME antennas predicts 13.6
dBi maximum reasonable gain. So that sounds about right.

tom
K0TAR


Here is a link to a table of a lot of high performance yagis.

http://www.sm2cew.com/gt.htm

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

"tom" wrote in message
. ..
On 2/17/2013 7:51 PM, tom wrote:

My calculation, based on a database of 100+ EME antennas predicts 13.6
dBi maximum reasonable gain. So that sounds about right.

tom
K0TAR


Here is a link to a table of a lot of high performance yagis.

http://www.sm2cew.com/gt.htm

tom
K0TAR



Thank you all for your thoughtful comments. I like the downspout idea. (I
was going to coat the wood boom with good epoxy paint, but, considering also
the weight issue, maybe I should go with the downspout. It's going on a
chimney mount, not a tower, making maintenance a bit simpler.)

I saw the T-match but never intended to try it. I did get my gamma match to
a 1.2:1 VSWR so, now I'm undecided.

I used to use YAGICAD running under a BASIC interpreter, I think, but a
lo-o-ong time ago. I will have a fresh look at it.

I thought after the first four or five directors were in place, their
spacing wouldn't be affected by adding more directors. Thanks for the
heads-up that it matters.

"Sal"

Homebrew 222 Mhz Beam Antenna Project
 

"Jeff Liebermann" wrote in message
...
On Fri, 15 Feb 2013 23:31:52 -0800, "Sal" salmonella@food
poisoning.org wrote:

I'm building a yagi from the measurement tables the ARRL Antenna Book.

Which Antenna Book and which yagi?

I have the driven element finished and getting a good SWRs with a
home-made
gamma match.

Think about using a T-match. Slightly better bandwidth and slightly
more symmetrical pattern. However, I will conceded that the Gamma
match (half a T-match) is simpler because it can be driven directly
without a balun.

I prefer a folded dipole driven element (200 ohms) and a 4:1 balun.
With 200 ohms.

I'm going to mount it on a wood 2 X 2 with as many directors as will fit
on
an 8 feet boom.

The problem with wood is that it doesn't survive well on top of a
tower. You could paint and preserve it, but by the time you're done,
a metal pipe would probably have been easier. 2x2 also seems a bit
light to support its own weight (plus any birds that may want to
roost). I would suggest a 2x4. Wood is also hygroscopic (absorbs
water), which might have an effect depending on how the antenna is
built.

Drivel: About 15 years ago, I had the semi-bright idea of building an
all wood portable yagi for 440MHz. It was built as if it were a
carpentry project complete with mostly non-metallic joinery. To turn
it into a real antenna, I covered the wooden dowel elements with
aluminum duct tape.
http://www.homedepot.com/Paint-Adhesives-Tape/h_d1/N-5yc1vZ1xhmZarpz/R-100030120/h_d2/ProductDisplay?catalogId=10053#.USBOGfIrFR0
The T-match and balun were attached with U shape staples. Sorry, I
didn't take any photos. After about month of tinkering, I turned it
into firewood. The problem was that trimming this antenna was rather
difficult. As the wood in the elements dried out, the velocity factor
changed, causing the element tuning to change. Of course, I used the
cheapest green lumber I could find, resulting in a continuously
changing VSWR as the wood slowly dried out in the sun. You won't have
that problem if you make only the boom out of wood.

Any advice? (I've already read that a gamma match is a poor choice but it
did work, so we can skip that one. :-)

Measure the 2:1 VSWR bandwidth of the antenna. If it's too narrow to
cover the 220 band, think about using a T-match and balun.

With an 8 foot boom, you'll probably fit 9 elements:
http://www.vk5dj.com/yagi.html
13dBi gain, 44 degree beamwidth.

Idea: I was at the hardware store today and noticed some 2"x3"x10ft
rectangular cross section vinyl rain gutter downspouts. A downspout
might make a usable boom for a yagi.
http://www.lowes.com/pd_12493-322-AW200_4294806370__?productId=1007997
It's quite light, doesn't sag, UV proof, and cheap.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Homebrew 222 Mhz Beam Antenna Project
 

"Jeff Liebermann" wrote in message
...
On Fri, 15 Feb 2013 23:31:52 -0800, "Sal" salmonella@food
poisoning.org wrote:

I'm building a yagi from the measurement tables the ARRL Antenna Book.

Which Antenna Book and which yagi?

snip

Jeff, I have the 18th Edition of the ARRL Antenna Book, copyright 1997.

I'm in Chapter 18, titled "VHF and UHF Antenna Systems." I'm using Table
16, titled "Dimensions for 16-element 3.9-wavelength 222-MHz Yagi."

I'm bugged by something else I'm seeing. Table 16 specifies a 664 mm driven
element (DE) It's longer than the DE of other construction articles. Most
articles call for something between 645 and 648 mm. (Example: On the same
page as Table 16, I see also Table 14, "Free-Space Dimensions for the
222-MHz Yagi Family." It gives a DE of 647 mm.)

Something is indisputably okay. My prototype DE (664 mm) is hanging by
strings above my bench and I'm getting a 1.2:1 - 1.3:1 with a short length
of cable. I can hit a repeater 15 miles away with one watt without even
turning my DE vertical. Too bad neither of my analyzers works at 222.

Yes, I fully expect the match to need adjusting after I add parasitic
elements. The road from here-to-there has so many branches!

"Sal"

Homebrew 222 Mhz Beam Antenna Project
 

On Sat, 23 Feb 2013 17:07:31 -0800, "Sal" salmonella@food
poisoning.org wrote:


"Jeff Liebermann" wrote in message
.. .
On Fri, 15 Feb 2013 23:31:52 -0800, "Sal" salmonella@food
poisoning.org wrote:

I'm building a yagi from the measurement tables the ARRL Antenna Book.

Which Antenna Book and which yagi?

snip

Jeff, I have the 18th Edition of the ARRL Antenna Book, copyright 1997.
I'm in Chapter 18, titled "VHF and UHF Antenna Systems." I'm using Table
16, titled "Dimensions for 16-element 3.9-wavelength 222-MHz Yagi."

I have the 19th edition. Same table on Pg 18-31.

I'm bugged by something else I'm seeing. Table 16 specifies a 664 mm driven
element (DE) It's longer than the DE of other construction articles. Most
articles call for something between 645 and 648 mm. (Example: On the same
page as Table 16, I see also Table 14, "Free-Space Dimensions for the
222-MHz Yagi Family." It gives a DE of 647 mm.)

That's easy. Both antennas have elements connected to the aluminum
boom (except for the driven element). Looks like the boom diameters
are different. When the elements are connected to the boom in this
manner, the boom becomes part of the element in that the conduction
path now goes around the boom. This tends to shorten the element
lengths. All the various yagi designer programs can include the boom
diameter in their calculations. I strongly suggest that unless you're
building EXACTLY what's in the article, that you use one of the
programs previous mentioned to grind the numbers correctly.

In addition, I have a suggestion. If you're using a solid rod for the
elements, round off the ends to a hemispherical radius. Use 1/2 the
distance between the base of the radius and the peak for the element
end point. If you're using hollow tubing, you can also cram a big
rivet or screw into the end to get the same rounded effect. This will
increase your usable bandwidth.

Something is indisputably okay. My prototype DE (664 mm) is hanging by
strings above my bench and I'm getting a 1.2:1 - 1.3:1 with a short length
of cable. I can hit a repeater 15 miles away with one watt without even
turning my DE vertical. Too bad neither of my analyzers works at 222.

Please note that you also get 1:1 with a dummy load. You can also
match just about anything with your gamma match. Tune the antenna for
gain, bandwidth, and/or F/B ratio. VSWR is easy to fix.

Also VSWR is not as important as pattern and gain. You can get
perfect VSWR, and have the signal sprayed all over the place. If you
look at the antenna patterns on the same pages as the tables, you'll
see that even with a properly designed antenna, you have a rather
strange and skewed pattern. Incidentally, T-match and balun should
fix the funny pattern.

Yes, I fully expect the match to need adjusting after I add parasitic
elements. The road from here-to-there has so many branches!

Not really. The first 4 or 5 elements are what provides the VSWR. Try
waving additional elements around the front of the antenna notice how
little the VSWR changes. However, the gain, directivity, and F/B
ratio certainly will be affected.

As for your lack of an antenna analyzer, this is actually a good
thing. What you really want to do is see what the antenna is doing
over a wide range of frequencies. For that, I suggest a return loss
bridge. I use a Telonic Rho-tector Model TRB-50 and a Texscan RCB-3.
Here's what's inside:
http://www.qsl.net/n9zia/rlb/texscan.png
Both will go from 0.5MHz to 1GHz. All you need is a decent RF sweep
generator, oscilloscope, terminators, and cables. You can see the
VSWR curve over the frequency range while you're tuning. You can also
do the same thing with a directional coupler and a diode detector, but
I think the return loss bridge is easier. I've also built a few for
microwave frequencies (2.4 and 5.7GHz).



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Homebrew 222 Mhz Beam Antenna Project
 

On 2/23/2013 9:33 PM, Jeff Liebermann wrote:
On Sat, 23 Feb 2013 17:07:31 -0800, "Sal" salmonella@food
poisoning.org wrote:


"Jeff Liebermann" wrote in message
...
On Fri, 15 Feb 2013 23:31:52 -0800, "Sal" salmonella@food
poisoning.org wrote:

I'm building a yagi from the measurement tables the ARRL Antenna Book.

Which Antenna Book and which yagi?

snip

Jeff, I have the 18th Edition of the ARRL Antenna Book, copyright 1997.
I'm in Chapter 18, titled "VHF and UHF Antenna Systems." I'm using Table
16, titled "Dimensions for 16-element 3.9-wavelength 222-MHz Yagi."

I have the 19th edition. Same table on Pg 18-31.

I'm bugged by something else I'm seeing. Table 16 specifies a 664 mm driven
element (DE) It's longer than the DE of other construction articles. Most
articles call for something between 645 and 648 mm. (Example: On the same
page as Table 16, I see also Table 14, "Free-Space Dimensions for the
222-MHz Yagi Family." It gives a DE of 647 mm.)

That's easy. Both antennas have elements connected to the aluminum
boom (except for the driven element). Looks like the boom diameters
are different. When the elements are connected to the boom in this
manner, the boom becomes part of the element in that the conduction
path now goes around the boom. This tends to shorten the element
lengths. All the various yagi designer programs can include the boom
diameter in their calculations. I strongly suggest that unless you're
building EXACTLY what's in the article, that you use one of the
programs previous mentioned to grind the numbers correctly.

In addition, I have a suggestion. If you're using a solid rod for the
elements, round off the ends to a hemispherical radius. Use 1/2 the
distance between the base of the radius and the peak for the element
end point. If you're using hollow tubing, you can also cram a big
rivet or screw into the end to get the same rounded effect. This will
increase your usable bandwidth.

Something is indisputably okay. My prototype DE (664 mm) is hanging by
strings above my bench and I'm getting a 1.2:1 - 1.3:1 with a short length
of cable. I can hit a repeater 15 miles away with one watt without even
turning my DE vertical. Too bad neither of my analyzers works at 222.

Please note that you also get 1:1 with a dummy load. You can also
match just about anything with your gamma match. Tune the antenna for
gain, bandwidth, and/or F/B ratio. VSWR is easy to fix.

Also VSWR is not as important as pattern and gain. You can get
perfect VSWR, and have the signal sprayed all over the place. If you
look at the antenna patterns on the same pages as the tables, you'll
see that even with a properly designed antenna, you have a rather
strange and skewed pattern. Incidentally, T-match and balun should
fix the funny pattern.

Yes, I fully expect the match to need adjusting after I add parasitic
elements. The road from here-to-there has so many branches!

Not really. The first 4 or 5 elements are what provides the VSWR. Try
waving additional elements around the front of the antenna notice how
little the VSWR changes. However, the gain, directivity, and F/B
ratio certainly will be affected.

As for your lack of an antenna analyzer, this is actually a good
thing. What you really want to do is see what the antenna is doing
over a wide range of frequencies. For that, I suggest a return loss
bridge. I use a Telonic Rho-tector Model TRB-50 and a Texscan RCB-3.
Here's what's inside:
http://www.qsl.net/n9zia/rlb/texscan.png
Both will go from 0.5MHz to 1GHz. All you need is a decent RF sweep
generator, oscilloscope, terminators, and cables. You can see the
VSWR curve over the frequency range while you're tuning. You can also
do the same thing with a directional coupler and a diode detector, but
I think the return loss bridge is easier. I've also built a few for
microwave frequencies (2.4 and 5.7GHz).




One thing to remember is you generally do not want elements that are
electrically connected to the boom. The connection is usually not very
good and eventually corrodes. This makes the antenna detune in an
unpredictable manner.

That said, you can weld elements to the boom, which works.

You are better off using insulated elements with inserts in the boom
holes such as Delrin.

This will change the correction factor, but that is a known.

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

"Jeff Liebermann" wrote in message
...


snip

As for your lack of an antenna analyzer, this is actually a good
thing. What you really want to do is see what the antenna is doing
over a wide range of frequencies. For that, I suggest a return loss
bridge. I use a Telonic Rho-tector Model TRB-50 and a Texscan RCB-3.
Here's what's inside:
http://www.qsl.net/n9zia/rlb/texscan.png
Both will go from 0.5MHz to 1GHz. All you need is a decent RF sweep
generator, oscilloscope, terminators, and cables. You can see the
VSWR curve over the frequency range while you're tuning. You can also
do the same thing with a directional coupler and a diode detector, but
I think the return loss bridge is easier. I've also built a few for
microwave frequencies (2.4 and 5.7GHz).

I have the o'scope and a sweep generator/ spectrum analyzer combination to
provide the RF. I'd have to check to see if the generator provides a sweep
signal for the scope's external horizontal input.

The bridge looks like a one-evening project although I might have to
hand-make those 1% resistors.

By the way, I found a way of using the sweeper/spec-an combination as a
crude antenna checker. I loop the generator directly into the analyzer, but
use a T-connector at one of the ports. Of, course, it produces a clean,
flat line. Next, if I connect an unterminated length of cable to the
T-connector, I see a comb pattern produced by reflected energy. (The comb's
appearance is dependent on the length of the cable and the test setup.)
Lastly, with an antenna on the end of the cable, the comb goes flat at the
frequency (ies) where the antenna is radiating ... reduced reflections at
some freqs since the antenna is radiating most of the forward power. It's
an interesting effect to observe but not sensitive enough for much more than
a GO/NOGO check.

If I put the T-connector at the antenna, itself, with one cable each to the
sweeper/spec-an, the pattern changes somewhat but I haven't analyzed what I
see.

"Sal"

Homebrew 222 Mhz Beam Antenna Project
 

"tom" wrote in message
. ..

snip

One thing to remember is you generally do not want elements that are
electrically connected to the boom. The connection is usually not very
good and eventually corrodes. This makes the antenna detune in an
unpredictable manner.

That said, you can weld elements to the boom, which works.

You are better off using insulated elements with inserts in the boom holes
such as Delrin.

This will change the correction factor, but that is a known.

tom
K0TAR


At the moment, my driven element is 664 mm of half-inch copper pipe, my
favorite medium for VHF/UHF antennas. I made some antennas for the RACES
station at the local firehouse about fifteen years ago and they're still up
there.

If I were to continue in that vein, I could weld (torch solder, really) the
elements to a longer piece of copper pipe.

I have seen the "known" correction factors referenced in vague terms, but
nothing that I ever got my arms around. Where should I be looking?

"Sal"
(KD6VKW)

Homebrew 222 Mhz Beam Antenna Project
 

On 2/23/2013 11:41 PM, Sal wrote:


At the moment, my driven element is 664 mm of half-inch copper pipe, my
favorite medium for VHF/UHF antennas. I made some antennas for the RACES
station at the local firehouse about fifteen years ago and they're still up
there.

If I were to continue in that vein, I could weld (torch solder, really) the
elements to a longer piece of copper pipe.

I have seen the "known" correction factors referenced in vague terms, but
nothing that I ever got my arms around. Where should I be looking?

"Sal"
(KD6VKW)



A good source is VE7BQH, Lionel. He has a lot of info related to EME
antennas that are as well engineered as possible for obvious reasons.

I've never looked at his correction factors as I have ones for through
the boom insulated that I know work for my build type. My corrections
are from WB0TEM.

What bands are you building for?

Here's a link to some of Lionel's information at SM2CEW. If you need to
correspond with him, contact me directly and I'll get you his email.

http://www.sm2cew.com/gt.htm

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

On 2/24/2013 8:43 PM, tom wrote:
On 2/23/2013 11:41 PM, Sal wrote:


At the moment, my driven element is 664 mm of half-inch copper pipe, my
favorite medium for VHF/UHF antennas. I made some antennas for the RACES
station at the local firehouse about fifteen years ago and they're
still up
there.

If I were to continue in that vein, I could weld (torch solder,
really) the
elements to a longer piece of copper pipe.

I have seen the "known" correction factors referenced in vague terms, but
nothing that I ever got my arms around. Where should I be looking?

"Sal"
(KD6VKW)



A good source is VE7BQH, Lionel. He has a lot of info related to EME
antennas that are as well engineered as possible for obvious reasons.

I've never looked at his correction factors as I have ones for through
the boom insulated that I know work for my build type. My corrections
are from WB0TEM.

What bands are you building for?

Here's a link to some of Lionel's information at SM2CEW. If you need to
correspond with him, contact me directly and I'll get you his email.

http://www.sm2cew.com/gt.htm

tom
K0TAR


I've done some searching for corrections for through the boom
uninsulated and found that the opinion is that it's not a good idea.
And it makes sense if you read why - the current is really high at the
center of the element and any variation in contact resistance to the
boom or material will change the result.

What you would like is the result to be based on only the insulated
element conductance and the shielding of the boom, which is easier to
calculate and less variable.

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

On 2/24/2013 9:13 PM, tom wrote:
I've done some searching for corrections for through the boom
uninsulated and found that the opinion is that it's not a good idea. And
it makes sense if you read why - the current is really high at the
center of the element and any variation in contact resistance to the
boom or material will change the result.

What you would like is the result to be based on only the insulated
element conductance and the shielding of the boom, which is easier to
calculate and less variable.

tom
K0TAR


Here's a reference that mentions reasons for not using uninsulated
through the boom connectio9ns. And has some nice graphs on insulated
through the boom.

http://g7rau.demon.co.uk/sm5bsz/antennas/sa/others.htm

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

"tom" wrote in message
. ..
On 2/23/2013 11:41 PM, Sal wrote:

snip


What bands are you building for?

Here's a link to some of Lionel's information at SM2CEW. If you need to
correspond with him, contact me directly and I'll get you his email.

http://www.sm2cew.com/gt.htm

tom
K0TAR


BANDS: This is a 220 beam intended for roof mount on my
daughter/son-in-law's house in Livermore CA to see if we can hit the Condor
Connection, which is all on 220. I'm in San Diego, with a nearby Condor
machine. My newly-licensed son-in-law thinks it would be a hoot if we could
talk directly, home-to-home. (I don't want to encourage him to buy an HF
rig for possible use on 10m, since fickle propagation has the potential to
be a buzz kill for a new ham. Upgrade to General is an unknown. He's not
ready for IRLP.)

Condor has two possible repeaters, one on Mount Hamilton (24 mi, by San
Jose) and one on Mount Vaca (50 mi.). Neither is a slam dunk from Livermore
because of terrain blockage. I'm hoping 50W & 10 dB gain will work. I did
some Longley Rice modeling here

http://lrcov.crc.ca/main/ and I'm hopeful.

I have alternate possibilities. The WIN System has 440-band repeaters on Mt
Oso (25 mi.) and on Loma Prieta (40 mi.) but also with terrain issues. ( I
already have a 26-element 440 beam; it models out to about 14 dBd gain.)

Those distances would be no problem except for the blockage. I can do 80
miles with 5 watts off an omni if my RF's don't bump into nuthin' first.

I expect the finished 220 beam to have about 10dBd gain and I have 50 watts
available.

Thanks for the link to Lionel's info. I'll check itout.

"Sal"
(KD6VKW)

Homebrew 222 Mhz Beam Antenna Project
 

"tom" wrote in message
. ..
On 2/24/2013 9:13 PM, tom wrote:
I've done some searching for corrections for through the boom
uninsulated and found that the opinion is that it's not a good idea. And
it makes sense if you read why - the current is really high at the
center of the element and any variation in contact resistance to the
boom or material will change the result.

What you would like is the result to be based on only the insulated
element conductance and the shielding of the boom, which is easier to
calculate and less variable.

tom
K0TAR


Here's a reference that mentions reasons for not using uninsulated through
the boom connectio9ns. And has some nice graphs on insulated through the
boom.

http://g7rau.demon.co.uk/sm5bsz/antennas/sa/others.htm

tom
K0TAR



OK, I'm convinced. What I need is some lightweight non-metallic material
for the
boom and I can build with the numbers I have for element lengths. I'll hit
the stores
in the morning.

I'll try a T-match, too.

"Sal"

Homebrew 222 Mhz Beam Antenna Project
 

On 2/25/2013 12:38 AM, Sal wrote:

BANDS: This is a 220 beam intended for roof mount on my
daughter/son-in-law's house in Livermore CA to see if we can hit the Condor
Connection, which is all on 220. I'm in San Diego, with a nearby Condor
machine. My newly-licensed son-in-law thinks it would be a hoot if we could
talk directly, home-to-home. (I don't want to encourage him to buy an HF
rig for possible use on 10m, since fickle propagation has the potential to
be a buzz kill for a new ham. Upgrade to General is an unknown. He's not
ready for IRLP.)

Condor has two possible repeaters, one on Mount Hamilton (24 mi, by San
Jose) and one on Mount Vaca (50 mi.). Neither is a slam dunk from Livermore
because of terrain blockage. I'm hoping 50W & 10 dB gain will work. I did
some Longley Rice modeling here

http://lrcov.crc.ca/main/ and I'm hopeful.

I have alternate possibilities. The WIN System has 440-band repeaters on Mt
Oso (25 mi.) and on Loma Prieta (40 mi.) but also with terrain issues. ( I
already have a 26-element 440 beam; it models out to about 14 dBd gain.)

Those distances would be no problem except for the blockage. I can do 80
miles with 5 watts off an omni if my RF's don't bump into nuthin' first.

I expect the finished 220 beam to have about 10dBd gain and I have 50 watts
available.

Thanks for the link to Lionel's info. I'll check itout.

"Sal"
(KD6VKW)



Sounds like a plan. Good luck.

If there are any 6m machines around the terrain becomes a lot less of a
problem. If, of course, you have a 6m FM rig. Around here, Minneapolis
metro, we have a few machines that have multiple inputs and outputs.
(Not really, they are individual cross-linked rptrs, but that's just
details). Maybe your area has some.

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

Sounds like a plan. Good luck.

If there are any 6m machines around the terrain becomes a lot less of a
problem. If, of course, you have a 6m FM rig. Around here, Minneapolis
metro, we have a few machines that have multiple inputs and outputs. (Not
really, they are individual cross-linked rptrs, but that's just details).
Maybe your area has some.

tom
K0TAR

Thanks. I've heard 6m is very good that way. I have 6m FM but not my
son-in-law ... yet. Besides, I haven't found any linking from Livermore to
me in Southern CA.

See, Livermore has plenty of repeaters, both local and in three nearby
cities, Tracy, Pleasanton and Danville. Once you get beyond that region,
mountains become an issue and the nearest known linked repeaters are not
line-of-sight. I'm hoping some antenna gain will let me use edge
diffraction to make one of the machines. I'm hoping the first edge out of
Livermore will do it. Yes, I have consulted terrain profiles.

Related: At Lowes today, I bought an 8-foot length of stiff, ribbed,
plastic channel called "lattice moulding" and it will be the boom for my
1.25m masterwork. It's very rigid in the vertical orientation, which is
what I want. If I have time, I'll rebuild the driven element with a
T-match.

"Sal"

Homebrew 222 Mhz Beam Antenna Project
 

On 2/25/2013 9:50 PM, Sal wrote:


Thanks. I've heard 6m is very good that way. I have 6m FM but not my
son-in-law ... yet. Besides, I haven't found any linking from Livermore to
me in Southern CA.

See, Livermore has plenty of repeaters, both local and in three nearby
cities, Tracy, Pleasanton and Danville. Once you get beyond that region,
mountains become an issue and the nearest known linked repeaters are not
line-of-sight. I'm hoping some antenna gain will let me use edge
diffraction to make one of the machines. I'm hoping the first edge out of
Livermore will do it. Yes, I have consulted terrain profiles.

Related: At Lowes today, I bought an 8-foot length of stiff, ribbed,
plastic channel called "lattice moulding" and it will be the boom for my
1.25m masterwork. It's very rigid in the vertical orientation, which is
what I want. If I have time, I'll rebuild the driven element with a
T-match.

"Sal"

So what you need is a design that will fit on an 8 foot boom. About 7
feet 11 and a half inches. I will see what might work well.

How much was the channel?

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

"tom" wrote in message
...
On 2/25/2013 9:50 PM, Sal wrote:


Thanks. I've heard 6m is very good that way. I have 6m FM but not my
son-in-law ... yet. Besides, I haven't found any linking from Livermore
to
me in Southern CA.

See, Livermore has plenty of repeaters, both local and in three nearby
cities, Tracy, Pleasanton and Danville. Once you get beyond that region,
mountains become an issue and the nearest known linked repeaters are not
line-of-sight. I'm hoping some antenna gain will let me use edge
diffraction to make one of the machines. I'm hoping the first edge out
of
Livermore will do it. Yes, I have consulted terrain profiles.

Related: At Lowes today, I bought an 8-foot length of stiff, ribbed,
plastic channel called "lattice moulding" and it will be the boom for my
1.25m masterwork. It's very rigid in the vertical orientation, which is
what I want. If I have time, I'll rebuild the driven element with a
T-match.

"Sal"

So what you need is a design that will fit on an 8 foot boom. About 7
feet 11 and a half inches. I will see what might work well.

How much was the channel?

tom
K0TAR


"I will see what might work well." So, do you think the design from the
antenna book is less than ideal?

The channel is priced at $15.94. I will put some masking tape on my piece
of channel, mark off element positions from various designs, attach the
elements temporarily (tape) and evaluate the resulting antenna.

I will set up a makeshift antenna range, with (1) my tracking generator
feeding a 220 whip radiating from my lawn while (2) a helper in the driveway
aims the antenna and while (3) it send its receive signal into the shack
where I, aka His Royal Hamminess, notes the received signal at various
azimuths. (We don't need any stinkin' anechoic chambers.)

Professionally, I've made quantitative measurements of field strength ...
Singer NM-25, anyone? ... but I have nothing approaching modern precision
gear as that which rents for hundreds of dollars a week.

RELATED: If you know, why do some yagis designs place the first director
quite a bit closer to the DE than the rest of the directors' spacing? In
other yagi designs, the spacing of the directors is relatively consistent,
where DE-to-first-director is about equal to the spacing of the remaining
directors. I haven't seen that difference explained ... yet. Thanks.

"Sal"

Homebrew 222 Mhz Beam Antenna Project
 

In article ,
Sal salmonella@food poisoning.org wrote:

RELATED: If you know, why do some yagis designs place the first director
quite a bit closer to the DE than the rest of the directors' spacing? In
other yagi designs, the spacing of the directors is relatively consistent,
where DE-to-first-director is about equal to the spacing of the remaining
directors. I haven't seen that difference explained ... yet. Thanks.

You might be looking at what has become known as an "optimized
wide-band" Yagi.

According to one article (http://www.naic.edu/~angel/kp4ao/ham/owa.html)
placing the first-director parasitic element very close to the
driven element, causes the antenna to be behave as if the driven
element's diameter is much larger than it is (approximating the
distance between the DE and the first director).

This has two useful effects: it increases the radiation resistance
(making the Yagi easier to match to the feedline) and increases the
bandwidth. You give up a small amount of forward gain, but this is
said to be modest and to be a worthwhile price to pay for the ease of
feeding (even a direct 50-ohm feed can be used in some cases) and the
increased bandwidth.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Homebrew 222 Mhz Beam Antenna Project
 

"Dave Platt" wrote in message
...
In article ,
Sal salmonella@food poisoning.org wrote:

RELATED: If you know, why do some yagis designs place the first director
quite a bit closer to the DE than the rest of the directors' spacing? In
other yagi designs, the spacing of the directors is relatively consistent,
where DE-to-first-director is about equal to the spacing of the remaining
directors. I haven't seen that difference explained ... yet. Thanks.

You might be looking at what has become known as an "optimized
wide-band" Yagi.

According to one article (http://www.naic.edu/~angel/kp4ao/ham/owa.html)
placing the first-director parasitic element very close to the
driven element, causes the antenna to be behave as if the driven
element's diameter is much larger than it is (approximating the
distance between the DE and the first director).

This has two useful effects: it increases the radiation resistance
(making the Yagi easier to match to the feedline) and increases the
bandwidth. You give up a small amount of forward gain, but this is
said to be modest and to be a worthwhile price to pay for the ease of
feeding (even a direct 50-ohm feed can be used in some cases) and the
increased bandwidth.


Wow! Thanks for such a clear explanantion. As I was constructing
my DE, with its gamma match, I didn't have much trouble getting a
decent match; What you say makes me sure that adding parasitic
elements will alter that match ... but the close-in first-director will
mitigate the problem. (I do plan to try the T-match; the gamma
match seems to be like ol' Rodney Dangerfield: No Respect.)

I have no shame in saying that this is my first beam, unless you
count the cookbook 20m 2-element quad for last year's Field Day.
On the flip side, I take pride in tackling everything new, especially
with the support of those who've scouted the road ahead for me.

Thanks again.

"Sal"

Homebrew 222 Mhz Beam Antenna Project
 

On 2/26/2013 3:57 PM, Dave Platt wrote:
In article ,
Sal salmonella@food poisoning.org wrote:

RELATED: If you know, why do some yagis designs place the first director
quite a bit closer to the DE than the rest of the directors' spacing? In
other yagi designs, the spacing of the directors is relatively consistent,
where DE-to-first-director is about equal to the spacing of the remaining
directors. I haven't seen that difference explained ... yet. Thanks.

You might be looking at what has become known as an "optimized
wide-band" Yagi.

According to one article (http://www.naic.edu/~angel/kp4ao/ham/owa.html)
placing the first-director parasitic element very close to the
driven element, causes the antenna to be behave as if the driven
element's diameter is much larger than it is (approximating the
distance between the DE and the first director).

This has two useful effects: it increases the radiation resistance
(making the Yagi easier to match to the feedline) and increases the
bandwidth. You give up a small amount of forward gain, but this is
said to be modest and to be a worthwhile price to pay for the ease of
feeding (even a direct 50-ohm feed can be used in some cases) and the
increased bandwidth.


Some of us old time EME/weak_signal builders call the first 4 elements
the K1FO launcher.

I did a lot of optimization over the last 25 years, but I didn't change
the first 4 elements of his design much. He got it right and it worked
especially well with a T match.

tom
K0TAR

Homebrew 222 Mhz Beam Antenna Project
 

"tom" wrote in message
. ..
On 2/26/2013 3:57 PM, Dave Platt wrote:
In article ,
Sal salmonella@food poisoning.org wrote:

RELATED: If you know, why do some yagis designs place the first
director
quite a bit closer to the DE than the rest of the directors' spacing?
In
other yagi designs, the spacing of the directors is relatively
consistent,
where DE-to-first-director is about equal to the spacing of the
remaining
directors. I haven't seen that difference explained ... yet. Thanks.

You might be looking at what has become known as an "optimized
wide-band" Yagi.

According to one article (http://www.naic.edu/~angel/kp4ao/ham/owa.html)
placing the first-director parasitic element very close to the
driven element, causes the antenna to be behave as if the driven
element's diameter is much larger than it is (approximating the
distance between the DE and the first director).

This has two useful effects: it increases the radiation resistance
(making the Yagi easier to match to the feedline) and increases the
bandwidth. You give up a small amount of forward gain, but this is
said to be modest and to be a worthwhile price to pay for the ease of
feeding (even a direct 50-ohm feed can be used in some cases) and the
increased bandwidth.


Some of us old time EME/weak_signal builders call the first 4 elements the
K1FO launcher.

I did a lot of optimization over the last 25 years, but I didn't change
the first 4 elements of his design much. He got it right and it worked
especially well with a T match.

tom
K0TAR


MID-TERM REPORT.

It's been a long time since I posted. Last month, in the middle of
my work, my 45 y/o son needed to come back to live with my
wife and me. We spent over a week moving him out of his
apartment, including more than two dozen cans of trash carried
to the dumpster. Bad scene.

When we had him settled, I loaded my van with raw material and my wife and I
headed to our daughter & son-in-law's house, in Livermore CA where we were
scheduled to house-sit for specific dates.

While there, I wanted to try for a remote 220 repeater, part of a linked
system that also exsts locally. It's called the Condor Connection. I have
two I can reach in San Diego; the "target repeater" for my son-in-law in
Livermore is on Mount Hamilton, east of San Jose. Blockage is the issue,
not distance.

Last month, here at home, I had earlier made a good gamma match using just
the driven element, alone. Last week, when I added the reflector and 8
directors, that match was out the window, as expected, but I got it back,
manipulating the gamma cap and the attachment point while standing on a
ladder with a 5W transceiver, a VHF/UHF VSWR meter and a screwdriver. It's
a pain in the butt to set but it was a learning experience. (I'm 70, now,
but I still value everything I learn now as much as I ever did.) Yes, I
will try everyone's favorite, a T-match. I'm not done experimenting.

In operation, I was able to bring up the Mt Hamilton repeater -- but just
barely. I had a 50W linear with a receive preamp. I needed the whole 50W
to bring up the repeater and it's response was so noisy as to be little more
than confirmation that I had "something." By swinging the antenna left and
right while the repeater was responding, I was able to infer that my antenna
hbas a fairly narrow beamwidth.

As an alternative to Condor, I arranged for my son-in-law to get into a
CALNET repeater in Stockton. I gave him my 27-element UHF beam. His 5W
FT-60R is plenty with that gain antenna. CALNET is represented down here,
so we can chat occasionally. He'll eventually upgrade, so we can use HF.
For now, linked repeaters constitute the only game in town.

I want to play more with that yagi. Having long elements (among the various
designs) it's no surprise to me that its VSWR low point (1.2:1) fell neart
222 MHz. I'll either shave the existing elements or make some new ones and
see if I can move the low-VSWR point up nearer 224. I also want to take
some pattern measurements. I described a method and I want to try it. My
plans were short-circujited by the family issues.

"Sal"