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NOAA yagis ?

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k9rzz

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I've got the bug to DX the NOAA weather stations and am looking for plans to build a 162 mhz beam. I ran across some small commercial yagis for that frequency range, but the cost is prohibitive. I've tried a few 3 element homebrew yagis that worked 'okay', but looking for more directivity.

Construction is not a problem, but I've never attempted to model any antennas on the computer, so the question is:

Does anyone have an modeling experience that can whip up a 6 or 10 element yagi, or does anyone have any URL's for such a beam?

A general VHF log periodic antenna would do, but I'm thinking more along the lines of two, 8 or 10 element freqency specific yagis, stacked side by side with vertical polarization.

Any takers?

John K9RZZ
Milwaukee
 

OpSec

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Sounds neat, but I gotta ask...why?

There are so many transmitters on the seven NOAA channels that even with a decent handheld scanner/radio you can run into problems with receiver capture during modest propogation enhancement.

A beam will just make this worse.
 

jrplmil

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Where I live I cant get them uless there is bad weather then they are activated. I would have to hear one 200 miles away otherwize.
 

k9rzz

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stateboy said:
Sounds neat, but I gotta ask...why?

There are so many transmitters on the seven NOAA channels that even with a decent handheld scanner/radio you can run into problems with receiver capture during modest propogation enhancement.

A beam will just make this worse.
That's why I need an antenna array with razor sharp directivity, to peak up on one direction and null all the rest.

My 3 element yagis have had enough of a dip off the back so that I can null, say Chicago, and pick up something else, but the front lobe is too broad to be selective. I can null Chicago, but am left with what ever captures the radio from any other direction. If I have two beams, each with a narrow front lobe, and then stack them side by side, then I should be able to point it at say Toledo, OH (which is some 240 miles at 110 degrees, and will be weak) and not pick up Grand Rapids (which is only 100 miles, 90 degrees, and much stronger).

The bigger the array, the sharper the pattern, and the happier I'll be. If I'm not pointed at it ... I don't want to hear it.

:^]

It's all a big experiment. I've seached the web and have yet to find anyone else that's been at all serious in how many weather stations they can pick up. If anyone finds someone, pass the info along! It should be fun.

Radio to be used is the Icom R7100.

John K9RZZ
Milwaukee
 

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flyingwolf

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I dont want to, I am right now looking at an old pro-28, and a Pro-92 with a major case of burn out.

Oh and did I forget, I live dead center Batavia Ohio, MARCs central.
 

kf4lne

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try this, take those 2m antenna measurements and knock 11% off of each measurement. there is a 11% difference from the 146MHz antennas and the 162MHz antennas. 16 MHz difference from 146 and 162, approx 11-12%, so by reducing those measurements you should have a pretty close cut antenna.

Also, i hate you too and for the same reason flyingwolf hates you.
 

k9rzz

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kf4lne said:
try this, take those 2m antenna measurements and knock 11% off of each measurement. there is a 11% difference from the 146MHz antennas and the 162MHz antennas. 16 MHz difference from 146 and 162, approx 11-12%, so by reducing those measurements you should have a pretty close cut antenna.

Also, i hate you too and for the same reason flyingwolf hates you.
:^]

Well, what I have pales in comparison to what other's have ... all my radios are 20 years old and I don't even have a tower !

I emailed the author of the article mentioned above (http://oldweb.clarc.org/Articles/uhf.htm) regarding scaling those antennas to 162 mhz - after all he's the one who designed them. Answer :


Subj: Re: Cheap Yagi Antennas for VHF/UHF
Date: 8/24/06 8:25:04 PM Central Daylight Time
From: wa5vjb@flash.net (Kent Britain)
To: J999w@aol.com

J999w@aol.com wrote:
Interesting antenna designs. Any thoughts on scaling these for 162 mhz to DX
the NWS weather stations between 162.4 and 162.55? Looking to build 6 to 11
elements, stacked side by side, vertically polarized, but have no experience in
modeling antennas on the computer.

Thanks,

John K9RZZ

Good timing, there is going to be a 155 MHz version in the next issue
of Popular Communications.

For the time being, you can take the dimensions for the 144 MHzversion, and multiple the lengths and spacings by 144/162.5 or .89. That will work.

I never went out to 11 elements on the 2 Meter one, kind of long for a wood boom.

Good luck with your project, Kent WA5VJB

. . .

So, I'm going shopping tomorrow.

GAME ON!

John K9RZZ
 

mass-man

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If you are dealing with an article by Kent, WA5VJB, then consider the info and the dimension adjustments to be spot on. He is here in the Dallas area, and is an antenna GURU...big time.

Good luck....
 

OpSec

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k9rzz said:
That's why I need an antenna array with razor sharp directivity, to peak up on one direction and null all the rest.

snippage

The bigger the array, the sharper the pattern, and the happier I'll be. If I'm not pointed at it ... I don't want to hear it.

:^]

It's all a big experiment. I've seached the web and have yet to find anyone else that's been at all serious in how many weather stations they can pick up. If anyone finds someone, pass the info along! It should be fun.
I'm all about it, and I hope it works out the way you want it to :)

From where I am in the far southern part of the state, I can hear no less than 10-12 NOAA transmitters during the most tame of band openings. I have used a 6 element commercial UHF (yes, a UHF...not a typo) beam sucessfully to notch out "offending" signals if I wanted to hear one in particular, but nothing as agressive as you are planning, since my outdoor antenna install doesn't allow for permanent placement of beam antennae.

Good luck, and post your results.
 

k9rzz

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Well, I was planning on a long bike ride for this afternoon, but was too tired ... SO I BUILT AN ANTENNA !! I didn't want to go whole hog and build this huge antenna only to find out it doesn't work, so I started off with a pair of 8 foot yagis, stacked side by side, just to test out the plans.

I stopped at a couple stores and bought three, 8 foot wooden 1x2's ($2 each), aluminum clothes line ($4), two U bolts ($0.99 each but only used one), and RG-6 (the most expensive part at $20!).



I followed the plans from the link above multiplying each dimension by 144/162 = 0.89. My 1x2's were 8 foot, so that allowed me to add a few elements to the 6 element plan. I continued with the same spacing and director length as the last one in the 2 meter plan, so I ended up with 8 elements. The third 1x2 I cut in half (44 inches), screwed them together to form the cross member. 44 inches is close to 5/8 wavelength at 162mhz, so I figured that would be a 'pretty' good spacing and easy to make. A wider spacing might help a little, but for initial tests, it should work.

Little by little though the afternoon I cut and drilled wood and wire - and here's what I came up with! :



I've got it mounted on a flag pole just so I could work on it.

To mount the elements, I simply drilled a 1/8 inch hole through the boom and fed the wire through it. It fits pretty tight, so they won't fall out. I wasn't sure how to handle the driven elements. I didn't need anything as fancy as the original article, so I just used #14 solid copper wire, cut it in half and mounted each half as above. There are currently no connectors on each driven element, I just wound the wire right on each element half to be soldered later.





I tried to pay some attention to the phasing of each beam by using an electrical half wavelength of RG6 on each side of the splitter. That would at least repeat the impeadance of each beam at the splitter and not get some goofy, unknown impeadance that I could never match. I used .78 as the velocity factor of the line. ((468\162) x 12) / .78 = 44 inches of RG6 to feed each beam.



Hooking up the SWR analyzer showed resonance at 150.5 mhz (always make your elements LONG, then trim them shorter!). Little by little I trimmed the driven elements ... PRESTO - 1.4:1 SWR! Good enough for me !



Now it's time to see how it works ... *GULP!*

I tuned my receiver to 162.55, placed one of my little FRS walkie talkies by the speaker and carried the other one out to the antenna. They have "VOX", so nobody has to press the push to talk button to get it to transmit.



Starting with the antenna pointed south, I had Chicago, about 90 miles away. Swinging east, across Lake Michigan, Grand Rapids was full quieting, 100 miles distant. Turning the whole thing around, now aiming west, I've got Madison, WI, also about 90 miles away over some pretty hilly land ! Do you want to hear? (I was recording when I did my intial tests)

http://members.aol.com/j999w/NOAA.wav

With my attic vertical, all I could hear was Grand Rapids with no indication of any other station. So it DOES work !!

It's not quite as sharp as I would like, but it works a heck of a lot better than my little 3 element beam I had made. Rejection off the back and sides seems pretty good. While I'm typing this up, I've got Sheboygan and Green Bay (130 miles) booming in with it turned north. I will ~try~ to squeeze it in the attic, but if not there, then maybe on the roof or even on a dedicated mast of it's own, with a rotator of course.

Would I like to go BIGGER??? YEAH!! But honestly, I'm not sure where I would put it right now. Let's see how this one works out and take it from there.



73!

John K9RZZ
Milwaukee
 

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prcguy

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Hey K9RZZ, you really work fast! You could use any two equal lengths of 75 ohm coax from the splitter to each antenna in your design since you are using a 75 ohm splitter. The phasing harness with 75 ohm ½ wavelength sections (minus the velocity factor) are to match two 50 ohm antennas to a 50 ohm feedline using a simple “T” connector.
prcguy
 

k9rzz

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Oh well. :^]

It's working well even though it's only 5 feet off the ground. I've logged two new ones:

WXJ57 162.400 South Bend Indiana 1000 watts
WNG672 162.425 Wolf Lake Michigan 1000 watts

Which is the first time I've ever heard anything on 162.4 other than local KEC60.

I've gotta get this thing in the air and on a rotator !

John K9RZZ
 
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k9rzz said:
Oh well. :^]

It's working well even though it's only 5 feet off the ground. I've logged two new ones:

WXJ57 162.400 South Bend Indiana 1000 watts
WNG672 162.425 Wolf Lake Michigan 1000 watts

Which is the first time I've ever heard anything on 162.4 other than local KEC60.

I've gotta get this thing in the air and on a rotator !

John K9RZZ
i'd like to use it for the railroad band. man that would be a killing!!!!!

Eric Burris
 

kb2vxa

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Here's the clincher guys;

"That's why I need an antenna array with razor sharp directivity, to peak up on one direction and null all the rest."

That'll never happen without an optimally spaced "long boomer" and they just don't make them for 162MHz, you'll have to build one and it'll cost a good chunk of change for the materials. Still it'll not meet your expectations, my experience with 2M tells me they're unrealistic. I hate to toss water on your fire but the channels are just too crowded 100+ miles out there regardless of what's in your local area and when the band opens it only gets worse.

Eric, you're already dead but now after reading the above you're beginning to realize it. John's antenna is only 5' off the ground, when he gets it up there he'll be whistling a different tune. I used a 22el 2M Yagi horizontal on a 60' tower for SSB and it worked great because the bottom of the band is pretty empty. I wouldn't THINK of it vertical for the crowded FM portion where stations step all over each other being I heard them from my mountain top mobile while they couldn't hear each other.

Guys, greed is counterproductive.
 
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