Jonathan Weaver
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Sharing projects, resources, and lessons learned

Whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks through Him to God the Father. ~ Colossians 3:17

G5RV Junior Antenna Install

6/3/2016

3 Comments

 
I finally decided to expand out of the VHF/UHF bands into HF. I wanted an "invisible" antenna, so I'm starting with an attic mounted G5RV antenna. The junior version from MFJ that covers 40 meters through 10 meters on the ham bands.
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Antenna mounted as high as practical. You can see it's clear of metal objects and the ladder line goes off to the right at a 90 degree angle. Not ideal, but I'm avoiding routing it near any air ducts and wiring in the attic.
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Since I have a hip roof, the radials are bent down. The supports are wire tie loops supported with nylon twine. This radial gets the closest to metal. The foil on the ducts may cause the antenna to have a null or contribute to an unwanted noise gain.
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You can see the end insulator, again supported with twine. And the duct work I'm trying to avoid.
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Here is the ladder line to coax transition. This was my first time installing a UHF connector on coax. It turned out neat with the blue heat shrink. Also, since this is a balanced multi-band antenna (not usually reasonant), MFJ recommended constructing a balun by looping the coax. This is 10 loops around 5" in diameter. The function of the loops is to provide high impedance to any common mode current. Ideally, in a balanced antenna, balanced feed line, all of the current would be differential mode. That is the current on the coax shield would be equal and in opposite direction from the current on the center conductor. If that's the case, the loops will not add impedance to the current and all the energy is radiated by the antenna. However, any current on the shield in addition to the differential mode current would see the inductance of the loops. That inductance helps to prevent and minimize common mode currents. You don't want common mode currents because they add to the noise of reception and can cause problems during transmission. This is because the common mode currents cause the coax to act as an antenna, and some of the energy is radiated by the coax shield instead of the antenna.

We'll see how it works when we get everything hooked up on the radio end.
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2M Clothes Hanger YAGI Antenna

9/28/2015

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I put my new home brew Yagi antenna up for a few minutes this past week.

Here are some pictures:

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Mounted around 17 feet in the air, on the end of a painter's pole. I was hitting the repeater at Ga Tech and Bank of America building 50 miles away with this set up.

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Leaned up on the car. The 2M 5 element Yagi is 66 inches long and 40 inches tall. Made out of 1/2 inch CPVC, six metal clothes hangers, and a few other parts. I'm going to add a few braces to support the pipe.

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Handheld radio and SWR meter to test antenna. The antenna tested pretty good (1.2 to 1.4 SWR or 3% signal loss). You can see the input connection on the antenna as well.

There is nothing in the box, no balun, no matching network.  Just one end of the driven element soldered to the center of the connector and the other end attached to the outer shield by being wrapped around a screw and compressed with a nut.  The insulating material on the outside of the clothes hanger wire was scraped off at the connecting ends.

The dimensions along the boom are:

Reflector to Driven Element: 0.433 meters (17 inches)

Reflector to Director One: 0.755 meters (29 3/4 inches)

Reflector to Director Two: 1.185 meters (46 5/8 inches)

Reflector to Director Three: 1.688 meters (66 7/16 inches) of

The lengths of the elements are:

Reflector: 1.048 meters (41 1/4 inches)

Driven Element: 0.978 meters (two halves) (38 1/2 inches)

Director One: 0.940 meters (37 inches)

Director Two: 0.944 meters (37 3/16 inches)

Director Three: 0.884 meters (34 13/16 inches)

I designed the antenna with a free software package called 4NEC2. Simulated properties were 1.0 to 1.2 SWR and gain of 10 db.  I didn't get that good, but not bad for a pile of clothes hangers. I definitely need to add reinforcement to keep the antenna as straight as it was on the floor when I laid it out. Still, it's fun on a stick!!!  And I learned a good bit researching how to build it!

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The Moon

11/19/2014

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On the night of November 9, I got to play with my Meade Jupiter Telescope.  My wife bought it for me for Christmas about ten years ago.  I've used it about a dozen times.  This was my first video I've captured through the telescope using its electronic eye.  It was a clear night around two days after a full moon.  The electronic eye sends out a standard NTSC video signal, that I captured on my laptop using a Pinnacle video capture device.  The video turned out awesome!

Everyone I've shown it to has the same response I do.  Isn't it amazing the things God has created and put in front of us that we all take for granted.  In a word, the moon is, by all measures an amazing creation of God.
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A Start

10/27/2014

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I'm embarking on a journey 95,000 feet into the air, a short voyage into near space. But I'm not really going. A camera, GPS receiver, radio, and some specialized electronics are hitching a ride on a weather balloon. I'm getting a start in high altitude ballooning, a recent "nerd" hobby. One of the parts is the radio. You need a radio so you can track and recover the balloon. What fun is it send a camera nearly to space unless you can get pictures off of it, right? A solution is to use APRS, which is a system built by HAM radio operators to exchange digital information including GPS coordinates. In fact, several websites tie into the system to provide you with maps and help you track objects reporting their GPS coordinates.  To use APRS, you need a HAM radio license. To get the license you have to pass an exam.

Tonight, I attended my first Tri County Amateur Radio Club meeting.  I walked up, introduced myself, and mentioned that I was interested in getting my license and had been studying.  The gentleman I was talking to said, you want to test tonight?  I said, why not?  And he called out to Roger, who was getting two other people ready for their exams.  I sat down, listened to the instructions, paid $10, and took the test by moonlight (we were outside and the sun was setting).  And, I passed the exam!!! My thanks to Roger, the VE (Volunteer Examiner), and to the Tri County Amateur Radio Club for their help and friendly welcome!

Jonathan Weaver (KM4FIK)

APRS Websites:

http://www.aprs.org/
http://www.findu.com/
http://www.openaprs.net/
http://aprs.fi/

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AZ Shelves

9/18/2014

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These are some AZ Shelves I made for Evan's room based on a picture Samantha showed me of some Pottery Barn Shelves that are out of manufacture. The hardest cuts were the 30 degree cuts on the inside of the A. I used a vertical sled to mount the board vertically on my table saw with the blade set at 60 degrees. The shelves turned out nice and the Sketchup model is available for download below.
azshelves.zip
File Size: 152 kb
File Type: zip
Download File

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    Husband. Father. Follower of Christ. Electrical Engineer. Electronics and woodworking hobbyist.

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