Tri-Band Repeater Antenna Build, cont'd

This is a few more photos of the new repeater antenna build, and some observations.While tearing down a 4-bay antenna on 154mhz for parts & materials, I measured things with my MFJ Antenna Analyzer, and took note of some dimensions...

First, the larger dipoles are from the 154mhz antenna. I made a little pigtail connector for the MFJ, and took some readings. Resonance and impedance of these types of antennas is impacted by proximity to the mounting mast and the width (these are 3") of the loop. They also require at least a 1/4 wl of mast above and below for proper operation. The larger units were resonant at about 154mhz, where I expected. These dipoles are 17" per side, from the mount to the end of the loop, total 35" tip to tip (counting the 1" dia mount in the middle). The loop is 3" wide, edge to edge, and they are 3" from the mounting mast to the edge of the dipole loop. These are the dipoles I will modify for 2 meters.

The smaller dipoles are 15" per side, from the mount to the end of the loop, total 31" tip to tip (counting the 1" dia mount in the middle). They were resonant at about 168mhz. I altered the formula to calculate the proper dipole size, and it clearly doesn't track as I alter the dimensions, so I'll be doing a bit empirical testing (read trial and error, hahaha) to work the bugs out of the 220 and 440 antennas.

Another interesting observation...using DB Products RG-11 cable, the matching sections were pretty much the same length as the tip-to-tip dimension of the folded dipole elements. We'll see how this works out when I get these tuned and installed on a test mast...

I plan to use the single mast section on the right (with the rain bonnet) to install a pair of folded dipoles for 2m, 220, and 440. My plans are to keep this a compact antenna. I realize it'll be a compromise antenna, but I need to keep size down for a DC grounded tri-bander. 

RG-11 in the original installation...

154 mhz vs 168 mhz...

This pair will be modded for the 147.39 repeater.

Dave WB4IUY
www.WB4IUY.net

10 Meter Repeater RX Antenna rebuild...

This is a Hy-Gain Super Penetrator CLR2 antenna I picked up many many years ago for the 10 meter repeater. For years, I used fiberglass antennas alike the Big Stick or the Antron 99 for the repeater. After several lightning strikes on the 10 meter repeater sites, as well as strikes on the 2m and 440 repeater sites using fiberglass antennas like the Diamond and Anli antennas, I'm DONE with fiberglass antennas. It's a proven fact that fiberglass antennas develop a strong opposing charge on the shell as wind blows across them during a storm, making them a target for lightning. They're not so bad for side-mounted or low altitude installations. Stay far, far away from a fiberglass antenna for high altitude repeater installations, use only DC grounded metal antennas. 

The first step in this rebuild is to remove years and years of oxidation from the aluminum. I like to use Scotch-Brite pads for this. They easily remove the oxidation and really bring an aluminum antenna back to a nice shine. Disassemble the antenna and be sure to clean into all of the joints. Here's a quick pic of before and after on the 10 meter receiver's receive antennas, after just a few seconds of cleaning with a red Scotch-Brite pad. I'm pointing at a spot I just cleaned...

Dave WB4IUY

www.WB4IUY.net

Tri-band Repeater Antenna Construction Underway...

I'm in the process of making arrangements to relocate my 147.39+ repeater, 224.80- repeater, and 442.400+ repeater to a top perch on my tower at home. After 30+ years experience with amateur radio repeaters, I decided I do not want a fiberglass antenna on my tower...only a metal DC grounded antenna. I decided to set about to design a triband antenna for tower top installation for these 3 repeaters, with the vertical mast robust enough to support the DC grounded antenna for my 10 meter repeater RX side. 

I've started with a batch of DB Products folded dipoles. These are easily modified for correct operation on 2m, 220, and 440. These will all be fed from a single run of hard line via a 3 band tri-plexer. I've successfully fed the 10m receive antenna, 2 meter repeater, and 440 repeater like this in the past. Here's a few pics of the parts I'm working with. I'll update with more blogs as the project progresses. You can keep up with it by looking in the RH column in the "Jump to Blogs of Specific Topics", and clicking on "Repeater-Antennas". 

The long antenna is a Hy-Gain CLR2 I am repairing / retuning to 29.520 mhz for the 10 meter repeater's receiver.  

 The Hy-Gain CLR2 is a DC grounded 5/8 wl CB antenna, and makes a great 10m antenna.

 

Here's a batch of the folded dipoles from DB Products that I am re-purposing  for this custom build. They typically run around 110 ohms, so I'll be building a phasing & impedance matching  harness for these, once tuned.

Load of parts, ready for cleaning and mods. I actually picked these up years ago and stored them away.

Dave WB4IUY

www.WB4IUY.net

Clayton Repeater Site 6/8/02

On 6/8/02, more work was done at the Clayton repeater site...mostly work/upgrades to the antenna systems. The folks out at the site were Steve KD4WIW, Jay KQ4MS, Reg W4REG, Ron K4JDR, and Dave WB4IUY. I took a few pictures while up the tower, to give some of you a better feel for what things look like at 200 feet above the ground, while standing on a piece of Rohn 25 tower... Here are 10 photos for your enjoyment:

This is a shot looking down at the ground from about 190 feet. Notice KQ4MS's truck (rh side) and Ron K4JDR's truck (LH side). The white antenna is used by the new K4JDR 444.150 pl 100hz repeater, and partially shared by the W4RAL-4 145.01 packet node.

 

Here's a picture of the 147.39 repeater antenna mounted on the top of the tower at 200'. Boy, the sky was nice and blue!

 

Here's a picture, taken through the tower, of the south side of Clayton. Whew, the birds love this tower, check out the white stuff. It was EVERYWHERE!

 

This picture is a bit farther south, shot through the tower at a different angle. The vertical tubing in the picture is part of a low-band 3-bay array that will soon be part of the 10 meter repeater's receiver system. This should dramatically improve the repeaters ability to receive weak signals on 29.520. 

 

This picture is of the water tower at hwy 42 and I-40's intersection...probably 10+ miles away. Visibility was pretty darn good from up there!

 

Hey Ron!!!! Hehehehe....there's Ron K4JDR at the bottom of the tower, looking up to help get the alignment correct of a bracket I was working on.

 

Waaaaaaayyyyyyy down there are two motorcycles... They are Steve KD4WIW and Dave WB4IUY's bikes. We rode those to the job. It was such a nice day out, it was a shame to waste it by riding in a steel cage!!

 

Here's a picture shot across the western edge of Clayton and towards Garner. Man, it's beautiful country to view from up there!

 

Here, I'm looking back down at the tower crew. Wow, they sure do look to be a loonnnggggggggg ways down there! Are they really people, or just bugs??

 

 This last picture is of the buildings in south Raleigh. I screwed the telephoto lens on for this shot, to help you see them better. The big towers on the left are channel 5 and others in the Aubern area.

After this work was done, the W4RAL-4 packet BBS node and the 444.150 pl 100 UHF repeater were returned to service. We rode out motorcycles (with KQ4MS in tow in his truck) over to Jimmy K4CMH's house to look at his tower work (to be done), and finally on to WA4MJF's shack to climb the tower and make an adjustment to the W4RAL-5 BPQ switch yagi. Twas a good day for antenna work, indeed! 

Dave WB4IUY

www.WB4IUY.net