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Converting Commscope dipole to ham use

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iceman977th

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I was given a pair of Commscope DB224 antennas that were sitting at a tower site unused for a couple years, the harnesses have been cut and the owner just wanted them out of the way. Since these were more than likely commercial antennas, I assume they are not DB224E's which would be the one ideal for ham use. I'd like to see if it's possible to build a new harness (or order one from Commscope) and I assume modify the spacing to tune down into the ham bands, ideally I would like to use it on our club's repeater until we acquire the funds to purchase one designed and tuned for it, which is the eventual plan. I got them for free, so it's not like we're out any cash if it's not possible.

Mike
 

prcguy

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Connect up just one of the dipoles and see where it resonates. Many of the commercial models cover 2m amateur with no tuning. If its a little high in frequency you can drill and tap the very top and bottom of an element and use a #10 SS screw to make the element a little longer. The dipoles are not really loops or folded dipoles, the bottom half is simply a fat element because its grounded on both sides and the top is a folded monopole.

Once you get the elements to resonate on 2m you can copy the harness from an exposed dipole project I designed here: 4-bay VHF dipole array project




I was given a pair of Commscope DB224 antennas that were sitting at a tower site unused for a couple years, the harnesses have been cut and the owner just wanted them out of the way. Since these were more than likely commercial antennas, I assume they are not DB224E's which would be the one ideal for ham use. I'd like to see if it's possible to build a new harness (or order one from Commscope) and I assume modify the spacing to tune down into the ham bands, ideally I would like to use it on our club's repeater until we acquire the funds to purchase one designed and tuned for it, which is the eventual plan. I got them for free, so it's not like we're out any cash if it's not possible.

Mike
 

rescue161

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I was recently given a DB224 that was resonant around 155. I have a DB224E (138-150), so I tried to use the elements from the 224E on the phasing harness of the 155 antenna. It was a failure. Even at 155, the performance was terrible. I typically just make a new phasing harness and bend new elements, but I was curious.

New elements are easy to bend out of 3/8" tubing or rod. They can be either tapped and screwed or brazed in place. The only problem with making new phasing harnesses is locating 35 Ohm coax. Usually, places like Times Microwave will only sell in bulk. I get my RG83 from here: Dx Ham Radio Supply - Specialty Low Loss Coax RG-83 They also have 125 Ohm RG62.

I cut the last antenna that I made for 146 and calculated the phasing harness for the same. I made it with only two elements at the new owner's request and it works great. I put the phasing harness on the inside of the mast for added protection. It just takes a little bit of time to make/modify your own, but it is worth it. It has been on top their tower for almost 2 years and is still going strong.
 

prcguy

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You can make a great phasing harness out of 75 ohm coax, either RG-6 or RG-11 and use compression F connectors and Tees. Most companies other than DB Products use 75 ohm.

The only problem with making new phasing harnesses is locating 35 Ohm coax. Usually, places like Times Microwave will only sell in bulk. I get my RG83 from here: Dx Ham Radio Supply - Specialty Low Loss Coax RG-83 They also have 125 Ohm RG62.

I cut the last antenna that I made for 146 and calculated the phasing harness for the same. I made it with only two elements at the new owner's request and it works great. I put the phasing harness on the inside of the mast for added protection. It just takes a little bit of time to make/modify your own, but it is worth it. It has been on top their tower for almost 2 years and is still going strong.
 

iceman977th

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Connect up just one of the dipoles and see where it resonates. Many of the commercial models cover 2m amateur with no tuning. If its a little high in frequency you can drill and tap the very top and bottom of an element and use a #10 SS screw to make the element a little longer. The dipoles are not really loops or folded dipoles, the bottom half is simply a fat element because its grounded on both sides and the top is a folded monopole.

Once you get the elements to resonate on 2m you can copy the harness from an exposed dipole project I designed here: 4-bay VHF dipole array project

I've seen your project, I'll have to give that a try. I assume I can use your method of tuning to check resonance on one of the dipoles? I'll get some pictures of the antenna tomorrow.

FYI... I've often read that the newer Commscope stacked dipole harnesses have a poor reputation for durability. Perhaps others can offer details.

I've heard the same since they were bought out, or been bought out (forget which it was).. I'm not sure if mine is a pre-buyout unit or not.. have to look at it.

I was recently given a DB224 that was resonant around 155. I have a DB224E (138-150), so I tried to use the elements from the 224E on the phasing harness of the 155 antenna. It was a failure. Even at 155, the performance was terrible. I typically just make a new phasing harness and bend new elements, but I was curious.

New elements are easy to bend out of 3/8" tubing or rod. They can be either tapped and screwed or brazed in place. The only problem with making new phasing harnesses is locating 35 Ohm coax. Usually, places like Times Microwave will only sell in bulk. I get my RG83 from here: Dx Ham Radio Supply - Specialty Low Loss Coax RG-83 They also have 125 Ohm RG62.

I cut the last antenna that I made for 146 and calculated the phasing harness for the same. I made it with only two elements at the new owner's request and it works great. I put the phasing harness on the inside of the mast for added protection. It just takes a little bit of time to make/modify your own, but it is worth it. It has been on top their tower for almost 2 years and is still going strong.

I appreciate the input. For the hell of it I messaged Commscope to see if they sell just the harnesses.. and of course, they don't.

You can make a great phasing harness out of 75 ohm coax, either RG-6 or RG-11 and use compression F connectors and Tees. Most companies other than DB Products use 75 ohm.

I'll keep that in mind. Any particular reason to pick one type over the other?

Also, I just realized I put this in commercial, not amateur.. not sure which it would be more fitting in.. d'oh.

Mike
 

AK9R

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Actually, you first posted this thread in Amateur Antennas. I moved it to here. Commercial antenna, not generally marketed for amateur radio uses, so it goes in the Commercial Antenna forum.
 

iceman977th

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Actually, you first posted this thread in Amateur Antennas. I moved it to here. Commercial antenna, not generally marketed for amateur radio uses, so it goes in the Commercial Antenna forum.

That makes a little more sense. Thought I was losing my mind. Been a long week.. sorry about that.

Mike
 

radioman2001

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Quote"
FYI... I've often read that the newer Commscope stacked dipole harnesses have a poor reputation for durability. Perhaps others can offer details.

Yes they definitely have harness issues, the ones made in Mexico go bad, and rather quickly. We installed one on a 150ft tower atop a 1800ft Mt and within 6 months we lost 1/2 of the antenna. The problem after dissecting the harness was in the junction of the coax's to each element inside the potted material. We replaced that antenna with a Super Base Commander and never looked back.
Whats worse is the antenna has only a 1 year warranty compared to 10 or 20 years for the fiberglass ones. I called to ask if they would replace the harness and was told no. I informed the service dept that our agency and the entire state procurement program would be notified of the issue and they didn't seem concerned. We actually then disposed of a number of brand new ones in the box to prevent going through this problem again. It ended up costing us about another $2400.00 in tower work to swap it out.
My personal opinion, don't buy one new and build your own harness on the one you have.

Quote"
I appreciate the input. For the hell of it I messaged Commscope to see if they sell just the harnesses.. and of course, they don't.

That's interesting maybe they have abandonded the product. I like the antenna, and used a LOT of them both UHF and VHF when I was down South in Mississippi. Most fiberglass antennas don't survive long with the lightning down there.
 

W5lz

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Open the vent, drain the moisture out of them, and fiberglass antennas will last as long a any other kind.
 

prcguy

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In about a 3yr span the coast guard lost two fiberglass Super Stationmaster antennas to lightning and the last one had a big chunk blown out of the top. We replaced it with a Sinclair exposed dipole array over 5yrs ago and no further problems and I expect it to outlive me. There are times and places for fiberglass antennas and other times and places where they are a poor choice, like the 5 to 10,000ft mountain tops sites in So Cal.

On the leaking harness on the newer Commscope dipoles, you could add weatherproofing at all the coax junctions like you would on a new coax run and that should fix the problem. Its sad you would have to do that on an otherwise fine new antenna.

Open the vent, drain the moisture out of them, and fiberglass antennas will last as long a any other kind.
 
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