Repeaer antenna testing

[arlojanis]

I have a DB-224 feed with 7/8 heliax on top of a 300 foot tower. The antenna and heliax are 20 years old. The tower is in town so there should not be any bullet holes. SWR on Bird meter is zero with 42 watts forward. The repeater range is not what it should be and there is some crackle on signals. There is a hollow rumble on the repeater squelch tail and the repeater does not drop out when it should. Everything is OK when I use a spare antenna. Will a cable fault measurement with a R2600C give any clue about problem cause? Will a MFJ antenna analyzer be helpful?

[xmo]

I suspect you will need to replace the DB-224. When they get old, the loops develop cracks. The antenna will still measure OK [forward reflected or return loss sweep] and may work fine for receive only use, but in repeater service the transmit RF 'illuminates' the cracks and the resulting PIM will degrade the repeater's receiver.

Depending on how many cracks there are and where they are, your transmit range may or may not be affected.

I doubt that any test you can run with the R2600 or MFJ will identify this sort of issue - you will need to get eyes on the antenna close-up.

[Jim202]

I have a DB-224 feed with 7/8 heliax on top of a 300 foot tower. The antenna and heliax are 20 years old. The tower is in town so there should not be any bullet holes. SWR on Bird meter is zero with 42 watts forward. The repeater range is not what it should be and there is some crackle on signals. There is a hollow rumble on the repeater squelch tail and the repeater does not drop out when it should. Everything is OK when I use a spare antenna. Will a cable fault measurement with a R2600C give any clue about problem cause? Will a MFJ antenna analyzer be helpful?

Your waisting your time trying to salvage an antenna that old. When I was working for a paging company, we would replace the phasing harness after 6 years. They tended to start leaking water and it caused all sorts of issues. As XMO has stated, it is hard to test an antenna without some real good equipment. Also his statement about the insulators hold the key to old antennas.

It just isn't worth trying to salvage an old antenna. With the antenna at the 300 foot level, your going to have to expend labor and cost just to get there. Do yourself a favor and bite the bullet. Replace the cable, connectors and antenna with new product. Make sure you have a good tower crew that will weather seal the connectors good.

Jim

[FMROB]

I would too agree. Those phasing harnesses can break down on cause crackles.

[AEC]

Time to check the rivets, metal to metal connections, and of course....the phasing harnesses.
Water ingress wreaks havoc on the cabling, not to mention UV damage after 20 + years in the sun.

The screw/nut cconnections on each dipole are not fully waterproof, and moisture does seep in.

The fiberglass separators on the dipole elements also degrade, and can become somewhat conductive over time, as well as the entire array
can promote PIM.

I would sweep each section of the phasing harness(difficult to do using 50 Ohm systems), but you can fabricate transformers to take care of that issue if need-be.

Oh schmidt, cost be damned...buy a new stick and be done with it.

[RADIOMAN2002]

If you are getting zero reflected, either the antenna or coax is full of water. There is always a little reflected power no antenna is perfect. The best way to test is to put the watt meter on the coax at the base of the antenna. If you get little or no power to the antenna the coax if full of water. If you get power, (less the normal coax loss which is about half for VHF and 300 ft of 7/8 coax) and you still get zero reflected, then you have a bad antenna.

[kb0ixm]

Just as a side note I have a brand new db224e up less than 6 months and it appears I have a bad phasing harness already. This antenna has only been up since late September so it's very unlikely it's even taken 1 lightning strike. Another bit of bad news you won't have any choice but to replace the antenna if you were thinking you could just replace the phasing harness they are not available as a single item from the manufacturer either. unless you want to build your own you will have to replace it all. The new antenna's are made south of the border, not sure if that has anything to do with the problem I'm having but it would appear quaility control maybe an issue.

[JD]

What is best for a VHF system folded dipole or fiber glass stick, (Super Station Master) ?

[Jim202]

What is best for a VHF system folded dipole or fiber glass stick, (Super Station Master) ?

The answer would depend on the use application and where the antenna is going to be used.

Do you have high winds and no ice or is there ice? The wind will do a number on a fiber glass pole in short order. You could put in a top support if the antenna is side mounted. They don't like constant flexing. You may have to bite the bullet and go for another brand other than the old work horse of the DB224 antenna.

My choice currently is not to buy a DB224 due to their currently poor survival and no replacement parts like the phasing harness. I would look at some of the other brands that make a close relative to the DB224.

Jim

[kb0ixm]

Not to beat a dead horse but I just got this information in a message today from a commercial installer/dealer down in Alabama regarding the DB224 antennas. I'm putting this out as a service to anyone looking at antenna's who hasn't yet purchased any specific model. You will want to know before you purchase a "New" db224E that Tessco who is now the supplier of these antenna's has known about an issue with the phasing harnesses on the new antenna's (water getting into the phasing harness) and has not yet corrected this problem. With that being said and with the knowledge they are having issues if you buy one and you have this problem they still won't replace just the phasing harness. They require you to return the entire antenna meaning you will have to go to the hassel of taking it down (no easy task any way you slice it) and pay to return it just to get warranty coverage. It's a very sad state of affairs when a company knows they have issues with a product and still send said product out to customers and then make the customers pay to get warranty coverage. Why can they not just have the dealer the antenna was purchased through verify the problem? Very very unhappy with the db224e I ordered. Would never order one now knowing what I do. I can only hope this knowledge helps others before they make the same mistake I did. Until Tessco fixes the phasing harnesses on the db224 series of antenna's you couldn't give me one. For what you pay for the new antenna this kind of customer service is crap.

[wavetar]

Tessco is simply a distributer, not the manufacturer of the antenna...Decibel aka 'Andrew' is. The antennas are available through a wide variety of suppliers. That said, if Tessco or any other supplier knows of an issue with the antennas, they certainly should not be selling them until the manufacturer rectifies the issue.

[Jim202]

Tessco is simply a distributer, not the manufacturer of the antenna...Decibel aka 'Andrew' is. The antennas are available through a wide variety of suppliers. That said, if Tessco or any other supplier knows of an issue with the antennas, they certainly should not be selling them until the manufacturer rectifies the issue.

Bottom line like I said earlier, the only way the problem is going to be fixed if for the industry radio shops to stop buying this antenna.

Andrew has taken a number of steps in the recent past that have not been to the improvement of their products. It is time that we as users stood up and send our message to them. There are other companies that care about their customers., Start using those other company products.

I am not a new comer to this radio field. Have been in it for well over 45 years and have seen a number of companies drop by the wayside because of their poor products and even poorer product support. I have spent many hours on the top of towers installing many different types of antennas. I too was a long time supporter of the DB-224. Not any more. If the DB-224 antenna has gone down this trail, then so be it and the company that makes them. You at one time could call about an antenna problem and the service rep would be more than glad to help resolve the problem. Those days are now long gone.

Jim

[Bill_G]

Jim - Is it just this model of antenna you don't like, or is it the style with the open loops and exposed terminations you aren't fond of? I, me, personally, myself, love this style of antenna. It's quieter, and has longer legs than comparable colinear antennas. It's always been a problem solver though occasionally we do have to take one down and refurb the connections.

[Jim202]

Jim - Is it just this model of antenna you don't like, or is it the style with the open loops and exposed terminations you aren't fond of? I, me, personally, myself, love this style of antenna. It's quieter, and has longer legs than comparable colinear antennas. It's always been a problem solver though occasionally we do have to take one down and refurb the connections.

I am a firm believer of the folded dipole style antenna. They work well and survive some real bad weather. It is the position the manufacturer is taking on supporting these antennas currently, that I have the problem with. I have probably installed over 100 of these antennas in the past. The big but is if they are not going to sell the phasing harnesses alone, but only with an antenna, then the long term usage of these antennas is no longer supportable. I have normally replaced the phasing harnesses 2 times before the antenna needs replacement.

Jim

[Bill_G]

Ah! Got it. Thanks.

[kb0ixm]

Tessco is simply a distributer, not the manufacturer of the antenna...Decibel aka 'Andrew' is. The antennas are available through a wide variety of suppliers. That said, if Tessco or any other supplier knows of an issue with the antennas, they certainly should not be selling them until the manufacturer rectifies the issue.

Yes that is my mistake. I know Andrews is the manufacturer and Tessco is the distributor or at least the distributor where my antenna came from. But the point still stands that both manuracturer and suppliers (especially the manufacturer) know the phasing harnesses have been failing. There is no excuse to send out products knowing issues exist in that same product. So far it would appear from my perspective anyway they are not standing behind their product. Jim you are correct when you state the phasing harness "should be available" as a seperate item also. Selling a product like this and having an integral part not be available seperately when the rest of the product is still usable is just wrong especially when you consider the cost for the product up front. They are going to find out in short order people won't put up with that kind of bad customer service. Just my two cents worth and if you can't tell Yes I am utterly disgusted with them.

[JD]

What manufacturer make a dipole that has the cabling harness inside the antenna, Sinclair?

[Bill_G]

Yes - Sinclair makes a series with fixed elements and internal cabling.

[kb0ixm]

Yes - Sinclair makes a series with fixed elements and internal cabling.

Bill do you know the model number of that antenna (VHF) version?
Thanks

[xmo]

I have been hearing bad things about the current DB224 from industry people I trust. They are saying that they are experiencing quality issues, that the new ones are poorly made and fail in service after a short time. They also tell me that the harness has been changed and now has some sort of stub on it. Maybe that stub optimizes tha antenna at the frequency it was ordered for but we always liked the broad frequecny response of the old version.

I asked on a couple of discussion lists for people's experience with the newest DB224 antennas and for recommendations of alternatives.

The consensus is to avoid the new DB 224. The top two alternatives are the Sinclair SD224 and the Telewave ANT150D.

http://www.sinctech.com/catalog/series.aspx?id=73

http://www.telewave.com/pdf/TWDS-7045.pdf

[wavetar]

You tend to pay more for the Sinclair, but I don't recall ever having to replace one (folded dipole) in the nearly 20 years we've been exclusively using them. And they send a roll of self-vulcanizing rubber tape and high quality electrical tape with each antenna...can't go wrong!

[KB2ZTX]

I had the same antenna issue on our SAR repeater. Antenna was at least 15 years old (guessing about 20) and 300' up the tower. This was a TX combined antenna with another provider who never used the radio. We found that our coverage got worse and worse to the point you could see the tower yet could not hear it. We had a new one installed and looked over the old one. All 4 lobes were broken in half but not to the point they fell off the tower. 3 of them were broken right where the hearnes hooked, while the other was broken at the end with the plastic spacer. While I wouldn't recommend leaving an antenna up this long, we all know how public safety works in rural america. Anyway we put up a new DB224 and have had no issues since. Its been up for over 2 years, and last winter we had lots of ice on the tower and antenna and had no issues.

we also have the DB with the enclosed harness at our other tower site with no issues.

[JD]

I called Sinclair yesterday, for 150 to 160 omni dipole , they no longer have one with enclosed harness, so they say. They have one with external harness.

[kb0ixm]

I had the same antenna issue on our SAR repeater. Antenna was at least 15 years old (guessing about 20) and 300' up the tower. This was a TX combined antenna with another provider who never used the radio. We found that our coverage got worse and worse to the point you could see the tower yet could not hear it. We had a new one installed and looked over the old one. All 4 lobes were broken in half but not to the point they fell off the tower. 3 of them were broken right where the hearnes hooked, while the other was broken at the end with the plastic spacer. While I wouldn't recommend leaving an antenna up this long, we all know how public safety works in rural america. Anyway we put up a new DB224 and have had no issues since. Its been up for over 2 years, and last winter we had lots of ice on the tower and antenna and had no issues.

we also have the DB with the enclosed harness at our other tower site with no issues.

If you have the one with the harness inside it's a different model than the 224 I'm pretty sure. I think they made a 264 or some such model that had the harness on the inside which would be preferable to it being on the outside but they to my understanding no longer make that model. As a follow up on my new DB224E issue I have an update and to their (Andrews) credit they are replacing the phasing harness without making me send in the entire antenna. While this is good news as one ham put it I now feel like I'm a beta tester (antenna style) for them which is still a pain in the but and a hassle but at least they came through with a new phasing harness. Well I haven't recieved it yet but have no reason to believe I won't. I don't know though if the harness is available seperately as mine is being replaced under warranty. I will try to find out though if they will be made available seperately. I just know I got bad information once from Tessco so I'm not bothering to check with them again. I'll go directly to the source. If they say no than I guess I'm just going to have to hope for long service from this phasing harness and when it does come time to replace I'll look at something else where I can get replacement parts even if the thing is out of warranty.

[morbat]

It can be difficult to get phasing harnesses but they were still available 30 days ago. I did just receive 4 DB222 harnesses to build a couple dual-stack VHF antennas from DB224 stock material. (An antenna you could order just order from the old DB Products company.)
The phasing harness design was changed at least 1-2 years ago. I have not observed any bandwidth changes yet.
The DB224 is normally a rugid and low noise antenna.
Several manufacturers have had product problems. The PD220 was rumored to have desense problems because internal connections used an epoxy instead of solder. The internal connections would fail rather quickly...
The DB224 has the split mast that makes it great for pulling up manlifts to structure tops or inside water towers. I did just install a couple in extremely cold conditions. So far they are holding up.
But like others have stated, I would not waste time re-building a 20 year old antenna.
DB Products is still missed as a stand-alone company. You could call and talk to an engineer who knew what he was doing and the quality was great.
Current manufacturers hardly know what a VHF antenna is.
Telewave and Commprod are other options.
If it is made in Mexico or China- buyer beware.

[DMartin]

Hi All:
I just came across this thread over morning coffee.
I'm in the process of bidding a public safety project and was going to spec DB222's.
I would assume they have the same issues as the DB224's, correct?
Or maybe the harness issues have been corrected by now?
Dwayne

[Jim202]

Hi All:
I just came across this thread over morning coffee.
I'm in the process of bidding a public safety project and was going to spec DB222's.
I would assume they have the same issues as the DB224's, correct?
Or maybe the harness issues have been corrected by now?
Dwayne

What I would suggest before you go too far with any action, is to call the company and inquire if any replacement parts, harness and the likes are available for these antennas.

Jim

[motorola_otaku]

It can be difficult to get phasing harnesses but they were still available 30 days ago. I did just receive 4 DB222 harnesses to build a couple dual-stack VHF antennas from DB224 stock material.

Curious to know who you call/email to order Andrew Decibel parts, and if there's a catalog or price sheet available. I've got a couple of folded groundplanes that were cut short that I'd love to order new elements for.

[jpatrou]

Another option is an antenna from RFI Antennas, out of Australia, sold through Bird. Internal harness, wide band, 136-174 without tuning, gain of 3 dBd, BA40-41 or 6 dBd, BA80-41. DHS has been using them for years with great sucess.

[RFguy]

Look at the Sinclair SD210 (single dipole), SD212 (dual dipole), and SD214 (four dipole) antennas.

They are very rugged, mountain top type antennas. No external harnesses, 136-174 mhz bandwidth.

[desperado]

quick thought on reflected power. What bird element were you seeing zero reflected with?
All to often I see a guy check forward power with a 100 watt element on a 50 watt station and then flip it and check reflected.
The meter is 5% accurate of it's full scale reading. This means that you are lost with the reading. 5% if 100 of course is 5 watts.
5 watts of reflected on a 50 watt radio is a high SWR. 5 watts is the variance of a 100 watt slug... you see where I am going with this.
Get a 5 watt slug and check it that way.

Also, keep in mind line loss. If you have 5 watts reflected and your line loss is 3 db you will only read 2.5 watts reflected. It's still a crap reading, but it's also still a wrong reading.
I know guys that live and die by their Bird. And for most things it's the standard that everything else is measured by and what they aspire to be. But they do have their limitations, and this is one of them.

[morbat]

motorola_otaku
You can contact Andrew by phone or email. It might take a couple calls to explain what you need. I last used (800)255-1479 option 1. Once you have the Andrew part numbers, Tessco can usually do a special order.
Sorry about the delay in responding. Work is demanding right now... Good luck
Also - DB222 phasing harnesses are not known for problems- in my experience.

[motorola_otaku]

motorola_otaku
You can contact Andrew by phone or email. It might take a couple calls to explain what you need. I last used (800)255-1479 option 1. Once you have the Andrew part numbers, Tessco can usually do a special order.
Sorry about the delay in responding. Work is demanding right now... Good luck

Thanks, that's a start. Will they email or fax me a parts number list or do I need to get each part number from them individually?

[morbat]

I had to explain what I was looking for and Andrew Support provided the part numbers. It would not surprise me if they could email information on a larger request.