What's everyone's antenna preference for commerical repeater use- a fiberglas omni or all aluminum multi-element folded dipole omni?
I see good and bad in both.
Repeater antenna opinions
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Depends on the application... Folded dipole array antennas have given me some flexibility in created null areas within my pattern depending upon the orientation of each element; overall radiation angle from higher peaks in practice appears to make a substantial difference in coverage (DB224 I believe is approx 16 degrees vertical beamwidth in relation to the horizon).
Unless you spend a serious amount of money on a commerical grade fiberglass vertical with proper downtilt depending upon the application, hands down I would go with a DB224 or DB228 if funds allowed for it. Rugged beyond belief compared to even medium duty fiberglass antennas.
I've removed several ham grade fiberglass verticals in the last few years from sites when they've upgraded to Celwave fiberglass verticals or DB folded dipole arrays... Almost every time there has been some sort of serious damage to the ham antenna from lightning or wind causing the brass elements to break solder joints or simply snap in half.
Unless you spend a serious amount of money on a commerical grade fiberglass vertical with proper downtilt depending upon the application, hands down I would go with a DB224 or DB228 if funds allowed for it. Rugged beyond belief compared to even medium duty fiberglass antennas.
I've removed several ham grade fiberglass verticals in the last few years from sites when they've upgraded to Celwave fiberglass verticals or DB folded dipole arrays... Almost every time there has been some sort of serious damage to the ham antenna from lightning or wind causing the brass elements to break solder joints or simply snap in half.
I've managed four "hot spots" in the last couple years, one of which I owned the land on... Almost all of them I required commerical grade antennas with hardline regardless of user, whether it be LMR, WISP, Ham, Public Safety, etc...
Seriously pissed off one WISP owner when I told him he couldn't run LMR400 up to his antenna at 215'... I guess he had just bought a couple thousand feet of it on some quantity deal. Had to bump down to LDF4 which caused some serious tension with the WISP guy. Perhaps he should have read the agreement more closely before purchasing so much cable.
One other thing that I have noticed is the move to more and more dipole arrays here. One of the hambones here went through 3 or 4 fiberglass Vomits before he finally bought a DB224... One strike by lightning and they're done for. He's had the DB224 through several serious cells and it hasn't bumped once, even though his lightning arrestor has popped twice.
Seriously pissed off one WISP owner when I told him he couldn't run LMR400 up to his antenna at 215'... I guess he had just bought a couple thousand feet of it on some quantity deal. Had to bump down to LDF4 which caused some serious tension with the WISP guy. Perhaps he should have read the agreement more closely before purchasing so much cable.
One other thing that I have noticed is the move to more and more dipole arrays here. One of the hambones here went through 3 or 4 fiberglass Vomits before he finally bought a DB224... One strike by lightning and they're done for. He's had the DB224 through several serious cells and it hasn't bumped once, even though his lightning arrestor has popped twice.
my .02
as a hammy repeater owner (3 quantars and counting)
i have two fiberglass stationmasters and one db224 in service.
i would offer that anything stamped COMET, DIAMOND, CUSHCRAFT, MFJ or _____ (insert hammy brand name there) - has NO PLACE in repeater or commercial tower service.... at the house, they are just fine, even on a small tower...but at a commercial site, they are nothing but a liability waiting to fly off the tower and land on something.
bottom line here is that between Celwave RFS and Andrew/Decibel - the price difference is about double. a "repeater grade" diamond is around $200, the DB224E i just bought was $430 (but shipping was $110....and tax $30...)
in coastal / high moisture / salty air... the fiberglass antennas hold up much better than anything made of aluminum.
as for lightning, I have a VHF celwave stationmaster on top of a 600ft bridge, with a UHF celwave stationmaster right next to it. they are on top of a concrete bridge pillar and are the only antennas on the pillar. you can bet they have taken multiple strikes over the last few years...and still perform just fine.
the DB224 i just placed in service was mainly just an experiment to see how well they did - and was a small $$ issue since celwave's just went up to over $500 wholesale. i expect nothing short of long life/good performance from the 224 though...and it's the highest stick at the top of a 300ft tower... it WILL take strikes.
one thing to note.... on the outside of the 224 was a tag labelled....
HECHO IN MEXICO
so i figure Andrews/Decibel probably paid about $12 for the antenna including labor and material.... nice markup! (no, this is not a custom cut antenna... DB224E 138-150 Mhz)
if i was faced with putting a hammy brand in service - or not having anything - i would put the piggy bank back on the shelf and hold a car wash or something to raise money.... why waste $200 for a hammy antenna that isn't going to last? save the money and buy a real antenna....you will NOT regret it.
if you REALLY look around, you can find removed-from-service commercial antennas at most any 2way shop... and most work just fine for hammy repeaters. the DB224's cut for 155 will work just fine in the ham band...just watch the SWR...and Celwaves cut in the 450 band work just fine on 70cm....there are TONS of 152Mhz pagers coming out of service these days...and some of those around here were on custom-cut Bogner BIG BIG $$$ antennas (rated for 200+ mph winds, etc)....free for the taking.
doug
i have two fiberglass stationmasters and one db224 in service.
i would offer that anything stamped COMET, DIAMOND, CUSHCRAFT, MFJ or _____ (insert hammy brand name there) - has NO PLACE in repeater or commercial tower service.... at the house, they are just fine, even on a small tower...but at a commercial site, they are nothing but a liability waiting to fly off the tower and land on something.
bottom line here is that between Celwave RFS and Andrew/Decibel - the price difference is about double. a "repeater grade" diamond is around $200, the DB224E i just bought was $430 (but shipping was $110....and tax $30...)
in coastal / high moisture / salty air... the fiberglass antennas hold up much better than anything made of aluminum.
as for lightning, I have a VHF celwave stationmaster on top of a 600ft bridge, with a UHF celwave stationmaster right next to it. they are on top of a concrete bridge pillar and are the only antennas on the pillar. you can bet they have taken multiple strikes over the last few years...and still perform just fine.
the DB224 i just placed in service was mainly just an experiment to see how well they did - and was a small $$ issue since celwave's just went up to over $500 wholesale. i expect nothing short of long life/good performance from the 224 though...and it's the highest stick at the top of a 300ft tower... it WILL take strikes.
one thing to note.... on the outside of the 224 was a tag labelled....
HECHO IN MEXICO
so i figure Andrews/Decibel probably paid about $12 for the antenna including labor and material.... nice markup! (no, this is not a custom cut antenna... DB224E 138-150 Mhz)
if i was faced with putting a hammy brand in service - or not having anything - i would put the piggy bank back on the shelf and hold a car wash or something to raise money.... why waste $200 for a hammy antenna that isn't going to last? save the money and buy a real antenna....you will NOT regret it.
if you REALLY look around, you can find removed-from-service commercial antennas at most any 2way shop... and most work just fine for hammy repeaters. the DB224's cut for 155 will work just fine in the ham band...just watch the SWR...and Celwaves cut in the 450 band work just fine on 70cm....there are TONS of 152Mhz pagers coming out of service these days...and some of those around here were on custom-cut Bogner BIG BIG $$$ antennas (rated for 200+ mph winds, etc)....free for the taking.
doug
BRAVO MIKE JULIET ALPHA
"You can do whatever you want, there are just consequences..."
IF SOMEONE PM'S YOU - HAVE THE COURTESY TO REPLY.
"You can do whatever you want, there are just consequences..."
IF SOMEONE PM'S YOU - HAVE THE COURTESY TO REPLY.
I picked up a slightly used DB228 (*8* element array) from the local paging company last winter for under $200... They moved from one tower to another and snapped the support beam in half... I work in a fabrication shop part time and had a full size replacement in less than an hour for under $30 bucks...the wild and crazy bat dude wrote:if you REALLY look around, you can find removed-from-service commercial antennas at most any 2way shop...
12 dbd offset pattern tuned to the 2m band for under $250... Unheard of in the hammy cheapo brands...
I currently have it side mounted at 105'... I spent more on the side mounting brackets and the heliax jumpers than the antenna
I had the opportunity to buy stuff in a hurry for a great site, and I plunked down $900 for a Celwave SuperStationmaster cut for 440-450 MHz. I had to add $100 for shipping since the thing is 22 ft long. I also added an anti-sway bar for another $350. The installation matches the other commercial equipment up there so you can't tell it's an amateur station.
It's up 400 ft on a 600 ft tower, ground is 640 ft ASL. Being fed with 500 ft of 7/8 Cellflex foam coax. It's being fed with 60 watts at the ground at 444.450 MHz and I have under 0.1 watts reflected as measured with a 5 watt element.
The only thing I hadn't considered was down-tilt. With such a good location, the signal tends to shoot over everyone within a 20 mile radius. If/when it ever needs to be replaced, I'd consider the same antenna or a DB Products multi-bay antenna.
Bob M.
It's up 400 ft on a 600 ft tower, ground is 640 ft ASL. Being fed with 500 ft of 7/8 Cellflex foam coax. It's being fed with 60 watts at the ground at 444.450 MHz and I have under 0.1 watts reflected as measured with a 5 watt element.
The only thing I hadn't considered was down-tilt. With such a good location, the signal tends to shoot over everyone within a 20 mile radius. If/when it ever needs to be replaced, I'd consider the same antenna or a DB Products multi-bay antenna.
Bob M.
Folded Dipole Antennas
I would never consider a fiberglass side mount. And the top mount won't like being an air terminal for lightning. Why risk it? Too narrow band as well. YMMV. Sinclair, Comprod, DB, TX/RX, whoever... just as long as it is 138-174 MHz on a heavy duty aluminum mast. And some of the masts I've had put up are multi-antenna VHF arrays that add almost 50' to the top of the tower. The mast (over 8" at the bottom and gets smaller as it gets higher) always extends a bit beyond the top of the top dipoles. After a few years, if an antenna goes bad or we have to replace, I find that the top dipole still takes hits. There is often evidence of lots of small hits (arc marks), and 2 to 3 burn thru holes. For the last many years I request the vendor to provide an 18" long lightning rod out the top of the mast. The cost is minor. Rigger time is not a minor expense when replacing an antenna. For this reason, we scrap any antenna coming off a tower, no matter what the condition.
http://www.sinctech.com/catalog/series.aspx?id=279 and check out the IMD specs! Multicoupling at VHF means low noise antennas. Not shown, imagine an 18" rod sticking out the top as well for some reasonable lightning protection for the top dipole. If you are stuck, the VHF folded dipole is also resonant on UHF (not normal practice, but it does work).
All depends on the application. You can play the game and take your chances. You have to live within your means. I've seen many commercial operators that would make even the hams shake their heads in disguist. If you operate a commercial, multicoupled facility, perhaps with public safety as well, you can't fool around.
RFDude
http://www.sinctech.com/catalog/series.aspx?id=279 and check out the IMD specs! Multicoupling at VHF means low noise antennas. Not shown, imagine an 18" rod sticking out the top as well for some reasonable lightning protection for the top dipole. If you are stuck, the VHF folded dipole is also resonant on UHF (not normal practice, but it does work).
All depends on the application. You can play the game and take your chances. You have to live within your means. I've seen many commercial operators that would make even the hams shake their heads in disguist. If you operate a commercial, multicoupled facility, perhaps with public safety as well, you can't fool around.
RFDude
Well, thing is that at 2.4GHz, he's probably running an amp at the top of the tower, which makes up for 200' of LMR400 loss at 2450MHz. If he's ampless, then yeah, he's got a huge resistor for feedline. I'd probably be pissed if I had an amp at the top and you told me to go buy hardline. LMR400, IIRC, is 100% shielded anyway.Cowboy wrote: Seriously pissed off one WISP owner when I told him he couldn't run LMR400 up to his antenna at 215'... I guess he had just bought a couple thousand feet of it on some quantity deal. Had to bump down to LDF4 which caused some serious tension with the WISP guy. Perhaps he should have read the agreement more closely before purchasing so much cable.
antennas and feedline
[quote="SlimBob"][quote="Cowboy"]
Seriously pissed off one WISP owner when I told him he couldn't run LMR400 up to his antenna at 215'... I guess he had just bought a couple thousand feet of it on some quantity deal. Had to bump down to LDF4 which caused some serious tension with the WISP guy. Perhaps he should have read the agreement more closely before purchasing so much cable.
[/quote]
I keep hearing stories about the LMR type cable causes noise to a repeater. Still would like to see that first hand and put some good test equipment on the line. Those that have used it and had problems, when it was heplaced with "Heliax" type cable, the noise went away. Myself, I like the "Heliax" type cable. Never had a problem with any of it.
As for the antennas, made a bet with one of my old bosses a number of years ago. He was hung up on buying a fiberglass stick from ASP. Told him not to get it. It showed up about a week later. Took it out of the shipping tube and it rattled like a tin can with stones. Told him it wouldn't last a month up on the mountain. We installed it and 2 weeks later replaced it. It went open and had zero gain.
I kind of like the folder dipole style for something that is going to last. Problem is if your in ice country. They fill up real fast in a storm and add a huge wind load in that condition. The SWR tends to climb when they fill up with ice on the elements. It's never easy to select an antenna.
Jim
Seriously pissed off one WISP owner when I told him he couldn't run LMR400 up to his antenna at 215'... I guess he had just bought a couple thousand feet of it on some quantity deal. Had to bump down to LDF4 which caused some serious tension with the WISP guy. Perhaps he should have read the agreement more closely before purchasing so much cable.
[/quote]
I keep hearing stories about the LMR type cable causes noise to a repeater. Still would like to see that first hand and put some good test equipment on the line. Those that have used it and had problems, when it was heplaced with "Heliax" type cable, the noise went away. Myself, I like the "Heliax" type cable. Never had a problem with any of it.
As for the antennas, made a bet with one of my old bosses a number of years ago. He was hung up on buying a fiberglass stick from ASP. Told him not to get it. It showed up about a week later. Took it out of the shipping tube and it rattled like a tin can with stones. Told him it wouldn't last a month up on the mountain. We installed it and 2 weeks later replaced it. It went open and had zero gain.
I kind of like the folder dipole style for something that is going to last. Problem is if your in ice country. They fill up real fast in a storm and add a huge wind load in that condition. The SWR tends to climb when they fill up with ice on the elements. It's never easy to select an antenna.
Jim
Re: Repeater antenna opinions
Question for other owners of the DB224E model or anyone with information on SWR issues with this antenna. I recently installed the DB224E model (bought brand new not used). The installation is on top of a building at 170 feet so it's not side mounted on a tower. After the installation I checked the SWR and it was 1.2 to 1 so all was great. 3 months later I have an issue with a nasty SWR problem. Eliminated the feedline as a potential problem by hooking up a different antenna with the same feedline and the standing wave is back down to virtually nothing. Being this installation is in North Dakota I do have a small amount of ice which I know can cause problems if it's heavy ice buildup but I wouldn't call this heavy at all. Besides these antenna's have been installed in worse conditions on towers all over where these kinds of things do occur. When I say SWR problems mine is just about pegging the needle on the SWR meter. Just seems that if a small amount of ice can build up that kind of Standing Wave there has to be some kind of problem on my antenna since this kind of issue (ice) is not new to these antenna's and like I said I know other users who have this antenna up in the same conditions and are not experiencing this drastic of a SWR problem. Waiting till Monday to talk to the folks at Tessco but very frustrating to say the least on a new antenna.
Re: Repeater antenna opinions
You likely have a failure in the phasing harness. That's not entirely uncommon. Wow, old thread -- I knew half of what I know now then! =P
Re: Repeater antenna opinions
Yes and unfortunately that part is not available by itself. I called the tech support for that company and they informed me that while the antenna is under warranty I have to return the whole thing which is no easy task as I have to uninstall the antenna and ship it back what a pain. So now I'm wondering if it wouldn't be worth just fixing it myself as opposed to going to the hassle of getting it off the top of the building it's located on and shipping it back or just take the phasing harness out off and seeing where the problem is. I know these are good antenna's but I'm wondering how much of this quality control is due to the fact they are no longer manufactured in the states and are now being put together down in Mexico. Not happy about that at all. Of course this couldn't happen in the summer either it has to happen at the coldest time of the year 
Re: Repeater antenna opinions
Be glad it's not 800 feet up a tower. Before you send it back, stand it up in the garage on wooden sawhorses and let the ice melt off of it. Check the SWR again. You may find it's a broken part somewhere instead.
Re: Repeater antenna opinions
I called them again today and asked if there was anyway possible to just send back the phasing harness for them to check and replace if necessary but they wouldn't do that. So now the fun begins NOT! The joys of owning your own repeaterSlimBob wrote:Be glad it's not 800 feet up a tower. Before you send it back, stand it up in the garage on wooden sawhorses and let the ice melt off of it. Check the SWR again. You may find it's a broken part somewhere instead.
Re: Repeater antenna opinions
For long life, and minimal trips to service the site, I prefer the exposed dipole arrangement.
Far longer life with wind/ice loading, and even though the dipoles are exposed, the open sections of each dipole can be covered with tape and sealed against moisture ingress to prevent future problems.
Fiberglass antennas do not stand up well with high winds as they tend to snap easily due to the constant flexing of the radome.
The interior design of most fiberglass stationmasters are of the 'corporate feed' design, and the connections are usually made through rigid hardline(like UT-141) and soldered contacts at each section.
Constant high winds easily destroy these antennas, even if the radome is unbroken, the internal sections end up with weak points that are prone to PIM and IMD troubles.
Forget the collinears and use a DB-420 for UHF(personal favorite).
Far longer life with wind/ice loading, and even though the dipoles are exposed, the open sections of each dipole can be covered with tape and sealed against moisture ingress to prevent future problems.
Fiberglass antennas do not stand up well with high winds as they tend to snap easily due to the constant flexing of the radome.
The interior design of most fiberglass stationmasters are of the 'corporate feed' design, and the connections are usually made through rigid hardline(like UT-141) and soldered contacts at each section.
Constant high winds easily destroy these antennas, even if the radome is unbroken, the internal sections end up with weak points that are prone to PIM and IMD troubles.
Forget the collinears and use a DB-420 for UHF(personal favorite).
Re: Repeater antenna opinions
While we are talking repeater antennas... can anyone offer an expert opinion on the "Low PIM" rated antennas vs. those without a rating.
We planned on installing a new VHF DB-224 exposed dipole at the top of a 250' commercial tower, for a 2m amateur P25 repeater. It will share space with two 800 MHz Bogners and a UHF stationmaster. The ham repeater coordinator is recommending against this antenna and says we should go with a Sinclair exposed dipole with the "Low PIM" rating. I have had excellent results with the DB-224 in the past in several public safety applications and have reservations over the Sinclair. Sinclair is the only manufacturer that I've seen with this "Low PIM" rating, is this significant or just a marketing tool?
Thanks in advance,
Jim
We planned on installing a new VHF DB-224 exposed dipole at the top of a 250' commercial tower, for a 2m amateur P25 repeater. It will share space with two 800 MHz Bogners and a UHF stationmaster. The ham repeater coordinator is recommending against this antenna and says we should go with a Sinclair exposed dipole with the "Low PIM" rating. I have had excellent results with the DB-224 in the past in several public safety applications and have reservations over the Sinclair. Sinclair is the only manufacturer that I've seen with this "Low PIM" rating, is this significant or just a marketing tool?
Thanks in advance,
Jim
Re: Repeater antenna opinions
PIM, or Passive Intermod Distortion affects collinear antennas fat more than the exposed ddiipole versions, in that the internal elements are not as rugged and do not 'like'
excessive flexing without problems arising, or section failure(one section still operates, while another is innoperative(but can still show good return loss, but changes the radiation angle,
as well as pattern).
PIM depends on how ruggedly the antennas are manufactures, and for what type of service as well; building sites or mountaintops, with high winds and heavy snow/ice loading.
Any fiberglass antenna on a mountain site, or in a high wind load area should have stays mounted to keep the antennas vertical at all times, this helps to eliminate the problems
Exposed ddipole antennas should also have stays attached to prevent flexing. This action alone causes failures of any antenna.
Our highband exposed dipole antennas on Pinal and Signal peak suffered from extreme ice loading and severe wind loading and snapped the aluminum at the brackets.
Fortunately, the antennas still worked, but we had to secure them to the tower until new ones arrived to replace the damaged antennas.
The fiberglass collinears were a mess...busted radomes, cracked radomes, and those that failed miserably were already on the ground, a tangled mess at the base of the towers.
excessive flexing without problems arising, or section failure(one section still operates, while another is innoperative(but can still show good return loss, but changes the radiation angle,
as well as pattern).
PIM depends on how ruggedly the antennas are manufactures, and for what type of service as well; building sites or mountaintops, with high winds and heavy snow/ice loading.
Any fiberglass antenna on a mountain site, or in a high wind load area should have stays mounted to keep the antennas vertical at all times, this helps to eliminate the problems
Exposed ddipole antennas should also have stays attached to prevent flexing. This action alone causes failures of any antenna.
Our highband exposed dipole antennas on Pinal and Signal peak suffered from extreme ice loading and severe wind loading and snapped the aluminum at the brackets.
Fortunately, the antennas still worked, but we had to secure them to the tower until new ones arrived to replace the damaged antennas.
The fiberglass collinears were a mess...busted radomes, cracked radomes, and those that failed miserably were already on the ground, a tangled mess at the base of the towers.