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Amateur Radio Antennas - For discussion of all amateur band designed antennas and related accoutrements. This includes base, handheld, mobile and repeater usage. For commercial antennas on the amateur bands please use Commercial Radio Antennas below.

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Old 03-04-2017, 7:40 PM
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Default Dual Band Ham Repeater Antenna

I am looking for a solid dual band repeater antenna, for this install fiberglass would be fine, icing can occur but not often, winds to 40-50mph have been known to occur as well as lightning (rare and no strikes at this site so far). Have a location that I would like a 6dbd antenna on UHF, VHF doesn't matter for gain and it's on a site that I need to keep lo-profile.

My favorite antennas are dipoles but I don't have the room to stack them in the case.
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Old 03-05-2017, 11:32 AM
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Are you planning on running two repeaters through one antenna? For instance, a two meter repeater and a 440 repeater through the same antenna?
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Old 03-05-2017, 3:14 PM
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I would use separate antennas for repeaters.
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Old 03-05-2017, 7:37 PM
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Quote:
Originally Posted by brushfire21 View Post
My favorite antennas are dipoles but I don't have the room to stack them in the case.
Sinclair 120-Cx (x= number of diploles) are designed for VHF, but are also resonate on 70cm.
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Old 03-05-2017, 7:45 PM
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It would be an interesting set of combiners to allow both VHF and UHF simultaneously, not to mention expensive.
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Old 03-05-2017, 7:48 PM
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Originally Posted by N4GIX View Post
It would be an interesting set of combiners to allow both VHF and UHF simultaneously, not to mention expensive.
Not really. A simple VHF/UHF diplexer will work just fine. Done this many times to have a UHF link radio and VHF repeater to use the same antenna(usually a Sinlcair 120-c2 or c4)
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Old 03-05-2017, 9:41 PM
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Years ago I set up a guy in town with a low power UHF repeater on a Comet GP-9 commercial version and he used the VHF side of the antenna with his shore station marine radio through a diplexer. It seemed to work fine. I would never put a Comet antenna on a mountain top where it would get extreme weather or winds but in town they hold up fine.
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Old 03-06-2017, 6:30 PM
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Quote:
Originally Posted by kayn1n32008 View Post
Not really. A simple VHF/UHF diplexer will work just fine. Done this many times to have a UHF link radio and VHF repeater to use the same antenna(usually a Sinlcair 120-c2 or c4)
My club tried this. We attempted to run a 2 meter Fusion repeater and a 440 Fusion repeater, both with their own set of cans, through a Diamond X-50 Dual band antenna with a simple diplexer downstream of the cans. It didn't work, at least not well.

The loss of gain in the dual band antenna and the loss through the diplexer rendered it impossible for those using only a handheld radio to get into the 2 meter repeated with any clarity. Those of us who could hit it with 50 watts or better didn't have any issues. We have since made the decision to dump the diplexer and put up a separate antenna for two meters. We had that configuration once before and no one had any issues with it.
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Old 03-06-2017, 8:57 PM
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Quote:
Originally Posted by k6cpo View Post
My club tried this. We attempted to run a 2 meter Fusion repeater and a 440 Fusion repeater, both with their own set of cans, through a Diamond X-50 Dual band antenna with a simple diplexer downstream of the cans. It didn't work, at least not well.

The loss of gain in the dual band antenna and the loss through the diplexer rendered it impossible for those using only a handheld radio to get into the 2 meter repeated with any clarity...


Hmmmm. Done it with various configurations, some in a portable setup as well running 2 repeaters, and having a link as well. These were however either V/UHF MSR2000 paired, GM300/MAXTRAC mobiles, or some other commercial repeater. Usual stuff done, double shielded jumpers, RESLOC duplexers, hardline to antennas, and high quality antennas. Never had issues. Our radio quality was significantly better in selectivity and squelch operation than the Yaesu fusion repeaters.

Very few repeaters where I live run more than 20-30w before the duplexer. A good diplexer should have little loss, less than .5-1dB, we use little else than 7/8" hardline for our feedline. We will however throw in a preselector and a low gain preamp. Usually a touch more gain than system loss.

At one time Sinclair made a diplexer that combined 136-174MHz and 400-470MHz. To one port. N connectors all around. One of the clubs I belong to has 4, with three actively deployed at repeater sites.

My preference is to have separate antennas for V/UHF repeaters at the same site. Sometimes this is just not an option. Quite often, in Alberta, we will use the 210-C2/C4, used for the 2m repeater, and diplex a UHF link radio to the antenna hardline. Works remarkably well.
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Old 03-07-2017, 12:07 AM
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This would be a single repeater with link radio as mentioned before in several posts. I will look into the Sinclair antenna but suspect it may be to tall and require more space then I have. Love having issue like this a figuring out a solution!

I appreciate everyone's input. Side note, to the user trying to use the x50 that was diplexed, I have heard other reports of others trying to use this same antenna with poor results in duplexed situation, something todo with it coupling into the feedline.
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Old 03-07-2017, 8:53 AM
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Quote:
Originally Posted by brushfire21 View Post
This would be a single repeater with link radio as mentioned before in several posts. I will look into the Sinclair antenna but suspect it may be to tall and require more space then I have. Love having issue like this a figuring out a solution!
A Sinclair 210-c2 is a shade over 8' long. that makes it slightly longer than a 2 piece fibreglass vertical from any of the hammy fibreglass verticals.

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Originally Posted by brushfire21 View Post
I appreciate everyone's input.
Lots of options. the advantage of the Sinclair antenna is that it is not some crappy hammy toy vertical. It will likely be the last antenna you buy for the repeater.

Quote:
Originally Posted by brushfire21 View Post
Side note, to the user trying to use the x50 that was diplexed, I have heard other reports of others trying to use this same antenna with poor results in duplexed situation, something todo with it coupling into the feedline.
Not sure what one expects, but when you buy cheap parts, you get cheap results. yea a $500 repeater looks attractive because it is cheap, but it is a $500 repeater with a couple of hammy toy mobiles in a box. Even a repeater made out of GM300 or MAXTRAC radios is going to be a better performer than a Fusion machine. Diamond fibreglass antennas are not something I would use for repeater service either. like a last resort. and even then, I would be more comfortable using(for a ham repeater only) a BSA kit with a 1/4 wave over a fibre-crap hammy antenna.

can not take short cuts with repeaters. Cheap repeater, cheap duplexer, cheap feedline, cheap antenna equals a crappy repeater.
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Old 03-07-2017, 10:54 AM
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Quote:
Originally Posted by N4GIX View Post
It would be an interesting set of combiners to allow both VHF and UHF simultaneously, not to mention expensive.
Amateur radio companies have been doing it for years, at least a dozen or so! It is called crossband repeat and is not very expensive at all I do not know why you would think that?
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Old 03-07-2017, 2:19 PM
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Link 'repeaters' are usually on a separate small yagi antenna horizontally polarized.

"Cheap repeater, cheap duplexer, cheap feedline, cheap antenna equals a crappy repeater." Exactly, no one wants to talk on a crappy repeater.
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Old 03-07-2017, 3:39 PM
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Quote:
Originally Posted by cmdrwill View Post
Link 'repeaters' are usually on a separate small yagi antenna horizontally polarized.
Not always. If it is a point to point link maybe, Repeaters that are linked in a 'hub and spoke' configuration that use a UHF repeater as a hub, and all the link antennas are vertically polarized.

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"Cheap repeater, cheap duplexer, cheap feedline, cheap antenna equals a crappy repeater." Exactly, no one wants to talk on a crappy repeater.
Those Fusion repeaters are not much of a deal when you end up at a high noise site...
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Last edited by W9BU; 03-07-2017 at 5:40 PM.. Reason: fixed quoting
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Old 03-08-2017, 9:31 PM
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no ham grade dual band antenna is designed for repeater service and will give you nothing but trouble

and they have ZERO lightning protection

the ONLY ham grade antennas I've ever used in repeater service are the g6-440 and the G6- 144

both are built like tanks and will survive hurricane force winds and heavy ice

stacked dipole antennas are the best way to go for repeaters
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Old 03-09-2017, 12:17 PM
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Look into Polyphaser for lightning protection. No antenna will come with that built in, and for a repeater it should be considered essential.

Companies like Antenna Experts ( Fiber Glass Collinear Antenna, AC9-150, 136 - 174 MHz., 9 dBi. Gain - Antenna Experts ) make military grade "rods" that look like the much cheaper ham collinear antennas, but these will withstand 125mph winds, that's something like a Cat3 hurricane.

Even with lightning protection, if you are located someplace high, you can expect the antenna may need to be replaced from time to time.
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Old 01-10-2018, 5:59 AM
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I run full duplex vhf 150 watts and a control link 70cm Uhf on X510HDM with no problems using Sinclair duplexes 6 pak and a Comet Dual band Diplexer.
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Old 01-10-2018, 8:00 AM
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just piling on
we run VHF and UHF machines on the same dual band fiber glass stick at 150ft fed with 7/8" line
both machines cover just as planned
each has it own set of BpBr cans feeding a diplexer and a polyphaser
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Old 01-10-2018, 9:35 AM
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Duplex operation with multiple transmitters and/or multiple bands can work, but it leaves you open to intractible desense problems that can be impossible to cure. The issue is low level mix products that are normally undetectable can manifest themselves on receiver frequencies that can't be filtered out.

Run a set of intermod calculations with a single transmitter frequency. Then do it again with the second transmitter. Add other on-site transmitters, and run it out to 5th and 7th order mixes. At some point, you realize that everything mixes with everything else, and mix products mix with other mix products, and it becomes amazing that anything works at all.

You might get products at -95 dBm that are too weak to radiate, but since they "live" in the antenna and feedline used by the effected receiver, you can't filter them out, if they fall on the receiver frequency.

In my opinion, this is why some people insist it works fine, and others insist it doesn't. You pay your money, you take your chances. Try it. If it doesn't work, just run separate antennas. Don't waste too much time trying to make it work. Especially if you don't have a clear and precise understanding of exactly what the problem is.
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Old 01-10-2018, 5:17 PM
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Quote:
Originally Posted by zz0468 View Post
You pay your money, you take your chances.
we got lucky and it worked right off (it also helps when the guy setting things up knows what is going on, as i sure dont)
and we also have anytime access to the site when we need it
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