Duplexer for UHF

[Flameout00]

I was considering a better duplexer for my current repeater. Right now it's just one of the mobile flat pack Celwave duplexers. Although it seems to work ok, I think I may get better preformance with something like a Bird 28-70-02 or maybe a EMR 65534/ENC or EMR 65544/SNC. And by the way, what the heck does the ENC and SNC(CT) on those EMR duplexers even mean? As you can tell, I'm not well versed on duplexers, although I've been trying, but it gets confusing real quick!

I know the 28-70-02 and 28-70-09 are vari-notch and the EMR's are Pass notch. I've been downloading spec sheets and reading what I can, but now I'm ready for some Tylenol! If I could get one of the above duplexers, which would work best for a GMRS repeater system. Repeater will either be a Motorola GR500 or an Icom IC-FR4000. Antenna and hardline are already ran. I also found a EMR 65534 that had 2 Band Pass Cavity Resonators with it. Would they help at all?

 

[prcguy]

Is the repeater at a site with other repeaters or transmitters? If so having good band pass capability in the duplexer is a must and flat packs are only notch type and a pass/notch will work better. Have you done any testing to see if you have desense? If so your existing duplexer may need some touch up tuning or its not up to the task with the power level your running.

The best, baddest UHF duplexer that I know of is the Phelps Dodge/Celwave and now EMR 526 series. These are rated upwards of 120dB isolation and work extremely well. The only problem with them is the cost and you need some good test equipment to get them tuned to specs. New prices start in the mid $2k range.

The Bird you mentioned is also good and rated around 100dB isolation. The EMR 65534/ENC is more in the low to mid 80dB isolation and the EMR 65544/SNC is a little better at up to 90dB isolation. All are expensive new but many are available used for good prices. I've picked up perfect Celwave 526 series for $250 and some good used Motorola 1500 series for $50 each and those are rated around 85dB isolation.

There are lots of other great models from Telewave and other companies.

 

[Flameout00]

Thanks for that information. There are no other repeaters are on site or even in the area so at least that won't be a problem. I'm definitely not looking at new, so I've just been checking on ebay and unfortunately, nothing is in the price range that you mentioned

So the higher the dB Isolation the better? I was thinking the opposite for some reason, so that will help. It seems a lot of the EMR ads also mention Celwave in their descriptions. Like this: EMR Celwave Radio repeater notched cavity duplexer which is confusing. Are the one in the same or two different companies? At least I'm learning as I search

 

[prcguy]

Thanks for that information. There are no other repeaters are on site or even in the area so at least that won't be a problem. I'm definitely not looking at new, so I've just been checking on ebay and unfortunately, nothing is in the price range that you mentioned

So the higher the dB Isolation the better? I was thinking the opposite for some reason, so that will help. It seems a lot of the EMR ads also mention Celwave in their descriptions. Like this: EMR Celwave Radio repeater notched cavity duplexer which is confusing. Are the one in the same or two different companies? At least I'm learning as I search

When shopping for the best performance its a tradeoff in price vs highest TX/RX isolation and lowest insertion loss. Higher isolation is better with 85dB being my minimum goal, 1.2dB insertion loss per leg is better than 2.0dB and so on. I've found a few good deals on eBay but you have to search multiple times a day and act quickly when you seen a great price. Otherwise the best deals I've found have been at ham flea markets, especially the Dayton HamsterVention.

I believe the 526 series duplexer came about in the Phelps Dodge days in the 1960s then companies were bought and sold so its also been under the Celwave and possible RFS brands before showing up under the EMR name. Same basic duplexer except for the color and the different types of coax used over the years.

 

[Flameout00]

If I'm reading the specs right, the two EMR's are (Min./ Typ.) 80/85 isolation (not sure what the min/typ means) and 2dB insertion loss and the Bird's are 0.6 dB insertion loss on the 28-70-02 and 1.25 on the 28-70-09. Both 100 dB Isolation. So just going by that, the better of those four would be the 28-70-09? But all close enough that I probably wouldn't notice a difference?

 

[prcguy]

If I'm reading the specs right, the two EMR's are (Min./ Typ.) 80/85 isolation (not sure what the min/typ means) and 2dB insertion loss and the Bird's are 0.6 dB insertion loss on the 28-70-02 and 1.25 on the 28-70-09. Both 100 dB Isolation. So just going by that, the better of those four would be the 28-70-09? But all close enough that I probably wouldn't notice a difference?

The Bird 28-70-02 is definitely the best of the bunch you listed. If you stick 50w into a duplexer with .6dB loss you will get 43.65w out. With a 2dB loss duplexer you will get 31.62 watts out. Same thing will happen on receive and you will probably notice a difference like weak handhelds are a little bit noisier with the 2dB loss duplexer. I like to limit duplexer loss to 1.5dB max if possible.

 

[xmo]

"Right now it's just one of the mobile flat pack Celwave duplexers. Although it seems to work ok, I think I may get better preformance with something like a Bird 28-70-02..."
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Given that the repeater is not located near other systems and absent RF interference, duplexer insertion loss is the primary performance limitation, it is hard to beat the Celwave on that parameter. Buying another duplexer could net no performance improvement at all.

If there are currently performance concerns, the entire system should have a complete performance assessment by a competent technician.

 

[prcguy]

"Right now it's just one of the mobile flat pack Celwave duplexers. Although it seems to work ok, I think I may get better preformance with something like a Bird 28-70-02..."
---
Given that the repeater is not located near other systems and absent RF interference, duplexer insertion loss is the primary performance limitation, it is hard to beat the Celwave on that parameter. Buying another duplexer could net no performance improvement at all.

If there are currently performance concerns, the entire system should have a complete performance assessment by a competent technician.

I've never seen a Celwave flatpack meet those specs, at best they are maybe 1.2dB insertion loss and high 70dB in isolation. If the flatpack is working perfectly and you have zero desense then buying a more elaborate duplexer might not improve much.

 

[xmo]

"I've never seen a Celwave flatpack meet those specs..."
------
Well, I have. More than one. The screen shot I posted is from one I tested personally.

Also, here are the results from one tested by Jeff, WN3A.

OP needs to have his equipment competently evaluated.

 

[xmo]

Also, here is a report for a unit tested by www.DuplexerRepair.com (no affiliation)

 

[Flameout00]

OP needs to have his equipment competently evaluated.

I would love to be able to do that. I just don't know of anyone around my area with the correct equipment to do so. I guess I could send the current duplexer out, but if I get one of the larger ones I mentioned, I will need to find someone local. I actually have 4 of the flat pack duplexers. One is Celwave, two are RFS (same as celwave?) and one Icom. Oh, and I also have 2 other Chinese Fumei duplexers, still in the box

 

[Project25_MASTR]

I've never seen a Celwave flatpack meet those specs, at best they are maybe 1.2dB insertion loss and high 70dB in isolation. If the flatpack is working perfectly and you have zero desense then buying a more elaborate duplexer might not improve much.

I've seen it (90 dB of isolation) when looking at tracking generator...but the second you actually try and put power to the thing you start seeing 5-6 dB of desense at rated power and can measure desense above 30W by ear.

Favorite UHF duplexer right now...Northcomm ION. Real world...>115 dB of isolation and less than 1 dB of desense at 125W.

 

[prcguy]

I've seen it (90 dB of isolation) when looking at tracking generator...but the second you actually try and put power to the thing you start seeing 5-6 dB of desense at rated power and can measure desense above 30W by ear.

Favorite UHF duplexer right now...Northcomm ION. Real world...>115 dB of isolation and less than 1 dB of desense at 125W.

The Northcomm appears to be a custom EMR 526 type and I would be surprised if it has any measurable desense. Even my older Celwave 526 has no measurable desense at 100w.

 

[TampaTyron]

Min/Type is Minimum/Typical, so the minimum expected performance to be considered a PASS /Typical expected performance if averaged over the band the duplexer is able to cover. TT