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What are your experiences and thoughts on new old stock duplexers?
If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
Troy
Troy Lousen
N7KAM
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I would say if it did, they have some MAJOR quality control problems at the plant. If it does that in storage, it will do it worse in the field. And it should absolutely last more than 25 years before it corrodes, outside of dealing with rodent infestations or poor site control letting it get exposed to weather, rain, etc.
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On 12/30/2024 12:37 PM, Troy Lousen via groups.io wrote: What are your experiences and thoughts on new old stock duplexers?
If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
Troy
Troy Lousen
N7KAM
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Troy,
If the duplexer is truly immaculate on the outside, I would have no hesitation purchasing such specimen. The likelihood of it being corroded inside with no trace of corrosion on the outside is slim.
Plus - duplexers made 25 years ago can exceed the capabilities the junk coming out of China today. I can't tell you how many of these duplexers are electrically and mechanically unstable.
Kevin W3KKC
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On 12/30/2024 12:37 PM, Troy Lousen via groups.io wrote: What are your experiences and thoughts on new old stock duplexers?
If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
Troy
Troy Lousen
N7KAM
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What are your experiences and thoughts on new old stock duplexers?
If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it
likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service? Way too many variables to provide an answer. I could give you a list of all of the possible reasons for age-related degradation, but without knowing exactly what kind of duplexer it is (make and model), many may not be applicable. "Oxidation and corrosion inside the cavities" is a pretty broad brush to start with, and certainly not the only thing that can happen over time. So, what kind of duplexer are you asking about? --- Jeff WN3A
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I’ve seen cavities that were barely recognizable on the outside that were perfect inside. If they are indeed pristine, then the likelihood of them having issues is low (but not impossible.) Matt AL0R
From: repeater-builder@groups.io <repeater-builder@groups.io> On Behalf Of Troy Lousen via groups.io
Sent: Monday, December 30, 2024 11:37
To: repeater-builder@groups.io
Subject: [repeater-builder] Thoughts on New Old Stock Duplexers What are your experiences and thoughts on new old stock duplexers? If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
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My Wacom 641, bought new in 1984, floated in water for 4 weeks after TS Harvey flooded the site...still clean on inside ...only notice was some oxidation on the bottoms...
Chris WB5ITT
I’ve seen cavities that were barely recognizable on the outside that were perfect inside. If they are indeed pristine, then the likelihood of them having issues is low (but not impossible.) Matt AL0R From: repeater-builder@groups.io <repeater-builder@groups.io> On Behalf Of Troy Lousen via groups.io
Sent: Monday, December 30, 2024 11:37
To: repeater-builder@groups.io
Subject: [repeater-builder] Thoughts on New Old Stock Duplexers What are your experiences and thoughts on new old stock duplexers? If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
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Thanks for the responses so far. To answer Jeff's question - the model out there now that I noticed is a DB4062-WOC-B.
Troy
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From: repeater-builder@groups.io <repeater-builder@groups.io> on behalf of Jeff DePolo WN3A via groups.io <jd0@...>
Sent: Monday, December 30, 2024 10:14 AM
To: repeater-builder@groups.io <repeater-builder@groups.io>
Subject: Re: [repeater-builder] Thoughts on New Old Stock Duplexers
> What are your experiences and thoughts on new old stock duplexers?
>
> If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it
> likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
Way too many variables to provide an answer. I could give you a list of all of the possible reasons for age-related degradation, but without knowing exactly what kind of duplexer it is (make and model), many may not be applicable. "Oxidation and corrosion
inside the cavities" is a pretty broad brush to start with, and certainly not the only thing that can happen over time. So, what kind of duplexer are you asking about?
--- Jeff WN3A
-- Troy Lousen N7KAM
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They are probably bad, beyond repair. You should send them to me so I can dispose of them 😊 Matt AL0R
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From: repeater-builder@groups.io <repeater-builder@groups.io> On Behalf Of Troy Lousen via groups.io Sent: Monday, December 30, 2024 12:42 To: repeater-builder@groups.io Subject: Re: [repeater-builder] Thoughts on New Old Stock Duplexers Thanks for the responses so far. To answer Jeff's question - the model out there now that I noticed is a DB4062-WOC-B.
> What are your experiences and thoughts on new old stock duplexers?
>
> If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it
> likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
Way too many variables to provide an answer. I could give you a list of all of the possible reasons for age-related degradation, but without knowing exactly what kind of duplexer it is (make and model), many may not be applicable. "Oxidation and corrosion inside the cavities" is a pretty broad brush to start with, and certainly not the only thing that can happen over time. So, what kind of duplexer are you asking about?
--- Jeff WN3A
--
Troy Lousen
N7KAM
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Ya, I'm hoping someone would send me one free too! It's pretty wild how much the price of these things has gone up in the past few years.
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From: repeater-builder@groups.io <repeater-builder@groups.io> on behalf of Matt <al0r@...>
Sent: Monday, December 30, 2024 11:10 AM
To: repeater-builder@groups.io <repeater-builder@groups.io>
Subject: Re: [repeater-builder] Thoughts on New Old Stock Duplexers
They are probably bad, beyond repair. You should send them to me so I can dispose of them
😊
Matt
AL0R
From: repeater-builder@groups.io <repeater-builder@groups.io>
On Behalf Of Troy Lousen via groups.io
Sent: Monday, December 30, 2024 12:42
To: repeater-builder@groups.io
Subject: Re: [repeater-builder] Thoughts on New Old Stock Duplexers
Thanks for the responses so far. To answer Jeff's question - the model out there now that I noticed is a DB4062-WOC-B.
> What are your experiences and thoughts on new old stock duplexers?
>
> If a duplexer looks immaculate on the outside, but was manufactured 25 years ago, is it
> likely that there could be significant oxidation and corrosion inside the cavities even if the duplexer was never placed into service?
Way too many variables to provide an answer. I could give you a list of all of the possible reasons for age-related degradation, but without knowing exactly what kind of duplexer it is (make and model), many may not be applicable. "Oxidation and corrosion
inside the cavities" is a pretty broad brush to start with, and certainly not the only thing that can happen over time. So, what kind of duplexer are you asking about?
--- Jeff WN3A
--
Troy Lousen
N7KAM
-- Troy Lousen N7KAM
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Older duplexers/cavity filters are usually better made with beryllium strips and invar rods. They are less likely to suffer from 'microphonics' or frequency shifts due to temperature.
Whenever I was rehabilitating a site for a customer I would ask what they wanted to do with the old filters that were still mounted in the racks or taking up floor space and making the lower half of the rack unavailable for use. Usually they would say that they were going to pull them out and junk them for scrap metal. I would (innocently) offer to take them out of their way and 'dispose' of them.
I accrued a large number of duplexers and filters that way; Most in the 900 MHz band but some that are UHF and even some larger VHF cannisters.
Surface corrosion can always be cleaned up with a scotchbrite and the exterior repainted with rattle-can paint. I always take apart the loops and clean them up (finding a few that were damaged by lightning). I have given away more filters than I currently own (retired now)
--
Tisha Hayes
AA4HA
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Most of my duplexers were purchased used and out of dozens I only remember one that had the crunchies when tuning, you could see lots of noise and intermittent jumps in frequency when tuning. Looking inside the tuning stub was tarnished and I ended up throwing it away. Otherwise it looked ok on the outside. I've had two PD/Celwave 526 series where a couple of tuning rods were frozen and would not budge due to rust or corrosion on the threads. All the rest tuned up fine and are in service with no problems.
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- Thanks for the responses so far. To answer Jeff's question - the model out there now that I noticed is a DB4062-WOC-B.
If it’s a later-vintage DB-4062 painted Decibel “Tek Black” then chances are you’ll be OK. If it is such a later unit, It should have an RG-214 harness. However, I have had some DB-4060 series duplexers that came from the factory with a harness made of seemingly-generic coax; the cables had no markings other than “RG-214” or maybe “RG-214/U”, no manufacturer’s name or part number or anything else on the cables. I’d be cautious of those; at the very least remove the connector from one end and inspect to braid to make sure it truly is silver-plated and not tin-plated as many non-Mil-spec RG-214 clones tend to be. If there is any doubt, replace the harness. The harness can become problematic as a duplexer ages, especially if they were low quality to start with or didn’t use mil-spec silver-braid cable. Most problems I’ve had with older DB-4060 series duplexers is with the plating shedding on the center conductor plunger. I’ve had them get noisy and regardless of what I tried to tame them, including a complete teardown, cleaning with solvent, applying DeOXit, etc., they never were completely quiet. These were mostly from the earlier eras when Decibel painted them beige or brown, but I had (and still have) one newer black DB-4062 that behaved the same. Note that is it not uncommon for them to make a scratching or squealing sound as you tune the center plunger as it rotates against the finger stock, so don’t confuse that with them being “noisy” in the RF sense. Even if they look pristine externally, I’d also suggest removing the coupling loop assemblies from each cavity one at a time (don’t mix them up!) by removing the screws attaching them to the top plate of the cavity. Give the unpainted contact surfaces of the top of the cavity and the coupling loop assembly “box” a good inspection, burnish/clean as necessary. 25 years is a long time… those unplated surfaces are carrying RF current and can become a source of noise as well. --- Jeff WN3A
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Kevin Custer
Chris Boone WB5ITT
Tisha Hayes