Jumper Cables and connectors

[LakeMan2]

I have read through the info at Repeater Builders and a few threads here on connector platting so I read the basics. The issue is I need some N type jumpers (repeater to duplexer) and I am having a hard time determining what plating the conductors have on the pre-made jumpers. Also, I understand the intermod issue at busy commercial sites, but I am wondering how much of a difference it really makes in my case and if I am being overly careful.

For example I have a 435-470MHz repeater (MTR2000 running at 50W) at an isolated site in a very rural area. One tower, one antenna, one transmitter running duplex ( 50' 1/2" Heliax hardline) nothing else near by. For jumpers I would like to get either RG214 MIL-C-17 or FSJ1-50A Superflex. In both case I cant figure out what connector plating is used.

In the RG214 case it uses Delta N connectors. According to the MFG site those can be either Silver, Nickle, or a tri-metal composite. The assembles don't say what they use other than "Delta N". So I have no way of knowing what the plating is, but the question is does it really matter in my case? These are used and significantly cheaper, so would be a nice way to go it they are good enough.

For the FSJ1-50A jumpers it also does not say what connector is used. On the Commscope site there does only appear to be two connectors for the FSJ1-50A, one "HF" which says is gold plated inner, silver plated outer, and the other connector says silver inner, tri-metal outer. But I can't find out what "tri metal" means. It may just be basically nickel. These are expensive, but I am ok with that if the connector quality is there and I don't have to worry about inducing any intermod, desense, etc. On the other hand, don't want to pay the premium if I still end up with basically nickel plated connectors. But again the question comes up if it really matters in my case....

Looking for any comments.

Edit: I suspect it may not matter (in my simple case) because I found the following for example:

https://www.mail-archive.com/repeater-builder@yahoogroups.com/msg54863.html

The part of interest is:

"Now, having said all of that, my real-world experience with
single-frequency-pair repeaters (not combiners or other multicarrier
systems) is that I've never had a PIM problem that I could attribute to
connector plating. Any connector that I install is silver-plated (or H+S
Succoplate), but I don't go to the trouble/expense of replacing
non-silver-plated connectors on equipment like duplexers, radios, etc.."


Thanks

 

[LakeMan2]

Another reference I found:

Duplexer cable harness question (ferrous or non-ferrous?) | QRZ Forums

"Unless you have multiple transmitters and receivers sharing a common antenna, and some of those common transmitters happen to be the right spacing to have products on a receiver frequency, you would never notice that.

This is why, from a practical standpoint, it does not matter. The exception is if multiple transmitters and receivers share the same antenna, or multiple transmitters share an antenna very close to receiver antennas."

I am beginning to come to the conclusion that for higher power (say 100W or more) at a high RF site, nickel connectors can be a problem. For low power (say 50W or less) at a isolated, single repeater pair site, you will not see any real world difference.

Still looking for any comments based on experience...

 

[Project25_MASTR]

Are the connectors on the equipment silver plated?

Sent from my SM-T350 using Tapatalk

 

[LakeMan2]

Are the connectors on the equipment silver plated?

Sent from my SM-T350 using Tapatalk

I don't really know for sure. The equipment is a MTR2000 and a Celwave\Moto pass reject duplexer. I don't know what Motorola used for the female connectors or what the duplexer uses for the inter cavity cables connectors. I don't know that I can visually tell the difference between silver plated and nickel plated on old connectors.

 

[Project25_MASTR]

I don't really know for sure. The equipment is a MTR2000 and a Celwave\Moto pass reject duplexer. I don't know what Motorola used for the female connectors or what the duplexer uses for the inter cavity cables connectors. I don't know that I can visually tell the difference between silver plated and nickel plated on old connectors.

Nickel plated has a silver/chrome look to it. Silver plated has more of a "white" look to it.

Personally I'd use the super flex as I think that the connectors are easier to install properly.

Sent from my SM-T350 using Tapatalk

 

[LakeMan2]

Nickel plated has a silver/chrome look to it. Silver plated has more of a "white" look to it.

Personally I'd use the super flex as I think that the connectors are easier to install properly.

Sent from my SM-T350 using Tapatalk

The issue is that the superflex connectors say silver inner conductor and tri-metal body. I don't know what the tri-metal really means and if those connectors are good enough.

Thanks

 

[LakeMan2]

Everything I have been able to find so far says that the Commscope Healiax/Superflex N connectors "trimetal" is low PIM. That would suggest that they are equal to or better than silver plated. I still don't know what the "trimetal" really is though. I also have not been able to find any real world experience that they are as good as silver plated or not.

 

[WA0CBW]

Working for Motorola and a Motorola Service shop for 30 years I can tell you that a single repeater at a lone site running 100 watts probably isn't going to have a PIM problem. PIM commonly occurs at multi-transmitter sites where the combined RF energy becomes high. Almost all of the commercial sites we installed use either RG214 or RG400 double shielded interconnecting cables. We found that superflex hardline isn't any better (from a shielding/intermod) than the coax mentioned above. Most problems are caused by improper tuning of duplexers and poor jumper cable connector installation or the use of foil/shield cables. Connector adapters can be a problem if they are improperly made (a recent problem of Chinese imports). If you use adapters like "T's" and right angles I would suggest checking them at the frequency being used for excessive loss and impedance. We have cut several open to find a small coil of wire connecting each end instead of a solid wire.
BB

 

[LakeMan2]

Thanks for sharing your experience. There is a lot of information out there but there are also a lot of factors and it seems to almost always comes down to the specifics of each particular situation. Without the experience, and trial and error, it is hard to determine what really does and does not matter.

 

[freddaniel]

There are may acceptable jumper cables and connectors. However, do you really want to just do an "acceptable" job? Regardless, if there is just one repeater or one hundred, there are levels of perfection ranging from acceptable, to excellent, and to best. Needless to say, every connector manufacturer says their product excels, but Field Engineers often stick with what they know and have relied upon over the years.

- First, you must rely upon name brand connectors shipped from known quality suppliers such as Allied, Mouser, Digikey, or Powell, to avoid receiving knock-offs from China made to look like the real thing. [I buy RF Industries silver plated type-N connectors from Powell for $3.84, which is not a bad deal. Search for the model RFN-1005-3C1 for RG-400 or 223.]
- Next consider the value of the plating:
-- Nickel plating is for acceptable performance. Sometimes plating is a mixture and works poor at UHF.
-- Tri-Metal or White Bronze is the next step up and contains some silver, and is better than nickel, but the finish may vary by manufacturer and batch
-- Silver is for superior performance, compared to all other plating except gold.

In the end, you must test the repeater for desense. Only then will you know if your connector choice was the "right" choice. For us that do not want to redo the job, doing it right the first time is always the best choice.

 

[cmdrwill]

If that is the Fred I knew way back.. then he is an authority on repeaters.

Any dis-similar metal contact may be a source of inter-mod, or PIM.