Duplexer cable harness question (ferrous or non-ferrous?)

[KV6O]

I had a few questions for all these duplexer experts out there. I am working on tuning a Sinclair Q202 4 cavity BpBr duplexer into the 2M band, it was originally tuned at 161.565/160.395 and the cable harness was too small for 2M – just couldn’t get it to tune in the upper end of 2M at all. I added 2 Amphenol 90deg elbows to each can (2 was better than 1), and was able to get it to tune. Now I am looking at building a permanent harness, and in typical frugal ham tradition, I am trying to use what I have rather than buy.

I have some 36” jumpers here that I could cut up – they are COLEMAN/CCI 8421 M17/164-00001 MIL-C-17 OJUD5 (exactly what’s printed on them) that as near as I can tell are RG-214 double shielded silver plated cables (I haven’t cut into them yet) – should be perfect for this application. My question is about the N connector currently on them – they are DELTA 1103005N000 connectors, which look like nickel barrels with silver plated contacts. An article on Repeater-Builder states that nickel is ferrous (??) and that nickel connectors should be avoided in a duplexer harness (http://www.repeater-builder.com/ante...-sys-coax.html). As far as I can tell, nickel is not ferrous… and my magnet seems to prove it.

However, RG-142/U is also recommended, and its construction consists of a silver plated steel center conductor! Steel is ferrous, so what’s the logic in building your entire harness out of a ferrous cable if ferrous anything is to be avoided? (http://www.repeater-builder.com/ante...lded-coax.html)

So, back to the actual question… Can I use the DELTA N connectors that are already attached, or should I cut them off and replace them? I have some Times Microwave TC-400-NMH connectors that hopefully will fit, and they are silver plated.

Opinions? It would appear that the experts on Repeater-Builder are contradicting themselves…

Steve
KV6O

[W9GB]

COLEMAN/CCI 8421 M17/164-00001 MIL-C-17 OJUD5 (exactly what’s printed on them) that as near as I can tell are RG-214 double shielded silver plated cables
(I haven’t cut into them yet) – should be perfect for this application.

Steve -

Coleman Cable (CCI) is HQ here in Chicago area,
Waukegan in Lake County - up the Lake Michigan shore from downtown Chicago.

Coleman Cable Inc.
1530 Shields Drive
Waukegan, IL 60085
+1 (800) 323-9355

CCI should be able to confirm the match of the military spec cable to RG-214 double shield.
IF it is RG-214 ... GREAT FIND .. that would be the coaxial cable I would use for harness construction.
http://www.colemancable.com/faq.aspx

Coleman Cable
Bob Holpuch, Product Development Engineer
+1 (847) 672-2373
rjh@coleman-cable.com
==

My question is about the N connector currently on them – they are DELTA 1103005N000 connectors,
which look like nickel barrels with silver plated contacts. An article on Repeater-Builder states that nickel is ferrous (??) and
that nickel connectors should be avoided in a duplexer harness.

As far a nickel -- it is not a ferrous material, like iron or iron alloys -- BUT Nickel is a naturally magnetostrictive material, meaning that,
in the presence of a magnetic field, the material undergoes a small change in length.
In the case of nickel, this change in length is negative (contraction of the material), which is known as negative magnetostriction and is on the order of 50 ppm.

Nickel is commonly used in alloys and as a plating metal over ferrous (iron) and brass (copper alloy) materials.
http://en.wikipedia.org/wiki/Nickel
Nickel and Copper are intermediate plating steps for chrome plating.

Can I use the DELTA N connectors that are already attached ??

Personally, IF the connectors are in good condition (mechanically and electrically) - I would use them.
I believe that the point trying to be made at Repeater Builders TIP -- Dielectric reactions of dis-similar metals (potental corrosion points)

==
w9gb

[WB2WIK]

RG-214/U and the Delta N connectors are perfect.

I've never had any problems at all with either, in cavity duplexer applications and this stuff is what is routinely supplied with a number of commercial duplexers.

[K7JEM]

The problem with nickel connectors is that they can generate more intermod products, especially at higher power. For most applications, there will be no problem, though.

If you were buying the connectors, I would recommend the silver plated type.

RG142 does have a steel inner conductor. But it is silver plated. The RF all fows on the silver plating, so there is no issue for intermod. As far as RF is concerned, it might as well be a solid silver conductor, due to skin effect.

Joe

[KV6O]

Great! Thanks for the quick replies!

Steve
KV6O

[KB4QAA]

The chemical symbol for iron is "Fe" = Ferrous.

Nickel is not ferrous (only iron is ferrous, by definition) but it can be more or less magnetic, particularly different alloys.

[W8JI]

As far as I know, much of the time nickle does have iron in it. It may not be enough to show with a magnet, but it is usually there.

RG-214/U and the Delta N connectors are perfect.

I've never had any problems at all with either, in cavity duplexer applications and this stuff is what is routinely supplied with a number of commercial duplexers.

I agree with this comment.

You only have a four cavity filter. I think I know the IMD effects being discussed, and they far over one hundred of dB down from the signals causing the IMD.

Here is the white paper: http://amphenolrf.com/simple/PIM%20Paper.pdf

Pay attention to this section in that paper:

PIM is normally
specified in terms of dBm or dBc. dBm
is a measure of power relative to 1
milliwatt. Zero dBm is 1 milliwatt into a
50 ohm load. dBc is a measure of dB
below a specified carrier level. For
example, 20 watts, or 43 dBm is a
typical input power level specified for
testing passive devices. A normal test
requirement for allowable PIM might be
–110 dBm. This would make the
specification –110-43, or -153 dBc.
The typical range seen today is –100
dBm to –120 dBm with two +43 dBm
carriers.

To show you power levels involved, 43 dBm is two 20 watt signals in the connector. With two 20 watt signal they are saying IM is -100 to -120 dBm, in the same cable.

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 wouldn't worry one bit.

As for what is INSIDE the center conductor, shink effect negates and worry there.

Look down to passive IM:

http://en.wikipedia.org/wiki/Intermodulation



.

[N3OX]

Nickel is not ferrous but it is "ferromagnetic..." i.e. shows nonlinearity and hysteresis like iron in the presence of a magnetic field with that's probably what the warning against "ferrous" metals is intended to be...

As for what is INSIDE the center conductor, shink effect negates and worry there.

I think you meant skin effect negates the worry...

To show you power levels involved, 43 dBm is two 20 watt signals in the connector. With two 20 watt signal they are saying IM is -100 to -120 dBm, in the same cable.

It seems to me that the paper suggests -100 to -120dBm with two +43dBm carriers as a typical level but then says that nickel beneath a (presumably very thin with respect to a skin depth) gold plate can increase intermodulation by 40-50dB. I wonder if that "typical level" is for connectors that are good for low intermodulation with thick silver plate or other things that keep the current confined in a more linear material or if that's across all types... if it's across all types including ones with ferromagnetic materials, something doesn't seem to quite add up?

If the -100 to -120dBm is for connectors that are "good" for IM and the IM for the nickel ones is 40-50dB higher that would start to be a problem, I'd think but maybe that's not what they mean?