[TowerTalk] Selecting Coax connectors
Bob K6UJ
k6uj at pacbell.net
Mon Sep 5 20:44:09 EDT 2016
Roger,
Great overview on connectors !
One thing that I am wondering about is whether or not to get the solder
type
center pin on the DIN connectors. I see them clamp or crimp style for
the outer shield and also
solder or non solder on the center pin. I like the crimp style outer
and clamp is fine too, but not sure
if getting a non solder center pin is a concern. Whats your view on
the center pin attachment ?
I remember discussions here on Tower Talk in the past about center pin
creep in type N connectors.
The DIN is a different animal though...........
Bob
K6UJ
On 9/5/16 5:08 PM, Roger (K8RI) on TT wrote:
> I see a lot of preferences from UHF, To :N: type, to DIN, but for the
> average ham, does it make a difference?
>
> Take UHF, essentially the design is crude and they are cheap! The loss
> figures are high, but those figures are for frequencies few hams ever
> approach and the connector specs say up to 300 MHz and 500 volts.. On
> HF the loss is minuscule. The arguments are those figures add up and
> they do, but it's still a very small value. With SO2R and remote
> antenna switches, plus the rotator loops and pigtails to the antennas
> I've counted as many as ten connectors between the rig and antennas,
> but the loss was barely detectable. Impedance bumps? Yes, they are
> there, but what do the mean? Added up for the 160 through 10 meter
> bands, they are insignificant. I can see where the reflections "might"
> make a difference with digital modes, but it's still very small. The
> only down side I can see is the learning curve for the solder types.
> "Probably" the average ham does a miserable job of soldering them,
> over heating the connector and coax when soldering the braid, turning
> the coax dielectric into a mass of goo, while getting solder on the
> exterior of the center conductor pin.
>
> Off brand UHF connectors: Many adherents say Amphenol
> http://www.amphenolrf.com/connectors/uhf.html is the only way to go
> and they do have reasonably good quality control. As I said at the
> beginning, the original connector design is crude, but it was designed
> long ago. They are easy to make, so there are many off brand
> connectors of various qualities. Amphenol lists both Nickel and silver
> finish as well as a whole slew of dielectrics from Phenolic and
> Styrene, to Teflon and more. The off brand stuff varies, but a good
> inspection by the Ham who knows what to look for, there are good ones
> out there. The typical Ham would do better sticking with known
> brands, but with the UHF design, the important point is whether the
> particular connector will pass the test of time. OTOH even
> top-of-the-line connectors are inexpensive and if you purchase very
> many, the discount makes them about the price of the stuff you see at
> the swaps..
>
> Installed according to the directions (braid on the inside and
> properly soldered), the connector will provide reasonable
> strength. NOTE UHF connectors are not weatherproof!
>
> N-Type. Not for those running "high power". By high power, I'm nor
> referring to 1500 watts.
> http://www.amphenolrf.com/connectors/n-type.html OK, so they
> represent less insertion loss with less impedance, but what do they
> gain us at 160 through 10?. Amphenol lists them "These connectors are
> used in all systems where excellent RF and mechanical performance is
> critical." I'm not sure by what they mean when they refer to
> mechanical performance, but I've never found the typical N-type
> connector I couldn't pull off the coax with my hands (crimp type
> excepted) In my experience, They have two limitations. Mechanical
> strength and center pin migration are the problems I've seen.
>
> Mechanical strength is pretty much self explanatory. Center Pin
> Migration? On vertical runs, the center conductor in many, if not most
> coax cables will slowly move downward This tends to pull the center
> pin, in on the top connector, and push the center pin out on the
> bottom connector. This doesn't happen with connectors where the center
> pin is captive.
>
> DIN (7-16) connectors.
> https://en.wikipedia.org/wiki/7/16_DIN_connector Is kinda like an
> N-connectors on steroids. The 7-16, or 7/16 is the size of the center
> pin (7 mm) and the ID of the outer connector (16 mm) They are still a
> bit on the expensive side and not for the ham who purchases connectors
> at swaps to save a buck, but " It is among the most widely used high
> power RF connectors in cellular network
> <https://en.wikipedia.org/wiki/Cellular_network> antenna systems." and
> "The 7-16 DIN connector out performs other non-flange options, such as
> N connectors <https://en.wikipedia.org/wiki/N_connector> or BNC
> connectors <https://en.wikipedia.org/wiki/BNC_connector>, when it
> comes to interference and intermodulation rejection or higher power
> handling at RF frequencies.^[1]
> <https://en.wikipedia.org/wiki/7/16_DIN_connector#cite_note-UTC-1>"
> (Quoted from the above Link)
>
> Adapters: Amphenol lists 689 adapters. Pages from
> http://www.amphenolrf.com/adapters.html However, other than the most
> common it's likely the distributor would need to special order them.
>
> Crimp, Vs solder. Other than requiring a specialized crimp tool, crimp
> connectors tend to be more uniform, faster to install, and
> mechanically stronger than the solder type. Properly adjusted cable
> prep tools (strippers) really speed things up and present identical
> cable ends to the connectors with the proper dimensions. Nearly
> identical crimp tools can be found with widely varying prices. One
> crimp tool with two sets of inserts can cover cables from RG-58
> through RG-8 (LMR-400) sizes. Depending on the vendor, nearly all
> connectors for these cables are available in solder or crimp versions.
>
> NOTE The RG designation has not been a specification for many years.
> It simply refers to cable sizes. Nothing more.
>
> So the question is, why would the average, or typical ham need
> anything other than the crimp, or solder, UHF connector?
>
> A SIDE NOTE: on weather proofing: There are several approaches to
> weatherproofing. One uses vinyl electrical tape wound sticky side out
> over the connectors, to keep the weatherproofing material (coax seal,
> various self vulcanizing tapes, and "flooded" heat shrink tubing)
> from sticking to the connector Flooded heat shrink tubing has a layer
> of hot melt glue on the inside. If you don't want the glue to stick to
> the connector, a film of Silicone grease or mold release agent, will
> allow for a seal without the glue sticking to the connector. Just
> don't get any on the coax jacket. Me? I make sure it's all clean and
> bond to the whole works.
>
> By bonding to the coax jackets and the connectors, the flooded heat
> shrink tubing makes for a very strong mechanical connection.
>
> One other comment: In over 55 years as a ham, I've only seen two bad
> connectors from Amphenol. I can't say that for the few "brand
> unknown", I've purchased from swaps.
>
> 73
>
> Roger (K8RI)
>
>
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