[TowerTalk] Selecting Coax connectors

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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