[Elecraft] loss of RX sensitivity

[donovanf at starpower.net]

If you have a vector network analyzer you'll discover that BNC 
connectors aren't all that great at VHF and above, l oss and 
impedance vary with connector axial alignment because the bayonnet 
shell doesn't support aligh the connector body very well. Strain relief 
is extremely important with BNC connectors. TNC connectors are 
far superior but not widely used. 


While professionally installed N connectors have superb RF 
characteristics, all too often they're improperly installed -- even by 
professionals -- leading to damaged connectors if the male pin is 
misaligned, or unreliable contact if the pin or socket depth is just a 
few millimeters less than the manufacturers specification. I use 
only captive pin male N connectors, avoiding the most severe 
problems. I never use female N connectors on cables, the N sockets 
are much too fragile. 


Its hard to beat high quality silver plated UHF connectors at HF and 
6 meters. But its important to use a tool to tighten them. That's a 
small price to pay for a very reliable connector. 


73 
Frank 
W3LPL 



----- Original Message -----

From: "Walter Underwood" <wunder at wunderwood.org> 
To: elecraft at mailman.qth.net 
Sent: Monday, September 17, 2018 11:45:10 PM 
Subject: Re: [Elecraft] loss of RX sensitivity 

The next time someone challenges me on why I only use BNC and Type N connectors, I’m going to send them this entire discussion. 

wunder 
K6WRU 
Walter Underwood 
CM87wj 
http://observer.wunderwood.org/ (my blog) 

> On Sep 17, 2018, at 4:41 PM, Don Wilhelm <donwilh at embarqmail.com> wrote: 
> 
> Andy, 
> 
> The PL259 to SO239 connector "end face" contact is provided only by pressure - it is not a sliding contact as you would find in a BNC or an N connector. The pressure is provided only by the tightening of the threaded portion of the PL259. 
> 
> I ask you - just how much resistance can be expected if you just touch two ends of wires together without further positive contact? 
> 
> The "insulating spacer" is any oxidation on either the SO239 or the PL259. That is why I like silver plated UHF connectors. They may look a bit corroded, but the silver oxide is conductive even though it can appear brown or black. If you are shopping for UHF connectors at hamfests, avoid all those nickel-plated ones that a not Amphenol, but flock to those that are oxidized, and silver plated with Mil Spec designations on them. 
> 
> 73, 
> Don W3FPR 
> 
> On 9/17/2018 6:39 PM, ANDY DURBIN wrote: 
>> " the threads of the PL259 are providing the only contact with the SO239" 
>> In the connectors that you are mating how do you prevent contact between the end face of the PL259 body and the end face of the SO239 body? You would need an insulating spacer for your statement to be true. 
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