[Elecraft] [KX3] BNC connector oddity on KX3

Wed Feb 21 16:14:14 EST 2018

If only Dale's comment were true... 

As far as I know all 75 ohm BNC connectors made in the USA use 
the correct diameter center pin. 

However... 

This is NOT true for many import connectors and adapters, even 
modern high bandwidth 75 ohm import connectors often have serious 
design and quality control problems. I've found three categories of 
serious reliability problems with import 75 ohm BNC connectors 
and adapters. 

- much smaller center pin diameter, they're copies of 40 year old 
obsolete "made in USA" 75 ohm BNC connectors 

- center pin slightly too small in diameter -- a quality control or 
manufacturing problem that causes unreliable connections. 

- tapered center pin with incorrect diameter over most of its length 
that causes unreliable connections 

Don't believe me? I have modern import connectors with all three 
types of problems. 

73 
Frank 
W3LPL 

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

From: "Chris Cox, N0UK" <chrisc at chris.org> 
To: "Dale Parfitt" <parinc1 at frontier.com> 
Cc: "Chris Cox, N0UK" <ygsoftrock40 at chris.org>, kx3 at yahoogroups.com, elecraft at mailman.qth.net 
Sent: Wednesday, February 21, 2018 4:25:15 PM 
Subject: Re: [Elecraft] [KX3] BNC connector oddity on KX3 

Indeed - i didn't know that. Thanks for the info, Dale. 

SO, if you have an OLD 75 Ohm BNC plug... :-) 
-- 
73 Chris Cox, N0UK, G4JEC 
chrisc at chris.org 

On Mon, 19 Feb 2018, Dale Parfitt wrote: 

> The center pin on 50 Ohm and 75 Ohm BNC’s has been identical for perhaps 20 
> years. The 75 Ohm impedance is now attained through modification of the 
> connector’s dielectric structure. 
> 
> 
> 
> Regards, 
> 
> 
> 
> Dale W4OP 
> 
> 
> 
> From: KX3 at yahoogroups.com [mailto:KX3 at yahoogroups.com] On Behalf Of 'Chris 
> Cox, N0UK' ygsoftrock40 at chris.org [KX3] 
> Sent: Monday, February 19, 2018 12:29 PM 
> To: rich hurd WC3T 
> Cc: kx3 at yahoogroups.com; elecraft at mailman.qth.net 
> Subject: Re: [KX3] BNC connector oddity on KX3 
> 
> 
> 
> 
> 
> Not saying this IS the problem but i fth emale BNC plug is a 75 ohm 
> connector, its centre pin will be a narrower diameter and may only be 
> making intermittent contact with the female socket on the KX3. 
> 
> -- 
> 73 Chris Cox, N0UK, G4JEC 
> chrisc at chris.org 
> 
> On Mon, 19 Feb 2018, rich hurd WC3T rich at wc3t.us [KX3] wrote: 
> 
> > Hi, 
> > 
> > I had an oddity with hooking an antenna to the BNC connector on my KX3 
> that 
> > happened enough times to be chalked up to something other than random 
> > chance. Looking for opinions on whether my solution aligned to your 
> > experience(s). 
> > 
> > I have a complete station - a KX3, a PX3, and a KXPA100. The KXPA100 is 
> > connected via a Cables On Demand connector with a PL259 on one end and a 
> > BNC connector on the other end. All other interface cables are Elecraft 
> > standard. 
> > 
> > This is NOT the first BNC connector that I've used. Prior to this last 
> > acquisition I had a couple of other BNC to PL259 jumpers that I was using, 
> > and the usual smattering of connectors and adapters in the junque box. 
> > 
> > No matter which one I used, If I removed the BNC connector from the rig 
> > (maybe to go portable, for example, or the last time it was because I 
> > installed Eneloop Pro batteries to the internal battery holders) I would 
> > put everything back together, and then would have severe - almost 
> > debilitating - signal attenuation when I got the rig fired up. If I 
> > twisted and spun the BNC connector on the jack, it would improve, and then 
> > get bad again more often than not. It could take up to 20 minutes to get 
> > everything "dialed in" so that the signal was appearing again. God help me 
> > if I accidentally moved something after that. And of course, while all 
> > this was happening the ATU was having fits, with 99:1 SWR readings and the 
> > amp was going offline; all kinds of weirdnesses. After things calmed 
> > down. the ATU behaved itself, the amp stopped being pouty, and all was 
> then 
> > good. 
> > 
> > Thankfully, now that I have the Cables On Demand product, things seem to 
> > have quieted down - although I still don't disconnect without provocation. 
> > :) Though I'm desperately afraid of when I start to go mobile after the 
> > snow melts and the weather gets nice again. :) Hope I can get my IC706 
> > fixed and back in service as my base station before that occurs. 
> > 
> > My question was going to be in desperation more than anything else if this 
> > last cable didn't work, but thankfully, that's been the only cable vendor 
> > that I trust for any of my specialized cables and they haven't failed me 
> > even with this one. 
> > 
> > Are BNC connectors that finicky? Is it possible that I just had a bad 
> > batch of low quality jumpers? I'm just wondering if anyone else has had 
> > excessive fiddling with their BNC connections. 
> > 
> > --- 
> > 72, 
> > Rich Hurd / WC3T / DMR: 3142737 
> > PA Army MARS, Northampton County RACES, EPA-ARRL Public Information 
> Officer 
> > for Scouting 
> > Latitude: 40.761621 Longitude: -75.288988 (40Â°45.68' N 75Â°17.33' W) 
> Grid: 
> > *FN20is* 
> > 
> 
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