[Elecraft] BNC connector oddity on KX3

[rich hurd WC3T]

Thanks Don; I remember that we went over this earlier in the thread.

Highly unlikely that I had legacy stuff as I became a ham in 2015 and
acquired most of my stuff new.

I am inclined to think that it was more possibly an out of spec 50 ohm
connector or a manufacturing defect.  I've already worked on the finger
bending thing but I ageee that given my lack of success that I'd be best
served by spending the $47 and just buying a new assembly and replacing it.


I appreciate all the help and suggestions from all the Elecraft community.

On Fri, Mar 9, 2018 at 17:48 Don Wilhelm <donwilh at embarqmail.com> wrote:

> Rich,
>
> Since you have traced the problem to the contact between the female BNC
> and the male (yes your twisting and applying pressure confirms that is
> the problem).
>
> It is entirely possible that if you had some old cables made with old 75
> ohm BNC male connectors, that they could have enlarged the female pin
> causing it to become marginal when used with the 50 ohm male connectors.
>
> You may have success with a very slender tool to bend the 'fingers' of
> the female connector toward the center, but the best cure is to replace
> that connector.
>
> Before we get into another long discussion of 50 ohm and 75 ohm center
> pin diameters, let me say that modern BNCs use the same diameter center
> pin for both.
> That was not always true, so beware when buying older BNC jumpers at
> hamfest flea markets - the old ones could be old 75 ohm BNCs with the
> larger center pin.  Those less than 10 or 15 years old are OK.
> It may also be that *some* imported BNC connectors do not have the
> proper diameter.  For best results, buy only Amphenol connectors or
> other trusted brands.
>
> 73,
> Don W3FPR
>
> On 3/9/2018 11:13 AM, rich hurd WC3T wrote:
> > I've pretty much exhausted most of the permutations of my cables and
> > connectors.  The only persistent behavior is that if I apply slight
> > pressure to the side of the BNC connector where it plugs into the jack on
> > the KX3, or sometimes if I twist it and then apply slight pressure just
> so,
> > I see a jump in the noise floor and instead of the internal ATU wearing
> > itself out and giving up with a 9:1 or 7:1 SWR, it immediately tunes to
> 1.0
> > or 1.1.   I have removed/swapped all my the antenna leads.  I have four
> of
> > them, all Cables On Demand (Amphenol) manufacture.  I also have a number
> of
> > BNC to banana plug jacks, and even an MFJ-1899T.  If I replace the leads
> > without doing the twisting-and-slight-pressure thing, I lose the RF
> > connection; the S meter has no indications on it, and the noise floor is
> > nonexistent.
> >
>
-- 
72,
Rich Hurd / WC3T / DMR: 3142737
PA Army MARS, Northampton County RACES, EPA-ARRL Public Information Officer
for Scouting
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