[Elecraft] loss of RX sensitivity

[Dave B]

Hi Jim.

Mostly, N connectors, BNC's, TNC's, SC and 7-16's.  And for the big
stuff, EIA flange connectors.  Plus some other weird stuff.  (3 lug
BNC's and such, to prevent the "wrong connection".)    The odd
appearance of the C connector on some US kit too.   Some "Spinner" 'BN'
series connectors to, also often seen in the European Broadcast industry
and some military.

A lot of US equipment also still use the various unique to the US
connectors, often seen on big Bird loads etc.  Not so common over hear.

That based on what I've seen on kit "being tested" at customers sites
over the last 28 years.

The only UHF series connector commercially used, that I've personally
seen in that time frame is on a very old design of screened room weld
crack detector, and it's a nightmare to use as it's always working loose.

To Charlie.

The threads have no part to play in the RF path on a UHF connector, it's
all down to the two outer mating faces being pressed together.  The
older (so called) MIL spec types, that had all the castelations at that
point were *MUCH* better because of it, as they sort of interlocked and
made a much better contact due to the metal to metal force
multiplication that results..   They also tended not to rotate relative
to each other so the retaining ring stayed tight.  Basic mechanical
design feature, missing on the modern versions, where the two parts can
rotate, even when the ring is (allegedly) tight.

The modern stuff with the 4 slots on the socket, and two bumps on the
plug, are just utter crap.  (Built down to a cost.)

I'm amazed that no maker has innovated gone back to the original design,
and fitted a crinkle spring washer behind the locking ring, so that
contact pressure can be maintained, and also helping to keep the threads
from working loose when subject to vibration...

But even then, they'd still only be of any practical use below 100MHz
due to the impedance mismatch issue.   (Originally for use below 30MHz.)

https://en.wikipedia.org/wiki/UHF_connector

Stick with BNC's, N's and if you have too, 7-16's.  They are all easy to
fit to cable with practice, no special tools needed unless you insist on
the crimp types, and then you *MUST* have the correct tooling for that
particular make of connector.

The pressure gland fitting types, are also easy to remove, clean up and
re-fit if a cable becomes damaged.

All it takes is some practice.  Buy some surplus ex-military patch
leads, and practice removing and refitting them.  After a few of each it
becomes very easy.

73.

    Dave G0WBX.


On 19/09/18 12:15, Jim Miller wrote:
> Hi Dave
>
> What does NATO use in place of pl259?
>
> Thanks!
>
> Jim ab3cv 
>
> On Sep 19, 2018, at 4:16 AM, Dave B via Elecraft <elecraft at mailman.qth.net> wrote:
>
> Wunder, I'll second you on that!
>
> Of all the 1000's of RF connectors I've assembled and used over the
> years for my own hobby and at work.  The venerable "UHF" series have
> always proved to be the nastiest most unreliable types ever.  Period.
>
> All my own personal radio kit, either get's them replaced (Sadly, not
> always an easy job) with a N or BNC (in one case, a TNC.)  Or a BNC (or
> N) adapter is securely fitted as a permanent fixture (including LocTite
> on the threads, in mobile/portable situations!)
>
> I also use BNC's at HF, as we do at work.   They can happily carry well
> over 150W at up to 220MHz even in the presence of some very bad VSWR's
> (6:1 or higher.)  Assemble them correctly and look after them
> physically, and they will last a lifetime.
>
> The UHF series are just plain unreliable.  It is no surprise that the
> military (NATO) don't use them any more.
>
> 73.
>
> Dave G0WBX (also G8KBV)
>
>
> ------------------------------------------------------------------------
>> On 18/09/18 19:45, elecraft-request at mailman.qth.net wrote:
>> Message: 1
>> Date: Mon, 17 Sep 2018 16:45:10 -0700
>> From: Walter Underwood <wunder at wunderwood.org>
>> To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
>> Subject: Re: [Elecraft] loss of RX sensitivity
>> Message-ID: <CEF1DF11-28D1-4409-8023-4C4CA0C81B4A at wunderwood.org>
>> Content-Type: text/plain;    charset=utf-8
>>
>> 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)

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