[time-nuts] TNC connectors

Robert Darlington rdarlington at gmail.com
Tue Jun 23 10:34:51 EDT 2009


I just bought two of these antennas from Bob (fluke.l) and asked him to
throw in adapters from TNC on the antenna to female F so I can use ordinary
75 ohm cable TV coax from rat shack.  He charged an extra $5 for the
adapters which I think is a pretty good deal.  Still waiting on delivery so
I don't know for sure what was thrown in the box but I'll let you guys know
if there was a problem.

-Bob

On Tue, Jun 23, 2009 at 7:50 AM, David C. Partridge <
david.partridge at dsl.pipex.com> wrote:

> Hmmm now all I have to do is find a TNC connector to fit FT100 (or RG6)
> without paying 5 times thet value of the connector for shipping - or just
> use RG58 as I've got BNC for this, and can easily get TNC for it too.
>
> Thanks to all
> Dave
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Dave Baxter
> Sent: 23 June 2009 13:40
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] TNC connectors
>
> > Message: 3
> > Date: Tue, 23 Jun 2009 07:54:02 -0400
> > From: Chuck Harris <cfharris at erols.com>
> > Subject: Re: [time-nuts] TNC connectors
> > To: Discussion of precise time and frequency measurement
> >       <time-nuts at febo.com>
> > Message-ID: <4A40C25A.7080403 at erols.com>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > Dave Baxter wrote:
> >
> > > Doing that with BNC's will lead to a flaky connection, as
> > the centre
> > > pin on the 75r ones is much smaller.  The other way round (50r plug
> > > into 75r
> > > socket) will damage the socket.  As TNC's are very similar
> > to BNC's ???
> >
> > You are thinking of the incompatibility between 50 ohm and 75 ohm *N*
> > connectors.
> >
> > 75 ohm BNC are use the same center pin hardware as 50 ohm BNC.  The
> > only difference is in the white plastic (teflon) insulator.  In the 50
> > ohm BNC, the center insulator goes all the way to the tip of the
> > center pin.  In the 75 ohm BNC, the center insulator is abbreviated.
> >
> > HP/Agilent uses 75 OHM BNC's on several of its devices that have
> > switchable impedances.  For example, the 3586C.
> >
> > -Chuck Harris
>
>
> Indeed looking as some more data sheets.
>
> However, I have somewhere in the deed box at home, some Ex BT BNC's, marked
> up as 75 Ohm, that have very much smaller center pin's than the common or
> garden 50r types, as well as less plastic in there too.
>
> We once had a Novell computer network in the office, that used 93r coax
> cable, and 50r BNC's, at 100MBPS.  Using Thomas Conrad cards I seem to
> remember.   We still have the real of 93r coax.
>
> (It was very much faster end to end, and much more stable than the TCP/IP
> based Microsoft network we have now, but I digress.)
>
> In general, yes indeed size for size, 75r coax will be less lossy than 50r
> types, but if the RX does present a nominal 50r load, they may be some
> potential issues.  However, if the antenna is an active type, it's probably
> not worth fussing over.  Enough people have used what's recomended I guess
> and found no problems.  Just use good quality cable, not the so called "Low
> loss" TV coax.  I'd guess the foam dielectric "Satelite LNB" cable would
> do.
> It fit's 'F' connectors too.
>
> Cheers All.
>
> Dave B.
>
>
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