[opendtv] Re: F-Type Connectors Now used past 2GHz What Standard?

  • From: JimDeFilippis <jim.defilippis@xxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sun, 13 Feb 2005 19:41:30 -0800

Colin,

Hey how's things going in OZ?  Just saw this post.  Did some work on F 
connectors back in 1997.  We were trying to use existing cable and MATV 
cable/connectors in a satellite distribution using band stacking.  We 
found that the cable and male connectors can go as high as 4GHz with 
return loss (the critical parameter for digital signal distribution) at 
15dB and above.   The problem is the female F connector.  In order to 
accomodate the variety of center conductor OD's, the design is a folded 
box type.  While this makes a good mechanical DC connection, it falls 
apart above 2GHz.  I experimented with different female F connector 
designs using a split center barrel type connection.  This worked fine 
up to 4GHz (beyond 4GHz there are coax cable issues).  I found a 
company that made a precision F female connector (Gilbert Engineering 
in Gilbert AZ, US).  The drawback is that while it will mate with both 
RG59 and RG6 cables, once you put a RG 6 into the connector it splayed 
the center barrel so that RG 59 would not work anymore.

I have more data if you'd like.  I also worked with an excellent RF 
engineer who resides in Sydney, John Sullivan.

Regards,

Jim DeFilippis

P.S.  Are you going to the ITU SG6 meetings this April?  We are going 
to try to put 720p50 forward for inclusion.  Unfortunately Spencer 
Lieng has cancelled 6P.  Do you have any information regarding the 
position of 720p50 in Australia?  jd


On Feb 13, 2005, at 4:47 AM, Colin R Wright wrote:

> Hi everyone,
>
> To change the subject from MPEG licensing and the FCC, there might be
> someone out there able to help us with a question we have about
> F-connectors.
>
> One of our Australian Standards work groups is updating the standard 
> for TV
> (MATV) distribution systems. This covers terrestrial, cable and 
> satellite
> distribution of analog and digital television and sound signals in 
> single
> and multiple (hi-rise apartment) domestic dwellings.
>
> The current standards for F-connectors appear to be IEC 60169-24 and
> ANSI/SCTE 01 1996 but they seriously lack necessary detail (See below).
> Since F-connectors are now being used for systems going up to 2150MHz 
> (Some
> say to 3GHz), the tolerances given in the old standards don't seem to 
> stack
> up for suitable return loss etc.
>
> To provide improved return loss and extended frequency response we are
> suggesting some  recommendations-
>
> 1. All F-Type male connectors shall use cable with an inner solid core
> conductor or have an integral inner pin, the diameter of which is not 
> less
> than 0.85mm and not more than 1.15 mm.
> 2. The characteristic impedance of these connectors be 75 ohms (plus 
> minus
> ?) and that the return loss of a mated pair be better than 20dB over 
> the VHF
> and UHF bands and better than 14dB in the range 950MHz to 2150MHz.
> 3. The contact reliability of a F-type male-female connection  shall 
> not
> exceed 20 milliohms as measured by the total series resistance of the 
> inner
> and outer.
> Note: Specifications 2 and 3 shall be met after 10 
> insertions/extractions
>
> Some Background:
>
> IEC 60169-24 was published in 1991 when the connector was generally 
> used for
> analog signals over a more restricted frequency range. It is now also 
> being
> used for digital signals with a frequency range extending above 2GHz.
> Although IEC 60169-24 states that it is "typically for use in 75 ohm 
> cable
> distribution systems", that standard does not include any return loss
> requirements; it includes only mechanical dimensions.
>
> The return loss of the coaxial connectors used throughout the 
> distribution
> system has become very important, now that they are used over a wide
> frequency range.  Intrinsically the return loss of the male part of 
> most "F"
> connectors is very good because it consists basically of the coaxial 
> cable
> centre conductor and insulation.
>
> Unfortunately however IEC 60169-24 allows the centre pin diameter to 
> have
> the very large diameter range of 0.51 to 1.69mm in order to accommodate
> variations in the centre conductor diameter of different sizes of 75 
> ohm
> coaxial cable and also variations in the dielectric constant of the 
> cable
> insulation (eg. solid or foamed  polyethylene). Because of this large 
> centre
> pin diameter range the centre female part of the socket is depicted in 
> IEC
> 60169-24 as a pair of "fingers".
>
> However a socket with such a structure probably would have either a
> significant roll off at frequencies above about 1GHz and/or poor return
> loss.
>
> Noting that the type of cables now used for antenna distribution 
> systems
> normally have a centre conductor diameter of  1.0 +/- 0.15mm many 
> modern "F"
> connectors use a different structure for the centre female socket with 
> a
> restricted range.  Such connectors can have very good return loss 
> figures
> over the full frequency range required by this specification.
>
> The related American standard ANSI/SCTE 01 1996 recommends that the 
> centre
> conductor have a maximum diameter of 1.30mm but what tolerance and 
> which
> cable types?
>
> ======================
> Someone out there should be able to advise us.
>
> Regards from downunder,
> Colin Wright
> Seven Network Australia
> 38-42 Pirrama Road
> Pyrmont (Sydney) NSW 2009
> AUSTRALIA
> cwright@xxxxxxxxxxxx
> colinrwright@xxxxxxxxxxxxxxx
> Tele: +61 2 8777 7710
> Cell:  +61 (0) 419 477 777
>
>
>
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