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BNCs

Don't know where anyone got the idea that BNCs made for RG-8x we 75 ohm. I worked in the tv industry for many years and we used hundreds of BNCs that were made specifically for 75 ohm video. By the way, RG-59 not RG-79. Now days I build hundreds of cables for RF out of rg-58 and rg-8x BNCs and they use 50 ohm connectors not 75 ohm connectors. Remember that the impedance of coax is based on the ratio of the center conductor to the outer conductor and if you compare the 75 ohm connector you will see that the center pin is much smaller in diameter.
Anyone need 200 silver plated 75 ohm BNCs?

Art

KC7GF
Rf Stuff.com
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Jim Brown-10

Re: BNCs

On Sun,10/12/2014 6:32 PM, Acbross via Elecraft wrote:
> Don't know where anyone got the idea that BNCs made for RG-8x we 75 ohm. I worked in the tv industry for many years and we used hundreds of BNCs that were made specifically for 75 ohm video. By the way, RG-59 not RG-79.

While you are entirely correct that there are 75 ohm and 50 ohm BNCs,
the difference DOES NOT MATTER at HF, because the connector is such a
small fraction of a wavelength and the difference is small. 75 ohm
connectors were important with analog video because of the smearing of
very fine detail in a high res image, and because studios do lots of
patching and routing.

73, Jim K9YC
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Michael Walker

Re: BNCs

Thanks Jim

I was going to ask that exact question. For the amateur world, does it
make a difference if a 75 ohm connector is installed on a 50 ohm feedline.

You made it very clear for everyone. Thanks!

Mike va3mw

On Mon, Oct 13, 2014 at 12:15 PM, Jim Brown <[hidden email]>
wrote:

> On Sun,10/12/2014 6:32 PM, Acbross via Elecraft wrote:
>
>> Don't know where anyone got the idea that BNCs made for RG-8x we 75 ohm.
>> I worked in the tv industry for many years and we used hundreds of BNCs
>> that were made specifically for 75 ohm video. By the way, RG-59 not RG-79.
>>
>
> While you are entirely correct that there are 75 ohm and 50 ohm BNCs, the
> difference DOES NOT MATTER at HF, because the connector is such a small
> fraction of a wavelength and the difference is small. 75 ohm connectors
> were important with analog video because of the smearing of very fine
> detail in a high res image, and because studios do lots of patching and
> routing.
>
> 73, Jim K9YC
>
> ______________________________________________________________
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Peter g3smt

Re: BNCs

In reply to this post by Jim Brown-10

Jim,

It may not make a difference to performance on HF but it does matter
because the centre pins have different diameters of solder pot / crimp
barrel to match the cable impedance used. Also incorrectly mated
connectors risk damage to their centre connectors by forcing the
engagement. Use the correct connector for the cable in use.

73

Peter

G3SMT

On 13/10/2014 16:15, Jim Brown wrote:

> On Sun,10/12/2014 6:32 PM, Acbross via Elecraft wrote:
>> Don't know where anyone got the idea that BNCs made for RG-8x we 75
>> ohm. I worked in the tv industry for many years and we used hundreds
>> of BNCs that were made specifically for 75 ohm video. By the way,
>> RG-59 not RG-79.
>
> While you are entirely correct that there are 75 ohm and 50 ohm BNCs,
> the difference DOES NOT MATTER at HF, because the connector is such a
> small fraction of a wavelength and the difference is small. 75 ohm
> connectors were important with analog video because of the smearing of
> very fine detail in a high res image, and because studios do lots of
> patching and routing.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
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Michael Walker

Re: BNCs

Peter

The larger concern is that most of us have no way of being able to tell the
difference from a 50 ohm bnc to a 75 ohm bnc. We buy these online and at
flee markets, which is part of the reality.

Is there an easy way to tell them apart?

I assume the same is also true for N connectors which are essentially a BNC
but with a different casing.

Mike va3mw

On Mon, Oct 13, 2014 at 12:30 PM, Peter Torry <[hidden email]>
wrote:

> Jim,
>
> It may not make a difference to performance on HF but it does matter
> because the centre pins have different diameters of solder pot / crimp
> barrel to match the cable impedance used. Also incorrectly mated
> connectors risk damage to their centre connectors by forcing the
> engagement. Use the correct connector for the cable in use.
>
> 73
>
> Peter
>
> G3SMT
>
>
>
> On 13/10/2014 16:15, Jim Brown wrote:
>
>> On Sun,10/12/2014 6:32 PM, Acbross via Elecraft wrote:
>>
>>> Don't know where anyone got the idea that BNCs made for RG-8x we 75 ohm.
>>> I worked in the tv industry for many years and we used hundreds of BNCs
>>> that were made specifically for 75 ohm video. By the way, RG-59 not RG-79.
>>>
>>
>> While you are entirely correct that there are 75 ohm and 50 ohm BNCs, the
>> difference DOES NOT MATTER at HF, because the connector is such a small
>> fraction of a wavelength and the difference is small. 75 ohm connectors
>> were important with analog video because of the smearing of very fine
>> detail in a high res image, and because studios do lots of patching and
>> routing.
>>
>> 73, Jim K9YC
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
>
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Jim Brown-10

Re: BNCs

In reply to this post by Peter g3smt

On Mon,10/13/2014 9:30 AM, Peter Torry wrote:
> It may not make a difference to performance on HF but it does matter
> because the centre pins have different diameters of solder pot / crimp
> barrel to match the cable impedance used.

What matters is that the connector match the physical dimensions of the
cable so that it can be properly installed, and this is true regardless
of impedance.

> Also incorrectly mated connectors risk damage to their centre
> connectors by forcing the engagement. Use the correct connector for
> the cable in use.

Zo depends upon o.d. of the center conductor with the connectors mated,
and would be established by the o.d. of the female pin receptacle, not
the o.d. of the male tip. Although I have not studied the mechanical
Standard for 75 ohm BNCs, I would VERY surprised if the dimensions of a
proper 75 ohm connector would prevent it from mating with a proper 50
ohm connector. Have you studied such a spec? I'm quite active in
international Standards work (with the AES) and that sort of
incompatibility is something we make certain to avoid!

73, Jim K9YC
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Rick M0LEP

Re: BNCs

On Mon 13 Oct Jim Brown wrote:
> the o.d. of the male tip. Although I have not studied the mechanical
> Standard for 75 ohm BNCs, I would VERY surprised if the dimensions of
> a proper 75 ohm connector would prevent it from mating with a proper
> 50 ohm connector. Have you studied such a spec? I'm quite active in
> international Standards work (with the AES) and that sort of
> incompatibility is something we make certain to avoid!

It's certainly possible, given a 75 Ohm male connector and a 50 Ohn
female connector, to end up without good electrical contact on the
central conductor, especially if you're dealing with cheap plugs and
sockets. Been there, suffered the consequences.

--
73, Rick, M0LEP (KX3 #3281)

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w5tvw

Re: BNCs

In reply to this post by Michael Walker

YES!!!! The 75 ohm series are UG-260/U connectors, the 50 ohm series is
the UG-88/U. If they don't have this stamped into the rear barrel of
the connector, THEY ARE Counterfeits or JUST PLAIN TRASH!

There is a lot of "crap" parts available at hamfests these days! Be
careful what you buy!!

73,
Sandy W5TVW
On 10/13/2014 11:18 AM, Michael Walker wrote:

> Thanks Jim
>
> I was going to ask that exact question. For the amateur world, does it
> make a difference if a 75 ohm connector is installed on a 50 ohm feedline.
>
> You made it very clear for everyone. Thanks!
>
> Mike va3mw
>
>
> On Mon, Oct 13, 2014 at 12:15 PM, Jim Brown <[hidden email]>
> wrote:
>
>> On Sun,10/12/2014 6:32 PM, Acbross via Elecraft wrote:
>>
>>> Don't know where anyone got the idea that BNCs made for RG-8x we 75 ohm.
>>> I worked in the tv industry for many years and we used hundreds of BNCs
>>> that were made specifically for 75 ohm video. By the way, RG-59 not RG-79.
>>>
>> While you are entirely correct that there are 75 ohm and 50 ohm BNCs, the
>> difference DOES NOT MATTER at HF, because the connector is such a small
>> fraction of a wavelength and the difference is small. 75 ohm connectors
>> were important with analog video because of the smearing of very fine
>> detail in a high res image, and because studios do lots of patching and
>> routing.
>>
>> 73, Jim K9YC
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
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> Help: http://mailman.qth.net/mmfaq.htm
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>
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w5tvw

Re: BNCs

In reply to this post by Elecraft mailing list

The big difference of the 75 and 50 ohm connectors is the fit of the
connectors to the coax size, NOT the center pin size which is the same.
BNC connectors are really NOT "constant impedance" especially at VHF/UHF
frequencies like "proper" "N" series connectors are. This makes no
difference "impedance" wise on HF gear. I guess this is also why no one
has "standardized" on a better connector for the HF frequency range
instead of the PL-259/SO-239"impedance bumps"!

73,
Sandy W5TVW
On 10/12/2014 8:32 PM, Acbross via Elecraft wrote:

> Don't know where anyone got the idea that BNCs made for RG-8x we 75 ohm. I worked in the tv industry for many years and we used hundreds of BNCs that were made specifically for 75 ohm video. By the way, RG-59 not RG-79. Now days I build hundreds of cables for RF out of rg-58 and rg-8x BNCs and they use 50 ohm connectors not 75 ohm connectors. Remember that the impedance of coax is based on the ratio of the center conductor to the outer conductor and if you compare the 75 ohm connector you will see that the center pin is much smaller in diameter.
> Anyone need 200 silver plated 75 ohm BNCs?
>
> Art
>
> KC7GF
> Rf Stuff.com
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
> This list hosted by: http://www.qsl.net
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Jim Brown-10

Re: BNCs

In reply to this post by Rick M0LEP

On Mon,10/13/2014 10:34 AM, Rick M0LEP wrote:
> especially if you're dealing with cheap plugs and sockets.

From my work on the AES Standards Committee Working Group on
Connectors, I can tell you that junk and even counterfeit connectors are
the problem, not the nominal Zo. Junk connectors of any sort are a
constant source of problems. Only a fool buys anything but name brand
connectors. This applies to ALL connector types -- UHF, BNC, RCA, DIN,
XLR, 1/8-in, 1/4-in. For UHF, this means Amphenol. For XLR, RCA, 1/8-in,
and 1/4-in this means Switchcraft and Neutrik. For DIN, that means
Switchcraft and Preh. I don't work enough with BNCs to know the good mfrs.

73, Jim K9YC
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Jim Wiley

Re: BNCs

Jim -

Good quality BNC connectors can be had from Amphenol and AMP. I
normally use AMP crimp-type connectors for BNC applications, have
_never_ had one fail, and I purchase them by the hundreds. Takes only a
few seconds to install one. One other good supplier of RF connectors
is Kings. It has been a few years since I had to buy any, so I am
assuming these suppliers still exist.

Having the correct tools to install these connectors is not a luxury,
and yes, they are expensive. Here again, you tend to get what you pay for.

And you are correct, money spent on a good quality connector is never
wasted. On the other hand, money spent on a cheap connector is almost
always wasted.

- Jim, KL7CC

On 10/13/2014 10:03 AM, Jim Brown wrote:

> On Mon,10/13/2014 10:34 AM, Rick M0LEP wrote:
>> especially if you're dealing with cheap plugs and sockets.
>
> From my work on the AES Standards Committee Working Group on
> Connectors, I can tell you that junk and even counterfeit connectors
> are the problem, not the nominal Zo. Junk connectors of any sort are a
> constant source of problems. Only a fool buys anything but name brand
> connectors. This applies to ALL connector types -- UHF, BNC, RCA, DIN,
> XLR, 1/8-in, 1/4-in. For UHF, this means Amphenol. For XLR, RCA,
> 1/8-in, and 1/4-in this means Switchcraft and Neutrik. For DIN, that
> means Switchcraft and Preh. I don't work enough with BNCs to know the
> good mfrs.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
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Joe Subich, W4TV-4

Re: BNCs

In reply to this post by Jim Brown-10

> While you are entirely correct that there are 75 ohm and 50 ohm BNCs,
> the difference DOES NOT MATTER at HF, because the connector is such a
> small fraction of a wavelength and the difference is small.

I disagree ... *DO NOT MIX 75 and 50 Ohm connectors*. 50 Ohm male
connectors will split the center contact of a 75 Ohm female wile 75 Ohm
male connectors will not make reliable connection with the center
contact of a 50 Ohm female.

In general, a 75 Ohm center pin will not accept the center conductor of
50 Ohm cable and a 50 Ohm center pin can not be *reliably* attached
(either crimp or solder) to the smaller center conductor of 75 Ohm cable
due to the relative sizes.

73,

... Joe, W4TV

On 2014-10-13 12:15 PM, Jim Brown wrote:

Joe Subich, W4TV-4

Re: BNCs

In reply to this post by Jim Brown-10

> Although I have not studied the mechanical Standard for 75 ohm BNCs,
> I would VERY surprised if the dimensions of a proper 75 ohm connector
> would prevent it from mating with a proper 50 ohm connector. Have you
> studied such a spec?

Yes, I have used both in the TV stations - 50 Ohm for RF systems and
75 for video systems. The center pin (male) and contact (female)
*ARE DIFFERENT SIZE*. Forcing a 50 Ohm connector into a 75 Ohm socket
will split the center contact while putting a 75 Ohm connector into a
50 Ohm socket will result in insufficient tension on the center pin
(and unreliable contact).

73,

... Joe, W4TV

On 2014-10-13 12:45 PM, Jim Brown wrote:

> On Mon,10/13/2014 9:30 AM, Peter Torry wrote:
>> It may not make a difference to performance on HF but it does matter
>> because the centre pins have different diameters of solder pot / crimp
>> barrel to match the cable impedance used.
>
> What matters is that the connector match the physical dimensions of the
> cable so that it can be properly installed, and this is true regardless
> of impedance.
>
>> Also incorrectly mated connectors risk damage to their centre
>> connectors by forcing the engagement. Use the correct connector for
>> the cable in use.
>
> Zo depends upon o.d. of the center conductor with the connectors mated,
> and would be established by the o.d. of the female pin receptacle, not
> the o.d. of the male tip. Although I have not studied the mechanical
> Standard for 75 ohm BNCs, I would VERY surprised if the dimensions of a
> proper 75 ohm connector would prevent it from mating with a proper 50
> ohm connector. Have you studied such a spec? I'm quite active in
> international Standards work (with the AES) and that sort of
> incompatibility is something we make certain to avoid!
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Dave-7

Re: BNCs

In reply to this post by Joe Subich, W4TV-4

According to the specs in the RF Industires catalog, pages 7 and 14 in
the version I have here, the center pins of 50 ohm and 75 ohm BNC's
are indeed the same size: .053 +/-.001 inch.

The difference is Zo is generated by using dielectric in the 50 ohm
but none in the 75 ohm, and slight difference in the inside dimensions
of the plus and sockets.

It is a little hard to tell from the drawings whether or not you can
plug a 50 into 75, and vise versa, with no issues. Although the pins
are the same size, there is a slight difference in the inside
diameters and the depths of the two fittings are different. This is
complicated by the fact that the 50 and 75 ohm fittings use different
reference planes to make the measurements.

The catalog is available on the RF Industries web site.

73 de dave
ab9ca/4

On 10/13/14 1:32 PM, Joe Subich, W4TV wrote:

>
> > While you are entirely correct that there are 75 ohm and 50 ohm BNCs,
> > the difference DOES NOT MATTER at HF, because the connector is such a
> > small fraction of a wavelength and the difference is small.
>
> I disagree ... *DO NOT MIX 75 and 50 Ohm connectors*. 50 Ohm male
> connectors will split the center contact of a 75 Ohm female wile 75 Ohm
> male connectors will not make reliable connection with the center
> contact of a 50 Ohm female.
>
> In general, a 75 Ohm center pin will not accept the center conductor of
> 50 Ohm cable and a 50 Ohm center pin can not be *reliably* attached
> (either crimp or solder) to the smaller center conductor of 75 Ohm cable
> due to the relative sizes.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 2014-10-13 12:15 PM, Jim Brown wrote:
>> On Sun,10/12/2014 6:32 PM, Acbross via Elecraft wrote:
>>> Don't know where anyone got the idea that BNCs made for RG-8x we 75
>>> ohm. I worked in the tv industry for many years and we used hundreds
>>> of BNCs that were made specifically for 75 ohm video. By the way,
>>> RG-59 not RG-79.
>>
>> While you are entirely correct that there are 75 ohm and 50 ohm BNCs,
>> the difference DOES NOT MATTER at HF, because the connector is such a
>> small fraction of a wavelength and the difference is small. 75 ohm
>> connectors were important with analog video because of the smearing of
>> very fine detail in a high res image, and because studios do lots of
>> patching and routing.
>>
>> 73, Jim K9YC
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
> .
>

Dave-7

Re: BNCs

In reply to this post by Joe Subich, W4TV-4

According to the specs in the RF Industries catalog, pages 7 and 14 in
the version I have here, the center pins of 50 ohm and 75 ohm BNC's
are indeed the same size: .053 +/-.001 inch.

The difference is Zo is generated by using dielectric in the 50 ohm
but none in the 75 ohm, and slight difference in the inside dimensions
of the plugs and sockets.

It is a little hard to tell from the drawings whether or not you can
plug a 50 into 75, and vise versa, with no issues. Although the pins
are the same size, there is a slight difference in the inside
diameters and the depths of the two fittings are different. This is
complicated by the fact that the 50 and 75 ohm fittings use different
reference planes to make the measurements.

The catalog is available on the RF Industries web site.

73 de dave
ab9ca/4

On 10/13/14 1:32 PM, Joe Subich, W4TV wrote:

Peter g3smt

Re: BNCs

In reply to this post by Jim Brown-10

Hello Jim,

I quite agree that what matters is that the connector match the physical
dimensions of the cable.

Originally they didn't mate, 50 Ohm was 50 Ohm and 75 was 75.The pins
were different diameters, and there were warranty warnings to only use
the correct connectors with equipment such as the old Tek 475 scope. A
50 Ohm plug would damage a 75 Ohm socket.

Now modern BNC connectors don't quite make their correct impedance
characteristics but will physically mate with each other without
mechanical issue if made to IEC 169-8. The electrical characteristics
vary between the different impedances and one should be wary of the 93 R
variety. I understand in the US MIL-STD 348B is similar but doesn't
state the Zo.Then we have the far eastern manufacturers that appear to
be slightly different again.

All in all a bit of a nightmare so that was why I suggested being
careful in selection and using branded connectors from a reputable
manufacturer.

On the Elecraft front my Def Spec connector doesn't mate correctly with
the BNC socket on the rear panel of the K3.

I think I had better retire to a dark room.

73

PeterG3SMT

On 13/10/2014 16:45, Jim Brown wrote:

> On Mon,10/13/2014 9:30 AM, Peter Torry wrote:
>> It may not make a difference to performance on HF but it does matter
>> because the centre pins have different diameters of solder pot /
>> crimp barrel to match the cable impedance used.
>
> What matters is that the connector match the physical dimensions of
> the cable so that it can be properly installed, and this is true
> regardless of impedance.
>
>> Also incorrectly mated connectors risk damage to their centre
>> connectors by forcing the engagement. Use the correct connector for
>> the cable in use.
>
> Zo depends upon o.d. of the center conductor with the connectors
> mated, and would be established by the o.d. of the female pin
> receptacle, not the o.d. of the male tip. Although I have not studied
> the mechanical Standard for 75 ohm BNCs, I would VERY surprised if the
> dimensions of a proper 75 ohm connector would prevent it from mating
> with a proper 50 ohm connector. Have you studied such a spec? I'm
> quite active in international Standards work (with the AES) and that
> sort of incompatibility is something we make certain to avoid!
>
> 73, Jim K9YC

Myron WVØH

Re: BNCs

In reply to this post by Joe Subich, W4TV-4

All,

And while the pin/receptacle dimensions are important to maintain physical integrity, the characteristic impedance doesn't come into play unless you experience a "considerable" phase length such as a 30 degree discontinuity at a given frequency.

So at HF the phase length of the 70-50 Ω discontinuity experienced by a BNC connector (or any other impedance) is very short. Important at UHF, yes, important at HF, nope.

Myron WVØH
Printed on Recycled Data

> On Oct 13, 2014, at 12:36 PM, Joe Subich, W4TV <[hidden email]> wrote:
>
> and unreliable contact).
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k6dgw

Re: BNCs

In reply to this post by w5tvw

On 10/13/2014 10:42 AM, Sandy Blaize wrote:

> There is a lot of "crap" parts available at hamfests these days! Be
> careful what you buy!!

Had cable problems with P3 when I first got it. Bob, K6XX, at Elecraft
and who I know well called me and said [only slightly tongue-in-cheek]
they'd send me a replacement cable ... *if* I promised to cut the old
one in small pieces and bury it at the bottom of our trash can so it
never could appear at a ham swap. :-) I did.

If you want connectors that fit, and that work all the time, you'll need
to totally avoid the cheap stuff. I use only Amphenol coax connectors.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2015 Cal QSO Party 3-4 Oct 2015
- www.cqp.org

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Re: BNCs

In reply to this post by w5tvw

The practical answer is try to insert your coax into the bushing. RG-59 and RG8X are the same size and RG-58 is smaller. If RG-58 is sloppy in the bushing and RG-59 or RG8X fits then it is OK to use unless you are trying to get an exact match for micro-wave. If you are a micro-wave engineer you are more qualified than I, but for 6 meters and below the extremely small bump will not be noticeable. You are jousting windmills to avoid an impedence bump that you cannot see.

Willis 'Cookie' Cooke, TDXS DX Chairman
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart

On Monday, October 13, 2014 12:42 PM, Sandy Blaize <[hidden email]> wrote:

YES!!!! The 75 ohm series are UG-260/U connectors, the 50 ohm series is
the UG-88/U. If they don't have this stamped into the rear barrel of
the connector, THEY ARE Counterfeits or JUST PLAIN TRASH!

There is a lot of "crap" parts available at hamfests these days! Be
careful what you buy!!

73,
Sandy W5TVW
On 10/13/2014 11:18 AM, Michael Walker wrote:

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