Sheffield & District Wireless Society

///////////////////////////////////////////
Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT
http://sheffieldwireless.org/2017/08...in-pdf-format/


PDF File versions for the Foundation Course





Fslide01-Introduction and Registration

Fslide02-Nature-of-Amateur-Radio

Fslide03-Safety

Fslide04-Licence-Conditions

Fslide05-Transmitters-and-Receivers

Fslide06-Propagation

Fslide07-Feeders-and-Antennas

Fslide08-EMC Fslide09-Technical-Basics

Fslide09-Technical-Basics

Fslide10-Repeaters-and-CTCSS

In message , S&DWS via
rec.radio.info Admin writes

Sheffield & District Wireless Society

///////////////////////////////////////////
Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT
http://sheffieldwireless.org/2017/08...in-pdf-format/


PDF File versions for the Foundation Course

Please may I offer one correction:

In 'Antennas & Feeders', the information about BNC connectors, you are
warned
"Take care not to mix incompatible 50 and 75 Ohm versions which have
different inner pin sizes".

This is NOT totally correct. While the profile of the pins are slightly
different (the 50 ohm usually has a somewhat stubbier point), the
diameters are the same. The difference in characteristic impedance is
achieved by the amount of PTFE dielectric.

As a result, you CAN physically mate 50 and 75 ohm BNC connectors (both
sexes).
--
Ian

On 19/08/2017 09:32, Ian Jackson wrote:

Sheffield & District Wireless Society

///////////////////////////////////////////
Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT
http://sheffieldwireless.org/2017/08...in-pdf-format/

PDF File versions for the Foundation Course

Please may I offer one correction:

In 'Antennas & Feeders', the information about BNC connectors, you are
warned "Take care not to mix incompatible 50 and 75 Ohm versions which have
different inner pin sizes".

This is NOT totally correct. While the profile of the pins are slightly
different (the 50 ohm usually has a somewhat stubbier point), the
diameters are the same. The difference in characteristic impedance is
achieved by the amount of PTFE dielectric.

As a result, you CAN physically mate 50 and 75 ohm BNC connectors (both
sexes).

This is far too technical for a 'training scheme' that produces Fulls
who have to ask the question "USB/LSB? I'm confused!".


--
Spike

In message , Spike
writes
On 19/08/2017 09:32, Ian Jackson wrote:

Sheffield & District Wireless Society

///////////////////////////////////////////
Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT

http://sheffieldwireless.org/2017/08...aterial-in-pdf
-format/

PDF File versions for the Foundation Course

Please may I offer one correction:

In 'Antennas & Feeders', the information about BNC connectors, you
are warned "Take care not to mix incompatible 50 and 75 Ohm versions
which have different inner pin sizes".

This is NOT totally correct. While the profile of the pins are
slightly different (the 50 ohm usually has a somewhat stubbier
point), the diameters are the same. The difference in characteristic
impedance is achieved by the amount of PTFE dielectric.

As a result, you CAN physically mate 50 and 75 ohm BNC connectors
(both sexes).

This is far too technical for a 'training scheme' that produces Fulls
who have to ask the question "USB/LSB? I'm confused!".

Don't worry - I can also confirm that both impedances of BNC connectors
are totally compatible with both USB and LSB.



--
Ian

"Ian Jackson" wrote in message
...
In message , S&DWS via
rec.radio.info Admin writes

Sheffield & District Wireless Society

///////////////////////////////////////////
Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT
http://sheffieldwireless.org/2017/08...in-pdf-format/


PDF File versions for the Foundation Course

Please may I offer one correction:

In 'Antennas & Feeders', the information about BNC connectors, you are
warned
"Take care not to mix incompatible 50 and 75 Ohm versions which have
different inner pin sizes".

This is NOT totally correct. While the profile of the pins are slightly
different (the 50 ohm usually has a somewhat stubbier point), the
diameters are the same. The difference in characteristic impedance is
achieved by the amount of PTFE dielectric.

As a result, you CAN physically mate 50 and 75 ohm BNC connectors (both
sexes).

when I was newly licensed and poor I used 75 ohm TV coax and belling lee
connectors on HF and got away with it .......

In message , Jimbo
writes

"Ian Jackson" wrote in message
...
In message , S&DWS via
rec.radio.info Admin writes

Sheffield & District Wireless Society

///////////////////////////////////////////
Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT
http://sheffieldwireless.org/2017/08...aterial-in-pdf
-format/


PDF File versions for the Foundation Course

Please may I offer one correction:

In 'Antennas & Feeders', the information about BNC connectors, you are
warned
"Take care not to mix incompatible 50 and 75 Ohm versions which have
different inner pin sizes".

This is NOT totally correct. While the profile of the pins are slightly
different (the 50 ohm usually has a somewhat stubbier point), the
diameters are the same. The difference in characteristic impedance is
achieved by the amount of PTFE dielectric.

As a result, you CAN physically mate 50 and 75 ohm BNC connectors (both
sexes).

when I was newly licensed and poor I used 75 ohm TV coax and belling lee
connectors on HF and got away with it .......

For 43 years, my day job was cable TV - so I've rarely used anything
other than 75 ohm coax!

Some cable TV trunk coax used to be (as one of my bosses put it) "as
thick as a horse's prick". Unfortunately, it was not too convenient for
home use.

But as for BNC connectors, they are essentially the same as the innards
of 50 ohm N-connectors. You can mate a female BNC with a male 50 ohm N.

However, note that you can't inter-mate 50 and 75 ohm N-connectors, as
the 75 ohm has a much thinner pin.

A 50 ohm female in a 75 ohm male won't make contact (unless you put a
bit of wire inside the female receptacle). A 50 ohm male fully mated
with a 75 ohm female will splay the receptacle, and cause usually
permanent damage.



--
Ian

On 19/08/2017 09:32, Ian Jackson wrote:

This is NOT totally correct. While the profile of the pins are slightly
different (the 50 ohm usually has a somewhat stubbier point), the
diameters are the same. The difference in characteristic impedance is
achieved by the amount of PTFE dielectric.

An interesting snippet, Ian, thanks.

Perhaps time to remind all that BNC is Bayonet-Neill-Concelman
and not Bayonet Navy Connector, as M3s and M6s past and present and
other similar CBers maintain.

On 19/08/2017 09:52, Ian Jackson wrote:
Spike writes
On 19/08/2017 09:32, Ian Jackson wrote:

Sheffield & District Wireless Society

///////////////////////////////////////////
Foundation Course Material in PDF Format

Posted: 18 Aug 2017 04:04 AM PDT

http://sheffieldwireless.org/2017/08...aterial-in-pdf
-format/

PDF File versions for the Foundation Course

Please may I offer one correction:

In 'Antennas & Feeders', the information about BNC connectors, you
are* warned "Take care not to mix incompatible 50 and 75 Ohm versions
which have* different inner pin sizes".

This is NOT totally correct. While the profile of the pins are
slightly* different (the 50 ohm usually has a somewhat stubbier
point), the* diameters are the same. The difference in characteristic
impedance is* achieved by the amount of PTFE dielectric.

As a result, you CAN physically mate 50 and 75 ohm BNC connectors
(both* sexes).

This is far too technical for a 'training scheme' that produces Fulls
who have to ask the question "USB/LSB? I'm confused!".

Don't worry - I can also confirm that both impedances of BNC connectors
are totally compatible with both USB and LSB.

I doubt knowing that would help the woodentop Full.


--
Spike

On 19/08/2017 10:34, Jimbo wrote:
sexes).

when I was newly licensed and poor I used 75 ohm TV coax and belling lee
connectors on HF and got away with it .......


And it was standard on 145MHz. (QQV03-10 anyone?)

In message , Jeff writes

However, note that you can't inter-mate 50 and 75 ohm N-connectors,
as the 75 ohm has a much* thinner pin.
A 50 ohm female in a 75 ohm male won't make contact (unless you put
a bit of wire inside the female receptacle). A 50 ohm male fully
mated with a 75 ohm female will splay the receptacle, and cause
usually permanent damage.

The 50 & 75 ohm BNCs that I have in front of me at the moment have
identical pin dimensions.

Also the spec sheets on Amphenol's website show the pins as being the
same dimension.

Are there any drawings? If so, do they show the 50 ohm pin being
somewhat 'bull-nosed', while the 75 is more pointed - and the
differences in the PTFE dielectric 'sleeve'?


--
Ian