[Milsurplus] question - on BNC RF connectors

Sun Sep 1 06:21:45 EDT 2013

Gene -

I am not sure what you are trying to say here. If there is indeed a 75 ohm
BNC, that I am still not convinced of, then the center contact both male and
female would be smaller in diameter than the 50 ohm versions, providing
everything else is identical. Just like in the N connector case, as the
impedance is determined by the outside diameter of the center conductor and
the inside diameter of the outer conductor along with the distance between
them and the dielectric used. As I mentioned previously, at HF frequencies,
and even low VHF, this is not even noticeable. 73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of W2HX
Sent: Saturday, August 31, 2013 6:57 PM
To: John Hutchins; Mike Feher
Cc: 'Milsurplus at mailman.qth.net'
Subject: Re: [Milsurplus] question - on BNC RF connectors

The other way will not work. Plus, because the female socket is a larger
diameter than the 50 ohm male, you will not have a good connection. Expect
diminished working frequency range.

73 Eugene W2HX

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of John Hutchins
Sent: Saturday, August 31, 2013 6:17 PM
To: Mike Feher
Cc: 'Milsurplus at mailman.qth.net'
Subject: Re: [Milsurplus] question - on BNC RF connectors

Group -

With the BNC connector Panel mount Female 75 Ohm will mate with a male
50 Ohm RG58C/U Pamona cable  just tried this out on my work table.
I am making up a few test fixtures, blocking capacitors, and such mounted in
little metal boxes needed for the signal generator to meet various receiver
alignment criteria.
Since we are talking about ~1/2" run length at most for the 75Ohm females
connector.  I do not think that a 50 Ohm load requirement for the signal
generator is going to suffer, that much of a miss-match.

Conclusion I have reached is that a 50 Ohm Male will mate with a 75 Ohm
Female.

Thanks for you assistance.
Hutch

On 8/31/2013 9:22 AM, Mike Feher wrote:
> I am not sure about that. N connectors definitely have different 
> diameter male and female sections and are not interchangeable without 
> either damage, or, an open circuit. However, from what I recall, BNCs 
> are interchangeable as the only difference between the two is the 
> dielectric loading within the connector. At low frequencies, the only 
> problem if they do mate would be a
> 1.5 to 1 impedance mismatch jump, not a big deal for most applications.
> Regards - Mike
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of J. Forster
> Sent: Saturday, August 31, 2013 10:02 AM
> To: John Hutchins
> Cc: Milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] question - on BNC RF connectors
>
> The real 50 and 75 Ohm BNCs do NOT intermate w/o damage. The center 
> connector pin is different.
>
> You should use what the generator has.
>
> -John
>
> ================
>
>
>> Group -
>> Have generators that are 50ohm  and 75ohm outputs respectively. 
>> Making blocking capacitor modules; and RMA ant simulator module to be 
>> used between the two different generators.  Do I use 50 Ohm BNC or 75 
>> Ohm BNC connectors? Or does it really matter.
>> Thanks
>> Hutch
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