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Re: Source for F to N/SO239 Adapters



If impedance of connectors doesn't matter to most amateurs than that is why
they are called "amateurs."

I'm tempted to send only the line above as I think it sums things up pretty
well, but I feel I need to go on (yes, I know brevity is the soul of whit).

Anyhow, connectors ARE made with impedance in mind by manufacturers (a 75
Ohm SMB is much different than a 50 Ohm SMB - but most hams have no idea
what an SMB is anyhow....).  And it is crucial.  The impedance of coax has
everything to do with the distance between the center conductor and the
shield.  That and the electrical characteristics of the dielectric are the
crucial factors.  Properly made connectors will effectively match that of
the cable with little impedance discontinuity.

Now your point about the connector impedance in the case of the 2880 is
quite correct.  It isn't important.  As someone else pointed out, it really
makes no difference to put a 50 Ohm connector on the 2880 because the 2880
was designed to work in a 75 Ohm system anyhow!  Well, that's a very good
point and with the signal levels and all involved an SWR of 1.5 at the 2880
to coax interface isn't gonna make much difference.

The reason why most hams don't care about connector impedances is that they
don't matter for  lower frequencies.  Shoot, at 160 M, you can use wire nuts
if you like and you won't see any problems!  However, when you venture into
the microwave region and extreme weak signal regions, your darn right
connector impedances are important!

I guess being an RF engineer at one point in my life made me into a purist.

73,

Jon
NA9D


on 2/27/01 12:19 AM, Lonnie (NT6B) at nt6b-vk7lm@dreamsoft.com wrote:

> Hello Jon....what you say is true in a sense and for one application, and
> it may be for some odd configurations where specialty connectors are
> required by design, coax etc but it doesn't apply for the connection that
> we are talking about as I said.....the "F" connector.  When we go to
> purchase a connector as amateurs we don't ask for anything except a
> connector for such and such a coax size, type etc because they are all 50
> ohms except one "N" connector and the PL-259 which has no family to relate
> to.     Yes, I have seen the connector that you describe...it is the UG-94A
> but that doesn't apply here ...Almost all connectors can be used for any
> feedline that is desired whether 50-51-52-53.5-62-75-82-93 or 125 Ohms
> depending on the adapter for the connector, availability, size of coax or
> hardline and the connection that it is made to mate to, etc., so the
> impedance importance of the connector is meaningless to most of us amateurs
> and especially in the situation of the 2880 wouldn't you agree?
> 
> 73's.....Lonnie  (NT6B)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Jon Ogden wrote:
>> on 2/26/01 11:42 AM, Lonnie (NT6B) at nt6b-vk7lm@dreamsoft.com wrote:
>> 
>>> Note the Input side or the top of the 2880?...."N" connector or for some,
>>> "50" ohms...Connectors in and of themselves are not rated in ohms, only
>>> "Type" such as "F", "N", "PL259", "BNC", "SMA" etc. Whatever design
>>> features of the output requiring 75 ohm coax (Through a "F" connector) is
>>> meaningless for us using the 2880.
>> 
>> This is NOT correct.  Connectors most certainly DO have impedances.  The
>> only one that does not is the PL-259 as it is a variable impedance connector
>> (there may be others as well).  But have you ever seen a 75 Ohm N-connector?
>> They sure do exist and if you try to mate a 50 Ohm male to a 75 Ohm female
>> you will destroy the 75 Ohm female as the center contacts on the 75 Ohm N
>> connectors are narrower.
>> 
>> Connectors do indeed have impedance assigned to them!  In fact, one of the
>> most crucial specs that manufacturers put on them is the VSWR specs.  This
>> is meaningless if they don't have an impedance.
>> 
>> 73,
>> 
>> Jon
>> NA9D
>> 
>> -------------------------------------
>> Jon Ogden
>> NA9D (ex: KE9NA)
>> 
>> Member:  ARRL, AMSAT, DXCC, NRA
>> 
>> http://www.qsl.net/ke9na
>> 
>> "A life lived in fear is a life half lived."
> 


-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Member:  ARRL, AMSAT, DXCC, NRA

http://www.qsl.net/ke9na

"A life lived in fear is a life half lived."

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