Re: [amsat-bb] N connectors-failures?

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

Hi Guys:

At 11:26 PM 1/9/2003 -0600, Jon Ogden wrote:
>on 1/9/03 8:00 PM, Stan at stan@capecod.com wrote:
>
>> Avoid the 2 part N's above 222 MHz
>
>I would disagree with this.  They are certainly fine up through UHF (heck,
>even PL-259s will work OK at 440 MHz!).  I wouldn't use them about 1 GHz
>though.

I really dislike the so called UHF connector for use above HF.  Yes they
are "OK" if you are not demanding good impedance matching or high power
performance (>200, 300w).  But note the ham mfrs are even providing them as
ant. connectors on newer ham rigs for 430 MHz+.  No savy moonbouncer uses
UHF connectors on his 2m system.  Nuff said!  Want maximum performance then
use a good connector and cable! 
 
>> I use N connectors at legal limit at 222 MHz and below.
>> I will probably use a 7/16-DIN connector for the legal limit 902 and
>> 1296 MHz amps...
>
>I'd say that's probably overkill, certainly for 902.  Properly mated Ns can
>handle a lot of power.  The 7/16 is getting popular with a lot of guys even
>at HF.  It's just so large that it can be impractical.

Agreed, though using near kW power levels above 1000 MHz requires very
careful assembly of the N-connector to assure good impedance and
conductivity.  Bad construction will cause heating and failure, especially
at the center pin.   Many eme'rs are moving to the 7/16 conn. though they
are expensive.  I am using N-conn up thru 2 GHz and prefer either sma or
waveguide at higher freqs.

It occured to me that the connector failure indicated by the originator of
this thread may have come from a combination of mechanical stress by the
coax on the connector and possibly poor assembly or wx-sealing.  If the
coax is not secured by other than the connector, that places a lot of
stress on the connector.  Always tie the connector to a support near the
connector to relieve any force on it.  

Most failure of feedlines I have experienced was due to wx exposure.  I did
have a technician support a 100-foot run of 1/2-inch heliax by the
connector once and the weight pulled the connector apart!  Amazing what
people think about when installing stuff!  This guy obviously didn't.

GL
Ed - AL7EB

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