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

[Jon Ogden <na9d-2@xxxxxxxxxxxxx>]

on 1/10/03 10:14 AM, Edward R. Cole at al7eb@ptialaska.net 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!

You're correct, Ed.  Although, I think a UHF could handle more power than an
N due to the much larger center pin.  The problem is that they are not a
constant impedance connector.  Yes, I am not crazy about them for much above
50 MHz.  For the average user on 2m, they are OK.  I don't know of many SSB
rigs though that use the PL-259 at 70cm.  The FT-847 has an N-connector for
70cm - not sure about the TS-2000.  I prefer N's for UHF work for sure.

>> 
>> 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.
> 
Agreed.  Running a KW above 1 GHz with an N-connector is pushing it.  I've
heard of them burning up in commercial applications with 2 KW total power at
900 MHz.    Agree on the rest too.

> 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.

Absolutely!  I am wondering as well if the original problem was due to water
leakage or mechanical stress.

73,

Jon
NA9D

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