[TowerTalk] RE: N connectors

Tue Sep 9 14:45:01 EDT 2003

One of the referenced posts from Tom said:
 >I am very interested in the claims that the much smaller pin of the
N, and the much smaller spacing from the conductor to ground can
handle more current and voltage than the larger pin and larger
spacing of the UHF connector.

 >I am especially interested because that runs contrary to my
experience and the experience of many others that I know over the
past 30 years.

 >All hyperbole and conjecture aside, please explain the mechanism
that allows a smaller conductor to safely dissipate more heat, or
have less surface resistance as frequency is increased, than a
conductor several times larger.

 >Also, please explain the mechanism that allows a much smaller air
gap to hold off more voltage than a larger airgap.

As Chuck pointed out in an earlier post, the UHF does have a larger 
diameter center conductor and, as a result, can carry more current, which I 
imagine is reflected in the appropriate RMS current ratings, if published.

Another practical power handling consideration would be the dissipation 
capability of the coax's center conductor, which, after all, is smaller 
than the pin of the UHF and is totally surrounded by plastic to boot.  I 
would think that the dielectric in the connector and the dielectric in the 
coax would be comparable in thermal resistivity.  The big difference would 
be the ohmic loss in the actual mating surface, and, in a high SWR 
situation, if the connector's at a current maximum, it's gonna cook.

However, on the voltage standpoint, the mating surface of a UHF connector 
has a fairly short creepage path across the face of the socket, which, 
being across a solid surface with an air space above it, is probably 
responsible for the relatively low voltage rating, compared to a comparable 
gap in free air. The typical UHF connector also has a rougher metal surface 
with more bumps and edges, greatly reducing HV capability.  There's also a 
fairly large air gap when the connector is mated (depending on the 
connector, etc.).

The N connector, on the other hand, has all machined surfaces, particularly 
where the dielectric surfaces mate.  The smoother surface finish and closer 
machined tolerances (necessary to get decent performance at higher 
frequencies) could account for the higher voltage rating.

Also, bear in mind that the "spec sheet guaranteed" voltage may not be what 
the connector will actually take. The UHF connector's 600V is a level that 
is suspiciously close to various electrical code thresholds (much as the 
voltage ratings for wire are 300 or 600V... standard house wire can easily 
hold off several kV, but is only rated to 600V).  I use drilled out and 
modified PL-259/SO-239 combinations for voltages up to 50-60 kV (in oil).

At 01:15 PM 9/9/2003 -0700, Hsu, Aaron wrote:
>The subject of N vs PL-259 comes up every year or so.  A missed presence 
>on this reflector (IMHO) and well respected engineer, W8JI, is a staunch 
>supporter of UHF connectors.  Here's a couple of archived posts I found by 
>doing a quick search of the TowerTalk archives using the following keys: 
>"+n +uhf +towertalk +connector +w8ji", I
>
>http://lists.contesting.com/_towertalk/2001-April/037711.html
>http://lists.contesting.com/_towertalk/2001-April/037724.html
>
>Unfortunately, Tom came under several personal character attacks and left 
>the list not long after this thread.  He's still around, just not as 
>active on the lists.
>
>73,
>
>   - Aaron, NN6O
>
>
>-----Original Message-----
>From: Dino Darling [mailto:k6rix at arrl.net]
>Sent: Monday, September 08, 2003 11:53 PM
>To: towertalk at contesting.com
>Subject: Re: [TowerTalk] N connectors
>
>
>There sure is a lot of speculation out here when it comes to
>N-Connectors!  Its almost embarrassing!
>
>N-Connectors are SUPERIOR to the UHF connector for many reasons...
>1- Weather proof
>2- Constant impedance to 11 Ghz
>3- Constant impedance.
>4- Able to withstand HIGHER voltages!  (1500 volts peak)
>http://www.amphenolrf.com/products/typen.asp
>
>UHF connectors are inferior...
>1- They are NOT weather proof!
>2- Only good to about 300Mhz.
>3- Not constant impedance
>4- Can't take as high of a voltage like the N can! (500 volts peak)
>http://www.amphenolrf.com/products/uhf.asp
>
>Ham Radio Outlet in Anaheim and Burbank sells an N-Connector that mounts
>like a PL-259 and employs a captured center pin.  Gold and silver!  They
>are not cheap, but worth every penny!  714-533-7373 (Anaheim)  These
>connectors are made by Andros Mfg out of New York...
>http://www.androsmfg.com/products.htm
>
>
>At 07:31 AM 09/05/2003 -0600, you wrote:
> >Hi All,
> >I was told that "N" connectors fail at full legal power levels.
> >Is this true? What is your experience?
> >Thanks.
> >73! Vitaly (VE6JO)
> >
> >_______________________________________________
>
>
>Dino...k6rix at arrl.net
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk at contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk