[Amps] "N, " "TNC" and "BNC" connectors are rated at 500 Watts and work a...

[TexasRF at aol.com]

N connector intermod causes:
 
What comes to mind is connector contact resistance. All metals, including  
silver have some resistance. The larger the center pin and shield 
connection,  the lower the resistance. Type N connectors have the same small diameter 
center  pin as a BNC connector.
 
With the high peak power associated with digital signal transmission, there 
 will be a small amount of heat generated in the contact resistance. This 
heating  will cause a very small instantaneous change in the loss of the 
connection as  the peak power of the complex waveform increases and descreases. 
A change such  as this would introduce a non linearity which is very small 
but present. This  non linearity then is the root of inter modulation of the 
multiple  signals/carriers present in the complex waveform.
 
This contact resistance is also the root of most failures of N connectors  
in amateur service. With elevated vswr, peak currents are much higher than 
low  vswr and heat losses are related to current squared. As a center pin 
heats up,  the base metal resistance increases on the order of 20 parts per 
million per  degree C and the whole process can begin a thermal runaway toward  
destruction.
 
Center pin sockets are not very robust and are easily bent if the center  
pin is not well centered. The usual socket has four slits to allow some 
flexure  for pin mating. When damaged, you can end up with only one interface 
instead of  the intended four contact points. That makes contact resistance 
four times as  much which increases the current density four X at the contact 
point. That  increases heat loss 16X.
 
Larger pins have lower contact resistance. The 7/16 style connector is an  
example that has lower IM performance. 
 
73,
Gerald K5GW
 
 
 
 
 
 
 
 
In a message dated 11/14/2013 2:14:45 A.M. Central Standard Time,  
wlfuqu00 at uky.edu writes:


The  cellular industry like them, as they generate less  intermodulation
distortion than N, though the IMD generated by N is not  significant
for amateur radio.

Dave

What property of N  connectors generate  IMD?
_______________________________________________
Amps mailing  list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps