[TowerTalk] Andrew CNT-240-FR

[Jim Brown]

> Add 0.25-0.50 dB for any connectors/adaptors if used above 50Mhz

This is another one of those old wives' tales that has no basis in fact 
-- they are the big lie that is believed simply because it is so often 
repeated. The loss in any decent RF connector is a tiny fraction of a 
dB.  W8JI has a rather simple way of helping us think through the 
silliness of your statement. 0.5dB is a power ratio of 0.8913.  If 
you're running 1.5kW through that connector, a loss of 0.5dB is 163 
watts. Think about the heat from a 163 watt light bulb inside that 
connector.  Or with a high duty cycle typical of contesting, 50 watts 
average power.

Such large losses only occur with junk connectors, like those with the 
tiny springs for a center conductor.  Now, I DID experience that kind of 
heating with that sort of junk connector, at at that power level -- it 
was VERY HOT after less than an hour of contesting.  When I replaced it 
with an Amphenol, it ran cool as a cucumber.

This spring, VE1RAC sent me documentation of some very good experimental 
work he had done showing that the loss in decent connectors at VHF is 
FAR lower than that -- a few HUNDREDTHS of a dB, as I recall.

73, Jim Brown K9YC