[Lowfer] Isolation transformer, Computer noise, etc.

[Mike.WE0H]

Thank you Bill for bring us up to speed on the transformer. I need to 
wind one for my HF vertical as the common mode noise is absolutely nuts 
on it. My 600m vertical is transformer coupled so it is stone quiet.

Things like this thread are what the email reflectors and Groups are 
good for. We all learn by the replies from everyone. It's like sitting 
in a virtual classroom with a little delay between people talking. hi hi

Mike
WE0H


Wild-Bill wrote:
> "I'd like to say someone said years ago that you want 4x the feedline impedance "for the primary & secondary of the transformer"
> 
> Correct, Mike, but the 4X relates to the inductive reactance of the primary and secondary of that transformer and this value of 

reactance is proportional to the frequency of use. The formula is: XL = 
2 x pi x F x  L    So set up the inducance (L) for the

lowest frequency of use. At higher frequencies the 'X' factor will be 
proportionally larger and this is OK.
> 
> One of the advantages of an isolation transformer back at the shack is that it prevents most of the powerline hash present 

on the house ground system from being sent out to the antenna site. To 
prove out this theory and determine how much the power line noise

is, connect a wire of the same length as the lead-in to the AC ground in 
your house and place the other end near the base of your antenna.

Listen to a weak signal at a frequency close to where you are operating 
and 'make' and 'break' the connection to AC ground. You should hear

a considerable increase in noise when the wire is connected.
> 
> Another way to determine the effectiveness of your isolation transformer is to temporarily jumper the return lines on both sides of 

the transformer. The noise should also increase by quite a bit.
> 
> Bill