[ARC5] Receiver input impedance...

[Richard Knoppow]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "ARC5" <arc5 at mailman.qth.net>
Sent: Sunday, October 19, 2014 9:26 AM
Subject: [ARC5] Receiver input impedance...


>I have wondered about how much of an improvement in 
>receiver operation
> could be achieved by adding an Un-Un to the antenna input.
>

     Keep in mind that for a receiver you are not concerned 
with _power_ transfer but rather voltage ratios. You want 
the highest voltage at the input device. A matched impedance 
will reduce the voltage at the input by half. Receiver noise 
level is determined by an equivalent resistor which is 
usually a combination of the equivalent noise resistance of 
the input stage and the equivalent noise resistance of the 
antenna and feed line.  For HF use the atmospheric noise is 
usually the determining limit. In a city electrical noise is 
usually the limit. It may be helpful to eliminate noise pick 
up by the feed line but if a balanced feeder is truly 
balanced or a coaxial line is properly shielded this is will 
not be affected by the match.
    Noise in the city is a very serious problem.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com