[ARC5] A simple receiver improvement

[Geoff]

Ken, the resistive part is low but the antenna is capacitive because it is 
so short and the reactance is thru the roof.
When you use a long wire, dipole, etc the VSWR at the radio is gonna be very 
high in the opposite direction.

Carl



----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Glen Zook" <gzook at yahoo.com>
Cc: "aRC-5 List" <arc5 at mailman.qth.net>
Sent: Tuesday, January 14, 2014 2:34 PM
Subject: Re: [ARC5] A simple receiver improvement


> On 14 Jan 2014 at 10:27, Glen Zook wrote:
>
>> Although definitely not an "exact" match, television baluns can work
>> wonders in matching the usual 50-ohm coaxial cable antennas to older
>> receivers.
>
> What I don't understand in this case is that the impedance of the original
> antennas on the aircraft is supposed to be on the order of 5 to 20 ohms.
>
> So, why does this help the receiver so much?
>
> Is the input impedance of the receiver really so high that the 300:75 ohm
> transformer really and actually improves matters as much as it appears to?
>
> BTW, in answer to a question I received off list, I connected my balun 
> with
> the 300 ohm side connected to the receiver antenna connector, and the 75
> ohm side connected to my antenna. I presumed that the receivers' input
> impedance was "high".
>
> Ken W7EKB
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