[ARC5] Receiver input impedance...

[Mike Feher]

Just be cautious to avoid self-resonances in that 80:1. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 

-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Kenneth G.
Gordon
Sent: Monday, October 20, 2014 11:50 AM
To: ARC5
Subject: Re: [ARC5] Receiver input impedance...

On 20 Oct 2014 at 8:08, J Mcvey wrote:

> The ARC-5 system was designed for low-Z (12 ohm?), short capacitive 
> antennas. So, in this case, the low Z side would be at the receiver
terminals?

Yes. Those are correct, yet the receiver input-impedance IS about 4K ohms.

Kinda like a VTVM with an 11 megohm input impedance being used to measure a
battery's voltage.

Probably this was done in this case so that one antenna could be connected
in parallel to mulitple receivers which all tune to different frequencies
(which was done in the original setup) without causing any interaction or
signal loss.

Possibly, the input circuitry was done the way it was so that it inherently
is already a type of impedance transformer.

As per the discussion here, I am coming to the conclusion that matching that
impedance is not really necessary, nor particularly useful or helpful, and
it appears, at this point, that doing so is hardly worth the effort.

To satisfy my curiousity, I MAY build an 80:1 Un-Un and take some
measurements....just to see...but at this point, I would not expect there to
be a noticeable improvement.

Ken W7EKB
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