[ARC5] Receiver input impedance.

[WA5CAB at cs.com]

Ken,

The 5 ohm source impedance was probably to mimic the expected antenna. The 
actual input impedance is quite high, being a parallel resonant coil and 
capacitor in parallel with a 2 meg resistor connected to the 12SK7 grid 
(through a DC blocking capacitor which you can ignore). This is why connecting 
coaxial cable to a Command Set antenna terminal detunes the input.

Neither BC-453-A nor BC-453-B ever had a Loop input. And the input is 
unbalanced, not balanced.


In a message dated 10/30/2012 15:35:50 PM Central Daylight Time, 
jeepp at comcast.net writes: 
> And I quote:  "Connect 5 ohm signal generator source to the "A" antenna 
> post.  (Connect to "L" antenna post on those receivers having two 
> antenna posts, one marked "A" and one marked "L")."  This is from an 
> original ARC book.  Any help?
> 
> Jeep - K3HVG
> 
> 
> On 10/30/2012 3:30 PM, Kenneth G. Gordon wrote:
> >Does anyone have accurate data on the BC-453B receivers' antenna input
> >impedance?
> >
> >I need to build an UN-BAL to match my BC-453B to a 3 foot diameter
> >Stoddart loop which is fed with twin-ax.
> >
> >I have the Stoddart data, but need the other data.
> >
> >My particular BC-453B does not have the loop connections.
> >
> >Can anyone help?
> >
> >Kenneth G. Gordon W7EKB
> 

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