[ARC5] Receiver input impedance.

[Brian Clarke]

How about this:

  1.. Short out the AGC / AVC
  2.. Attach a non-inductive resistor of the correct value across the headphone terminals = audio load
  3.. Feed a modulated RF signal to the ANT terminal in series with a variable. non-inductive resistor - may need to be several MegOhm
  4.. Set this resistor at 0 Ohm. 
  5.. Feed in an RF signal - between 1 and 10 uV or so - in the approximately linear range - no overloading the input or IF stages
  6.. Tune the Rx and ALIGN INPUT for maximum audio load Voltage
  7.. Measure the Voltage across the audio load resistor
  8.. Increase the resistance in series with the ANT terminal till the audio output Voltage falls to half that registered in step 7
  9.. Measure that resistor
  10.. Repeat for several input frequencies
  11.. Chart the results of Z in vs frequency
  12.. Share with the ARC5 list.

73 de Brian, VK2GCE.

 
> ----- Original Message ----- 
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: <Arc5 at mailman.qth.net>
> Sent: Tuesday, October 30, 2012 12:30 PM
> Subject: [ARC5] Receiver input impedance.
> 
> 
>> 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