[Elecraft] Receiver impedance?

[David Gilbert]

Are you certain that overdriving the front end of the KX3 that hard 
isn't affecting the input impedance?  It's an active front end.

73,
Dave   AB7E



On 5/25/2022 10:54 AM, Ingo Meyer DK3RED wrote:
> Hello Wunder,
>
>
>> What is a typical input impedance for modern receivers, or 
>> specifically Elecraft receivers?
>>
>> I’m asking because antenna tuners are a frequent question on an SWL 
>> group I follow and I’m pretty sure that they are not needed for most 
>> situations. If the receiver input impedance is not 50 Ω, that is a 
>> big data point.
>>
>> My belief is that receivers are generally medium or high impedance, 
>> depending on whether the first RF preamp is bipolar or FET, but 
>> either way, mostly voltage-oriented.
>>
>> And, yes, I know that antenna tuners can be a LPF or HPF, depending 
>> on their configuration.
>
> You ask for the receiver impedance, not the tramsmitter impedance. I 
> didn't know the answer. But I always assumed that it wasn't 50 ohms. 
> Therefore, I measured the impedance.
>
> Meter: Vector Antenna Analyzer FA-VA5
> <https://www.box73.de/product_info.php?products_id=4019>
> Output Power: 5.6 dBm (S9+78.6 dB)
> Impedanz: 50 ohms
> Frequency: 7030 kHz
>
> Object under test: Elecraft KX3
> Conditions: ATU BYP, FREQ 7030 kHz, PRE OFF, ATT OFF
> Measured data: Z = 76.0 ohms + j 9.0 ohms
> Magnitude Z = 76,5 ohms,  L = 204 nH
> SWR = 1.56
>
>
> 73/72 de Ingo, DK3RED - Don't forget: the fun is the power!
> www.qrp4fun.de - dk3red at qrp4fun.de
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