[Elecraft] Receiver impedance?

[Ingo Meyer DK3RED]

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