[Elecraft] KPA-1500 ATU not working well

[John Oppenheimer]

Putting the Elecraft CP1 through the paces with a 2 port VNA can be
enlightening. The CP1 seems to be representative of Elecraft directional
couplers across the line. There's a picture of the W2 high power HF
coupler in the manual, it's just larger cores.

Sweeping a 20 dB CP1 across the band with a VNWA with a 60 Ohm load,
1.2:1, results with a relative constant -40 dB reflected gain and a -20
forward gain. A closer match to 50 Ohm fall's apart with a wide -40 db
to -70 dB dip at 7 MHz reflected across the band at 50 Ohm.

I can agree, 1.2 : 1 is about the limit.

John KN5L

On 06/22/2018 01:11 PM, Wes Stewart wrote:
> That's a return loss of ~20 dB.  Now I have 
> no idea of what the directivity of the coupler is in the KAT500 or KPA1500 but 
> considering it has to work from 1.8 to 54 MHz and to keep the numbers easy, 20 
> dB wouldn't be unreasonable.