[Elecraft] KX3 IQ Outputs - What to expect?

[John Huggins, kx4o]

On Tue, March 17, 2015 05:16, Peter Lambert wrote:
Thanks Peter.  Good clues and I will have a look.  Schematics printed and
heading to work where we maintain an electronics lab that is an
anti-static wonderland.

I wonder, though, if there isn't some external forensics to try first.  I
mean if the I or Q are not proper at the points you mention, there should
be some evidence in the operation right?  Although I do note proper I an Q
levels when the VFO is close to the test frequency and within the
demodulating bandwidth.

Elecraft has been sent a note along with o-scope plots of the IQ out
connector, but I will perform a visual inspection of the spots you
mention.

John

> Hello again John,
>
>
> Looking at the schematic, any difference you see should be so slight that
>  you'd not make comment on it.  If it were me I'd take a look at the
> inductors LD-LG (on page 4 of the schematic) to see if there is the
> possibility of one of them being shorted.  I haven't had look at these
> but it's common to twist the terminating wires together - a likely spot
> for a short.
>
> I'd stick the CRO on the output of each of the 4 inductors (where the
> circuit shows "RX_I" and "RX_Q" and the opposite side of C1K and C1L) all
> the levels here should be pretty much identical.
>
> Of course you can only expect this over the range of +- 96kHz or so.
>
>
> 73's Peter VK4JD
>
>