Hi Jack,
Lyle was referring to tracking of signal levels (i.e. level changes),
not absolute gain.
In our case, the IF output was designed specifically for internal use by
a possible future Elecraft option and fully meets our design needs in
this area. It has sufficient signal for this use and clearly works with
other external devices that are designed to handle these levels, as
noted by Lyle. We were very concerned about having an overly strong IF
signal inside the K3 and kept this level as low as possible to avoid
additional RX and TX spur generation inside the radio. Our intent was to
have it amplified by an external, higher input impedance, amplifier as
noted in your email.
Regards,
Eric
Jack Smith wrote:
Lyle:
As we have discussed, the K3 does not follow the normal
commercial/military practice of providing a 1:1 relationship between
the IF sample and the signal level at the antenna port. Since the K3
has a switchable pre-amp, the 1:1 relationship would presumably be
with the pre-amp off.
......
Now, a Softrock or Larry's LP-PAN has enough sensitivity to overcome
most or all of this loss, but it's still a design error.
(The IF sample can also be amplified by an external amplifier such as
my Z10000-U. If configured in high Z input mode, the J310's output
impedance becomes a non-issue.)
Jack K8ZOA
www.cliftonlaboratories.com
Lyle Johnson wrote:
...There is just no tracking of levels at the I F
out with what is fed into the antenna input of the receiver.
If that were true, LP-PAN, SDR-14 and SDR0IQ could not be used as
panadaptors. But they can and are being used, so one can only
conclude that the output at the IF jack most assuredly follows the
signal at the input.
Note that there are a mulititude of signals at the IF output
connector since this is the unfiltered output from the mixer
post-amplifier. These signals must be accounted for in any device
which attaches to the IF output jack. See <
URL:http://www.telepostinc.com/LP-PAN.html > and scroll about halfway
down the page to "L.O. leakage / isolation:" for details
The lower the impedance of the attached load, the lower the gain (or
increased loss) there will be at the IF output. We're talking
microvolt levels here, not hundreds of millivolts.
73,
Lyle KK7P
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