One possibility for an "add in" S-meter module would be an AD8307 log
amp module paralleling the IF amplifier's input. This will give you an
honest 80 to 90 dB linear output (db in, linear output), if you can
manage the shielding, and close to 100 dB if you don't mind a bit of
non-linearity at the extremes. To avoid loading down the IF amp input,
you probably need a isolation amplifier.
And, of course, there's always a concern when mucking about inside the
signal chain. The buffer amplifier I offer with my Z90 digital
panadapter samples the K2's IF at an earlier point, just after the
2N5109 post-mixer amplifier, but the design could easily be used to
sample after the filters. (The Z90 uses an AD8307 log amp detector, so I
have some experience with it.)
The log amp's output could then drive an external moving coil meter, or
it could be digitized via an ADC and brought out on a RS-232 compatible
port for other purposes. Serial output would require an on-board PIC and
would have to carefully constructed to avoid introducing unwanted noise
into the K2, but an all-analog solution would be simple enough if the
output device is to be a D'Arsonval meter movement.
If there's a groundswell of demand for such a beast I will consider it
as a future kit offering.
Jack K8ZOA
www.cliftonlaboratories.com
[EMAIL PROTECTED] wrote:
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I also looked for a solution to the S meter calibration problem. I
discussed the problem with Greg Ordy w8wwv Author of the great
program called S meter light. Unfortunately the K2 does not return
8 data bits via the serial port so the calibration accuracy would
be close to useless. If the K2 did return 8 data bits you could
obtain 0.1 db accuracy using Gregs program. 8 data bits returned
via the data port is available on the 756PRO and several other
radios. Elecraft cloned the Kenwood command set which returns 4 or
5 bits or something like that.
Maybe Elecraft would consider this as a future external option for
the K2 . It certainly would be a first for a ham radio, that is
having a inbuilt calibrated S meter. The crunched up S meter
bargraph is highly annoying and close to useless on the k2.
Craig
VK3HE
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