[Elecraft] When S-Meters are Useful (WAS: When do you use fast AGC?)

Wed Oct 18 04:38:59 EDT 2006

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I would be the first to order a unit Jack

Theres some excellent plotting software just waiting for a S meter
interface as you describe.

http://www.g4hfq.co.uk/plphelp/plphelp.htm

Theres little alternative available for those seeking a accurate S
meter on a ham radio transceiver.  Besides i see no harm  as hams
being professional in our approach to signal measurements. After
all who would buy any test instrument today if it had a 200% error
in accuracy, but thats what we have today in every radio receiver
and transceiver.

Craig
VK3HE

On Tue, 17 Oct 2006 02:30:47 -0700 Jack Smith
<jack.smith at cliftonlaboratories.com> wrote:
>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
>
>
>
>charliedelta at hushmail.com 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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