I seemed to have misplaced my original invoice, and the Elecraft website seems
to no longer list the ref osc upgrade, but I recall the "F/W corrected" verbiage
on the invoice for my K3S. This was always a puzzle to me, but not enough to
investigate. Frankly, I don't know what that means. According to the schematic
there is a V control pin on the TCXO but without the external reference option,
it connects to nothing.
Furthermore, even with the ext ref option my understanding is that it doesn't
actually tune the internal ref, it just measures it and tweaks the ref cal every
four seconds.
Wes N7WS
On 3/31/2022 12:30 PM, Bob McGraw wrote:
The TCXO is the reference frequency for about everything that takes place in
the radio. It is the master clock. If it is incorrect, then everything else
is incorrect, for the most part.
A 5 ppm TCXO, or 5 parts per million, can have an error of +/-250 Hz on 6
meters. Where as a 0.5 ppm TCXO can have an error of 25 Hz on 6 meters. It
just depends on how accurate and stable you desire your radio to be.
Oh, the frequency read-out on the front is just that, a read out. It is not a
frequency measurement of the exact frequency. Many will put their radio on
14.255.000 and swear it is on that frequency. But with a 5 ppm TCXO it could
be +/- 71 Hz. Where as with a 0.5 ppm it would be +/- 7 Hz. Of course one
must consider crystal and component ageing and perform very easy calibration
procedure at regular intervals. I check and adjust mine once a month and can
maintain +/- 2 Hz or or better.
I ordered mine with the 1 ppm TCXO with F/W corrected to 0.5 ppm.
73
Bob, K4TAX
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