[Elecraft] TCXO

[Wes]

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