[Elecraft] REF CAL

[Wes Stewart]

Paul,

I suppose I should have added "necessarily more accurate."

What I'm getting at is that the K3 received frequency varies as the DSP bandwidth is adjusted.  So for example, if one was going to read the frequency of a beat note on a sound card, without other tuning, the beat note will change with bandwidth changes.  

Maybe I'm overlooking something (always a good possibility) but I cannot see any use for a GPSDO (other than bragging rights) besides FMTs or UHF/microwave weak signal work.

Frankly, I haven't kept up with the current methodology in the FMT, but if it includes relying on an audio beat note then I'm suggesting that this is suspect.

If I'm in error, I would be happy to be educated.

Wes

--- On Sat, 9/12/09, Paul Christensen <w9ac at arrl.net> wrote:

From: Paul Christensen <w9ac at arrl.net>
Subject: Re: [Elecraft] REF CAL
To: "Elecraft Reflector" <elecraft at mailman.qth.net>
Date: Saturday, September 12, 2009, 12:44 PM

>> Being able to lock my K3 to an external 10MHz reference might be nice
someday though.

> That might make it more stable but it won't make it more accurate.
>
> For the reason why, see: 
> http://n2.nabble.com/Ref-Osc-Cal-Method-4-td2595451.html#a2595451

Wes,

I read your description, but are you also implying that a 10 MHz GPSDO would 
not provide additional accuracy to the K3?   When a precision 10 MHz time 
base is used as a superhet receiver's frequency reference, the accuracy is 
generally not as good as the precision time base itself owing to decimation 
error, but it is still significantly better than an internal TCXO even when 
the best calibration methods are used.

For example, when a GPSDO is used with the Icom 7700, absolute accuracy does 
not approach the 1x10^-11 long-term accuracy of the GPSDO and can be off by 
~ 0.05 Hz at 1 MHz and probably rivals the real-world accuracy of its 
internal 0.05 ppm OCXO.  But the K3's optional TCXO is specified at 1.0 ppm 
accuracy.  So, if the K3 were combined with a GPSDO or a high-quality OCXO, 
I would expect much better accuracy and stability than that of the Elecraft 
TCXO.

Paul, W9AC