[TenTec] [Orion] O2 versus Orion

[Martin, AA6E]

On 1/9/06, Bill Tippett <btippett at alum.mit.edu> wrote:

> Mixing architecture for the analog stages has been rearranged to
> provide self-correction for frequency stability.
>
> ***comment*** Academic issue IMHO. Frequency stability in Orion is
> not an issue for normal amateur use.
>

Does anyone understand this point?  I used to think all the Orion (1)
frequencies were derived from the TCXO.  I've had reasonable luck
tweaking the oscillator for better accuracy, as have others.  I
typically use the SPOT tone for zero-beating in CW mode.  That works
nicely, except I'm not quite sure that the SPOT tone has full TCXO
accuracy (not specified), but it seems OK, especially as a transfer
standard for WWV comparison.

Now that I look at the schematics, I see that the CODEC has a separate
"14.360 MHz" clock crystal.  Maybe that's the problem.  It should be
generated from the TCXO.  Is that the birdie I hear at 14,351.770? 
(.05% low)  This would introduce a minor offset, which is cancelled
out if you calibrate against WWV.  Or is there more to it?

Orion's accuracy and stability are good, but none too high, IMO.  This
shows up in netting accuracy at the higher freqs.  Of course, 95% of
rigs out there are worse.  The new IC-7000 has a much better spec: 
+/- 0.5 ppm vs Orion's +/- 3 ppm.  Probably cost them a couple of
bucks more.  The IC-7800 claims +/-.05 ppm 0-50C "after warmup", for a
price.

It would be nice if the master oscillator was at least upgradeable or
syncable to an external reference, for the few folks who are looking
for very high precision.

73 Martin AA6E
--
martin.ewing at gmail.com
http://blog.aa6e.net