[Elecraft] WTB Trimble ThunderBolt for K3EXREF / QS1R
Edward R Cole
kl7uw at acsalaska.net
Fri Apr 10 13:42:44 EDT 2015
David, G4DMP:
I won't disagree. I guessed you missed my first sentence: "I am
using a Morion OCXO as 10-MHz reference..."?
The Double-Oven may be more stable at 2xE-12 vs mine 5xE-12 but doubt
you will ever measure the difference let alone discern it in actual
use (unless you are operating on high freq microwaves). Mine is
single-oven, model MV62.
I use a LM7805 for the Vf lead using a 10-turn Helipot (think it is
100K). The frequency control input takes very little current. My
counter only resolves 1-Hz so I can only guess how close I have it
adjusted (but less than a Hz). Actually, I can adjust it by
monitoring my 3400-MHz transverter LO which is a PLL referenced to
the OCXO. The LO runs at 3255-MHz which is several multiples above
10-MHz, so if it reads exact then the reference is much more accurate
than 1-Hz ( depends on the divider ratio in the PLL). I float charge
a 17AH battery so the voltage level is regulated by the battery (an
the Astron PS). Advantage of the battery is that the OCXO is immune
to power outages, so it remains very stable.
Long-term stability is about 5xE-8 (28*5/100 = 1.4 Hz per year at
28-MHz) so one should check for drift about every six months. I use
my Rubidium as my local frequency reference for this. I only run it
for about an hour to be stable for the check. My mw counter is
connected to the Rb for ext ref.
I bought my Morion for about $45 a few years ago on e-bay. Recently
I bought two sine-wave OCXO for $27.99 with free shipping from a
Chinese source on e-bay; too two weeks to arrive.
73, Ed - KL7UW
At 04:29 AM 4/10/2015, David G4DMP wrote:
>Ed & others -
> From my experience in using Rubidium and GPS disciplined standards, I
>feel that a far better bet is to use an MV89A 10MHz Double-oven CXO. It
>requires only a 12V d.c. supply.
>
>I built one into a Hammond die-cast box (with no ventilation) with its
>own integral linear PSU, regulated with an L78S12CV regulator. On
>switch-on it draws 34W from the supply mains, which steadily reduces to
>9W after about 12 minutes when the oven attains its working temperature.
>
>Using a 10-turn 10K pot the frequency can be finely adjusted to within
>1/100 of a Hz and it locks the K3 perfectly with the K3EXREF installed.
>
>100% recommended.
>
>The MV89A is available on eBay and the datasheet is at
>http://morion.com.ru/catalog_pdf/MV89-OCXO.pdf
>
>73 de David G4DMP
>
> >> A caveat regarding the use of simple "wall wart" 12v PS for supplying
> >> a OCXO.
> >>
> >> I am using a Morion OCXO as 10-MHz reference for my K3EXREF and for my
> >> synthesized A32 PLL in my DEMI 1296 transverter. I got reports of
> >> 120-Hz sidebands on my signal (-10dBc) turned out to be due to
> >> excessive AC ripple riding on the 12v coming from my wall wart supply
> >> that I was using to power the OCXO.
>
>--
> + - - - - - - - - - - - - - - - - +
> | David M Pratt, Kippax, Leeds. |
> | Website: http://www.g4dmp.co.uk |
> + - - - - - - - - - - - - - - - - +
73, Ed - KL7UW
http://www.kl7uw.com
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