Bob wrote:
You really want to use Helium. Hydrogen is a bit reactive.
I don't think it's a problem. The alternators on mains powerplants are
filled with Hydrogen under fair pressure, and the internal materials and
conditions are not that different from a crystal oscillator inside an
oven.
On 6/8/2017 5:08 PM, Bob kb8tq wrote:
Hi
In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very
much do
not want water running around inside your crystal holder… Helium is inert.
Bob
Exactly right Bob. The 10811 guys used to go nuts
about keeping water out of the
Hi
In this case hydrogen + oxygen (like from oxidized metal) goes to H20. You very
much do
not want water running around inside your crystal holder… Helium is inert.
Bob
> On Jun 8, 2017, at 7:18 PM, Charles Steinmetz wrote:
>
> Bob wrote:
>
>> You really want to use Helium. Hydrogen is a
Bob is exactly right. Read up on "mean free path" physics.
Just a little air will take care of conduction.
Full atmospheric pressure would drop the Q something like
a factor of 2.
In any event, conduction through the crystal mounts is
plenty adequate for the tiny thermal mass of the crystal
itse
Yes, that's right. The copper oven mass
has two pieces: a main piece and a lid.
The main piece has a wall around the outside
into which the cover fits, using an O-ring.
In the center, there is a cylindrical cavity
into which the crystal mounts. It is like
a 10811 crystal, except the height is r
Hi
You really want to use Helium. Hydrogen is a bit reactive.
Bob
> On Jun 8, 2017, at 5:49 PM, Alan Melia wrote:
>
> Hi Bob, it also depends on what you allow to leak into the vacuum. Hydrogen
> is a pretty effective remover of heat :-))
> Alan
> G3NYK
>
> - Original Message - From
Hi Mark and list,
On 6/6/2017 9:39 PM, Mark Sims wrote:
If you run it on a system with an accurately set clock, Lady Heather
can measure the offset (and standard deviation and ADEVs) between
the time in the receiver time code message and when the last byte of
the time code message comes in.
Hi Bob, it also depends on what you allow to leak into the vacuum. Hydrogen
is a pretty effective remover of heat :-))
Alan
G3NYK
- Original Message -
From: "Bob kb8tq"
To: "Discussion of precise time and frequency measurement"
Sent: Thursday, June 08, 2017 9:19 PM
Subject: Re: [tim
On Wed, 7 Jun 2017 14:21:52 -0700
"Richard (Rick) Karlquist" wrote:
> The crystal case is well connected to the oven mass and gets
> heated by conduction. I don't think radiation is a player.
Do I interpret the papers correctly, that the oven mass is
a closed can, with the crystal holder "mold
Hi
If you look at the thermal conductivity vs very low pressures, the conductivity
comes up pretty quickly from a hard vacuum. There is essentially no impact
on Q.
Bob
> On Jun 8, 2017, at 4:03 PM, Attila Kinali wrote:
>
> On Thu, 8 Jun 2017 06:55:07 -0400
> Bob kb8tq wrote:
>
>> The simpl
On Thu, 8 Jun 2017 06:55:07 -0400
Bob kb8tq wrote:
> The simple answer is that the backfill is done because it does matter in a
> lot of
> cases.
This raises the question, why there is backfill (just for thermal conductivity?)
and how much it affects the Q of the crystal.
And there was the HP 540 and the HP 2590B... I still use a HP 2590B for
frequency measurement and in conjunction with a HP 851B display as a spectrum
analyzer.
John WA4WDL
>
> On June 8, 2017 at 8:35 AM Scott McGrath wrote:
>
> The heterodyne trick has been done before the first
>
Hi
The heterodyne approach dates back at least into the 1930’s in general lab use.
I’m
sure it dates well before that on an experimental basis. The LM and BC-221
frequency
meters are good examples of it’s use. Adding an “error multiplier” to the setup
could
give you a very impressive resolution
The heterodyne trick has been done before the first
'Modern' frequency counter the HP 5245 used plug ins to extend its range to 18
Ghz by doing exactly that. The plug in contained a tunable LO mixer and
indicator to show tuning lock
These were a pain to use but they beat the 'frequency meter
Hi
> On Jun 8, 2017, at 3:41 AM, Hal Murray wrote:
>
>
> att...@kinali.ch said:
>> Keep in mind that you will need a good voltage reference as well to reach
>> anything close to 12bit. Your LDO is _not_ a good voltage reference
>> (depending on type and load/source conditions they vary eaily b
Hi
> On Jun 8, 2017, at 2:18 AM, Hal Murray wrote:
>
>
> kb...@n1k.org said:
>> The crystal enclosure may (or may not … who knows ..) be back filled with a
>> low level of helium. It does not take much of a backfill for conduction
>> inside the crystal holder to dominate the heat transfer vs r
att...@kinali.ch said:
> Keep in mind that you will need a good voltage reference as well to reach
> anything close to 12bit. Your LDO is _not_ a good voltage reference
> (depending on type and load/source conditions they vary eaily by 1-2%... not
> to talk about their noise)
That applies when u
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