[time-nuts] [qs1r] Looking for good, cheap, external reference
rstanphill at austin.rr.com
Wed Sep 22 23:58:20 UTC 2010
Is there anyway to tell without opening the box if you have:
1) "better oscillator" (=Trimble labeled) Anything visible from SW
(Tboltmon or LH)? Any behavior fingerprint?
2) "newer firmware" (=rev 3.00) Does show up in SW.
3) "newer brain dead temp sensor" (= ?). Anything
visible from SW (Tboltmon or LH)? Any behavior fingerprint? What is the
new sensor you changed to?
----- Original Message -----
From: "Ed Palmer" <ed_palmer at sasktel.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Wednesday, September 22, 2010 6:39 PM
Subject: Re: [time-nuts] [qs1r] Looking for good, cheap, external reference
> And if you buy a newer unit with the better oscillator, new firmware, and
> newer (but brain-dead) temperature sensor, it's trivial to replace the
> sensor. It took me longer to take the unit apart than to change the chip
> and I don't have a lot of experience with surface mount.
> Bob Camp wrote:
>> That's my feeling. The firmware isn't the issue. The OCXO and the temp
>> sensor are the important points. The firmware is just an easy way to get
>> the right OCXO.
>> On Sep 22, 2010, at 7:00 PM, Mark Spencer <mspencer12345 at yahoo.ca> wrote:
>>> Would a newer unit with the 3.00 firmware, the trimble branded OCXO and
>>> the older temperature sensor be one of the better (or perhaps best ?)
>>> TBOLT combinations ?
>>> ----- Original Message ----
>>> From: John Miles <jmiles at pop.net>
>>> To: lester at veenstras.com; Discussion of precise time and frequency
>>> measurement <time-nuts at febo.com>; David <n7aig at yahoo.com>
>>> Sent: Wed, September 22, 2010 12:42:06 PM
>>> Subject: Re: [time-nuts] [qs1r] Looking for good, cheap, external
>>>> John, unless I am going mad, the ADEV plots for both auctions you
>>>> mentioned look the same - maybe the bad one has been replaced since
>>>> you posted your message?
>>> The black-and-white plot that everybody uses is from the original
>>> Thunderbolt data sheet, which was way conservative even for the older
>>> Towards the bottom of the 290308733659 auction, though, the seller has
>>> appended a half-dozen or so photographs of a TSC 5120A screen showing
>>> are (for a Thunderbolt) some weak results. The ADEV plot shows poor
>>> long-term disciplining and the PN plot doesn't look good either.
>>> he's using a noisy reference, or the unit was tested during a 2-day-long
>>> I've never seen one do ~-88 dBc/Hz at 10 Hz. Even my original one with
>>> lower-quality OCXO was good for -105 dBc/Hz, while the ones with the
>>> Trimble-labelled OCXO can do -130 or better. Likewise the 'good' ones
>>> do several dB better than the -150 dBc/Hz broadband floor he shows.
>>> I've also never seen one in a black anodized(?) housing like that (has
>>> anyone else?) Mark is right in that the 3.00 firmware doesn't
>>> do much for you, but the newer units also had the good OCXOs, which IMO
>>> more important than the temp sensor.
>>> -- john, KE5FX
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