I am interested especially in whether it's phase noise content would be within tolerance so as not to compromise the excellent response of the 6000 series.
Ken - NM9P, Elmer
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Posted 3 years ago
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Keith - AC9S
- 198 Posts
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If you search BG7TBL on ebay you will find them, The thread below shows all the different versions.
http://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/
Some testing someone did
http://www.ke5fx.com/gpscomp.htm
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Since I have no possible way to measure phase noise or receiver parameters - I have no idea how it relates to performance or if anything has changed.
Maybe someone here with $$$$ of test equipment has conducted a trial and came to a judgement in which case I am all ears . . in the meantime, I will keep it plugged in and the little antenna sits on the window sill. Been running for months and the software that configures it tells me there have been no dropouts.
Got mine from force12inc in colorado - got it in about 3 days.
Cheers!
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Personally, I went with the internal GPS in case additional s/w functionality is added in the future (Time server / I-Q timestamping etc.)
_..--
TiM
George Molnar, KF2T, Elmer
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Any update for additional functionality for the GPSDO?
Tim - W4TME, Customer Experience Manager
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Tim - W4TME, Customer Experience Manager
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Peter K1PGV, Elmer
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Peter
K1PGV
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http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=234
If you need more info, maybe send them an email with your questions
Cheers
Peter K1PGV, Elmer
- 541 Posts
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Measured phase noise of standard (TCXO) version is equal or better than
-120 dBc/Hz at 100 Hz
-133 dBc/Hz at 1 kHz
-137 dBc/Hz at 10 kHz
-140 dBc/Hz at 100 kHz
-144 dBc/Hz at 1 MHz
Not bad... but not great.
That and the output power level are the only specifications given.
There's a "custom low phase noise version" available on the Force-12 web site. This seems to have about -5dBc better performance in close.
I'd like to know more about the hold-over accuracy (the web page says a "continuous GPS" reception is required, and with a TXCO (as opposed to a single or double OXCO), that sounds likely to be true).
But, for the price (about US$270... NOT including the cost of a suitable antenna US$15) this seems like quite an amazing little unit. This is true even when compared to the Jackson Labs LC-XO-Plus which is approximately twice the cost.
I *would* like to hear somebody from Flex comment on the importance (or lack thereof) of Phase Noise in providing an external 10MHz reference to the 6xxxx.
Peter
K1PGV
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http://www.ebay.com/itm/121530825744
Sure is reasonably priced. Does anyone have one?
Jon...kf2e
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Peter K1PGV, Elmer
- 541 Posts
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My curiosity and questions were with respect to the commercial Bodnar unit being sold by Force-12 here is the States, not the BG7TBL from eBay.
Peter
K1PGV
George Molnar, KF2T, Elmer
- 1612 Posts
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Got to say, though, the 6500 is pretty darn stable on its own. My XV144 with TCXO and some after-market styrofoam work seems to be quite good, too. +/- just a few Hz on 2m, once I got it netted to a known good source.
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Paul Christensen, W9AC, Elmer
- 322 Posts
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The higher-priced version of the Bodnar is still > 30 dB worse at a 100 Hz offset than a Trimble Thunderbolt with a Piezo-branded OCXO when powered from a low-noise, lab-grade supply. For example, typical Trimble PN at 100 Hz is -160 dBc. The upper-grade Bodnar unit is about -125 dBc.
Compared to what's available on the new and used markets, the Bodnar's performance is probably better characterized as good, but not excellent. For Flex users it may not be an issue, but if the device is driving other test gear, that 30 dB difference may mean a lot.
The Trimbles were once plentiful on eBay for USD $99. Scarcity has driven that up but with persistence, a watchful eye can still spot one for a reasonable price.
I ended up installing a Trimble unit and Lambda linear supply into a customized enclosure:
Paul, W9AC
- 257 Posts
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KE5FX thinks the Trimble-branded OCXO's are the ones that perform to the specs you list, viz a viz, the Piezo. Also, note that those specs can only be reached if the Trimble OCXO is removed from the PCB.
It's hard to tell precisely, but the Piezo looks like it lands somewhere around -142dBc at 100Hz. I do wonder what it would have been if he had tested the Piezo after removing it from the PCB, which is how he tested the HP and Trimble.
Check the following link, especially near the bottom, under "October 24, 2011: Further notes on the Thunderbolt OCXO":
Paul Christensen, W9AC, Elmer
- 322 Posts
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Even the Piezo model has a (roughly) 20 dB phase noise advantage at a 100 Hz offset over the precision Bodnar unit. A decade later and the Thunderbolt performance is still extraordinary when powered from a low-noise supply.
Look for Thunderbolt Rev. E units with a 2004 date code (or later) for the best chance of getting one with the Trimble OCXO.
Paul, W9AC
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