[time-nuts] Vanguard TCXO

Mark Goldberg marklgoldberg at gmail.com
Thu Feb 8 08:34:06 EST 2018

What is the phase noise like on the cheap TCXO? Being on frequency is far
from the only characteristic that matters. I did some research on cheap
TCXOs for Kenwood radios and found truly awful phase noise and lots of
spurs above and below the oscillator frequency. I don't know if these
characteristics are important for your unit.

One eBay source says -125 dBc/1kHz. (Should be stated as -125 dBc/Hz @ 1
kHz). That is not very good. I found the cheap TCXOs I tested actually had
worse phase noise at 15 - 20 kHz offset.


On Feb 8, 2018 4:24 AM, "Thomas Allgeier" <th.allgeier at gmail.com> wrote:

> Hello All,
> This is for the medium-precision nuts amongst us. I have invested £14.50
> in one of these Vanguard 0.1ppm TCXO's to pimp my Siglent FG which has a
> footprint for it. It is its internal ref at 25 MHz. The swapping-in was
> simple to do and the FG works fine with it. Since it has a counter mode I
> did a quick check to show whether it was worthwile: I made it count the 10
> MHz from my Proteus GPSDO. The Siglent reads to 1 Hz and straight after
> turn-on it went straight to 10.000000 MHz. Over about 1 day I never saw it
> more than +/-1 Hz off, and this involved a deliberate temperature change of
> just over 5 deg C, basically by having the heating in the room off and on.
> For most of the time the display sat solidly at 10.000000.
> So, to summarise, in a rough sort of way the thing lives up to its 0.1ppm
> spec, at least around the 20C temperature mark. I bought it from a Hong
> Kong seller on Ebay - naturally there is always a chance that other devices
> sold with the same description/label might not perform as well.
> I'm quite aware that the generator (DDS) suffers from other sources of
> error, which won't be improved by the clock being better, but at least the
> nominal frequencies it outputs are now going to be very close to the mark
> without the need for an external ref.
> Kind regards,
> Thomas.
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