That's probably a really bad idea.  The phase noise from the TIMEPULSE
output is pretty bad compared to a "real" RF source, and by the time
it's multiplied up to 10 GHz you'll have more noise than signal.
Attached are some phase noise plots and a couple of spectrum analyzer
captures to give you some idea what to expect.

BTW, even the Bodnar unit may not look too good at 10 GHz -- remember
that you increase phase noise by 20 dB for 10 times multiplication.

John

On 3/29/21 12:25 PM, Chris Wilson wrote:

Hi

…. a very normal way to get to 10 GHz is to lock up a low noise VHF oscillator
as a “cleanup” device. This is true even with a very good 10 MHz source. The
20 log N stuff simply beats you up to much.

Some math:

A really good 10 MHz source might be in the -170 dbc/ Hz range far removed from carrier.
That gets to -150 with an ideal multiplication to 100 MHz. Any more “normal” source will
be worse than that 10 MHz OCXO. The 100 MHz will be even worse as a result. If your
source is in the -140 to -150 range, the output will be -120 to -130 dbc/ Hz.

For not a lot of money, you can get small VCXO’s at VHF with pretty good noise numbers.
A part that hits -160 dbc / Hz at 10 KHz offset is not all that unusual. That will give you a
lot of noise reduction vs that -120 to -130 dbc/Hz.

By the time you get to 10 GHz, you add another 40 db to the 100 MHz numbers. -120
goes to -80 dbc/ Hz. That’s a lot of noise ….

Bob

On 3/29/21 10:14 AM, John Ackermann N8UR wrote:

What's the signal bandwidth from Es'Hail?

The optimum strategy is a very quiet crystal oscillator that you
discipline with the 1pps, and choose that oscillator so its frequency is
what you need.

What we've done in the past is use the reference to clock a NCO in FPGA,
and use one of the well known spur reduction techniques that pushes the
spurs away from the center before running it to the DAC. This degrades
the performance at, say, 100kHz away, but improves the performance
within 1 kHz. This relies on knowing what the loop bandwidth is in your
10GHz LO PLL, since inside that bandwidth it's the reference, but
outside it's the DRO or GaAs oscillator.

There might be some DDS chips that implement this kind of thing - the
latest chips from ADI are pretty sophisticated.

Hello everyone

Monday, March 29, 2021

Thanks for the replies, some went a little over my head, which is not hard :) I am wondering how people successfully use a Leo Bodnar programmable GPS source to provide an external LO for an LNB as opposed to its internal xtal. What is different, in simple terms please, between my Ublox output and the Leo Bodnar one?

Best regards,
Chris        mailto:chris@chriswilson.tv

LJ> On 3/29/21 10:14 AM, John Ackermann N8UR wrote:

LJ> What's the signal bandwidth from Es'Hail?

LJ> The optimum strategy is a very quiet crystal oscillator that you
LJ> discipline with the 1pps, and choose that oscillator so its frequency is
LJ> what you need.

LJ> What we've done in the past is use the reference to clock a NCO in FPGA,
LJ> and use one of the well known spur reduction techniques that pushes the
LJ> spurs away from the center before running it to the DAC. This degrades
LJ> the performance at, say, 100kHz away, but improves the performance
LJ> within 1 kHz. This relies on knowing what the loop bandwidth is in your
LJ> 10GHz LO PLL, since inside that bandwidth it's the reference, but
LJ> outside it's the DRO or GaAs oscillator.

LJ> There might be some DDS chips that implement this kind of thing - the
LJ> latest chips from ADI are pretty sophisticated.

LJ> _______________________________________________
LJ> time-nuts mailing list -- time-nuts@lists.febo.com -- To
LJ> unsubscribe send an email to time-nuts-leave@lists.febo.com
LJ> To unsubscribe, go to and follow the instructions there.

Chris,

It may be that the modulation and subsequent demodulation scheme used for
satellite TV and the
like is rather more robust than many people give it credit for.

Dana

On Wed, Mar 31, 2021 at 7:09 AM Chris Wilson chris@chriswilson.tv wrote:

More to do with amateurs using narrow band modulations, and the LB GPSDO
being moderately good close in.  Phase noise out beyond a few kHz goes
more or less unnoticed on SSB

Andy
www.g4jnt.com

On Wed, 31 Mar 2021 at 13:35, Dana Whitlow k8yumdoober@gmail.com wrote:

Andy, I agree with you if that's the intended use.  But unless I've missed
something, the
original inquirer has yet to state what he is trying to do, so the sky's
the limit.

Dana

On Wed, Mar 31, 2021 at 7:40 AM Andy Talbot andy.g4jnt@gmail.com wrote:

Hi

When you add noise to the local oscillator that down converts the signal,
that noise shows up on the output of the LNB. Depending on what you are
doing, this or that kind of noise can be a major or a not so major issue.

Indeed the uBlox output is more noisy than the Leo Bodnar device ….

Bob

Hi Chris --

The difference is that the ublox module is outputting a signal that's
being generated without much concern for its phase noise.  The digital
process used creates a  lot of jitter in the edges of the output
waveform.  It simply wasn't intended for the TIMEPULSE output to be used
in RF (analog) circuits.

The Bodnar GPSDO follows the GPS output with a synthesizer chip that
also functions as a "jitter attenuator" which in addition to allowing a
wide range of frequency outputs also cleans up the input signal.  The
synth chip output has much lower phase noise than the GPS by itself.

But the synth output is still noisier than a simple crystal oscillator
and might not be sufficiently good to be multiplied up to the 10 GHz
range.  That's why others have suggested starting the LO chain with a
higher frequency XO that is locked (in a narrow loop bandwidth) to the
GPS signal.  That will result in significantly lower phase noise when
multiplied up to 10 GHz.

73,
John

On 3/31/21 8:09 AM, Chris Wilson wrote: