GPSDO Tutorial?

User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Wed Apr 25, 2018 9:08 am

Thanks for the info Scott . Showing as $89.99 here (plus vat) in EU which is a great price.
https://www.ebay.com/itm/NEW-10MHz-Sinwave-PLL-GPSDO-GPS-DISCIPLINED-OSCILLATOR-adapter-GPS-ANT-/262038924752?hash=item3d02bcadd0

I see Leo Bodnar has a single output for £100.00, I wonder which one is better bang for buck ?

http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301
JA2GXU
Posts: 6
Joined: Tue Jun 26, 2018 8:52 am

Re: GPSDO Tutorial?

Postby JA2GXU » Mon Aug 27, 2018 5:37 am

Phase noise problem for use general kind of GPSDO.

Degrading phase noise occurs desired weak signal buried in increased noise floor
I recommend don't use general kind of GPSDO due to degrading phase noise.
Improved GPSDO includes VC_OCXO and PLL have more than 100 seconds loop time constant, thus don't occur degrading phase noise.
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Fri Aug 31, 2018 12:33 pm

Cross posting this from the Yahoo group mailing list so that it does not get lost in the sands of time, as it is valuable discussion worthy of preserving:

John Ackermann N8UR jra@febo.com [apache-labs] <apache-labs@yahoogroups.com>
8:28 AM (3 minutes ago)
to apache-labs

Rob, you're correct that the ANAN and other HPSDR radios use a PLL to
lock their internal reference to an external source. More precisely,
there is a very low phase noise 122.88 MHz VCXO that is locked either to
an internal 10 MHz TCXO or external reference.

But an important note on external references with the HPSDR radios. A
few of us have tried to use Hermes-based radios for precise frequency
measurements and have discovered that there is an issue in the PLL
circuit that results in phase jumps at random intervals (usually in the
10s of seconds apart). These are severe enough to destroy sensitive
measurements. I think they are inherent to all the radios that derive
from the Hermes schematic and firmware.

After experimenting we've found one fairly simple fix that at some point
Phil will put into the production firmware. But even after that fix
there is a problem (though of much smaller magnitude) that I haven't
been able to track down yet. As I have time I'm continuing to work on that.

This problem doesn't affect phase noise or real-world frequency
stability, but does show up in sensitive measurements as random "ticks"
in the transmitted phase.

73,
John
----

On 08/31/2018 01:35 AM, Rob Sherwood. rob@nc0b.com [apache-labs] wrote:
> Hi Scott,
>
>
> I don’t know anything about the oscillators or GPSDOs you mentioned.
>
> My main Denver Rubidium is an Efratom M-100 military unit I purchased
> NOS at least 15 years ago that has been running 25/7 ever since. The
> backup Rb in Denver and my only Rb at Ault are Lucent branded with
> Efratom physics packages. My only GPSDO is a rack mount Trak Systems in
> Denver I use to verify my Rubidiums are happy. They all test very clean
> with noise about -135 dBm / Hz at 10 kHz. Not like my Wenzel, but
> reasonable house standards from a frequency standpoint. The Austron
> distribution amp feeds all the HP test equipment except the 8662As and
> the 8642As in Denver.
>
> I will be locking the 7000DLE to the Rb at Ault. I have two 8642As at
> Ault, so one of them will be my signal source. I have no idea which
> clock is in the 7000. Has that changed over time? Warren said an
> external reference locks to the external reference as opposed to
> replacing it.
>
> As a second test I’ll feed in the other 8642A in as the reference. The
> 8642A noise at 10 kHz offset is about -153 dBm/Hz.
>
> What level is optimum for feeding in the 10 MHz reference to the 7000DLE?
>
> Rob, NC0B
>
>
> Sent from my iPad
>
> On Aug 30, 2018, at 4:03 PM, Scott Traurig scott.traurig@gmail.com
> <mailto:scott.traurig@gmail.com> [apache-labs]
> <apache-labs@yahoogroups.com <mailto:apache-labs@yahoogroups.com>> wrote:
>
>> That will be very interesting, Rob. Do you have BG7TBL unit there and,
>> if so, which OCXO is it equipped with? That makes a big difference, of
>> course. The one I have here is equipped with the excellent Russian
>> Morian MV89 OCXO..
>>
>> 73!
>>
>> Scott/w-u-2-o
>>
>>
>> On August 30, 2018 5:51:28 PM EDT, "Rob Sherwood. rob@nc0b.com
>> <mailto:rob@nc0b.com> [apache-labs]" <apache-labs@yahoogroups..com>
>> wrote:
>>
>> I’ll test this, too, on a 7000DLE on Sunday or Monday. Rob, NC0B
>>
>> Sent from my iPad
>>
>> On Aug 30, 2018, at 2:56 PM, wa3jbt@usa.com
>> <mailto:wa3jbt@usa.com> [apache-labs] <apache-labs@yahoogroups.com
>> <mailto:apache-labs@yahoogroups.com>> wrote:
>>
>>> I have a GPS Disciplined Oscillator, Model BG7TBL that I got on
>>> Ebay from China that I used to use with my 200D. I now am using
>>> a 7000DLE and I'm wondering if this unit will degrade my receiver
>>> in regard to phase noise. I believe Scott you are using or were
>>> using this model of GPSDO
>>>
>>> Frank, W2SDR
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Fri Aug 31, 2018 1:01 pm

Rob,

On the Orion MKII based hardware, I believe the 122.8MHz oscillator is a Crystek CVHD-950 (click the hot links in this post for the datasheets), with the following advertised phase noise performance:

Image

The on-board 10MHz TCXO I believe is a Connor-Winfield M100F with the following advertised phase noise performance:

Code: Select all

SSB Phase Noise for Fo=12.8 MHz
 @ 10 Hz offset -90 dBc/Hz
 @ 100 Hz offset -120 dBc/Hz
 @ 1 KHz offset -140 dBc/Hz
 @ 10 KHz offset -150 dBc/Hz
 @ 100 KHz offset -150 dBc/Hz
 @ 1 MHz offset -152 dBc/Hz

As you can see from those spec's, the out of the box performance should be quite good. The cheap eBay/Chinese GPSDOs will probably degrade that by 5dB, give or take, depending on the TCXO or OCXO in the GPSDO, but a more serious, more expensive GPSDO should be OK. As noted previously, I'm happy to give up a little phase noise performance for the convenience of cheap frequency accuracy and long term stability.

With respect to appropriate input levels for an external reference, I find that anything between +7 and +13dBm works. Below +7 I've observed inconsistent performance. Levels above +13dBm could put the input differential amplifier circuit at risk for damage.

Here is a snippet of the schematic showing the external clock input and automatic selection circuit.

The jumpers at the input provide options with respect to a differential or single ended input (J24) and a 50 ohm or high impedance termination (J22), whichever your external clock source requires. If you are having problems first ensure that these jumpers are configured properly for your external clock source.

Next up is a sine to square wave converter formed from a two-transistor differential amplifier. This allows the use of either sine or square wave external clock sources. The resulting square wave goes to IN0 on the 74LVC1G97 which acts as a switch.

The square wave also goes to a circuit that derives a logic level for IN2 on the 784LVC1G97. When an external clock is attached that level will be high and the output of the switch (Y) will be sourced from the external clock on IN0. When no external clock is present that level will be low and the output of the switch will be sourced from TCXO U26 on IN1.

The same logic level on IN2 also is applied to the gate of Q1, and when high due to the presence of an external clock, will drive the P-channel FET to cutoff and turn off power to the on-board TCXO.

Image

As for the firmware PLL problems that John mentions, I looked at the code and all I can tell you is that the code uses the standard Intel (nee Altera) "altpll" megafunction. You would think that a standard megafunction would be bug free?

I'll be very interested in whatever measurements you are going to make, Rob.

73!

Scott
k6avp
Posts: 26
Joined: Mon Apr 10, 2017 1:41 am

Re: GPSDO Tutorial?

Postby k6avp » Mon Nov 19, 2018 3:34 am

I just got one of these and it has a CTS 970-2178-46 oscillator in it with uBlox GPS. It seems to be an older CTS model 115 OCXO. 10MHz output is ~10Vrms unloaded.

I have an ANAN-100B (Hermes) so am going to add an auto-select/buffer board (w7ay/Kok Chen Hermes Reference Oscillator with no OCXO loaded) to my radio before attaching it.
*************

Tony EI7BMB wrote:Thanks for the info Scott . Showing as $89.99 here (plus vat) in EU which is a great price.
https://www.ebay.com/itm/NEW-10MHz-Sinwave-PLL-GPSDO-GPS-DISCIPLINED-OSCILLATOR-adapter-GPS-ANT-/262038924752?hash=item3d02bcadd0

I see Leo Bodnar has a single output for £100.00, I wonder which one is better bang for buck ?

http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Mon Nov 19, 2018 2:12 pm

Thanks for the info on the "new" BG7TBL unit :) CTS is a fine company and that OCXO probably has some good spec's. It's so old I couldn't find a data sheet online, but if you called CTS I bet they could dredge one up for you.
k6avp
Posts: 26
Joined: Mon Apr 10, 2017 1:41 am

Re: GPSDO Tutorial?

Postby k6avp » Tue Nov 20, 2018 9:54 pm

I did messed up on the output. It is ~1.5Vrms unloaded and ~1.2Vrms/15dbmW into 50 Ohms.
User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Thu Jul 11, 2019 9:23 am

Here is another option for anyone who wants to make their own GPSDO. We currently use the RF zero board as the EI 6m beacon and I use the carrier to calibrate my TX in OpenHPSDR/Thetis , not 100% accurate of course because of doppler over the air but I've checked my TX against friends who are GPS locked and its right on the money.

From WA8TOD "I have breadboarded the RFzero together with an ADF4351 evaluation board. For frequencies up to 200 MHz I can use the RFzero directly. From 200 MHz to 4.4 GHz (yes, you read that correctly..... GHz!) the RFzero supplies 25 MHz, GPS-disciplined reference to the ADF4351. Everything in the picture, including the kitchen cutting board base, cost less than $100."


https://groups.io/g/RFzero/topic/2650_h ... 0,31676551

Image
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Thu Jul 11, 2019 10:28 am

Looks like fun for the experimenter. But quite a rat's nest! Once you add in real packaging the price is going to come up, and for $125 or thereabouts you can have a nice BG7TBL clone or even Leo Bodnar's entry level unit, and either will probably be more reliable because the parts count is so much lower.
User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Thu Jul 11, 2019 10:42 am

True Scott but bear in mind its a lot simpler with less parts and cost for freqs less than 200 mhz , its basically the RF zero board @ $75 plus a case and display if needed.
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Thu Jul 11, 2019 1:07 pm

Tony EI7BMB wrote:True Scott but bear in mind its a lot simpler with less parts and cost for freqs less than 200 mhz , its basically the RF zero board @ $75 plus a case and display if needed.
So the output is not 10MHz?
User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Thu Jul 11, 2019 1:37 pm

Yes it can be set to 10mhz or any freq required , more info here http://www.rfzero.net/
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Thu Jul 11, 2019 6:05 pm

User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Thu Aug 29, 2019 7:00 pm

With a 7000 mk 2 on the way I gave in to temptation and bought the BG7 based unit on aliexpress (item 33055900193) for $163 including shipping . I know its more expensive than the stock BG7 but I'm a sucker for good looking toys .

Image
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Thu Aug 29, 2019 11:26 pm

Nice! Did you get it yet? Curious to know what kind of OCXO it uses.
User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Fri Aug 30, 2019 7:56 am

Thanks Scott, just ordered so 3/4 weeks I guess . I'll take a look and let you know when it gets here.
User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Tue Sep 24, 2019 6:53 pm

Unit arrived today and works fine after I made up an external mount for the supplied GPS antenna. Have not had time to look for the OXCO type so far as I've been monitoring the EI0SIX beacon all day. Nice display too

gpsdisplay.png
gpsdisplay.png (1.07 MiB) Viewed 35323 times
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Tue Sep 24, 2019 10:31 pm

200 microHertz error. How on Earth do you find that acceptable? ;)
User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Wed Sep 25, 2019 7:50 am

LOL guess I'll have to live with it :D

Edit: think I'm ok now
10mhz.png
10mhz.png (2.07 MiB) Viewed 35295 times
NI0Z
Posts: 16
Joined: Thu Jun 01, 2017 11:44 pm

Re: GPSDO Tutorial?

Postby NI0Z » Thu Jun 03, 2021 4:38 pm

Does anything need to be change on a 7000 MKII to use an external GDPO 10mhz reference signal into the back of the radio?

Thanks!
NI0Z
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Fri Jun 04, 2021 2:02 am

Negative.
NI0Z
Posts: 16
Joined: Thu Jun 01, 2017 11:44 pm

Re: GPSDO Tutorial?

Postby NI0Z » Fri Jun 04, 2021 11:49 am

Thank you, this would be a nice add to the manuals.
User avatar
dl6eat
Posts: 45
Joined: Wed Feb 14, 2018 1:31 pm
Location: Ellerhoop - JO43VR
Contact:

Re: GPSDO Tutorial?

Postby dl6eat » Fri Mar 11, 2022 4:46 pm

w-u-2-o wrote:Run it at the maximum setting. This will get you a 3.3v square wave output signal.

I bought the Chinese unit, which was riskier, of course, because I wanted access to the uBlox GPS chip serial data output and a 1pps output, neither of which the Bodnar unit has. I did not need or want an adjustable frequency output. I also wanted an OXCO for better flywheel performance, the Bodnar unit only uses a TXCO.

It was a bit tricky to identify a version of the Chinese unit on eBay that was the correct configuration, but I managed it and actually received a unit that works beautifully.


Hi Scott,

I face difficulties connecting a Leo Bognar device to my ANAN-7000. If I connect the GPSDO on lowest level (8mA) the ADC overload is flashing already. If I go lower (-10dB with an external att) it stops flashing.
But whatever I do I can't see that the GPSDO has taken over the frequency control. Any shift is not resulting in a shift of the radio. It seems that the build-in TCXO is still running the show.
I have not found any switch in Thetis to switch to the GPSDO manually......so I saw it should work automatically.
But the power level of Leo Bognar's GPSDO is very high (also on 8mA) and nothing happens or changes.
Any advise from your end is much apprechiated.....mni tnx,

Andy
No knobs, Pure Signal and Thetis (open source)
ANAN 7000, ANAN 10, Intel NUC 8i7 32 GB + 16 GB Optane
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Fri Mar 11, 2022 7:45 pm

Andy,

Connecting an external reference to the ANAN at any input power level should not cause ADC overload indications under any circumstances. I have to ask the dumb question: what connector on the back of the ANAN are you attaching to?

If we assume the answer is "The one marked '10MHz In'", then I can only guess that perhaps they built the thing wrong at the factory and accidentally swapped the XVTR and 10MHz connections internally. You may need to take the back off to check.

As for drive levels, the Bodnar units are specified to drive into a 50 ohm impedance. This means that, internal to the ANAN, you want jumpers placed at both J24 and J22. See the schematic posted about a dozen posts above this one. Again, you may need to take things apart a little to check.

You also want approx. +10dBm drive level into that 50 ohms. You didn't say which Bodnar unit you have, but check the directions to determine the drive level setting that gets closest to +10dBm and set it for that. Do not exceed +13dBm. If the jumpers are not placed inside the ANAN as discussed above then you will have to set a much lower drive level. It'll be guesswork in such a case, or you could try adding a tee connector a the ANAN end and placing a 50 ohm terminator on the other side of the tee.

The fun thing about the Bodnar units is that you can intentionally program them to put out, say, 9.9999MHz, thereby proving that the unit has switched over the external reference. After appreciating the 100Hz error, then put it back to 10.0MHz.

73,

Scott
User avatar
dl6eat
Posts: 45
Joined: Wed Feb 14, 2018 1:31 pm
Location: Ellerhoop - JO43VR
Contact:

Re: GPSDO Tutorial?

Postby dl6eat » Fri Mar 11, 2022 9:28 pm

Hi Scott,

Many thanks for your quick reply - much appreciated!
So I connected the Bognar device to the 10 MHz input (SMA-connector on rear)......but I tried the other as well (just in case they mixed it up).
The Bognar device is the mini - just one port. It can be switched between 8 mA and 24 mA in 4 steps......where 8 mA equals approx. + 5 dBm; 24 mA equals to about 14,6 dBm

So I have no time at present to open the box and put it in pieces but I will do that - I am guessing there are both jumpers not set.

But here is another interesting point: When I set the GPSDO to 10 MHz - and hit "calibrate frequency" it comes up with a correction factor of 1,000000000....... if I change the GPSDO output slightly the correction result is visible - it changes also!
But I have to start the calibration once again to make that happen.
As long as I do not start the freq cal again any frequency change is not resulting in anything.

Once again: Frequency changes of the GPSDO result in different correction factors after starting the cal menu.....being back to exactly 10 MHz it comes back to a correction factor of exactly 1,000000000.
It is simply not happening live - all manual only.
Above -5 dBm (10 dB external att at 8mA) the ADC overload identicator is blinking......

We have another ANAN 7000 in our team - I am waiting to hear what's happening there.....

I will provide further feedback.
73,

Andy
No knobs, Pure Signal and Thetis (open source)
ANAN 7000, ANAN 10, Intel NUC 8i7 32 GB + 16 GB Optane
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Fri Mar 11, 2022 10:11 pm

Andy,

You may be misunderstanding how it works.

When you are calibrating are you tuned to WWV with the dial set to the exact frequency of the WWV station, and with the mode set to DSB?

Assuming you are properly tuned to WWV, and the mode set to DSB, then when you kick off a calibration in Setup > General > Calibration:

- If the external reference is set to 10MHz and working properly, then the answer should be 1.0.

- If the external reference is set to not exactly 10MHz and working properly, then the calibration factor should reflect that offset.

If I'm reading your previous post correctly, your tests are giving those results and therefore you have proven that the ANAN has selected the Bodnar as the reference signal and that the Bodnar unit is working properly.

At that point all you need to do is set the Bodnar unit to 10MHz, manually set the correction factor to 1.0, and then enjoy your highly stable and accurate radio. Indeed, you do not need to use the frequency calibration function at all when using a properly operating GPSDO as an external frequency reference. Just leave the correction factor at 1.0. You only need to use the calibration function when your frequency reference is less perfect than that of a properly performing GPSDO, for instance the internal oscillator.

Assuming you've made it this far, don't lose confidence in your Bodnar. If you are within 1Hz or less of WWV that's perfect. It's hard to measure better than that because of ionospheric doppler on the WWV signal.

73,

Scott
User avatar
Tony EI7BMB
Posts: 651
Joined: Sun Apr 09, 2017 2:31 pm
Location: Dublin
Contact:

Re: GPSDO Tutorial?

Postby Tony EI7BMB » Sat Mar 12, 2022 11:13 am

Hi Andy, if you have 6m set up you can also use the OZ 6m beacon which is GPS locked as a reference.
User avatar
dl6eat
Posts: 45
Joined: Wed Feb 14, 2018 1:31 pm
Location: Ellerhoop - JO43VR
Contact:

Re: GPSDO Tutorial?

Postby dl6eat » Sat Mar 12, 2022 4:42 pm

Hi dear Scott, dear Tony,

The problem got fixed at the end. I opened the ANAN-7000 today and checked the cables.
Scott you were right - they mixed up the cables of transverter and RF Ref In.....unbelievable! The box was never open - done by the factory.
I added the 2 jumpers and corrected the cables. After that I had to remount everything again and checked it.
It works !

As long as the external reference is somehow near 10 MHz it works fine - if the reference is too much apart it jumps back to the internal TCXO.
The signal is down to about S6 when Leo Bognar's device is switched to 16 mA. This equals to 12,8 mW or +11 dBm. At 8 mA output (the lowest possible) it jumps to +5 dBm.
The ANAN works fine with just + 5dBm - the signal on 10 MHz is down to -97 dBm which is S5 only. I will leave it there...

Once again, I appreciate your help, your advises and the time you spent on helping me!
Have a great weekend gents!

73,

Andy
DL6EAT - W6EAT
No knobs, Pure Signal and Thetis (open source)
ANAN 7000, ANAN 10, Intel NUC 8i7 32 GB + 16 GB Optane
User avatar
w-u-2-o
Posts: 5539
Joined: Fri Mar 10, 2017 1:47 pm

Re: GPSDO Tutorial?

Postby w-u-2-o » Sat Mar 12, 2022 5:05 pm

dl6eat wrote:Scott you were right - they mixed up the cables of transverter and RF Ref In.....unbelievable! The box was never open - done by the factory.
That's just really sad, isn't it?

As long as the external reference is somehow near 10 MHz it works fine - if the reference is too much apart it jumps back to the internal TCXO.
It can't do that. That makes no sense. You should be able to set it to 9MHz and it will still use the external reference. The automatic switching circuit, shown in my post above, switches based on the presence of a sufficiently large external signal. There is no other logic involved.

The signal is down to about S6 when Leo Bognar's device is switched to 16 mA. This equals to 12,8 mW or +11 dBm. At 8 mA output (the lowest possible) it jumps to +5 dBm.
The ANAN works fine with just + 5dBm - the signal on 10 MHz is down to -97 dBm which is S5 only. I will leave it there...
I would run more than +5dBm, closer to +10dBm. Yes, the internal crosstalk on the ANAN is absolutely terrible, but at least you only get the interference on the WWV frequencies (10 and 20MHz) so it's not really a big deal.
User avatar
dl6eat
Posts: 45
Joined: Wed Feb 14, 2018 1:31 pm
Location: Ellerhoop - JO43VR
Contact:

Re: GPSDO Tutorial?

Postby dl6eat » Sun Mar 13, 2022 7:25 pm

Yes Scott I agree - let me just provide some more feedback to this topic as I spent some more time and started measurements.

First of all we compared results on 2 different ANANs (one 7000DLE and one 7000DLE MKII black face)
Both jump back to 10 MHz reference if the external reference jumps too much apart. You can not do much more than a couple KHz.....
If the reference is 1 MHz away it simply realizes that and uses again the internal TCXO......simply test it. May be the PLL is not locking any longer???

The ANAN is not accepting a GPSDO at 9 MHz.....but I do NOT understand "why".....both ANANs did the very same on this test.
My friend is 500 Km away - he did his own test and confirmed that as well. We both use professional Rohde equipment (signal generators up to several GHz) to simulate the GPSDO.

With both jumpers set the reference needs to exceed -16 dBm....it will be really stable from -14 dBm input level.
In my little world its normally enough if you go 10 dB higher......this would be -4 dBm.
I am now using +5 dBm (another 9 dB higher). What is the benefit going to even +10dBm? Crosstalk is not good at all and higher levels produce more interference. Also Leo Bognar’s device transmits no sine wave - more rectangular. If the signal gets too strong IMDs become visible…..

At this level (+5 dBm) the signal is visible on 10 MHz at -97 dBm - exactly S5.....which is reasonable low.
The MKII showed a bit lower level - better cross talk but my friend did not use the internal 50 Ohms but the external tee and 50 Ohms there....also no grounding jumper.

Ah - forgot to say my internal TCXO is 23 Hz too low - but that‘s easy since it can be corrected via Thetis. Absolute frequency is never an issue. - more frequency variation and drift…. all gone via GPSDO :D

Hope I could provide a bit as well ...

Thanks again and 73,

Andy
No knobs, Pure Signal and Thetis (open source)
ANAN 7000, ANAN 10, Intel NUC 8i7 32 GB + 16 GB Optane

Return to “Everything Else: Antennas, Relays, Switches, Power, Grounding, Cooling, etc.”