Re: [time-nuts] Spectrum Analyzer Specifications [Phase noise tester Bare Boards and Layout]

[Oz-in-DFW]

On 3/24/2016 1:08 PM, Bob Bownes wrote:
> Don't really need anyone who can order up bare boards in bulk anymore. 
Oshpark; www.oshpark.org does 2 layer for $5/sq in and 4 layer for
$10/sq.  That price gets you three boards. Designs can be made public so
anyone can buy them. I buy from them all the time. About 2 weeks turn.

There are several Chinese suppliers that will do 2 X 2 inch boards for
about $20 for 10 copies, about $30 by the time you have them in your
hands. Also about 2 Weeks turn, though may end up as much as 4 weeks.
> Many
> of the board houses will make them on demand for single customers. They fit
> them into empty spaces in larger board orders.
>
> I'd love one if someone is willing to draw it up. I'll even put together a
> Mouser BOM that can be shared if N8UR will layout the board. :)
If we can hash out a schematic, I can do a layout as a spare time
project - but I don't have a huge amount of spare time in the plan
before June or July.  I'd use KiCAD

We can do a public BoM on Digikey or Mouser so folks in the EU most of
the rest of the world have easy access.

There are few questions I have - surface mount or through-hole.  Through
hole parts are getting harder to get.  If you are afraid of SM we have
have a low cost service like Macrofab build small batches (they'll do as
few as one) and if we use parts from their standard parts list we only
pay the part cost, not the insertion cost. They'll also buy boards from
Oshpark. If you are not afraid of SM, buy a stencil from Oshstencils
https://oshstencils.com and get your hotplate out.

Connectors: SMA are cheap and reliable. More delicate than TNC, but not
by much, and a whole lot cheaper and more available as surplus.

> Bob
> KI2L
Oz, N1OZ

-- 
mailto:o...@ozindfw.net
Oz
POB 93167 
Southlake, TX 76092 (Near DFW Airport) 



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Re: [time-nuts] Spectrum Analyzer Specifications

[Magnus Danielson]

Bruce,

The anti-correlated thermal noise can however create big havoc to the 
measurement. That catastrophy has yet to sink in to some. Effectively, 
some is overstating their noise performance as a consequence.


However, it depends on the power-splitter being used.

Cheers,
Magnus

On 03/25/2016 02:31 AM, Bruce Griffiths wrote:

Actually if you split the signal and then amplify each output independently 
then the PN performance of the RF amps is not too critical in that cross 
correlation averages the amplifier PN down as well as that of the mixers.I've 
done this with the Timepod using quite noisy amps as nothing else was 
immediately to hand.It just takes a little longer but works very well. I 
measured the output PN noise of an LTC6957 evaluation board this way using a 
couple of minicircuits HELA10s which are fairly noisy at 10MHz.
If you don't need a PN floor below -180dBc/Hz then there are simple inexpensive 
one transistor (plus another for biasing) circuits that will achieve a few dB 
of gain with a PN noise floor well below -170dBc/Hz.The only real limitation is 
due to the presence of anti correlated thermal noise at the splitter outputs.

Bruce


 On Friday, 25 March 2016 2:06 PM, Bob Camp  wrote:


  Hi

That’s another good point about the need to work out a target device. Both
of the possible target devices I mentioned have enough channels to do at least a
dual channel measurement. That would add another mixer and a pair of power
splitters along with another amp chain.

The other part of that news is the RF drive power required goes up. You can do 
a pretty good job
of saturating an RPD-1 with +7 dbm. Most (but not all) OCXO’s and other gizmos 
will
provide that without any amplifiers involved. Adding a 3 db splitter gets you 
into the 10 dbm
range. That is getting fairly close to the limit for a lot of devices.

You can add an amp. The ones that work without impacting the phase noise of a 
high quality
OCXO  cost as much as the audio cards or USB devices. Cost wise, I’d keep that 
sort
of thing off the main board.

So what is the second channel worth?

The basic single channel design will get you into the -173 to -176 dbc / Hz 
range on a fairly high
power pair of OCXO’s. The cross correlation “stuff” will get you past that 
point. Is that worth taking
the BOM (without board and power supply) up to $80 or so? Consider that with 
the board and
power supply, it likely is over $100.

Would I do it as an accessory to a Janus or QA401? Maybe. You would need to 
pick one or
the other. In the case of the Janus, there are more software issues and some 
noise floor testing.
The QA401 is mighty expensive. The original idea was to use the sound card you 
already have ….

Bob



On Mar 24, 2016, at 5:30 PM, Bruce Griffiths  wrote:

If the software implements acquisition of cross power spectra
Then one could implement a near state of the art cross correlation PN test set
based on this.
With a suitable preamp the sound card could also be used for power supply and
reference noise measurement.

Bruce

On Thursday, March 24, 2016 04:54:47 PM Bob Camp wrote:

Hi

The board is pretty non-critical. It’s 90% audio. The biggest hassle is a
power supply. You would *like* a fairly high voltage, at least if you are
driving a spectrum analyzer. That may not be quite the case with a sound
card. It depends a *lot* which one you are running. Something like a QA401:

https://www.quantasylum.com/content/Products/QA401.aspx

Would make a good target device. It’s based on the AKM 5397 So might some
Janus boards. They are based on the earlier(?) AKM 5394. The QA401 has the
advantage of a nice box and full USB isolation (ground loops are a pain)..
It also has drivers and all the OS hooks. The Janus is a bit more “DIY”
with no drivers or interface (let alone isolation). The Janus is < 1/4 the
price.

The high voltage (+/- 18V linear regulated)  supply approach makes a lot of
sense with the QA401. It probably does not make as much sense with the
Janus. Switching regulators of any sort are something I would strongly
recommend against in a system like this that is trying to measure noise
floor at audio ….

The schematic changes a bit depending on what the target is. I can draw it
up if there is a consensus on the target. One example: If the “sound card”
is DC coupled, you can use it to indicate (and check) quadrature. If it’s
an AC device, you need some sort of isolated output for another indicator.

Bob


On Mar 24, 2016, at 1:31 PM, John Ackermann N8UR  wrote:

I'd be willing to assist with board layout if someone wanted to make this
into a real project (e.g., fully developed schematic).  TAPR might be
talked into supplying at least bare boards; we'd have to get a sense of
demand before committing to a full kit or assembled unit.

John


On 3/24/2016 9:04 AM, jimlux wrote:

More like $40 in parts, without a board, etc.
The RPD-1 is $20.70
LT1678/LT1679 is a 

Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Ian Stirling]

On 03/25/2016 05:55 PM, Bruce Griffiths wrote:

As long as BNC connectors are avoided as their phase shift isnt that stable.. A 
small mechanical disturbance will change it significantly. Actually low noise 
PN measurement systems can be very sensitive to cable movement. Bolting modules 
to a metal baseplate helps a lot as does using intermodule connections 
comprising SMA(m)-SMA(m) barrels rather than cables.
There's also the question of mixer port termination.The nist paper by Walls and 
Stein indicates that capacitive termination of the IF port may be effective in 
reducing noise whilst maintaining a flat response fro dc to around 50KHz.Small 
value resistors in series with the RF and LO ports are then useful in reducing 
the VSWR.


I replaced the faulty attenuator in one of my HP 8648 signal generators.
The "plumbing" in them is fascinating and instructive, rigid metal
tubes with smooth, continuous bends rather than flexible coaxial cable,
and mating with SMA connectors on both ends. My 8468C is good from
9 kHz to 3200 MHz, and where my 8568B only went to 1.5 GHz, I was able
to test the 8468C with the least spec. Signal Hound, SA44B, that goes
to 4.4 GHz.

Ian, G4ICV, AB2GR
--
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Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Alexander Pummer]

Use TNC, which is free of the problem and it fits into the same hole...
73
KJ6UHN
Alex

On 3/25/2016 3:46 PM, Bob Camp wrote:

Hi

The sensitivity of BNC connectors goes up quite a bit as they wear out. Both 
sides of
the connection are subject to wear. Replacing both sides is often the only 
solution when
they get noisy. That said, “screw down” connectors are a better way to go.

The “capacitive loading” termination of the mixer is something that a number of 
us
tried to reproduce when the paper came out. Even after fairly extensive 
conversations
with the authors, the effect seems be quite difficult to reproduce. It 
certainly is not a
“general solution” to the problem.

Bob



On Mar 25, 2016, at 5:55 PM, Bruce Griffiths  wrote:

As long as BNC connectors are avoided as their phase shift isnt that stable.. A 
small mechanical disturbance will change it significantly. Actually low noise 
PN measurement systems can be very sensitive to cable movement. Bolting modules 
to a metal baseplate helps a lot as does using intermodule connections 
comprising SMA(m)-SMA(m) barrels rather than cables.
There's also the question of mixer port termination.The nist paper by Walls and 
Stein indicates that capacitive termination of the IF port may be effective in 
reducing noise whilst maintaining a flat response fro dc to around 50KHz.Small 
value resistors in series with the RF and LO ports are then useful in reducing 
the VSWR.
Bruce


On Saturday, 26 March 2016 10:10 AM, Bob Camp  wrote:



Hi


On Mar 25, 2016, at 1:55 PM, jimlux  wrote:

On 3/25/16 5:07 AM, Bob Camp wrote:

Hi

The reverse isolation issue is indeed one of the weaknesses of this setup. For 
testing
OCXO’s isolation is not a big deal. A normal OCOX has very good output buffering
to give it the stability you are after. If you are running (maybe) a VCO with 
no buffering, that
assumption falls apart. The VCO will  / can injection lock through the mixer. 
In that
case you *do* need an amp to provide enough isolation to prevent the injection 
lock.



But if someone were building a little module for a cheap and cheerful noise 
analyzer, then the buffer amp would be a separate module.

That’s how I have always done it in the past. The need for the bufferer is rare 
enough that including it in the
basic analyzer module is not cost effective. The HP 3048 has the same basic 
issue (isolation) and they made
the same decision there.

Bob



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Re: [time-nuts] Spectrum Analyzer Specifications

[Charles Steinmetz]

Bob wrote:

I've been quite cheap and patient and have put together a quite 
capable 22GHz HP 7 MMS series SA  *  *  * That gets you down to 10Hz RBW

 *  *  *
Other options also exist. My 8565 SA was less than $1K when I bought 
it. It will get a RBW down to about 1KHz.


For laboratory work at VHF and below, an RBW of 1kHz is completely 
useless (as I mentioned before, some field work is different).  Even 
10Hz is not very useful.  I rarely use an RBW greater than 1Hz (other 
than for simply finding signals in a wide swath of spectrum, as 
opposed to analyzing them), and often use RBWs in the mHz region.


Best regards,

Charles


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Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Bob Camp]

Hi

The sensitivity of BNC connectors goes up quite a bit as they wear out. Both 
sides of 
the connection are subject to wear. Replacing both sides is often the only 
solution when
they get noisy. That said, “screw down” connectors are a better way to go. 

The “capacitive loading” termination of the mixer is something that a number of 
us 
tried to reproduce when the paper came out. Even after fairly extensive 
conversations 
with the authors, the effect seems be quite difficult to reproduce. It 
certainly is not a 
“general solution” to the problem. 

Bob


> On Mar 25, 2016, at 5:55 PM, Bruce Griffiths  
> wrote:
> 
> As long as BNC connectors are avoided as their phase shift isnt that stable.. 
> A small mechanical disturbance will change it significantly. Actually low 
> noise PN measurement systems can be very sensitive to cable movement. Bolting 
> modules to a metal baseplate helps a lot as does using intermodule 
> connections comprising SMA(m)-SMA(m) barrels rather than cables.
> There's also the question of mixer port termination.The nist paper by Walls 
> and Stein indicates that capacitive termination of the IF port may be 
> effective in reducing noise whilst maintaining a flat response fro dc to 
> around 50KHz.Small value resistors in series with the RF and LO ports are 
> then useful in reducing the VSWR.
> Bruce
> 
> 
>On Saturday, 26 March 2016 10:10 AM, Bob Camp  wrote:
> 
> 
> 
> Hi
> 
>> On Mar 25, 2016, at 1:55 PM, jimlux  wrote:
>> 
>> On 3/25/16 5:07 AM, Bob Camp wrote:
>>> Hi
>>> 
>>> The reverse isolation issue is indeed one of the weaknesses of this setup. 
>>> For testing
>>> OCXO’s isolation is not a big deal. A normal OCOX has very good output 
>>> buffering
>>> to give it the stability you are after. If you are running (maybe) a VCO 
>>> with no buffering, that
>>> assumption falls apart. The VCO will  / can injection lock through the 
>>> mixer. In that
>>> case you *do* need an amp to provide enough isolation to prevent the 
>>> injection lock.
>>> 
>> 
>> 
>> But if someone were building a little module for a cheap and cheerful noise 
>> analyzer, then the buffer amp would be a separate module.
> 
> That’s how I have always done it in the past. The need for the bufferer is 
> rare enough that including it in the 
> basic analyzer module is not cost effective. The HP 3048 has the same basic 
> issue (isolation) and they made
> the same decision there. 
> 
> Bob
> 
> 
>> 
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Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Bruce Griffiths]

As long as BNC connectors are avoided as their phase shift isnt that stable.. A 
small mechanical disturbance will change it significantly. Actually low noise 
PN measurement systems can be very sensitive to cable movement. Bolting modules 
to a metal baseplate helps a lot as does using intermodule connections 
comprising SMA(m)-SMA(m) barrels rather than cables.
There's also the question of mixer port termination.The nist paper by Walls and 
Stein indicates that capacitive termination of the IF port may be effective in 
reducing noise whilst maintaining a flat response fro dc to around 50KHz.Small 
value resistors in series with the RF and LO ports are then useful in reducing 
the VSWR.
Bruce
 

On Saturday, 26 March 2016 10:10 AM, Bob Camp  wrote:
 

 
Hi

> On Mar 25, 2016, at 1:55 PM, jimlux  wrote:
> 
> On 3/25/16 5:07 AM, Bob Camp wrote:
>> Hi
>> 
>> The reverse isolation issue is indeed one of the weaknesses of this setup. 
>> For testing
>> OCXO’s isolation is not a big deal. A normal OCOX has very good output 
>> buffering
>> to give it the stability you are after. If you are running (maybe) a VCO 
>> with no buffering, that
>> assumption falls apart. The VCO will  / can injection lock through the 
>> mixer. In that
>> case you *do* need an amp to provide enough isolation to prevent the 
>> injection lock.
>> 
> 
> 
> But if someone were building a little module for a cheap and cheerful noise 
> analyzer, then the buffer amp would be a separate module.

That’s how I have always done it in the past. The need for the bufferer is rare 
enough that including it in the 
basic analyzer module is not cost effective. The HP 3048 has the same basic 
issue (isolation) and they made
the same decision there. 

Bob


> 
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Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Bruce Griffiths]

On Friday, March 25, 2016 10:55:59 AM jimlux wrote:
> On 3/25/16 5:07 AM, Bob Camp wrote:
> > Hi
> > 
> > The reverse isolation issue is indeed one of the weaknesses of this setup.
> > For testing OCXO’s isolation is not a big deal. A normal OCOX has very
> > good output buffering to give it the stability you are after. If you are
> > running (maybe) a VCO with no buffering, that assumption falls apart. The
> > VCO will  / can injection lock through the mixer. In that case you *do*
> > need an amp to provide enough isolation to prevent the injection lock.
> But if someone were building a little module for a cheap and cheerful
> noise analyzer, then the buffer amp would be a separate module.
> 
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Yes that way one can tailor the amp gain and/or operating frequency to the 
task at hand.
As a general guide for amps employing 1-2 transistors if a reverse isolation 
of 40dB or more is required:

For a gain of 0-3dB a CB stage offers the lowest noise.
For higher gain and/or output push pull CB stages  are required.

For a gain of 3-10dB a series shunt feedback amplifier can be effective 
particularly if the output is taken from a transformer connected between the 
collector and the shunt feedback resistor. This configuration is useful in that 
one can employ the same output transformer for a wide range of gains.
The gain is changed by changing the value of a pair of resistors.

HP used discrete series shunt feedback stages in some of their PN measurement 
gear. However these suffered from relatively poor close in PN which can be 
cured by substituting a lower noise biasing system.

As long as the amp uses low noise biasing and low noise supplies together with 
sufficient  RF negative feedback then its flicker noise wont be an issue.

With a cross correlation system employing independent amps for each channel an 
amp with a noise figure < 6dB will usually suffice in that the added noise 
penalty can be traded off against a longer averaging time to reduce the system 
PN noise.

Bruce
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Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Bob Camp]

Hi

> On Mar 25, 2016, at 1:55 PM, jimlux  wrote:
> 
> On 3/25/16 5:07 AM, Bob Camp wrote:
>> Hi
>> 
>> The reverse isolation issue is indeed one of the weaknesses of this setup. 
>> For testing
>> OCXO’s isolation is not a big deal. A normal OCOX has very good output 
>> buffering
>> to give it the stability you are after. If you are running (maybe) a VCO 
>> with no buffering, that
>> assumption falls apart. The VCO will  / can injection lock through the 
>> mixer. In that
>> case you *do* need an amp to provide enough isolation to prevent the 
>> injection lock.
>> 
> 
> 
> But if someone were building a little module for a cheap and cheerful noise 
> analyzer, then the buffer amp would be a separate module.

That’s how I have always done it in the past. The need for the bufferer is rare 
enough that including it in the 
basic analyzer module is not cost effective. The HP 3048 has the same basic 
issue (isolation) and they made
the same decision there. 

Bob


> 
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Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[jimlux]

On 3/25/16 5:07 AM, Bob Camp wrote:

Hi

The reverse isolation issue is indeed one of the weaknesses of this setup. For 
testing
OCXO’s isolation is not a big deal. A normal OCOX has very good output buffering
to give it the stability you are after. If you are running (maybe) a VCO with 
no buffering, that
assumption falls apart. The VCO will  / can injection lock through the mixer. 
In that
case you *do* need an amp to provide enough isolation to prevent the injection 
lock.




But if someone were building a little module for a cheap and cheerful 
noise analyzer, then the buffer amp would be a separate module.


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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Bownes]

> Yes, good spec
> ​t​
> rum analyzers usually costs more than 2000 USD even as used. Also, a "high
> end" used 2000 USD spec
> ​t​
> rum analyzer can be much better than brand new "entry level" 1 USD spec
> ​t​
> rum
> ​analyzer. And if you need any kind of vectored signal analysis,
> demodulation capability of modern communications etc. then the price will
> be very high.
>

​You would be surprised. I've been quite cheap and patient and have put
together a quite capable 22GHz HP 7 MMS series SA for under $1KUS. If
you are impatient, it can be done for under $2KUS​. That gets you down to
10Hz RBW, color display, all digital. Not small, but very capable and
expandable. Another $1k (if patient, ~$2.2k if not) will add VNA
capabilities to 40GHz and all the capabilities we talked about using the
Microwave Transition Analyzer + the 70340 1-20GHz signal generator. All
with GPIB control.

Other options also exist. My 8565 SA was less than $1K when I bought it. It
will get a RBW down to about 1KHz. up to 22G without external mixers.
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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

If the objective is to come up with something that runs over a wide range
of power levels, a gate is not the best choice. The mixer it’s self will run
fine with one input fully driven and a fairly low signal on the other side. It
is not as sensitive in this case, but your normal calibration process still
gives you accurate data. 

If you want an amp that runs over the full range of the mixer, a gate that 
does well over 1 MHz to 100 MHz (or 10 to 200 with the SYPD-2) is a bit
tough to find. They are not as good an idea at 100 MHz as at 10 MHz. 

The next thing is that the amp’s gain needs to be quite low. That sounds simple,
just put in an attenuator. If you want good noise figure (you do), the 
attenuator
must go on the output of the amp. For 3 db of gain on your 23 db amp, you need
a 20 db attenuator. With +5 dbm into your amp, it’s producing a clean, 
undistorted, low noise +28 dbm ahead of your attenuator. Yes, those are
random numbers, they do illustrate what the problem is. 

The traditional solution was a common base amp with a transformer in 
the collector. It’s not ideal, but it is relatively cheap and simple. To get the
most out of the system, you want it to be as good as the mixer *with* the 
amps running. A “normal” common base will likely degrade the system
by several db at floor. It could degrade the close in by quite a bit more. 

Bob

> On Mar 24, 2016, at 10:05 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> 
> Could you use a gate instead of an amp?
> 
> Bob
> 
> On Thu, 3/24/16, Bob Camp <kb...@n1k.org> wrote:
> 
> Subject: Re: [time-nuts] Spectrum Analyzer Specifications
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts@febo.com>
> Date: Thursday, March 24, 2016, 5:48 PM
> 
> Hi
> 
> That’s another good point about the need to
> work out a target device. Both 
> of the
> possible target devices I mentioned have enough channels to
> do at least a 
> dual channel measurement.
> That would add another mixer and a pair of power
> splitters along with another amp chain. 
> 
> The other part of that news is
> the RF drive power required goes up. You can do a pretty
> good job
> of saturating an RPD-1 with +7 dbm.
> Most (but not all) OCXO’s and other gizmos will
> provide that without any amplifiers involved.
> Adding a 3 db splitter gets you into the 10 dbm 
> range. That is getting fairly close to the
> limit for a lot of devices.
> 
> You can add an amp. The ones that work without
> impacting the phase noise of a high quality 
> OCXO  cost as much as the audio cards or USB
> devices. Cost wise, I’d keep that sort
> of
> thing off the main board. 
> 
> So what is the second channel worth? 
> 
> The basic single channel
> design will get you into the -173 to -176 dbc / Hz range on
> a fairly high
> power pair of OCXO’s. The
> cross correlation “stuff” will get you past that point.
> Is that worth taking 
> the BOM (without board
> and power supply) up to $80 or so? Consider that with the
> board and
> power supply, it likely is over
> $100.
> 
> Would I do it as an
> accessory to a Janus or QA401? Maybe. You would need to pick
> one or 
> the other. In the case of the Janus,
> there are more software issues and some noise floor testing.
> 
> The QA401 is mighty expensive. The original
> idea was to use the sound card you already have ….
> 
> Bob 
> 
> 
>> On Mar 24, 2016, at 5:30
> PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz>
> wrote:
>> 
>> If the
> software implements acquisition of cross power spectra
>> Then one could implement a near state of
> the art cross correlation PN test set 
>> 
> based on this.
>> With a suitable preamp
> the sound card could also be used for power supply and 
>> reference noise measurement.
>> 
>> Bruce
>> 
>> On Thursday, March
> 24, 2016 04:54:47 PM Bob Camp wrote:
>>> Hi
>>> 
>>> The board is pretty non-critical.
> It’s 90% audio. The biggest hassle is a
>>> power supply. You would *like* a
> fairly high voltage, at least if you are
>>> driving a spectrum analyzer. That may
> not be quite the case with a sound
>>> 
> card. It depends a *lot* which one you are running.
> Something like a QA401:
>>> 
>>> https://www.quantasylum.com/content/Products/QA401.aspx
>>> 
>>> Would make a
> good target device. It’s based on the AKM 5397 So might
> some
>>> Janus boards. They are based
> on the earlier(?) AKM 5394. The QA401 has the
>>> advantage of a nice box and full USB
> isolation (ground loops are a pain).
>>>

Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Bob Camp]

Hi

The reverse isolation issue is indeed one of the weaknesses of this setup. For 
testing 
OCXO’s isolation is not a big deal. A normal OCOX has very good output 
buffering 
to give it the stability you are after. If you are running (maybe) a VCO with 
no buffering, that 
assumption falls apart. The VCO will  / can injection lock through the mixer. 
In that 
case you *do* need an amp to provide enough isolation to prevent the injection 
lock.

Bob 

> On Mar 25, 2016, at 12:27 AM, Bruce Griffiths  
> wrote:
> 
> http://www.ko4bb.com/getsimple/index.php?id=low-noise-high-reverse-isolation-low-distortion-rf-amplifier
> Bruce
> 
> 
> 
>On Friday, 25 March 2016 4:57 PM, Bruce Griffiths 
>  wrote:
> 
> 
> If 40-50dB reverse isolation is sufficient one can easily build suitable low 
> gain (<10dB) amps with a single RF transistor (plus output transformer 
> together with a low frequency transistor plus LED for bias stabilisation). 
> Retrofitting a similar biasing scheme to the RF amps in some early HP PN 
> measurement gear apparently does wonders for their PN at low offsets.
> One could even use a square wave drive from the output of a 74UHS125 or 
> similar CMOS buffer to drive the phase detector input. There is a NIST paper 
> that indicates a square wave LO drive for some mixers improves the 
> performance somewhat. 
> 
> If reverse isolation isnt an issue a pushpull transformer feedback Norton amp 
> works well.
> 
> I just bought the HELA10's on evaluation PCBs complete with brass metalwork..
> 
> Bruce
> 
> 
> 
>On Friday, 25 March 2016 4:02 PM, Bob Camp  wrote:
> 
> 
> Hi
> 
> If you think the HELA10 is fun at 10 MHz, try it at 1 MHz :)
> 
> The RPD-1 is a 1 MHz to 100 MHz part. That pretty well covers *most* of the 
> low 
> phase noise OCXO’s that people find running around in their junk boxes. To be 
> “general purpose”, an amp would need to cover the same range. With two OCXO’s 
> and two mixers, you would need 4 amps if they are after the splitters. By the 
> time you
> get even the HELA10’s on heatsinks and boards you probably are around $40 an 
> amplifier. Finding a part that is “as good as” the HELA10 is at 100 MHz, but 
> at 1 MHz, 
> is not very easy ….
> 
> =
> 
> Sort of on a bit different part of the same topic:
> 
> There is nothing magic about the RPD-1 other than it is easy to dead bug and 
> attach leaded 
> parts to. If one is doing a pc board, the SYPD-1 is the same thing in a 
> cheaper 
> surface mount package. The $5.70 you save will pay for a few square inches of 
> pc board. 
> 
> Bob
> 
> 
>> On Mar 24, 2016, at 9:31 PM, Bruce Griffiths  
>> wrote:
>> 
>> Actually if you split the signal and then amplify each output independently 
>> then the PN performance of the RF amps is not too critical in that cross 
>> correlation averages the amplifier PN down as well as that of the 
>> mixers.I've done this with the Timepod using quite noisy amps as nothing 
>> else was immediately to hand.It just takes a little longer but works very 
>> well. I measured the output PN noise of an LTC6957 evaluation board this way 
>> using a couple of minicircuits HELA10s which are fairly noisy at 10MHz.
>> If you don't need a PN floor below -180dBc/Hz then there are simple 
>> inexpensive one transistor (plus another for biasing) circuits that will 
>> achieve a few dB of gain with a PN noise floor well below -170dBc/Hz.The 
>> only real limitation is due to the presence of anti correlated thermal noise 
>> at the splitter outputs.
>> 
>> Bruce
>> 
>> 
>> On Friday, 25 March 2016 2:06 PM, Bob Camp  wrote:
>> 
>> 
>> Hi
>> 
>> That’s another good point about the need to work out a target device. Both 
>> of the possible target devices I mentioned have enough channels to do at 
>> least a 
>> dual channel measurement. That would add another mixer and a pair of power
>> splitters along with another amp chain. 
>> 
>> The other part of that news is the RF drive power required goes up. You can 
>> do a pretty good job
>> of saturating an RPD-1 with +7 dbm. Most (but not all) OCXO’s and other 
>> gizmos will
>> provide that without any amplifiers involved. Adding a 3 db splitter gets 
>> you into the 10 dbm 
>> range. That is getting fairly close to the limit for a lot of devices.
>> 
>> You can add an amp. The ones that work without impacting the phase noise of 
>> a high quality 
>> OCXO  cost as much as the audio cards or USB devices. Cost wise, I’d keep 
>> that sort
>> of thing off the main board. 
>> 
>> So what is the second channel worth? 
>> 
>> The basic single channel design will get you into the -173 to -176 dbc / Hz 
>> range on a fairly high
>> power pair of OCXO’s. The cross correlation “stuff” will get you past that 
>> point. Is that worth taking 
>> the BOM (without board and power supply) up to $80 or so? Consider that with 
>> the board and
>> power 

Re: [time-nuts] Spectrum Analyzer Specifications

[Esa Heikkinen]

time...@metachaos.net kirjoitti:


I have another question about test equipment. When using a spectrum analyzer
to examine the output of a frequency standard, what are the minimum
specification needed? Bandwidth, resolution, sensitivity, etc?


It depends what you want to measure from there. In general, analysis of 
this kind of strong signals are not very difficult but if you want to 
find weak spuriouses there then the dynamic range of the SA may become a 
problem.



Looking at spectrum analyzers on eBay, I see quite a bit of difference between
various models. Some have a resolution of 10Hz but others are 30Hz or even
100Hz.


This usually means resolution bandwith (RBW) and it has nothingh to do 
with actual frequency resolution. RBW means the bandwith of the 
adjustable IF filter in the SA signal path. With low bandwith you can 
see signals which are very close to each other but the sweeping will be 
slow. With high bandwith you can sweep large frequency areas in 
milliseconds but any sinals closer than RBW will be shown as one signal 
peak only. That's why it's very important to select correct RBW 
depending of what we are measuring. Usually the RBW selection is done 
auotmatically based on frequency span setting.


What comes to actual frequency resoltion you can usually set the center 
frequency with few decimals, it's not very accurate and it even doesn't 
have to be. When you sweep, you can analyze the peaks found in the trace 
with marker, but this is not accurate unless your spectrum analyzer is 
equipped with frequency counter function.


With counter function you can select the peak to be analyzed with marker 
and then use marker count function to see the actual frequency with that 
peak with the resolution of the counter (can be 1 Hz or 0.1 Hz for 
example -not as precise as with universal couner). But the difference 
with universal counter here is that you can count very faint signals 
also (for example less than -100 dBm) and you can select the signal to 
be counted even when there's multiple signals mixed. You may have some 
strong signal where your universal counter locks but then there's some 
faint signal mixed with it. If you want to count this faint signal you 
can do this with spectrum analyzer's counter easily.


With the counter function you will also need option to feed external 10 
MHz reference to the SA. Without external ref the counter is mostly 
useless because it may have serious frequency error. This error is also 
stongly dependent of the frequnecy what you count. For example if you 
want to count something around 10 GHz, only 1 Hz error in the 10 MHz 
refernce means 1000 Hz error in the counted value at 10 GHz.



Some have a minimum frequency of 0.01Hz, 100Hz or even in the kHz
range. Some are only sensitive to 60dBm, but others over 100dBm.


It's -60dBm or -100dBm. Both are quite poor values for spectrum analyzer 
but may be adequate if you only analyze strongs signals like oscillators.



Are any of the cheaper USB spectrum analyzers worth getting?


If you want to analyze only "easy" signals like oscillators etc. then 
yes. For anything more precise or very faint signals, I'd say no.



Most of these are appallingly expensive, so knowing what is needed can
certainly help guide a purchase or to minimize cost. And if a "deal" is found,
knowing that it is or is not adequate can help.


Yes, good specrum analyzers usually costs more than 2000 USD even as 
used. Also, a "high end" used 2000 USD specrtum analyzer can be much 
better than brand new "entry level" 1 USD specrum analyer. And if 
you need any kind of vectored signal analysis, demodulation capability 
of modern communications etc. then the price will be very high.


Hope this helps...

--
73s!
Esa
OH4KJU
___
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Spectrum Analyzer Specifications

[Bruce Griffiths]

One issue with CMOS gates is that a really quiet power supply is needed or the 
PN contribution of the gate is severely degraded. Fortunately this is an easy 
problem to solve.On solution is to use an independent noisy supply for each 
gate.
Bruce

 

On Friday, 25 March 2016 5:01 PM, Bob Stewart <b...@evoria.net> wrote:
 

 Hi Bob,

Could you use a gate instead of an amp?

Bob

On Thu, 3/24/16, Bob Camp <kb...@n1k.org> wrote:

 Subject: Re: [time-nuts] Spectrum Analyzer Specifications
 To: "Discussion of precise time and frequency measurement" 
<time-n...@febo..com>
 Date: Thursday, March 24, 2016, 5:48 PM
 
 Hi
 
 That’s another good point about the need to
 work out a target device. Both 
 of the
 possible target devices I mentioned have enough channels to
 do at least a 
 dual channel measurement.
 That would add another mixer and a pair of power
 splitters along with another amp chain. 
 
 The other part of that news is
 the RF drive power required goes up. You can do a pretty
 good job
 of saturating an RPD-1 with +7 dbm.
 Most (but not all) OCXO’s and other gizmos will
 provide that without any amplifiers involved.
 Adding a 3 db splitter gets you into the 10 dbm 
 range. That is getting fairly close to the
 limit for a lot of devices.
 
 You can add an amp. The ones that work without
 impacting the phase noise of a high quality 
 OCXO  cost as much as the audio cards or USB
 devices. Cost wise, I’d keep that sort
 of
 thing off the main board. 
 
 So what is the second channel worth? 
 
 The basic single channel
 design will get you into the -173 to -176 dbc / Hz range on
 a fairly high
 power pair of OCXO’s. The
 cross correlation “stuff” will get you past that point.
 Is that worth taking 
 the BOM (without board
 and power supply) up to $80 or so? Consider that with the
 board and
 power supply, it likely is over
 $100.
 
 Would I do it as an
 accessory to a Janus or QA401? Maybe. You would need to pick
 one or 
 the other. In the case of the Janus,
 there are more software issues and some noise floor testing.
 
 The QA401 is mighty expensive. The original
 idea was to use the sound card you already have ….
 
 Bob 
 
 
 > On Mar 24, 2016, at 5:30
 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 wrote:
 > 
 > If the
 software implements acquisition of cross power spectra
 > Then one could implement a near state of
 the art cross correlation PN test set 
 >
 based on this.
 > With a suitable preamp
 the sound card could also be used for power supply and 
 > reference noise measurement.
 > 
 > Bruce
 > 
 > On Thursday, March
 24, 2016 04:54:47 PM Bob Camp wrote:
 >> Hi
 >> 
 >> The board is pretty non-critical.
 It’s 90% audio. The biggest hassle is a
 >> power supply. You would *like* a
 fairly high voltage, at least if you are
 >> driving a spectrum analyzer. That may
 not be quite the case with a sound
 >>
 card. It depends a *lot* which one you are running.
 Something like a QA401:
 >> 
 >> https://www.quantasylum.com/content/Products/QA401.aspx
 >> 
 >> Would make a
 good target device. It’s based on the AKM 5397 So might
 some
 >> Janus boards. They are based
 on the earlier(?) AKM 5394. The QA401 has the
 >> advantage of a nice box and full USB
 isolation (ground loops are a pain).
 >> It also has drivers and all the OS
 hooks. The Janus is a bit more “DIY”
 >> with no drivers or interface (let
 alone isolation). The Janus is < 1/4 the
 >> price.
 >> 
 >> The high voltage (+/- 18V linear
 regulated)  supply approach makes a lot of
 >> sense with the QA401. It probably does
 not make as much sense with the
 >>
 Janus. Switching regulators of any sort are something I
 would strongly
 >> recommend against in
 a system like this that is trying to measure noise
 >> floor at audio ….
 >> 
 >> The
 schematic changes a bit depending on what the target is. I
 can draw it
 >> up if there is a
 consensus on the target. One example: If the “sound
 card”
 >> is DC coupled, you can use
 it to indicate (and check) quadrature. If it’s
 >> an AC device, you need some sort of
 isolated output for another indicator.
 >> 
 >> Bob
 >> 
 >>> On Mar
 24, 2016, at 1:31 PM, John Ackermann N8UR <j...@febo.com>
 wrote:
 >>> 
 >>> I'd be willing to assist with
 board layout if someone wanted to make this
 >>> into a real project (e.g., fully
 developed schematic).  TAPR might be
 >>> talked into supplying at least
 bare boards; we'd have to get a sense of
 >>> demand before committing to a full
 kit or assembled unit.
 >>> 
 >>> John
 >>>
 
 >>> 
 >>> On 3/24/2016 9:04 AM, jimlux
 wrote:
 >>>> More like $40 

Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Bruce Griffiths]

http://www.ko4bb.com/getsimple/index.php?id=low-noise-high-reverse-isolation-low-distortion-rf-amplifier
Bruce



On Friday, 25 March 2016 4:57 PM, Bruce Griffiths 
 wrote:
 

 If 40-50dB reverse isolation is sufficient one can easily build suitable low 
gain (<10dB) amps with a single RF transistor (plus output transformer together 
with a low frequency transistor plus LED for bias stabilisation). Retrofitting 
a similar biasing scheme to the RF amps in some early HP PN measurement gear 
apparently does wonders for their PN at low offsets.
One could even use a square wave drive from the output of a 74UHS125 or similar 
CMOS buffer to drive the phase detector input. There is a NIST paper that 
indicates a square wave LO drive for some mixers improves the performance 
somewhat. 

If reverse isolation isnt an issue a pushpull transformer feedback Norton amp 
works well.

I just bought the HELA10's on evaluation PCBs complete with brass metalwork..

Bruce

 

On Friday, 25 March 2016 4:02 PM, Bob Camp  wrote:
 

 Hi

If you think the HELA10 is fun at 10 MHz, try it at 1 MHz :)

The RPD-1 is a 1 MHz to 100 MHz part. That pretty well covers *most* of the low 
phase noise OCXO’s that people find running around in their junk boxes. To be 
“general purpose”, an amp would need to cover the same range. With two OCXO’s 
and two mixers, you would need 4 amps if they are after the splitters. By the 
time you
get even the HELA10’s on heatsinks and boards you probably are around $40 an 
amplifier. Finding a part that is “as good as” the HELA10 is at 100 MHz, but at 
1 MHz, 
is not very easy ….

=

Sort of on a bit different part of the same topic:

There is nothing magic about the RPD-1 other than it is easy to dead bug and 
attach leaded 
parts to. If one is doing a pc board, the SYPD-1 is the same thing in a cheaper 
surface mount package. The $5.70 you save will pay for a few square inches of 
pc board. 

Bob


> On Mar 24, 2016, at 9:31 PM, Bruce Griffiths  
> wrote:
> 
> Actually if you split the signal and then amplify each output independently 
> then the PN performance of the RF amps is not too critical in that cross 
> correlation averages the amplifier PN down as well as that of the mixers.I've 
> done this with the Timepod using quite noisy amps as nothing else was 
> immediately to hand.It just takes a little longer but works very well. I 
> measured the output PN noise of an LTC6957 evaluation board this way using a 
> couple of minicircuits HELA10s which are fairly noisy at 10MHz.
> If you don't need a PN floor below -180dBc/Hz then there are simple 
> inexpensive one transistor (plus another for biasing) circuits that will 
> achieve a few dB of gain with a PN noise floor well below -170dBc/Hz.The only 
> real limitation is due to the presence of anti correlated thermal noise at 
> the splitter outputs.
> 
> Bruce
> 
> 
>    On Friday, 25 March 2016 2:06 PM, Bob Camp  wrote:
> 
> 
> Hi
> 
> That’s another good point about the need to work out a target device. Both 
> of the possible target devices I mentioned have enough channels to do at 
> least a 
> dual channel measurement. That would add another mixer and a pair of power
> splitters along with another amp chain. 
> 
> The other part of that news is the RF drive power required goes up. You can 
> do a pretty good job
> of saturating an RPD-1 with +7 dbm. Most (but not all) OCXO’s and other 
> gizmos will
> provide that without any amplifiers involved. Adding a 3 db splitter gets you 
> into the 10 dbm 
> range. That is getting fairly close to the limit for a lot of devices.
> 
> You can add an amp. The ones that work without impacting the phase noise of a 
> high quality 
> OCXO  cost as much as the audio cards or USB devices. Cost wise, I’d keep 
> that sort
> of thing off the main board. 
> 
> So what is the second channel worth? 
> 
> The basic single channel design will get you into the -173 to -176 dbc / Hz 
> range on a fairly high
> power pair of OCXO’s. The cross correlation “stuff” will get you past that 
> point. Is that worth taking 
> the BOM (without board and power supply) up to $80 or so? Consider that with 
> the board and
> power supply, it likely is over $100.
> 
> Would I do it as an accessory to a Janus or QA401? Maybe. You would need to 
> pick one or 
> the other. In the case of the Janus, there are more software issues and some 
> noise floor testing. 
> The QA401 is mighty expensive. The original idea was to use the sound card 
> you already have ….
> 
> Bob 
> 
> 
>> On Mar 24, 2016, at 5:30 PM, Bruce Griffiths  
>> wrote:
>> 
>> If the software implements acquisition of cross power spectra
>> Then one could implement a near state of the art cross correlation PN test 
>> set 
>> based on this.
>> With a suitable preamp the sound card could also be used for power supply 
>> and 
>> reference noise 

Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Stewart]

Hi Bob,

Could you use a gate instead of an amp?

Bob

On Thu, 3/24/16, Bob Camp <kb...@n1k.org> wrote:

 Subject: Re: [time-nuts] Spectrum Analyzer Specifications
 To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com>
 Date: Thursday, March 24, 2016, 5:48 PM
 
 Hi
 
 That’s another good point about the need to
 work out a target device. Both 
 of the
 possible target devices I mentioned have enough channels to
 do at least a 
 dual channel measurement.
 That would add another mixer and a pair of power
 splitters along with another amp chain. 
 
 The other part of that news is
 the RF drive power required goes up. You can do a pretty
 good job
 of saturating an RPD-1 with +7 dbm.
 Most (but not all) OCXO’s and other gizmos will
 provide that without any amplifiers involved.
 Adding a 3 db splitter gets you into the 10 dbm 
 range. That is getting fairly close to the
 limit for a lot of devices.
 
 You can add an amp. The ones that work without
 impacting the phase noise of a high quality 
 OCXO  cost as much as the audio cards or USB
 devices. Cost wise, I’d keep that sort
 of
 thing off the main board. 
 
 So what is the second channel worth? 
 
 The basic single channel
 design will get you into the -173 to -176 dbc / Hz range on
 a fairly high
 power pair of OCXO’s. The
 cross correlation “stuff” will get you past that point.
 Is that worth taking 
 the BOM (without board
 and power supply) up to $80 or so? Consider that with the
 board and
 power supply, it likely is over
 $100.
 
 Would I do it as an
 accessory to a Janus or QA401? Maybe. You would need to pick
 one or 
 the other. In the case of the Janus,
 there are more software issues and some noise floor testing.
 
 The QA401 is mighty expensive. The original
 idea was to use the sound card you already have ….
 
 Bob 
 
 
 > On Mar 24, 2016, at 5:30
 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz>
 wrote:
 > 
 > If the
 software implements acquisition of cross power spectra
 > Then one could implement a near state of
 the art cross correlation PN test set 
 >
 based on this.
 > With a suitable preamp
 the sound card could also be used for power supply and 
 > reference noise measurement.
 > 
 > Bruce
 > 
 > On Thursday, March
 24, 2016 04:54:47 PM Bob Camp wrote:
 >> Hi
 >> 
 >> The board is pretty non-critical.
 It’s 90% audio. The biggest hassle is a
 >> power supply. You would *like* a
 fairly high voltage, at least if you are
 >> driving a spectrum analyzer. That may
 not be quite the case with a sound
 >>
 card. It depends a *lot* which one you are running.
 Something like a QA401:
 >> 
 >> https://www.quantasylum.com/content/Products/QA401.aspx
 >> 
 >> Would make a
 good target device. It’s based on the AKM 5397 So might
 some
 >> Janus boards. They are based
 on the earlier(?) AKM 5394. The QA401 has the
 >> advantage of a nice box and full USB
 isolation (ground loops are a pain).
 >> It also has drivers and all the OS
 hooks. The Janus is a bit more “DIY”
 >> with no drivers or interface (let
 alone isolation). The Janus is < 1/4 the
 >> price.
 >> 
 >> The high voltage (+/- 18V linear
 regulated)  supply approach makes a lot of
 >> sense with the QA401. It probably does
 not make as much sense with the
 >>
 Janus. Switching regulators of any sort are something I
 would strongly
 >> recommend against in
 a system like this that is trying to measure noise
 >> floor at audio ….
 >> 
 >> The
 schematic changes a bit depending on what the target is. I
 can draw it
 >> up if there is a
 consensus on the target. One example: If the “sound
 card”
 >> is DC coupled, you can use
 it to indicate (and check) quadrature. If it’s
 >> an AC device, you need some sort of
 isolated output for another indicator.
 >> 
 >> Bob
 >> 
 >>> On Mar
 24, 2016, at 1:31 PM, John Ackermann N8UR <j...@febo.com>
 wrote:
 >>> 
 >>> I'd be willing to assist with
 board layout if someone wanted to make this
 >>> into a real project (e.g., fully
 developed schematic).  TAPR might be
 >>> talked into supplying at least
 bare boards; we'd have to get a sense of
 >>> demand before committing to a full
 kit or assembled unit.
 >>> 
 >>> John
 >>>
 
 >>> 
 >>> On 3/24/2016 9:04 AM, jimlux
 wrote:
 >>>> More like $40 in
 parts, without a board, etc.
 >>>> The RPD-1 is $20.70
 >>>> LT1678/LT1679 is a nice low
 noise opamp that does rail to rail and is
 >>>> about $5
 >>>> etc
 >>>> 
 >>>> On 3/24/16 4:42 AM, Bob Camp
 wrote:
 >>>>> Hi
 >>>>&g

Re: [time-nuts] Spectrum Analyzer Specifications --> phase noise test set

[Bob Camp]

Hi

If you think the HELA10 is fun at 10 MHz, try it at 1 MHz :)

The RPD-1 is a 1 MHz to 100 MHz part. That pretty well covers *most* of the low 
phase noise OCXO’s that people find running around in their junk boxes. To be 
“general purpose”, an amp would need to cover the same range. With two OCXO’s 
and two mixers, you would need 4 amps if they are after the splitters. By the 
time you
get even the HELA10’s on heatsinks and boards you probably are around $40 an 
amplifier. Finding a part that is “as good as” the HELA10 is at 100 MHz, but at 
1 MHz, 
is not very easy ….

=

Sort of on a bit different part of the same topic:

There is nothing magic about the RPD-1 other than it is easy to dead bug and 
attach leaded 
parts to. If one is doing a pc board, the SYPD-1 is the same thing in a cheaper 
surface mount package. The $5.70 you save will pay for a few square inches of 
pc board. 

Bob


> On Mar 24, 2016, at 9:31 PM, Bruce Griffiths  
> wrote:
> 
> Actually if you split the signal and then amplify each output independently 
> then the PN performance of the RF amps is not too critical in that cross 
> correlation averages the amplifier PN down as well as that of the mixers.I've 
> done this with the Timepod using quite noisy amps as nothing else was 
> immediately to hand.It just takes a little longer but works very well. I 
> measured the output PN noise of an LTC6957 evaluation board this way using a 
> couple of minicircuits HELA10s which are fairly noisy at 10MHz.
> If you don't need a PN floor below -180dBc/Hz then there are simple 
> inexpensive one transistor (plus another for biasing) circuits that will 
> achieve a few dB of gain with a PN noise floor well below -170dBc/Hz.The only 
> real limitation is due to the presence of anti correlated thermal noise at 
> the splitter outputs.
> 
> Bruce
> 
> 
>On Friday, 25 March 2016 2:06 PM, Bob Camp  wrote:
> 
> 
> Hi
> 
> That’s another good point about the need to work out a target device. Both 
> of the possible target devices I mentioned have enough channels to do at 
> least a 
> dual channel measurement. That would add another mixer and a pair of power
> splitters along with another amp chain. 
> 
> The other part of that news is the RF drive power required goes up. You can 
> do a pretty good job
> of saturating an RPD-1 with +7 dbm. Most (but not all) OCXO’s and other 
> gizmos will
> provide that without any amplifiers involved. Adding a 3 db splitter gets you 
> into the 10 dbm 
> range. That is getting fairly close to the limit for a lot of devices.
> 
> You can add an amp. The ones that work without impacting the phase noise of a 
> high quality 
> OCXO  cost as much as the audio cards or USB devices. Cost wise, I’d keep 
> that sort
> of thing off the main board. 
> 
> So what is the second channel worth? 
> 
> The basic single channel design will get you into the -173 to -176 dbc / Hz 
> range on a fairly high
> power pair of OCXO’s. The cross correlation “stuff” will get you past that 
> point. Is that worth taking 
> the BOM (without board and power supply) up to $80 or so? Consider that with 
> the board and
> power supply, it likely is over $100.
> 
> Would I do it as an accessory to a Janus or QA401? Maybe. You would need to 
> pick one or 
> the other. In the case of the Janus, there are more software issues and some 
> noise floor testing. 
> The QA401 is mighty expensive. The original idea was to use the sound card 
> you already have ….
> 
> Bob 
> 
> 
>> On Mar 24, 2016, at 5:30 PM, Bruce Griffiths  
>> wrote:
>> 
>> If the software implements acquisition of cross power spectra
>> Then one could implement a near state of the art cross correlation PN test 
>> set 
>> based on this.
>> With a suitable preamp the sound card could also be used for power supply 
>> and 
>> reference noise measurement.
>> 
>> Bruce
>> 
>> On Thursday, March 24, 2016 04:54:47 PM Bob Camp wrote:
>>> Hi
>>> 
>>> The board is pretty non-critical. It’s 90% audio. The biggest hassle is a
>>> power supply. You would *like* a fairly high voltage, at least if you are
>>> driving a spectrum analyzer. That may not be quite the case with a sound
>>> card. It depends a *lot* which one you are running. Something like a QA401:
>>> 
>>> https://www.quantasylum.com/content/Products/QA401.aspx
>>> 
>>> Would make a good target device. It’s based on the AKM 5397 So might some
>>> Janus boards. They are based on the earlier(?) AKM 5394. The QA401 has the
>>> advantage of a nice box and full USB isolation (ground loops are a pain)..
>>> It also has drivers and all the OS hooks. The Janus is a bit more “DIY”
>>> with no drivers or interface (let alone isolation). The Janus is < 1/4 the
>>> price.
>>> 
>>> The high voltage (+/- 18V linear regulated)  supply approach makes a lot of
>>> sense with the QA401. It probably does not make as much sense with the
>>> Janus. Switching regulators of 

Re: [time-nuts] Spectrum Analyzer Specifications

[Bruce Griffiths]

Actually if you split the signal and then amplify each output independently 
then the PN performance of the RF amps is not too critical in that cross 
correlation averages the amplifier PN down as well as that of the mixers.I've 
done this with the Timepod using quite noisy amps as nothing else was 
immediately to hand.It just takes a little longer but works very well. I 
measured the output PN noise of an LTC6957 evaluation board this way using a 
couple of minicircuits HELA10s which are fairly noisy at 10MHz.
If you don't need a PN floor below -180dBc/Hz then there are simple inexpensive 
one transistor (plus another for biasing) circuits that will achieve a few dB 
of gain with a PN noise floor well below -170dBc/Hz.The only real limitation is 
due to the presence of anti correlated thermal noise at the splitter outputs.

Bruce
  

On Friday, 25 March 2016 2:06 PM, Bob Camp  wrote:
 

 Hi

That’s another good point about the need to work out a target device. Both 
of the possible target devices I mentioned have enough channels to do at least 
a 
dual channel measurement. That would add another mixer and a pair of power
splitters along with another amp chain. 

The other part of that news is the RF drive power required goes up. You can do 
a pretty good job
of saturating an RPD-1 with +7 dbm. Most (but not all) OCXO’s and other gizmos 
will
provide that without any amplifiers involved. Adding a 3 db splitter gets you 
into the 10 dbm 
range. That is getting fairly close to the limit for a lot of devices.

You can add an amp. The ones that work without impacting the phase noise of a 
high quality 
OCXO  cost as much as the audio cards or USB devices. Cost wise, I’d keep that 
sort
of thing off the main board. 

So what is the second channel worth? 

The basic single channel design will get you into the -173 to -176 dbc / Hz 
range on a fairly high
power pair of OCXO’s. The cross correlation “stuff” will get you past that 
point. Is that worth taking 
the BOM (without board and power supply) up to $80 or so? Consider that with 
the board and
power supply, it likely is over $100.

Would I do it as an accessory to a Janus or QA401? Maybe. You would need to 
pick one or 
the other. In the case of the Janus, there are more software issues and some 
noise floor testing. 
The QA401 is mighty expensive. The original idea was to use the sound card you 
already have ….

Bob 


> On Mar 24, 2016, at 5:30 PM, Bruce Griffiths  
> wrote:
> 
> If the software implements acquisition of cross power spectra
> Then one could implement a near state of the art cross correlation PN test 
> set 
> based on this.
> With a suitable preamp the sound card could also be used for power supply and 
> reference noise measurement.
> 
> Bruce
> 
> On Thursday, March 24, 2016 04:54:47 PM Bob Camp wrote:
>> Hi
>> 
>> The board is pretty non-critical. It’s 90% audio. The biggest hassle is a
>> power supply. You would *like* a fairly high voltage, at least if you are
>> driving a spectrum analyzer. That may not be quite the case with a sound
>> card. It depends a *lot* which one you are running. Something like a QA401:
>> 
>> https://www.quantasylum.com/content/Products/QA401.aspx
>> 
>> Would make a good target device. It’s based on the AKM 5397 So might some
>> Janus boards. They are based on the earlier(?) AKM 5394. The QA401 has the
>> advantage of a nice box and full USB isolation (ground loops are a pain)..
>> It also has drivers and all the OS hooks. The Janus is a bit more “DIY”
>> with no drivers or interface (let alone isolation). The Janus is < 1/4 the
>> price.
>> 
>> The high voltage (+/- 18V linear regulated)  supply approach makes a lot of
>> sense with the QA401. It probably does not make as much sense with the
>> Janus. Switching regulators of any sort are something I would strongly
>> recommend against in a system like this that is trying to measure noise
>> floor at audio ….
>> 
>> The schematic changes a bit depending on what the target is. I can draw it
>> up if there is a consensus on the target. One example: If the “sound card”
>> is DC coupled, you can use it to indicate (and check) quadrature. If it’s
>> an AC device, you need some sort of isolated output for another indicator.
>> 
>> Bob
>> 
>>> On Mar 24, 2016, at 1:31 PM, John Ackermann N8UR  wrote:
>>> 
>>> I'd be willing to assist with board layout if someone wanted to make this
>>> into a real project (e.g., fully developed schematic).  TAPR might be
>>> talked into supplying at least bare boards; we'd have to get a sense of
>>> demand before committing to a full kit or assembled unit.
>>> 
>>> John
>>> 
>>> 
>>> On 3/24/2016 9:04 AM, jimlux wrote:
 More like $40 in parts, without a board, etc.
 The RPD-1 is $20.70
 LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
 about $5
 etc
 
 On 3/24/16 4:42 AM, Bob Camp wrote:
> Hi
> 
> Pretty 

Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

That’s another good point about the need to work out a target device. Both 
of the possible target devices I mentioned have enough channels to do at least 
a 
dual channel measurement. That would add another mixer and a pair of power
splitters along with another amp chain. 

The other part of that news is the RF drive power required goes up. You can do 
a pretty good job
of saturating an RPD-1 with +7 dbm. Most (but not all) OCXO’s and other gizmos 
will
provide that without any amplifiers involved. Adding a 3 db splitter gets you 
into the 10 dbm 
range. That is getting fairly close to the limit for a lot of devices.

You can add an amp. The ones that work without impacting the phase noise of a 
high quality 
OCXO  cost as much as the audio cards or USB devices. Cost wise, I’d keep that 
sort
of thing off the main board. 

So what is the second channel worth? 

The basic single channel design will get you into the -173 to -176 dbc / Hz 
range on a fairly high
power pair of OCXO’s. The cross correlation “stuff” will get you past that 
point. Is that worth taking 
the BOM (without board and power supply) up to $80 or so? Consider that with 
the board and
power supply, it likely is over $100.

Would I do it as an accessory to a Janus or QA401? Maybe. You would need to 
pick one or 
the other. In the case of the Janus, there are more software issues and some 
noise floor testing. 
The QA401 is mighty expensive. The original idea was to use the sound card you 
already have ….

Bob 


> On Mar 24, 2016, at 5:30 PM, Bruce Griffiths  
> wrote:
> 
> If the software implements acquisition of cross power spectra
> Then one could implement a near state of the art cross correlation PN test 
> set 
> based on this.
> With a suitable preamp the sound card could also be used for power supply and 
> reference noise measurement.
> 
> Bruce
> 
> On Thursday, March 24, 2016 04:54:47 PM Bob Camp wrote:
>> Hi
>> 
>> The board is pretty non-critical. It’s 90% audio. The biggest hassle is a
>> power supply. You would *like* a fairly high voltage, at least if you are
>> driving a spectrum analyzer. That may not be quite the case with a sound
>> card. It depends a *lot* which one you are running. Something like a QA401:
>> 
>> https://www.quantasylum.com/content/Products/QA401.aspx
>> 
>> Would make a good target device. It’s based on the AKM 5397 So might some
>> Janus boards. They are based on the earlier(?) AKM 5394. The QA401 has the
>> advantage of a nice box and full USB isolation (ground loops are a pain).
>> It also has drivers and all the OS hooks. The Janus is a bit more “DIY”
>> with no drivers or interface (let alone isolation). The Janus is < 1/4 the
>> price.
>> 
>> The high voltage (+/- 18V linear regulated)  supply approach makes a lot of
>> sense with the QA401. It probably does not make as much sense with the
>> Janus. Switching regulators of any sort are something I would strongly
>> recommend against in a system like this that is trying to measure noise
>> floor at audio ….
>> 
>> The schematic changes a bit depending on what the target is. I can draw it
>> up if there is a consensus on the target. One example: If the “sound card”
>> is DC coupled, you can use it to indicate (and check) quadrature. If it’s
>> an AC device, you need some sort of isolated output for another indicator.
>> 
>> Bob
>> 
>>> On Mar 24, 2016, at 1:31 PM, John Ackermann N8UR  wrote:
>>> 
>>> I'd be willing to assist with board layout if someone wanted to make this
>>> into a real project (e.g., fully developed schematic).  TAPR might be
>>> talked into supplying at least bare boards; we'd have to get a sense of
>>> demand before committing to a full kit or assembled unit.
>>> 
>>> John
>>> 
>>> 
>>> On 3/24/2016 9:04 AM, jimlux wrote:
 More like $40 in parts, without a board, etc.
 The RPD-1 is $20.70
 LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
 about $5
 etc
 
 On 3/24/16 4:42 AM, Bob Camp wrote:
> Hi
> 
> Pretty simple:
> 
> Double balanced mixer, RPD-1 is one option, there are others.
> 
> Fairly simple L/C lowpass between the mixer and an op-amp.
> 
> 20 db positive (non-inverting) op-amp amplifier string after the mixer
> 
> Output of the string goes to the sound card. Use a good (dual / quad)
> audio op amp
> 
> Quadrature amp picks off the output of the first op amp stage, switch
> and resistors to set gain, pot to set op point.
> 
> 
> 
> So what you have is an old style quadrature phase noise amp and “PLL”.
> More or less a very junior version
> of the 3048 test box. Like any setup of this sort, you check two
> similar oscillators. They run in quadrature and
> you do a few “measure this with switch in position A” sort of things
> to set things up each time.
> 
> Nothing exotic.
> 
> Bob
> 
>> Any 

Re: [time-nuts] Spectrum Analyzer Specifications

[Tom Holmes]

Bob...

This is not related to your comment below but is still related to the thread..

Most SA's will generate noticeable internal distortion products at about -20 
dBm to the first mixer. Internal or external attenuator will knock down the 
much louder 10 MHz from the Oscillator under test to that level. The old 
reliable "add 10 dB of attenuation" test and look for commensurate changes in 
distortion products vs the fundamental is essential for this. If you add 10 dB 
and the trash changes by 20 or more, then they are in the SA.

Most close-in stuff won’t be affected, but as has been mentioned, the phase 
noise of the SA will likely be the limiting factor for what you will see unless 
you are testing a pretty bad synthesizer or using a current generation SA. With 
the modern boxes you can see more but it still won’t be clean enough to 
evaluate many XO's. You'd use the XO to find the PN of the SA!

Tom Holmes, N8ZM


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Thursday, March 24, 2016 4:55 PM
To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
Subject: Re: [time-nuts] Spectrum Analyzer Specifications

Hi

The board is pretty non-critical. It’s 90% audio. The biggest hassle is a power 
supply. 
You would *like* a fairly high voltage, at least if you are driving a spectrum 
analyzer. That
may not be quite the case with a sound card. It depends a *lot* which one you 
are running. 
Something like a QA401:

https://www.quantasylum.com/content/Products/QA401.aspx

Would make a good target device. It’s based on the AKM 5397 So might some Janus 
boards. 
They are based on the earlier(?) AKM 5394. The QA401 has the advantage of a 
nice box
and full USB isolation (ground loops are a pain). It also has drivers and all 
the OS hooks. 
The Janus is a bit more “DIY” with no drivers or interface (let alone 
isolation). The Janus is
 < 1/4 the price. 

The high voltage (+/- 18V linear regulated)  supply approach makes a lot of 
sense with the QA401. 
It probably does not make as much sense with the Janus. Switching regulators of 
any sort are
something I would strongly recommend against in a system like this that is 
trying to measure
noise floor at audio ….

The schematic changes a bit depending on what the target is. I can draw it up 
if there is a 
consensus on the target. One example: If the “sound card” is DC coupled, you 
can use it to
indicate (and check) quadrature. If it’s an AC device, you need some sort of 
isolated output for
another indicator. 

Bob


> On Mar 24, 2016, at 1:31 PM, John Ackermann N8UR <j...@febo.com> wrote:
> 
> I'd be willing to assist with board layout if someone wanted to make this 
> into a real project (e.g., fully developed schematic).  TAPR might be talked 
> into supplying at least bare boards; we'd have to get a sense of demand 
> before committing to a full kit or assembled unit.
> 
> John
> 
> On 3/24/2016 9:04 AM, jimlux wrote:
>> More like $40 in parts, without a board, etc.
>> The RPD-1 is $20.70
>> LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
>> about $5
>> etc
>> 
>> 
>> 
>> On 3/24/16 4:42 AM, Bob Camp wrote:
>>> Hi
>>> 
>>> Pretty simple:
>>> 
>>> Double balanced mixer, RPD-1 is one option, there are others.
>>> 
>>> Fairly simple L/C lowpass between the mixer and an op-amp.
>>> 
>>> 20 db positive (non-inverting) op-amp amplifier string after the mixer
>>> 
>>> Output of the string goes to the sound card. Use a good (dual / quad)
>>> audio op amp
>>> 
>>> Quadrature amp picks off the output of the first op amp stage, switch
>>> and resistors to set gain, pot to set op point.
>>> 
>>> 
>>> 
>>> So what you have is an old style quadrature phase noise amp and “PLL”.
>>> More or less a very junior version
>>> of the 3048 test box. Like any setup of this sort, you check two
>>> similar oscillators. They run in quadrature and
>>> you do a few “measure this with switch in position A” sort of things
>>> to set things up each time.
>>> 
>>> Nothing exotic.
>>> 
>>> Bob
>>> 
>>>>> 
>>>> 
>>>> Any documentation on this $40 phase noise test set?
>>>> 
>>>> Rick N6RK
>>> 
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
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> time-nuts mailing list -- time-nuts@febo.com
> To

Re: [time-nuts] Spectrum Analyzer Specifications

[Bruce Griffiths]

If the software implements acquisition of cross power spectra
Then one could implement a near state of the art cross correlation PN test set 
based on this.
With a suitable preamp the sound card could also be used for power supply and 
reference noise measurement.

Bruce

On Thursday, March 24, 2016 04:54:47 PM Bob Camp wrote:
> Hi
> 
> The board is pretty non-critical. It’s 90% audio. The biggest hassle is a
> power supply. You would *like* a fairly high voltage, at least if you are
> driving a spectrum analyzer. That may not be quite the case with a sound
> card. It depends a *lot* which one you are running. Something like a QA401:
> 
> https://www.quantasylum.com/content/Products/QA401.aspx
> 
> Would make a good target device. It’s based on the AKM 5397 So might some
> Janus boards. They are based on the earlier(?) AKM 5394. The QA401 has the
> advantage of a nice box and full USB isolation (ground loops are a pain).
> It also has drivers and all the OS hooks. The Janus is a bit more “DIY”
> with no drivers or interface (let alone isolation). The Janus is < 1/4 the
> price.
> 
> The high voltage (+/- 18V linear regulated)  supply approach makes a lot of
> sense with the QA401. It probably does not make as much sense with the
> Janus. Switching regulators of any sort are something I would strongly
> recommend against in a system like this that is trying to measure noise
> floor at audio ….
> 
> The schematic changes a bit depending on what the target is. I can draw it
> up if there is a consensus on the target. One example: If the “sound card”
> is DC coupled, you can use it to indicate (and check) quadrature. If it’s
> an AC device, you need some sort of isolated output for another indicator.
> 
> Bob
> 
> > On Mar 24, 2016, at 1:31 PM, John Ackermann N8UR  wrote:
> > 
> > I'd be willing to assist with board layout if someone wanted to make this
> > into a real project (e.g., fully developed schematic).  TAPR might be
> > talked into supplying at least bare boards; we'd have to get a sense of
> > demand before committing to a full kit or assembled unit.
> > 
> > John
> > 
> > 
> > On 3/24/2016 9:04 AM, jimlux wrote:
> >> More like $40 in parts, without a board, etc.
> >> The RPD-1 is $20.70
> >> LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
> >> about $5
> >> etc
> >> 
> >> On 3/24/16 4:42 AM, Bob Camp wrote:
> >>> Hi
> >>> 
> >>> Pretty simple:
> >>> 
> >>> Double balanced mixer, RPD-1 is one option, there are others.
> >>> 
> >>> Fairly simple L/C lowpass between the mixer and an op-amp.
> >>> 
> >>> 20 db positive (non-inverting) op-amp amplifier string after the mixer
> >>> 
> >>> Output of the string goes to the sound card. Use a good (dual / quad)
> >>> audio op amp
> >>> 
> >>> Quadrature amp picks off the output of the first op amp stage, switch
> >>> and resistors to set gain, pot to set op point.
> >>> 
> >>> 
> >>> 
> >>> So what you have is an old style quadrature phase noise amp and “PLL”.
> >>> More or less a very junior version
> >>> of the 3048 test box. Like any setup of this sort, you check two
> >>> similar oscillators. They run in quadrature and
> >>> you do a few “measure this with switch in position A” sort of things
> >>> to set things up each time.
> >>> 
> >>> Nothing exotic.
> >>> 
> >>> Bob
> >>> 
>  Any documentation on this $40 phase noise test set?
>  
>  Rick N6RK
> >> 
> >> ___
> >> time-nuts mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to
> >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >> and follow the instructions there.
> > 
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> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the
> > instructions there.
> 
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Re: [time-nuts] Spectrum Analyzer Specifications

[John Ackermann N8UR]

On 3/24/2016 4:54 PM, Bob Camp wrote:


Would make a good target device. It’s based on the AKM 5397 So might some Janus 
boards.
They are based on the earlier(?) AKM 5394. The QA401 has the advantage of a 
nice box
and full USB isolation (ground loops are a pain). It also has drivers and all 
the OS hooks.
The Janus is a bit more “DIY” with no drivers or interface (let alone 
isolation). The Janus is
  < 1/4 the price.


TAPR's been trying to find a good use for the Janus boards -- it was a 
product used with first-generation software defined radio systems, so 
we'd love to repurpose it.  There is room to make a deal if someone 
comes up with a project to use a bunch of them.


John
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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

I’ve built maybe a dozen of these over the years. I have never used a board for 
any of them. 
They all go down on a piece of scrap copper clad and point to point / dead bug 
wire up. You
get a good ground and leaded parts are easier to work with anyway. 

Bob

> On Mar 24, 2016, at 9:04 AM, jimlux  wrote:
> 
> More like $40 in parts, without a board, etc.
> The RPD-1 is $20.70
> LT1678/LT1679 is a nice low noise opamp that does rail to rail and is about $5
> etc
> 
> 
> 
> On 3/24/16 4:42 AM, Bob Camp wrote:
>> Hi
>> 
>> Pretty simple:
>> 
>> Double balanced mixer, RPD-1 is one option, there are others.
>> 
>> Fairly simple L/C lowpass between the mixer and an op-amp.
>> 
>> 20 db positive (non-inverting) op-amp amplifier string after the mixer
>> 
>> Output of the string goes to the sound card. Use a good (dual / quad) audio 
>> op amp
>> 
>> Quadrature amp picks off the output of the first op amp stage, switch and 
>> resistors to set gain, pot to set op point.
>> 
>> 
>> 
>> So what you have is an old style quadrature phase noise amp and “PLL”. More 
>> or less a very junior version
>> of the 3048 test box. Like any setup of this sort, you check two similar 
>> oscillators. They run in quadrature and
>> you do a few “measure this with switch in position A” sort of things to set 
>> things up each time.
>> 
>> Nothing exotic.
>> 
>> Bob
>> 
 
>>> 
>>> Any documentation on this $40 phase noise test set?
>>> 
>>> Rick N6RK
>> 
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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

Most of mine used OP-27 and OP-37 op amps. The typical destination was a 3561
in most cases. It was nice because it had built in “normalize to 1 Hz” 
capability. 

Many sound cards will go below 20 Hz. The problem is often that the noise rises 
fairly quickly as you go below 10 Hz. You also get into some interesting 
settings issues
with the normal operating system based drivers. “Twitter needs to change the 
audio level
to send you an alert” is a gotcha.

Bob

> On Mar 24, 2016, at 9:31 AM, Richard (Rick) Karlquist  
> wrote:
> 
> Thanks for the explanation.  I actually built
> something like that 30 years ago using an LT-1028
> op amp, only it used an HP3582 FFT box instead of
> a sound card (which didn't exist at the time).
> Does anyone have any experience with the low
> frequency cutoff of sound cards?  You would
> think 20 Hz, but maybe they go lower??  Any
> recommended sound cards (or USB things that
> work like sound cards)?
> 
> Rick
> 
> On 3/24/2016 4:42 AM, Bob Camp wrote:
>> Hi
>> 
>> Pretty simple:
>> 
>> Double balanced mixer, RPD-1 is one option, there are others.
>> 
>> Fairly simple L/C lowpass between the mixer and an op-amp.
>> 
>> 20 db positive (non-inverting) op-amp amplifier string after the mixer
>> 
>> Output of the string goes to the sound card. Use a good (dual / quad) audio 
>> op amp
>> 
>> Quadrature amp picks off the output of the first op amp stage, switch and 
>> resistors to set gain, pot to set op point.
>> 
>> 
>> 
>> So what you have is an old style quadrature phase noise amp and “PLL”. More 
>> or less a very junior version
>> of the 3048 test box. Like any setup of this sort, you check two similar 
>> oscillators. They run in quadrature and
>> you do a few “measure this with switch in position A” sort of things to set 
>> things up each time.
>> 
>> Nothing exotic.
>> 
>> Bob
>> 
>> 
>> 
>>> On Mar 24, 2016, at 12:25 AM, Richard (Rick) Karlquist 
>>>  wrote:
>>> 
>>> 
>>> 
>>> On 3/23/2016 3:56 PM, Bob Camp wrote:
>>> 
 and standard covered. If you want to do spurs, spend $40 and build a phase
 noise test set that will drive the sound card on your PC.
 
 Lots of choices ….
 
 Bob
 
>>> 
>>> Any documentation on this $40 phase noise test set?
>>> 
>>> Rick N6RK
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>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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>> 
>> 
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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

The board is pretty non-critical. It’s 90% audio. The biggest hassle is a power 
supply. 
You would *like* a fairly high voltage, at least if you are driving a spectrum 
analyzer. That
may not be quite the case with a sound card. It depends a *lot* which one you 
are running. 
Something like a QA401:

https://www.quantasylum.com/content/Products/QA401.aspx

Would make a good target device. It’s based on the AKM 5397 So might some Janus 
boards. 
They are based on the earlier(?) AKM 5394. The QA401 has the advantage of a 
nice box
and full USB isolation (ground loops are a pain). It also has drivers and all 
the OS hooks. 
The Janus is a bit more “DIY” with no drivers or interface (let alone 
isolation). The Janus is
 < 1/4 the price. 

The high voltage (+/- 18V linear regulated)  supply approach makes a lot of 
sense with the QA401. 
It probably does not make as much sense with the Janus. Switching regulators of 
any sort are
something I would strongly recommend against in a system like this that is 
trying to measure
noise floor at audio ….

The schematic changes a bit depending on what the target is. I can draw it up 
if there is a 
consensus on the target. One example: If the “sound card” is DC coupled, you 
can use it to
indicate (and check) quadrature. If it’s an AC device, you need some sort of 
isolated output for
another indicator. 

Bob


> On Mar 24, 2016, at 1:31 PM, John Ackermann N8UR  wrote:
> 
> I'd be willing to assist with board layout if someone wanted to make this 
> into a real project (e.g., fully developed schematic).  TAPR might be talked 
> into supplying at least bare boards; we'd have to get a sense of demand 
> before committing to a full kit or assembled unit.
> 
> John
> 
> On 3/24/2016 9:04 AM, jimlux wrote:
>> More like $40 in parts, without a board, etc.
>> The RPD-1 is $20.70
>> LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
>> about $5
>> etc
>> 
>> 
>> 
>> On 3/24/16 4:42 AM, Bob Camp wrote:
>>> Hi
>>> 
>>> Pretty simple:
>>> 
>>> Double balanced mixer, RPD-1 is one option, there are others.
>>> 
>>> Fairly simple L/C lowpass between the mixer and an op-amp.
>>> 
>>> 20 db positive (non-inverting) op-amp amplifier string after the mixer
>>> 
>>> Output of the string goes to the sound card. Use a good (dual / quad)
>>> audio op amp
>>> 
>>> Quadrature amp picks off the output of the first op amp stage, switch
>>> and resistors to set gain, pot to set op point.
>>> 
>>> 
>>> 
>>> So what you have is an old style quadrature phase noise amp and “PLL”.
>>> More or less a very junior version
>>> of the 3048 test box. Like any setup of this sort, you check two
>>> similar oscillators. They run in quadrature and
>>> you do a few “measure this with switch in position A” sort of things
>>> to set things up each time.
>>> 
>>> Nothing exotic.
>>> 
>>> Bob
>>> 
> 
 
 Any documentation on this $40 phase noise test set?
 
 Rick N6RK
>>> 
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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Bownes]

Don't really need anyone who can order up bare boards in bulk anymore. Many
of the board houses will make them on demand for single customers. They fit
them into empty spaces in larger board orders.

I'd love one if someone is willing to draw it up. I'll even put together a
Mouser BOM that can be shared if N8UR will layout the board. :)

Bob
KI2L


On Thu, Mar 24, 2016 at 1:31 PM, John Ackermann N8UR  wrote:

> I'd be willing to assist with board layout if someone wanted to make this
> into a real project (e.g., fully developed schematic).  TAPR might be
> talked into supplying at least bare boards; we'd have to get a sense of
> demand before committing to a full kit or assembled unit.
>
> John
> 
>
> On 3/24/2016 9:04 AM, jimlux wrote:
>
>> More like $40 in parts, without a board, etc.
>> The RPD-1 is $20.70
>> LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
>> about $5
>> etc
>>
>>
>>
>> On 3/24/16 4:42 AM, Bob Camp wrote:
>>
>>> Hi
>>>
>>> Pretty simple:
>>>
>>> Double balanced mixer, RPD-1 is one option, there are others.
>>>
>>> Fairly simple L/C lowpass between the mixer and an op-amp.
>>>
>>> 20 db positive (non-inverting) op-amp amplifier string after the mixer
>>>
>>> Output of the string goes to the sound card. Use a good (dual / quad)
>>> audio op amp
>>>
>>> Quadrature amp picks off the output of the first op amp stage, switch
>>> and resistors to set gain, pot to set op point.
>>>
>>> 
>>>
>>> So what you have is an old style quadrature phase noise amp and “PLL”.
>>> More or less a very junior version
>>> of the 3048 test box. Like any setup of this sort, you check two
>>> similar oscillators. They run in quadrature and
>>> you do a few “measure this with switch in position A” sort of things
>>> to set things up each time.
>>>
>>> Nothing exotic.
>>>
>>> Bob
>>>
>>>
>
 Any documentation on this $40 phase noise test set?

 Rick N6RK

>>>
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Re: [time-nuts] Spectrum Analyzer Specifications

[Tom Miller]

Most of the USB sound cards have a capacitor coupled input. If you jumper 
the cap they will go down to DC.


T
- Original Message - 
From: "Richard (Rick) Karlquist" <rich...@karlquist.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts@febo.com>

Sent: Thursday, March 24, 2016 9:31 AM
Subject: Re: [time-nuts] Spectrum Analyzer Specifications



Thanks for the explanation.  I actually built
something like that 30 years ago using an LT-1028
op amp, only it used an HP3582 FFT box instead of
a sound card (which didn't exist at the time).
Does anyone have any experience with the low
frequency cutoff of sound cards?  You would
think 20 Hz, but maybe they go lower??  Any
recommended sound cards (or USB things that
work like sound cards)?

Rick

On 3/24/2016 4:42 AM, Bob Camp wrote:

Hi

Pretty simple:

Double balanced mixer, RPD-1 is one option, there are others.

Fairly simple L/C lowpass between the mixer and an op-amp.

20 db positive (non-inverting) op-amp amplifier string after the mixer

Output of the string goes to the sound card. Use a good (dual / quad) 
audio op amp


Quadrature amp picks off the output of the first op amp stage, switch and 
resistors to set gain, pot to set op point.




So what you have is an old style quadrature phase noise amp and “PLL”. 
More or less a very junior version
of the 3048 test box. Like any setup of this sort, you check two similar 
oscillators. They run in quadrature and
you do a few “measure this with switch in position A” sort of things to 
set things up each time.


Nothing exotic.

Bob



On Mar 24, 2016, at 12:25 AM, Richard (Rick) Karlquist 
<rich...@karlquist.com> wrote:




On 3/23/2016 3:56 PM, Bob Camp wrote:

and standard covered. If you want to do spurs, spend $40 and build a 
phase

noise test set that will drive the sound card on your PC.

Lots of choices ….

Bob



Any documentation on this $40 phase noise test set?

Rick N6RK
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Re: [time-nuts] Spectrum Analyzer Specifications

[Magnus Danielson]

Rick,

Depending on the "card" (it's more like USB dongle now) and their 
choices of ADCs and  DACs, you may or may not bypass the DC blocking caps.


I know that people playing around with laser-shows use this trick, but 
it was quite some time since I look at was is available.


Would be interesting to see what is available.

If one has ADCs and DACs, when one could implement the loop in digital, 
which have the additional benefit that adjusting it can be automated.


Cheers,
Magnus

On 03/24/2016 02:31 PM, Richard (Rick) Karlquist wrote:

Thanks for the explanation.  I actually built
something like that 30 years ago using an LT-1028
op amp, only it used an HP3582 FFT box instead of
a sound card (which didn't exist at the time).
Does anyone have any experience with the low
frequency cutoff of sound cards?  You would
think 20 Hz, but maybe they go lower??  Any
recommended sound cards (or USB things that
work like sound cards)?

Rick

On 3/24/2016 4:42 AM, Bob Camp wrote:

Hi

Pretty simple:

Double balanced mixer, RPD-1 is one option, there are others.

Fairly simple L/C lowpass between the mixer and an op-amp.

20 db positive (non-inverting) op-amp amplifier string after the mixer

Output of the string goes to the sound card. Use a good (dual / quad)
audio op amp

Quadrature amp picks off the output of the first op amp stage, switch
and resistors to set gain, pot to set op point.



So what you have is an old style quadrature phase noise amp and “PLL”.
More or less a very junior version
of the 3048 test box. Like any setup of this sort, you check two
similar oscillators. They run in quadrature and
you do a few “measure this with switch in position A” sort of things
to set things up each time.

Nothing exotic.

Bob




On Mar 24, 2016, at 12:25 AM, Richard (Rick) Karlquist
 wrote:



On 3/23/2016 3:56 PM, Bob Camp wrote:


and standard covered. If you want to do spurs, spend $40 and build a
phase
noise test set that will drive the sound card on your PC.

Lots of choices ….

Bob



Any documentation on this $40 phase noise test set?

Rick N6RK
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Re: [time-nuts] Spectrum Analyzer Specifications

[John Ackermann N8UR]

I'd be willing to assist with board layout if someone wanted to make 
this into a real project (e.g., fully developed schematic).  TAPR might 
be talked into supplying at least bare boards; we'd have to get a sense 
of demand before committing to a full kit or assembled unit.


John

On 3/24/2016 9:04 AM, jimlux wrote:

More like $40 in parts, without a board, etc.
The RPD-1 is $20.70
LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
about $5
etc



On 3/24/16 4:42 AM, Bob Camp wrote:

Hi

Pretty simple:

Double balanced mixer, RPD-1 is one option, there are others.

Fairly simple L/C lowpass between the mixer and an op-amp.

20 db positive (non-inverting) op-amp amplifier string after the mixer

Output of the string goes to the sound card. Use a good (dual / quad)
audio op amp

Quadrature amp picks off the output of the first op amp stage, switch
and resistors to set gain, pot to set op point.



So what you have is an old style quadrature phase noise amp and “PLL”.
More or less a very junior version
of the 3048 test box. Like any setup of this sort, you check two
similar oscillators. They run in quadrature and
you do a few “measure this with switch in position A” sort of things
to set things up each time.

Nothing exotic.

Bob





Any documentation on this $40 phase noise test set?

Rick N6RK



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Re: [time-nuts] Spectrum Analyzer Specifications

[jimlux]

More like $40 in parts, without a board, etc.
The RPD-1 is $20.70
LT1678/LT1679 is a nice low noise opamp that does rail to rail and is 
about $5

etc



On 3/24/16 4:42 AM, Bob Camp wrote:

Hi

Pretty simple:

Double balanced mixer, RPD-1 is one option, there are others.

Fairly simple L/C lowpass between the mixer and an op-amp.

20 db positive (non-inverting) op-amp amplifier string after the mixer

Output of the string goes to the sound card. Use a good (dual / quad) audio op 
amp

Quadrature amp picks off the output of the first op amp stage, switch and 
resistors to set gain, pot to set op point.



So what you have is an old style quadrature phase noise amp and “PLL”. More or 
less a very junior version
of the 3048 test box. Like any setup of this sort, you check two similar 
oscillators. They run in quadrature and
you do a few “measure this with switch in position A” sort of things to set 
things up each time.

Nothing exotic.

Bob





Any documentation on this $40 phase noise test set?

Rick N6RK



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Re: [time-nuts] Spectrum Analyzer Specifications

[Richard (Rick) Karlquist]

Thanks for the explanation.  I actually built
something like that 30 years ago using an LT-1028
op amp, only it used an HP3582 FFT box instead of
a sound card (which didn't exist at the time).
Does anyone have any experience with the low
frequency cutoff of sound cards?  You would
think 20 Hz, but maybe they go lower??  Any
recommended sound cards (or USB things that
work like sound cards)?

Rick

On 3/24/2016 4:42 AM, Bob Camp wrote:

Hi

Pretty simple:

Double balanced mixer, RPD-1 is one option, there are others.

Fairly simple L/C lowpass between the mixer and an op-amp.

20 db positive (non-inverting) op-amp amplifier string after the mixer

Output of the string goes to the sound card. Use a good (dual / quad) audio op 
amp

Quadrature amp picks off the output of the first op amp stage, switch and 
resistors to set gain, pot to set op point.



So what you have is an old style quadrature phase noise amp and “PLL”. More or 
less a very junior version
of the 3048 test box. Like any setup of this sort, you check two similar 
oscillators. They run in quadrature and
you do a few “measure this with switch in position A” sort of things to set 
things up each time.

Nothing exotic.

Bob




On Mar 24, 2016, at 12:25 AM, Richard (Rick) Karlquist  
wrote:



On 3/23/2016 3:56 PM, Bob Camp wrote:


and standard covered. If you want to do spurs, spend $40 and build a phase
noise test set that will drive the sound card on your PC.

Lots of choices ….

Bob



Any documentation on this $40 phase noise test set?

Rick N6RK
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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

Pretty simple:

Double balanced mixer, RPD-1 is one option, there are others.

Fairly simple L/C lowpass between the mixer and an op-amp. 

20 db positive (non-inverting) op-amp amplifier string after the mixer 

Output of the string goes to the sound card. Use a good (dual / quad) audio op 
amp 

Quadrature amp picks off the output of the first op amp stage, switch and 
resistors to set gain, pot to set op point.



So what you have is an old style quadrature phase noise amp and “PLL”. More or 
less a very junior version
of the 3048 test box. Like any setup of this sort, you check two similar 
oscillators. They run in quadrature and
you do a few “measure this with switch in position A” sort of things to set 
things up each time. 

Nothing exotic.

Bob



> On Mar 24, 2016, at 12:25 AM, Richard (Rick) Karlquist 
>  wrote:
> 
> 
> 
> On 3/23/2016 3:56 PM, Bob Camp wrote:
> 
>> and standard covered. If you want to do spurs, spend $40 and build a phase
>> noise test set that will drive the sound card on your PC.
>> 
>> Lots of choices ….
>> 
>> Bob
>> 
> 
> Any documentation on this $40 phase noise test set?
> 
> Rick N6RK
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Re: [time-nuts] Spectrum Analyzer Specifications

[jimlux]

On 3/23/16 10:38 AM, Ian Stirling wrote:

On 03/23/2016 01:23 AM, time...@metachaos.net wrote:


I have another question about test equipment. When using a spectrum
analyzer
to examine the output of a frequency standard, what are the minimum
specification needed? Bandwidth, resolution, sensitivity, etc?


   Spectrum analysers are not precision frequency counters.
A few years ago I bought an HP 8568B "boat anchor" spectrum analyser
from the site. It is a wonderful instrument, over USA $30,000 when it
was in production until 1997. But it sits unused because my
http://signalhound.com USB-SA44B — 4.4 GHz Spectrum Analyser with
a laptop Windows 7 computer is so much more convenient.
The SA44B is effectively a superbly calibrated measuring receiver
with software that makes it a spectrum analyser.
Indeed, I have listened to NPR on 93.9 MHz on it.



I use a SA-44 a lot at work. There are some good and bad things about 
the software (both the earlier version and the latest Spike software).. 
but overall, for under a kilobuck, it's not a bad device.



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Re: [time-nuts] Spectrum Analyzer Specifications

[Richard (Rick) Karlquist]

On 3/23/2016 3:56 PM, Bob Camp wrote:


and standard covered. If you want to do spurs, spend $40 and build a phase
noise test set that will drive the sound card on your PC.

Lots of choices ….

Bob



Any documentation on this $40 phase noise test set?

Rick N6RK
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Re: [time-nuts] Spectrum Analyzer Specifications

[timenut]

Thanks everybody! You have all given me a bit to think about. Clearly, what I
thought that I needed is not necessarily what I actually need. To summarize...

   1. There are various options and approaches for a Spectrum Analyzer. BUT, I
  probably don't actually need one because they are inadequate to the task
  at hand. One that might be sufficient would probably cost as much as a
  small house (or new car). Not cost effective for me.

   2. The next big test tool should probably be a time interval counter, with
  possibly a cheaper higher-precision frequency counter without time
  interval capabilities before that.

   3. But first, a GPSDO for a frequency reference is a good idea (I was
  already planning on that, in any case). I also think that a higher
  precision DMM (one of the 6 or 7 digit meters) is probably also a good
  idea.


Mike

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Re: [time-nuts] Spectrum Analyzer Specifications

[Brooke Clarke]

Hi Mike:

A lot depends on what you are going to be doing.

For example a few decades ago I built an automated system to measure mixer spurs where the frequency of the spurs was 
known because I had control of the LO and RF frequency.

IF = +/-LO*n +/-RF*m
The first attempt used the HP 8350B sweeper for the LO and RF sources, but the phase noise was huge so that when you 
looked at the IF on the spectrum analyzer the amplitude was jumping up and down many dB.  Switched to synthesized signal 
generators and that problem went away.  Note that the instrument with the best LO was the source for the external 
reference inputs for the other two instruments so that they all agreed on the frequency.

http://www.prc68.com/I/RASS_PP.html#Spur

PS A trick to save time is to set the start and stop frequencies so that the IF is just past the start frequency rather 
than being centered.  That way you can stop the sweep a little after the IF frequency cutting the sweep time by more 
than a factor of 10.


PPS First generation spectrum analyzers use analog processing and so the resolution bandwidth is directly tied to the 
sweep speed.  A digital IF overcomes this limitation (is much faster) and also allows measuring noise power (I^2 + Q^2) 
where the analog SA used peak detection.  Also a digital IF allows for 1 Hz real RBW which in turns makes for fantastic 
sensitivity.  You can wrap a wire around a radio and see it's LO frequency.  The HP/Agilent 4395A is such a digital IF SA.

http://www.prc68.com/I/4395A.shtml

Example of measuring LO frequency with the 4395A and a good 10 MHz external 
reference.
http://www.prc68.com/I/BlkBox.shtml

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 

Hi,

I have another question about test equipment. When using a spectrum analyzer
to examine the output of a frequency standard, what are the minimum
specification needed? Bandwidth, resolution, sensitivity, etc?

Looking at spectrum analyzers on eBay, I see quite a bit of difference between
various models. Some have a resolution of 10Hz but others are 30Hz or even
100Hz. Some have a minimum frequency of 0.01Hz, 100Hz or even in the kHz
range. Some are only sensitive to 60dBm, but others over 100dBm.

Are any of the cheaper USB spectrum analyzers worth getting?

Most of these are appallingly expensive, so knowing what is needed can
certainly help guide a purchase or to minimize cost. And if a "deal" is found,
knowing that it is or is not adequate can help.

Clearly, better specifications are preferable, but I'm also sure that the
intended application makes a large difference. What is needed for examining a
10Mhz frequency standard might be remarkably different from what is needed for
high-frequency RF work.


Mike

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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

The “spurs and noise” you see plotted on an OCXO are the output of a 
phase noise tester. No spectrum analyzer or SDR out there has enough 
dynamic range to look at the phase noise on a good OCXO. You are dealing
with +10 dbm signals so “sensitivity” is not the issue. The range between 
the signal and the noise with that signal applied is the issue (= dynamic 
range). 

A 40 year old surplus counter for < $100 from eBay will get you 9 digits of 
frequency in 1 second. It will get you to 10 or 11 digits before you get 
totally 
bored waiting for the reading. For about 5X that, you can add another digit. 

The counter by it’s self does not have a lot of use. You need some sort of
reference for it. A GPSDO (again I’d recommend surplus commercial gear) 
is the best bang for the buck there. There are a lot of candidates in the $100 
to $200 range. Once you have that, a telecom Rubidium standard can be 
bought for about the same amount of money. 

Before I’d spend $20,000 to $50,000 on a good spectrum analyzer, I’d get the 
counter
and standard covered. If you want to do spurs, spend $40 and build a phase
noise test set that will drive the sound card on your PC. 

Lots of choices ….

Bob

> On Mar 23, 2016, at 8:45 AM, time...@metachaos.net wrote:
> 
> Charles,
> 
>>> When using a spectrum analyzer to examine the output of a frequency 
>>> standard, what are the minimum specification needed? Bandwidth, 
>>> resolution, sensitivity, etc?
> 
>> It very much depends on what you hope to see with it.  That said, 
>> virtually no SA will do anything useful in this application without a 
>> fair amount of preprocessing.
> 
>> . . .
> 
>> I am all for having one or several SAs around the lab, but I fear
>> that an SA may not be very useful for the particular tasks you are 
>> hoping it will perform.
> 
> Being new to this, I don't actually know what I need to see with it. However,
> I see charts that show the "spurs" on the output of an oscillator. I assume
> that I will want to do similar tasks. As I understand it, those are the main
> problem when multiplying the frequency by very much because they get
> multiplied as well. Thus, one of the differences between a "good" OCXO and a
> "bad" OCXO.
> 
>> Pay attention to ergonomics -- suffering with an SA that doesn't
>> think like you do will drive you crazy.  For example, I prefer 
>> HP/Agilent SAs over Tek SAs because the HPs allow you to specify a 
>> start and stop frequency *or* a center frequency and span, while the 
>> Teks only allow you to specify a center frequency and span.
> 
> As an example, I currently have a broken MTI 260 which I am repairing. I
> currently have it cleanly disassembled so that it can be reassembled with no
> damage. I know what needs to be done to fix it (at least the first pass) and
> am waiting on a tool that I need. But, if I succeed in repairing it, what
> test equipment do I need to determine the quality of output?
> 
> I can measure frequency to a point (7 digits, uncalibrated - 8 once I have a
> frequency standard). That is not enough to determine very small deviations
> from 10Mhz, but it will tell me that I have a sine wave at approximately the
> correct frequency. The last one I (sort of) repaired, gave me a sine wave but
> with a duty cycle that wasn't exactly 50-50. So there must be some distortion
> present. Not surprising in that case because of the hacking that I did.
> 
> However, I understand that the quality of the OCXOs can vary widely. What
> tools do I need to determine the quality of output? I assumed that a spectrum
> analyzer would be a first step - to look for large spurs, overtones and
> consistent noise (e.g. 120 kHz components) at unusual frequencies. Even jitter
> and phase noise should show up that way - at least with sufficient resolution,
> which might be unrealistic.
> 
> 
> Mike
> 
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Re: [time-nuts] Spectrum Analyzer Specifications

[Charles Steinmetz]

Peter wrote:

May I suggest the use of a software defined receiver (SDR) used with 
suitable attenuators on its antenna input.


The task the OP needs performed is to simultaneously receive a CW 
signal at ~ +13dBm, while at the same time resolving and 
differentiating sidebands as close as fractions of a Hz at ~ -80dBm 
and lower.  Yes, the signal can be attenuated (say, CW signal at 
-10dBm and close-in sidebands at -103dBm and below, or CW signal at 
-30dBm and close-in sidebands at -133dBm and below).  Anyway you cut 
it, that is a dynamic range of more than 90dB at frequency offsets of 
fractional Hz.  The phase noise of the receiver's LO will completely 
swamp the phase noise of the oscillator being tested, by tens of dB 
(called reciprocal mixing).


Best regards,

Charles


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Re: [time-nuts] Spectrum Analyzer Specifications

[Charles Steinmetz]

Mike wrote:

Being new to this, I don't actually know what I need to see with it. 
However, I see charts that show the "spurs" on the output of an 
oscillator. I assume that I will want to do similar tasks.


I can measure frequency to a point (7 digits, uncalibrated - 8 once 
I have a frequency standard).


I understand that the quality of the OCXOs can vary widely. What 
tools do I need to determine the quality of output?  I assumed that 
a spectrum analyzer would be a first step


No, a spectrum analyzer (with much support from ancillary equipment, 
as I said in my last message) is the last step.  Actually, it is 
beyond the last step for all but a very few time-nuts -- mostly ones 
who design precision oscillators.  You are trying to step from 
nowhere near time-nuts capability (7 or 8 digit counter) to 
post-doctoral time-nuts capability.  I believe you would be much 
better served by doing it in steps (and probably leaving out that last step).


First, you need a time interval counter (reciprocal counter) with 12+ 
digits.  With that (and some creativity), you can take series 
(plural) of time-stamped "phase" (time interval) data, which you can 
then analyze (post-process) for phase noise (short-term instability) 
and xDEV (long-term instability).  The list archives are full of 
discussions of exactly these procedures.  The phase noise analyses 
will give you a good picture of how the oscillator will 
multiply.  The TI analyzer will also give you the frequency of your 
oscillator to time-nuts levels of precision.


The usual suspects are the HP 5370A or B, the Stanford Research 
SR620, and the HP 5345A.  There are others, but those three are the 
likely value leaders.


Best regards,

Charles



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Re: [time-nuts] Spectrum Analyzer Specifications

[Ian Stirling]

On 03/23/2016 01:23 AM, time...@metachaos.net wrote:


I have another question about test equipment. When using a spectrum analyzer
to examine the output of a frequency standard, what are the minimum
specification needed? Bandwidth, resolution, sensitivity, etc?


  Spectrum analysers are not precision frequency counters.
A few years ago I bought an HP 8568B "boat anchor" spectrum analyser
from the site. It is a wonderful instrument, over USA $30,000 when it
was in production until 1997. But it sits unused because my
http://signalhound.com USB-SA44B — 4.4 GHz Spectrum Analyser with
a laptop Windows 7 computer is so much more convenient.
The SA44B is effectively a superbly calibrated measuring receiver
with software that makes it a spectrum analyser.
Indeed, I have listened to NPR on 93.9 MHz on it.

Ian, G4ICV, AB2GR
--

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Re: [time-nuts] Spectrum Analyzer Specifications

[Peter Torry]

Fellow Timenuts,

May I suggest the use of a software defined receiver (SDR) used with 
suitable attenuators on its antenna input.  I use a device called 
SDRPlay that is low cost, covers 100kHz to 2000MHz, and has a more 
sensitivity than most low cost Spectrum analysers.  Used with care the 
qualitative display is quite reasonable and compares well with my main 
analyser the only drawback being the  limited display width of 8MHz.  It 
would then leave more resources to purchase the important equipment.


Regards

Peter Torry

On 23/03/2016 14:04, jimlux wrote:

On 3/23/16 4:11 AM, Bob Camp wrote:

Hi

If you can see harmonics down to -60 dbc, that is about the most a 
normal spectrum
analyzer will do for you on a frequency standard. This *assumes* the 
part has a sine
wave output. Most standards are in the 10 MHz range, so an analyzer 
that will work to

= 40 MHz is probably a good idea.


Can you do this with a USB gizmo? Sure you can. Can you trust the 
results? That will
depend on the exact unit you get and your ability to calibrate it. 
Might it “only” be useful
to -50 dbc? Might it work to -100 dbc? That is part of the “did you 
pay $X or 10 times

that much question.






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Re: [time-nuts] Spectrum Analyzer Specifications

[jimlux]

On 3/23/16 4:11 AM, Bob Camp wrote:

Hi

If you can see harmonics down to -60 dbc, that is about the most a normal 
spectrum
analyzer will do for you on a frequency standard. This *assumes* the part has a 
sine
wave output. Most standards are in the 10 MHz range, so an analyzer that will 
work to

= 40 MHz is probably a good idea.


Can you do this with a USB gizmo? Sure you can. Can you trust the results? That 
will
depend on the exact unit you get and your ability to calibrate it. Might it 
“only” be useful
to -50 dbc? Might it work to -100 dbc? That is part of the “did you pay $X or 
10 times
that much question.




Spectrum analyzers are also nice when debugging a new circuit.. 
unexpected oscillations at other frequencies, spurs, etc.


For this kind of thing, limited dynamic range isn't as big a problem. 
Would the difference between a 8 bit and more bits in the ADC make a 
difference? Maybe, maybe not.


However, with respect to this new analyzer, the thing to really look at 
is the software that runs it.  Does it do what you need it to do, 
*today*?  Does it work on your PC platform (Win, Mac, *nix), *today*?


Today is important.  There may be all sorts of planned upgrades (and 
hey, lots of folks do "open source", so conceivably, someone else could 
do the upgrade), but they may never materialize: the people doing the 
work may get onto another project; there's not enough market for what 
you want.


More than one software controlled device I've worked with worked fine 
with the supplied software, but what I was really interested in was 
controlling it with other software, and the promised open API never 
really existed, was documented, or delivered.


This is particularly pervasive in the amateur radio community, where the 
original developer was motivated to "scratch an itch", solved their 
problem, and then cast their product out to the big wide world, along 
with grand plans to make it even better, then found that it was more 
work, and work that didn't scratch the itch.


Likewise with products/software that are the result of somone's masters 
or PhD thesis.  They get far enough along to finish the dissertation, 
publish it as open source (good for them and us), but there it 
languishes, 85% complete, with all the (useful to me) corner cases 
untested or undeveloped.



In neither of these last two, would I cast aspersions on the authors (or 
even forge and machine aspersions): they did what they said they 
were going to do, and in general, their description of what they 
actually did matches what they did.


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Re: [time-nuts] Spectrum Analyzer Specifications

[timenut]

Charles,

>>When using a spectrum analyzer to examine the output of a frequency 
>>standard, what are the minimum specification needed? Bandwidth, 
>>resolution, sensitivity, etc?

> It very much depends on what you hope to see with it.  That said, 
> virtually no SA will do anything useful in this application without a 
> fair amount of preprocessing.

> . . .

> I am all for having one or several SAs around the lab, but I fear
> that an SA may not be very useful for the particular tasks you are 
> hoping it will perform.

Being new to this, I don't actually know what I need to see with it. However,
I see charts that show the "spurs" on the output of an oscillator. I assume
that I will want to do similar tasks. As I understand it, those are the main
problem when multiplying the frequency by very much because they get
multiplied as well. Thus, one of the differences between a "good" OCXO and a
"bad" OCXO.

> Pay attention to ergonomics -- suffering with an SA that doesn't
> think like you do will drive you crazy.  For example, I prefer 
> HP/Agilent SAs over Tek SAs because the HPs allow you to specify a 
> start and stop frequency *or* a center frequency and span, while the 
> Teks only allow you to specify a center frequency and span.

As an example, I currently have a broken MTI 260 which I am repairing. I
currently have it cleanly disassembled so that it can be reassembled with no
damage. I know what needs to be done to fix it (at least the first pass) and
am waiting on a tool that I need. But, if I succeed in repairing it, what
test equipment do I need to determine the quality of output?

I can measure frequency to a point (7 digits, uncalibrated - 8 once I have a
frequency standard). That is not enough to determine very small deviations
from 10Mhz, but it will tell me that I have a sine wave at approximately the
correct frequency. The last one I (sort of) repaired, gave me a sine wave but
with a duty cycle that wasn't exactly 50-50. So there must be some distortion
present. Not surprising in that case because of the hacking that I did.

However, I understand that the quality of the OCXOs can vary widely. What
tools do I need to determine the quality of output? I assumed that a spectrum
analyzer would be a first step - to look for large spurs, overtones and
consistent noise (e.g. 120 kHz components) at unusual frequencies. Even jitter
and phase noise should show up that way - at least with sufficient resolution,
which might be unrealistic.


Mike

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Re: [time-nuts] Spectrum Analyzer Specifications

[Charles Steinmetz]

Mike wrote:

When using a spectrum analyzer to examine the output of a frequency 
standard, what are the minimum specification needed? Bandwidth, 
resolution, sensitivity, etc?


It very much depends on what you hope to see with it.  That said, 
virtually no SA will do anything useful in this application without a 
fair amount of preprocessing.  SA front ends do not have the dynamic 
range to handle the fundamental frequency and resolve any useful 
detail down at the oscillator noise level.  You will generally need 
to both filter out the fundamental with a very sharp filter and also 
use a very narrow SA bandwidth -- less than 1Hz -- to analyze the 
residue.  You may also need an ultra-low-noise amplifier to get the 
residual noise above the SA input noise.


The HP 3561A "dynamic signal analyzer" is supplied as part of the HP 
3048A phase noise measurement system, and has usable bandwidths down 
to the uHz range.  It is arguably the most useful SA for analyzing 
oscillators.  However, it only handles frequencies up to 115kHz, so 
it needs the rest of the 3048A to be useful -- or at least an offset 
oscillator (better than the one you are testing) and mixer to 
heterodyne the oscillator you are testing down to the useful range of 
the instrument, plus a sharp filter to attenuate the carrier.


Personally, I have rarely needed resolution bandwidths larger than 
300Hz for laboratory work (field work is different), and I frequently 
want RBWs considerably smaller than 1Hz.  I can highly recommend the 
HP 3588A, which operates in both sweep mode and also in FFT mode.


A tracking generator is nearly indispensable for much of what you 
will (probably) eventually do with an SA, so try to hold out for one 
with this feature.


Pay attention to ergonomics -- suffering with an SA that doesn't 
think like you do will drive you crazy.  For example, I prefer 
HP/Agilent SAs over Tek SAs because the HPs allow you to specify a 
start and stop frequency *or* a center frequency and span, while the 
Teks only allow you to specify a center frequency and span.


Also personally, I wouldn't waste money on any of the new plastic SAs 
that are flooding the market, or on any USB SA.  I would stick with 
used HP and Tek instruments (and *possibly* one or two others).


You can find operator's manuals (and service manuals) for the HP and 
Tek instruments on-line.  Study them carefully to figure out which 
ones have the features and ergonomics you want.  You will also pick 
up information that allows you to ask sellers detailed questions to 
increase the probability you will get a working unit.


I am all for having one or several SAs around the lab, but I fear 
that an SA may not be very useful for the particular tasks you are 
hoping it will perform.


Best regards,

Charles


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Re: [time-nuts] Spectrum Analyzer Specifications

[Bob Camp]

Hi

If you can see harmonics down to -60 dbc, that is about the most a normal 
spectrum
analyzer will do for you on a frequency standard. This *assumes* the part has a 
sine
wave output. Most standards are in the 10 MHz range, so an analyzer that will 
work to
>= 40 MHz is probably a good idea. 

Can you do this with a USB gizmo? Sure you can. Can you trust the results? That 
will 
depend on the exact unit you get and your ability to calibrate it. Might it 
“only” be useful
to -50 dbc? Might it work to -100 dbc? That is part of the “did you pay $X or 
10 times 
that much question. 

Bob



> On Mar 23, 2016, at 1:23 AM, time...@metachaos.net wrote:
> 
> Hi,
> 
> I have another question about test equipment. When using a spectrum analyzer
> to examine the output of a frequency standard, what are the minimum
> specification needed? Bandwidth, resolution, sensitivity, etc?
> 
> Looking at spectrum analyzers on eBay, I see quite a bit of difference between
> various models. Some have a resolution of 10Hz but others are 30Hz or even
> 100Hz. Some have a minimum frequency of 0.01Hz, 100Hz or even in the kHz
> range. Some are only sensitive to 60dBm, but others over 100dBm.
> 
> Are any of the cheaper USB spectrum analyzers worth getting?
> 
> Most of these are appallingly expensive, so knowing what is needed can
> certainly help guide a purchase or to minimize cost. And if a "deal" is found,
> knowing that it is or is not adequate can help.
> 
> Clearly, better specifications are preferable, but I'm also sure that the
> intended application makes a large difference. What is needed for examining a
> 10Mhz frequency standard might be remarkably different from what is needed for
> high-frequency RF work.
> 
> 
> Mike
> 
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Re: [time-nuts] Spectrum Analyzer Specifications

[Jason Gardner]

Unless you are interested in the spectral purity of the source's output, I
wouldn't bother with a spectrum analyser. The frequency resolution would
not be sufficient, nor would the frequency accuracy, to make meaningful
frequency measurements of a frequency standard.

I would instead go looking for a decent counter.

Regards

Jason
On 23 Mar 2016 08:01,  wrote:

> Hi,
>
> I have another question about test equipment. When using a spectrum
> analyzer
> to examine the output of a frequency standard, what are the minimum
> specification needed? Bandwidth, resolution, sensitivity, etc?
>
> Looking at spectrum analyzers on eBay, I see quite a bit of difference
> between
> various models. Some have a resolution of 10Hz but others are 30Hz or even
> 100Hz. Some have a minimum frequency of 0.01Hz, 100Hz or even in the kHz
> range. Some are only sensitive to 60dBm, but others over 100dBm.
>
> Are any of the cheaper USB spectrum analyzers worth getting?
>
> Most of these are appallingly expensive, so knowing what is needed can
> certainly help guide a purchase or to minimize cost. And if a "deal" is
> found,
> knowing that it is or is not adequate can help.
>
> Clearly, better specifications are preferable, but I'm also sure that the
> intended application makes a large difference. What is needed for
> examining a
> 10Mhz frequency standard might be remarkably different from what is needed
> for
> high-frequency RF work.
>
>
> Mike
>
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Re: [time-nuts] Spectrum Analyzer Specifications

[David J Taylor]

For non-time-nuts quality, there is fast spectrum analyser software now 
available for the Airspy receiver.  Although based on an RTL tuner, this 
receiver has a 12-bit ADC, so better dynamic range than the typical dongle.


 http://airspy.com/download/
 http://airspy.com/specifications/

I have no commercial interest in the Airspy, just thought you might like to 
know.  This receiver plus a suitable table makes a very handy portable 
simple spectrum analyser.


Mike: I have a Rigol DSA815 analyser and tracking generator, and it's good 
value for money.  Not HP-class, of course.  I do wish it went higher than 
1.5 GHz, though.


Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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[time-nuts] Spectrum Analyzer Specifications

[timenut]

Hi,

I have another question about test equipment. When using a spectrum analyzer
to examine the output of a frequency standard, what are the minimum
specification needed? Bandwidth, resolution, sensitivity, etc?

Looking at spectrum analyzers on eBay, I see quite a bit of difference between
various models. Some have a resolution of 10Hz but others are 30Hz or even
100Hz. Some have a minimum frequency of 0.01Hz, 100Hz or even in the kHz
range. Some are only sensitive to 60dBm, but others over 100dBm.

Are any of the cheaper USB spectrum analyzers worth getting?

Most of these are appallingly expensive, so knowing what is needed can
certainly help guide a purchase or to minimize cost. And if a "deal" is found,
knowing that it is or is not adequate can help.

Clearly, better specifications are preferable, but I'm also sure that the
intended application makes a large difference. What is needed for examining a
10Mhz frequency standard might be remarkably different from what is needed for
high-frequency RF work.


Mike

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