[time-nuts] time-nuts Digest, Vol 190, Issue 3
Perry Sandeen
sandeenpa at yahoo.com
Sun May 3 00:32:21 UTC 2020
GPSDO Questions
Learned Gentlemen,
First off, any GPSDO is better than none.
Now it's been stated on postings that some chicom GPSDO's are frequency locked (apparently not a good idea) and those that are phase locked. So how does one know what you are getting? I suspect asking the vendor would be pointless.
Bert posted a while back that his Tbolt occasionally had a hiccup that he was able to find when comparing it to a HP Rb and HP Cs.
So what can do other than live with these situations, which maybe in the long run, might for most of us, a minor unsolvable nuisance?
Also BTW are the Lucent GPSDO's a phase locked GPSDO since I have 2?
Regards,
Perrier
On Saturday, May 2, 2020, 9:00:11 AM PDT, time-nuts-request at lists.febo.com <time-nuts-request at lists.febo.com> wrote:
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Today's Topics:
1. Re: GPSDO advice (Bob kb8tq)
2. Re: GPSDO advice (Wes)
3. Re: GPSDO advice (Richard Solomon)
4. Re: GPSDO advice (Bill Notfaded)
5. Re: power supplies (Poul-Henning Kamp)
6. Re: power supplies (ed breya)
7. Re: FE-5680A - Newbie capacitor question (Matthias Welwarsky)
8. Re: FE-5680A - Newbie capacitor question (Didier Juges)
9. Re: GPSDO advice (Bob kb8tq)
10. Pre-averaging Phase Data (Simon Lewis)
11. Re: GPSDO advice (Wes)
12. Re: Pre-averaging Phase Data (Bob kb8tq)
13. Re: Pre-averaging Phase Data (Poul-Henning Kamp)
----------------------------------------------------------------------
Message: 1
Date: Fri, 1 May 2020 22:29:29 -0400
From: Bob kb8tq <kb8tq at n1k.org>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] GPSDO advice
Message-ID: <A6F3A633-827B-4841-8FCF-663A103927E0 at n1k.org>
Content-Type: text/plain; charset=utf-8
Hi
I would guess that the vast majority of folks on the list and an even
larger percentage doing the FMT are buying their GPSDO?s on eBay.
Which ones they buy and how well the work is very much a ?that depends
sort of thing?.
The crop of devices at low(er) prices changes every 3 to 5 years. Whatever
is being torn apart right now will be contributing the low cost stuff. If you bought
5 years ago your choices were very different. Go back 5 or 10 years past that and
the devices change again and then again.
There?s no reason to believe that ?things were better in the old days?. Mostly just
different. The issues have been worked out on stuff that hit eBay 20 years ago.
That?s just the way it works. How well they have been worked out ?. that depends
on the device and how picky you are.
This does not simply apply to GPSDO?s. A while back eBay was awash in telecom
Rb?s. Some bought so many they can?t keep track of all of them. Today a $35 listing
for an Rb is pretty unusual. That?s just supply and demand. Wait another 5 or 10
years and we probably will be awash in cheap ones again.
Right now ?entry level? GPSDO?s are still below $100 delivered. That?s not all that
crazy compared to a lot of gear in a typical shack or on a typical bench.
Bob
> On May 1, 2020, at 9:25 PM, Wes <wes at triconet.org> wrote:
>
> An update on this:
>
> I emailed both Jackson and Brandywine for prices on both the Desktop Fury, in Jackson's case, and the board versions from each of them.
>
> The good news is that they both were responsive. The bad news is they are both out of my price range. Jackson by about 3 dB. Brandywine clearly didn't want to sell me anything, as exemplified by a fee of $47 to use a credit card.
>
> As much as I would like to be more nutty, I can't justify spending this kind of money just to participate in ARRL FMTs where the only direction I have to go is down.
>
> Wes N7WS
>
> On 4/24/2020 11:56 AM, Wes wrote:
>> Taking some of the advice offered, I've emailed them for P&A. I'll let you know if I hear back.
>>
>> Wes
>>
>> On 4/24/2020 10:45 AM, Kevin Rowett wrote:
>>>> On Apr 24, 2020, at 10:32 AM, Mark Spencer <mark at alignedsolutions.com> wrote:
>>>>
>>>> Speaking both as an amateur radio operator and some one who modestly pursues precision time and frequency as a hobby, I am extremely happy with my Jackson Labs Fury
>>>> GPSDO.
>>>
>>> Speaking of Jackson Labs, has anyone heard from them, since the lockdown commenced?
>>>
>>> KR
>>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
------------------------------
Message: 2
Date: Fri, 1 May 2020 20:25:10 -0700
From: Wes <wes at triconet.org>
To: time-nuts at lists.febo.com
Subject: Re: [time-nuts] GPSDO advice
Message-ID: <8c410a26-6463-1a4b-750f-bb6b72eb9564 at triconet.org>
Content-Type: text/plain; charset=utf-8; format=flowed
Hi Bob,
According to the USPS tracking number I'll have a BG7TBL GPSDO on Monday :-)
I really wanted to "Buy American" but a 10 dB price difference is worth taking
the risk.
Wes
On 5/1/2020 7:29 PM, Bob kb8tq wrote:
> Hi
>
> I would guess that the vast majority of folks on the list and an even
> larger percentage doing the FMT are buying their GPSDO?s on eBay.
> Which ones they buy and how well the work is very much a ?that depends
> sort of thing?.
>
> The crop of devices at low(er) prices changes every 3 to 5 years. Whatever
> is being torn apart right now will be contributing the low cost stuff. If you bought
> 5 years ago your choices were very different. Go back 5 or 10 years past that and
> the devices change again and then again.
>
> There?s no reason to believe that ?things were better in the old days?. Mostly just
> different. The issues have been worked out on stuff that hit eBay 20 years ago.
> That?s just the way it works. How well they have been worked out ?. that depends
> on the device and how picky you are.
>
> This does not simply apply to GPSDO?s. A while back eBay was awash in telecom
> Rb?s. Some bought so many they can?t keep track of all of them. Today a $35 listing
> for an Rb is pretty unusual. That?s just supply and demand. Wait another 5 or 10
> years and we probably will be awash in cheap ones again.
>
> Right now ?entry level? GPSDO?s are still below $100 delivered. That?s not all that
> crazy compared to a lot of gear in a typical shack or on a typical bench.
>
> Bob
>
>> On May 1, 2020, at 9:25 PM, Wes <wes at triconet.org> wrote:
>>
>> An update on this:
>>
>> I emailed both Jackson and Brandywine for prices on both the Desktop Fury, in Jackson's case, and the board versions from each of them.
>>
>> The good news is that they both were responsive. The bad news is they are both out of my price range. Jackson by about 3 dB. Brandywine clearly didn't want to sell me anything, as exemplified by a fee of $47 to use a credit card.
>>
>> As much as I would like to be more nutty, I can't justify spending this kind of money just to participate in ARRL FMTs where the only direction I have to go is down.
>>
>> Wes N7WS
>>
>> On 4/24/2020 11:56 AM, Wes wrote:
>>> Taking some of the advice offered, I've emailed them for P&A. I'll let you know if I hear back.
>>>
>>> Wes
>>>
>>> On 4/24/2020 10:45 AM, Kevin Rowett wrote:
>>>>> On Apr 24, 2020, at 10:32 AM, Mark Spencer <mark at alignedsolutions.com> wrote:
>>>>>
>>>>> Speaking both as an amateur radio operator and some one who modestly pursues precision time and frequency as a hobby, I am extremely happy with my Jackson Labs Fury
>>>>> GPSDO.
>>>> Speaking of Jackson Labs, has anyone heard from them, since the lockdown commenced?
>>>>
>>>> KR
------------------------------
Message: 3
Date: Fri, 1 May 2020 18:39:45 -0700
From: Richard Solomon <dickw1ksz at gmail.com>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] GPSDO advice
Message-ID:
<CAC5FBO-V2KgKQHFMG93spo7Joc4W41XtLcFrtJG=oj0VNZayLQ at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Why not just get a Trimble T-Bolt ?
Lots of them are still around.
73, Dick, W1KSZ
On Fri, May 1, 2020 at 6:26 PM Wes <wes at triconet.org> wrote:
> An update on this:
>
> I emailed both Jackson and Brandywine for prices on both the Desktop Fury,
> in
> Jackson's case, and the board versions from each of them.
>
> The good news is that they both were responsive. The bad news is they are
> both
> out of my price range. Jackson by about 3 dB. Brandywine clearly didn't
> want to
> sell me anything, as exemplified by a fee of $47 to use a credit card.
>
> As much as I would like to be more nutty, I can't justify spending this
> kind of
> money just to participate in ARRL FMTs where the only direction I have to
> go is
> down.
>
> Wes N7WS
>
> On 4/24/2020 11:56 AM, Wes wrote:
> > Taking some of the advice offered, I've emailed them for P&A. I'll let
> you
> > know if I hear back.
> >
> > Wes
> >
> > On 4/24/2020 10:45 AM, Kevin Rowett wrote:
> >>> On Apr 24, 2020, at 10:32 AM, Mark Spencer <mark at alignedsolutions.com>
> wrote:
> >>>
> >>> Speaking both as an amateur radio operator and some one who modestly
> pursues
> >>> precision time and frequency as a hobby, I am extremely happy with my
> >>> Jackson Labs Fury
> >>> GPSDO.
> >>
> >> Speaking of Jackson Labs, has anyone heard from them, since the
> lockdown
> >> commenced?
> >>
> >> KR
> >
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
------------------------------
Message: 4
Date: Fri, 1 May 2020 20:37:06 -0700
From: Bill Notfaded <notfaded1 at gmail.com>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] GPSDO advice
Message-ID:
<CADToqn3RY6LhoLYp04AGfJ6AeyjOGDhSinoX+a8A7+Ez2bRgkw at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Did you get a newer one with late 2019 at least on the front BG7TBL panel?
The one I got doesn't have the frequency offset bug and works really well.
It locks on multiple birds really quickly. For the money it's hard to
beat. I've been comparing it to my Thunderbolt E. It obviously doesn't
provide the extra info you get with Trimble protocol (so no ocxo info in
Lady Heather) but I'd say it locks onto a lot more and faster than my
Trimble does even if I put it on GPS only constellation for fair playing
field. I hate to say it but I'm not sure my Thunderbolt is really much
better. You won't be sorry if it's a later BG7TBL GNSS model. I've been
running mine on GPS and Galileo lately.
Bill
On Fri, May 1, 2020, 8:25 PM Wes <wes at triconet.org> wrote:
> Hi Bob,
>
> According to the USPS tracking number I'll have a BG7TBL GPSDO on Monday
> :-)
>
> I really wanted to "Buy American" but a 10 dB price difference is worth
> taking
> the risk.
>
> Wes
>
> On 5/1/2020 7:29 PM, Bob kb8tq wrote:
> > Hi
> >
> > I would guess that the vast majority of folks on the list and an even
> > larger percentage doing the FMT are buying their GPSDO?s on eBay.
> > Which ones they buy and how well the work is very much a ?that depends
> > sort of thing?.
> >
> > The crop of devices at low(er) prices changes every 3 to 5 years.
> Whatever
> > is being torn apart right now will be contributing the low cost stuff.
> If you bought
> > 5 years ago your choices were very different. Go back 5 or 10 years past
> that and
> > the devices change again and then again.
> >
> > There?s no reason to believe that ?things were better in the old days?.
> Mostly just
> > different. The issues have been worked out on stuff that hit eBay 20
> years ago.
> > That?s just the way it works. How well they have been worked out ?. that
> depends
> > on the device and how picky you are.
> >
> > This does not simply apply to GPSDO?s. A while back eBay was awash in
> telecom
> > Rb?s. Some bought so many they can?t keep track of all of them. Today a
> $35 listing
> > for an Rb is pretty unusual. That?s just supply and demand. Wait another
> 5 or 10
> > years and we probably will be awash in cheap ones again.
> >
> > Right now ?entry level? GPSDO?s are still below $100 delivered. That?s
> not all that
> > crazy compared to a lot of gear in a typical shack or on a typical bench.
> >
> > Bob
> >
> >> On May 1, 2020, at 9:25 PM, Wes <wes at triconet.org> wrote:
> >>
> >> An update on this:
> >>
> >> I emailed both Jackson and Brandywine for prices on both the Desktop
> Fury, in Jackson's case, and the board versions from each of them.
> >>
> >> The good news is that they both were responsive. The bad news is they
> are both out of my price range. Jackson by about 3 dB. Brandywine clearly
> didn't want to sell me anything, as exemplified by a fee of $47 to use a
> credit card.
> >>
> >> As much as I would like to be more nutty, I can't justify spending this
> kind of money just to participate in ARRL FMTs where the only direction I
> have to go is down.
> >>
> >> Wes N7WS
> >>
> >> On 4/24/2020 11:56 AM, Wes wrote:
> >>> Taking some of the advice offered, I've emailed them for P&A. I'll
> let you know if I hear back.
> >>>
> >>> Wes
> >>>
> >>> On 4/24/2020 10:45 AM, Kevin Rowett wrote:
> >>>>> On Apr 24, 2020, at 10:32 AM, Mark Spencer <
> mark at alignedsolutions.com> wrote:
> >>>>>
> >>>>> Speaking both as an amateur radio operator and some one who modestly
> pursues precision time and frequency as a hobby, I am extremely happy with
> my Jackson Labs Fury
> >>>>> GPSDO.
> >>>> Speaking of Jackson Labs, has anyone heard from them, since the
> lockdown commenced?
> >>>>
> >>>> KR
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
------------------------------
Message: 5
Date: Sat, 02 May 2020 06:45:55 +0000
From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>, jimlux <jimlux at earthlink.net>
Subject: Re: [time-nuts] power supplies
Message-ID: <51396.1588401955 at critter.freebsd.dk>
Content-Type: text/plain; charset="us-ascii"
--------
In message <73bfcf33-8b29-38a6-d5a7-9192375d4f0e at earthlink.net>, jimlux writes:
>I suppose I can package a bunch of those up in a bigger box with banana
>jacks or binding posts.
Use power-pole connectors, they are cheap and *so* much better.
I'm using a couple of fused West Mountain Radio distributors to
spread my 24VDC and 12VDC around the lab, highly recommended.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
------------------------------
Message: 6
Date: Fri, 1 May 2020 23:50:53 -0700
From: ed breya <eb at telight.com>
To: time-nuts at lists.febo.com
Subject: Re: [time-nuts] power supplies
Message-ID: <af879375-2c73-d61e-a2bf-510e8debb7e8 at telight.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Power supplies are indeed mostly commodity items, but absolutely
essential. I have a large collection of OEM open-frame units, in linear
and SMPS, and a small collection of commercial bench supplies, and some
home-made ones.
You can of course get a bunch of bench units and set them up for every
possible need, and with a dazzling array of readouts and adjustments.
What matters is what you mostly need to do, and what you want not to
happen. If you have to work on one thing at a time, with one to a few
voltages, it's pretty straightforward to set up and be ready to monitor
what's going on. If you have a bunch of things that use standard
supplies, that just need to run simultaneously, I think it's better to
just have simple supplies that put out a bunch of standard voltages for
them, with no fancy controls or measurement capability.
I've designed and built and used many SMPSs over the years, which is why
I prefer good old-school linear supplies. If you don't need high power
density or levels, you should go with linear, regardless of whether it's
a commercial bench unit, OEM, or slapped together yourself. It will
start out much cleaner, involving less grief when it comes to noise
control - almost a guaranteed issue in time-nut type situations. You
can't avoid SMPS noise entirely, since we're awash with their signals
all around us, from PCs and equipment and appliances and practically
everything else, but at least you can try to not add too much more right
in the middle of your work. Don't get me wrong - I love SMPSs and
related technology, and all the stuff they enable us to have and enjoy.
Life would be a lot different and less fun (but quieter) without them.
If you just need an assortment of supply voltages at modest currents,
one way is to put together an OEM linear supply like a standard +/-15V &
+5V one, with some three-terminal regulator circuits at other desired
voltages, and means to hook them up to the items. Refinements like
OVP/RVP etc can be added, but of course add some complexity.
One thing I always do, especially carefully for high-value or
one-of-a-kind items, is add intrinsic protection against any anticipated
powering faults like over-voltage and reverse polarity. No matter how
fancy your supplies are, it's still possible to make a mistake in hookup
or settings, and ruin the device being powered.
The same applies to the power supplies themselves. With a bench supply,
you don't necessarily know what would happen to it and its load, if you
say, accidentally short a +12V supply to the +5V. Would it damage the
supply and its load? If you fully know the characteristics and specs and
what's behind the front panel, you can predict the outcome. If you built
it yourself, you know that that you've (hopefully) anticipated the
possibility and provided for this event, or, the supply may not be
protected, but you've already added intrinsic protection to the load device.
So, it can get complicated, and as always, it depends...
Ed
------------------------------
Message: 7
Date: Sat, 02 May 2020 09:58:55 +0200
From: Matthias Welwarsky <time-nuts at welwarsky.de>
To: time-nuts at lists.febo.com, John Bievenour <john at bvnhr.net>
Subject: Re: [time-nuts] FE-5680A - Newbie capacitor question
Message-ID: <4852208.V09MV4QL1C at linux-5fgm.suse>
Content-Type: text/plain; charset="iso-8859-1"
On Freitag, 1. Mai 2020 23:42:46 CEST John Bievenour wrote:
> I'm an amateur electronics hobbyist who's still a newbie (especially to
> SMD), so please forgive the basic question.
>
> I recently acquired a FE-5680A that was failing to lock on frequency (pin 3
> never went low). It will power up, sweep up and down, and finally settle to
> fluctuate around 9.9999999 to 10.0000000.
>
> When I opened the case, I found that one of the capacitors had blown, which
> I believe might be the reason. Looking at the top of the board, with the
> DB9 on your left, the capacitor in question directly across from the right
> hand 2941 voltage regulator. It has 105 on the first row, 35 followed by a
> stylized K on the second row, and 333 on the last row.
>
> I'd like to attempt to replace the blown cap. After doing lots of searching
> and reading, I'm pretty sure this is a Kemet 35 VDC 1uF SMD Tantalum
> Capacitor (never knew these existed until yesterday). I've narrowed down
> the options on Mouser, but I can't figure out:
>
> 1) is my identification correct?
Sounds about right, going by the images I found.
> 2) is it a T489, T491, T494, T495, T496, T498, or T499 (the band at the top
> makes me think it's a T498, T491, T494, T495, T498, or a T499) ? 3) is the
> tolerance 10% or 20% (I think it's 10%)?
> 4) what is the ESR (I have options from 1 Ohm to 83 mOhms)?
I don't think you need to worry about that too much. The capacitor is probably
for filtering on the input of the regulator. For output filtering it's too
small. The datasheet for the LM2941 I found says at least 22?F is needed for
stable operation and ESR between 100mOhm 1 Ohm. So, the output filter cap must
be somewhere else.
Just make sure the size matches. The band on the top only marks the positive
side of the capacitor.
> 5) for future reference, how am I able to tell the tolerance, ESR, and
> series just by decoding the writing on it?
Without knowing the exact part number and looking up the values in the data
sheet it's impossible to know these details. I usually compare the top
markings against manufacturer data sheets until I find a close match and then
go from there.
>
> Thank you very much in advance.
> - John
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow
> the instructions there.
------------------------------
Message: 8
Date: Sat, 2 May 2020 06:57:03 -0500
From: Didier Juges <shalimr9 at gmail.com>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] FE-5680A - Newbie capacitor question
Message-ID:
<CAMQqFunaDdZR_3AXThqHZyVXLy7c8gA2Qp8fO5CuX-ocQMAuCw at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Tantalum capacitors are known to occasionally short for no good reason.
Give them a reason and they'll be happy to oblige.
Things that can damage a tantalum cap in a hurry include excessive voltage,
reverse polarity, overheating (likely with hand soldering) and current
spikes.
If it were me, and assuming it is at the input of a linear regulator, I
would put a ceramic multilayer capacitor in its place.
It will likely be much smaller (requiring a short jumper to match the
solder pads of the larger tantalum) but a lot more reliable, and you are
less likely to damage it by hand soldering.
(some linear regulators are unstable with a large ceramic capacitor on the
output without proper damping, but there is typically no issue at the input)
Didier KO4BB
On Sat, May 2, 2020 at 2:59 AM Matthias Welwarsky <time-nuts at welwarsky.de>
wrote:
> On Freitag, 1. Mai 2020 23:42:46 CEST John Bievenour wrote:
> > I'm an amateur electronics hobbyist who's still a newbie (especially to
> > SMD), so please forgive the basic question.
> >
> > I recently acquired a FE-5680A that was failing to lock on frequency
> (pin 3
> > never went low). It will power up, sweep up and down, and finally settle
> to
> > fluctuate around 9.9999999 to 10.0000000.
> >
> > When I opened the case, I found that one of the capacitors had blown,
> which
> > I believe might be the reason. Looking at the top of the board, with the
> > DB9 on your left, the capacitor in question directly across from the
> right
> > hand 2941 voltage regulator. It has 105 on the first row, 35 followed by
> a
> > stylized K on the second row, and 333 on the last row.
> >
> > I'd like to attempt to replace the blown cap. After doing lots of
> searching
> > and reading, I'm pretty sure this is a Kemet 35 VDC 1uF SMD Tantalum
> > Capacitor (never knew these existed until yesterday). I've narrowed down
> > the options on Mouser, but I can't figure out:
> >
> > 1) is my identification correct?
>
> Sounds about right, going by the images I found.
>
> > 2) is it a T489, T491, T494, T495, T496, T498, or T499 (the band at the
> top
> > makes me think it's a T498, T491, T494, T495, T498, or a T499) ? 3) is
> the
> > tolerance 10% or 20% (I think it's 10%)?
>
> > 4) what is the ESR (I have options from 1 Ohm to 83 mOhms)?
>
> I don't think you need to worry about that too much. The capacitor is
> probably
> for filtering on the input of the regulator. For output filtering it's too
> small. The datasheet for the LM2941 I found says at least 22?F is needed
> for
> stable operation and ESR between 100mOhm 1 Ohm. So, the output filter cap
> must
> be somewhere else.
>
> Just make sure the size matches. The band on the top only marks the
> positive
> side of the capacitor.
>
> > 5) for future reference, how am I able to tell the tolerance, ESR, and
> > series just by decoding the writing on it?
>
> Without knowing the exact part number and looking up the values in the
> data
> sheet it's impossible to know these details. I usually compare the top
> markings against manufacturer data sheets until I find a close match and
> then
> go from there.
>
> >
> > Thank you very much in advance.
> > - John
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and
> follow
> > the instructions there.
>
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
------------------------------
Message: 9
Date: Sat, 2 May 2020 08:33:20 -0400
From: Bob kb8tq <kb8tq at n1k.org>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] GPSDO advice
Message-ID: <CFD62CF1-B20E-4D0E-94C8-10C5CDFC6304 at n1k.org>
Content-Type: text/plain; charset=utf-8
Hi
Like pretty much all electronics GPSDO?s have been a ?designed in
the USA / built across the ocean? sort of thing for a long time. The
current crop of Trimble and Symmetrical salvage parts on eBay
are simply the latest wave. They are the ?next generation? of the parts
we all bought 10 or 15 years ago. No better / no worse, just different.
Bob
> On May 1, 2020, at 11:25 PM, Wes <wes at triconet.org> wrote:
>
> Hi Bob,
>
> According to the USPS tracking number I'll have a BG7TBL GPSDO on Monday :-)
>
> I really wanted to "Buy American" but a 10 dB price difference is worth taking the risk.
>
> Wes
>
> On 5/1/2020 7:29 PM, Bob kb8tq wrote:
>> Hi
>>
>> I would guess that the vast majority of folks on the list and an even
>> larger percentage doing the FMT are buying their GPSDO?s on eBay.
>> Which ones they buy and how well the work is very much a ?that depends
>> sort of thing?.
>>
>> The crop of devices at low(er) prices changes every 3 to 5 years. Whatever
>> is being torn apart right now will be contributing the low cost stuff. If you bought
>> 5 years ago your choices were very different. Go back 5 or 10 years past that and
>> the devices change again and then again.
>>
>> There?s no reason to believe that ?things were better in the old days?. Mostly just
>> different. The issues have been worked out on stuff that hit eBay 20 years ago.
>> That?s just the way it works. How well they have been worked out ?. that depends
>> on the device and how picky you are.
>>
>> This does not simply apply to GPSDO?s. A while back eBay was awash in telecom
>> Rb?s. Some bought so many they can?t keep track of all of them. Today a $35 listing
>> for an Rb is pretty unusual. That?s just supply and demand. Wait another 5 or 10
>> years and we probably will be awash in cheap ones again.
>>
>> Right now ?entry level? GPSDO?s are still below $100 delivered. That?s not all that
>> crazy compared to a lot of gear in a typical shack or on a typical bench.
>>
>> Bob
>>
>>> On May 1, 2020, at 9:25 PM, Wes <wes at triconet.org> wrote:
>>>
>>> An update on this:
>>>
>>> I emailed both Jackson and Brandywine for prices on both the Desktop Fury, in Jackson's case, and the board versions from each of them.
>>>
>>> The good news is that they both were responsive. The bad news is they are both out of my price range. Jackson by about 3 dB. Brandywine clearly didn't want to sell me anything, as exemplified by a fee of $47 to use a credit card.
>>>
>>> As much as I would like to be more nutty, I can't justify spending this kind of money just to participate in ARRL FMTs where the only direction I have to go is down.
>>>
>>> Wes N7WS
>>>
>>> On 4/24/2020 11:56 AM, Wes wrote:
>>>> Taking some of the advice offered, I've emailed them for P&A. I'll let you know if I hear back.
>>>>
>>>> Wes
>>>>
>>>> On 4/24/2020 10:45 AM, Kevin Rowett wrote:
>>>>>> On Apr 24, 2020, at 10:32 AM, Mark Spencer <mark at alignedsolutions.com> wrote:
>>>>>>
>>>>>> Speaking both as an amateur radio operator and some one who modestly pursues precision time and frequency as a hobby, I am extremely happy with my Jackson Labs Fury
>>>>>> GPSDO.
>>>>> Speaking of Jackson Labs, has anyone heard from them, since the lockdown commenced?
>>>>>
>>>>> KR
>
>
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------------------------------
Message: 10
Date: Sat, 2 May 2020 14:24:47 +0200
From: Simon Lewis <siaclewis at gmail.com>
To: time-nuts at lists.febo.com
Subject: [time-nuts] Pre-averaging Phase Data
Message-ID:
<CALp6zztjqTJ-wrPTjbF06BUc_f3+tO6LVLuriPygZ6kW1hBoQA at mail.gmail.com>
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Hi all,
I have a fairly newbie question on averaging of phase data, prior to ADEV.
In a paper by Sherman and Jordens (https://arxiv.org/pdf/1605.03505.pdf) on
oscillator metrology using SDR (Ettus N210), for long term measurements (1
tau up) the group estimates an average phase to reduce the data volume.
They use both a novel lower-bound variance estimate, and what I assume was
a rectangular average of N samples per second (original data rate was
1Msamples/s). Both apparently provided similar results.
>From what I've read/tried to understand, pre-averaging phase isn't
practically a good idea, considering the ADEV natively does this, and you
end up with a lower estimate than reality. They state that time interval
counters effectively do this for frequency measurements.
I know that one can do this with caveats, and in essence this is what MDEV
does (I believe?), but is it not more 'real' to just downsample the phase
data? That is, drop N-1 samples per second (not decimating which would
filter the higher order components), and then ADEV the downsampled data.
I'm sure I'm missing some understanding here!
Thanks,
Simon
------------------------------
Message: 11
Date: Sat, 2 May 2020 06:39:29 -0700
From: Wes <wes at triconet.org>
To: time-nuts at lists.febo.com
Subject: Re: [time-nuts] GPSDO advice
Message-ID: <6d7e095b-8413-6060-03d6-98747e67c1ce at triconet.org>
Content-Type: text/plain; charset=utf-8; format=flowed
Good question and the answer is, I don't know.? The photo shows June 2018, but
who know whether that's representative.? Being antsy, I opted to buy from a
seller in the US with quick shipping, rather than waiting six weeks for one from
Asia.
On 5/1/2020 8:37 PM, Bill Notfaded wrote:
> Did you get a newer one with late 2019 at least on the front BG7TBL panel?
> The one I got doesn't have the frequency offset bug and works really well.
> It locks on multiple birds really quickly. For the money it's hard to
> beat. I've been comparing it to my Thunderbolt E. It obviously doesn't
> provide the extra info you get with Trimble protocol (so no ocxo info in
> Lady Heather) but I'd say it locks onto a lot more and faster than my
> Trimble does even if I put it on GPS only constellation for fair playing
> field. I hate to say it but I'm not sure my Thunderbolt is really much
> better. You won't be sorry if it's a later BG7TBL GNSS model. I've been
> running mine on GPS and Galileo lately.
>
> Bill
------------------------------
Message: 12
Date: Sat, 2 May 2020 11:14:56 -0400
From: Bob kb8tq <kb8tq at n1k.org>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] Pre-averaging Phase Data
Message-ID: <4D24832F-8127-411A-8566-973AC6F5D473 at n1k.org>
Content-Type: text/plain; charset=utf-8
Hi
In general the way you go from 1 to 10 to 100 seconds is to decimate
( = throw away) the data to get a phase record at the tau you are after.
Any averaging that you do will filter out some noise. Since ADEV is a
measure of noise, getting rid of it is not a real good idea. You can indeed
make your results look *very* good by doing this. What those results
would actually represent ?. who knows ?.
Bob
> On May 2, 2020, at 8:24 AM, Simon Lewis <siaclewis at gmail.com> wrote:
>
> Hi all,
>
> I have a fairly newbie question on averaging of phase data, prior to ADEV.
>
> In a paper by Sherman and Jordens (https://arxiv.org/pdf/1605.03505.pdf) on
> oscillator metrology using SDR (Ettus N210), for long term measurements (1
> tau up) the group estimates an average phase to reduce the data volume.
> They use both a novel lower-bound variance estimate, and what I assume was
> a rectangular average of N samples per second (original data rate was
> 1Msamples/s). Both apparently provided similar results.
>
> From what I've read/tried to understand, pre-averaging phase isn't
> practically a good idea, considering the ADEV natively does this, and you
> end up with a lower estimate than reality. They state that time interval
> counters effectively do this for frequency measurements.
>
> I know that one can do this with caveats, and in essence this is what MDEV
> does (I believe?), but is it not more 'real' to just downsample the phase
> data? That is, drop N-1 samples per second (not decimating which would
> filter the higher order components), and then ADEV the downsampled data.
> I'm sure I'm missing some understanding here!
>
> Thanks,
> Simon
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
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> and follow the instructions there.
------------------------------
Message: 13
Date: Sat, 02 May 2020 15:55:19 +0000
From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>, Bob kb8tq <kb8tq at n1k.org>
Subject: Re: [time-nuts] Pre-averaging Phase Data
Message-ID: <53514.1588434919 at critter.freebsd.dk>
Content-Type: text/plain; charset="us-ascii"
--------
In message <4D24832F-8127-411A-8566-973AC6F5D473 at n1k.org>, Bob kb8tq writes:
>In general the way you go from 1 to 10 to 100 seconds is to decimate
>( = throw away) the data to get a phase record at the tau you are after.
The problem with that, is that decimation may _also_ throw away noise.
As a general scientific rule, if you measured, you use the measurements,
you cannot "pick & choose" amongst your measurements, not even if
you do it in a certifiably random way.
As I understand it, that is one of the minor problems the Modified
Allan Variance was (also) supposed to fix ?
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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