Frequency counter recommendation wanted
Am 2023-03-14 0:38, schrieb Bob Camp via time-nuts:
Hi
So here’s another “twist or two” to the decision process:
Back in the day, you had fancy counters and more generic stuff. The
5345/5360/5370 all are in
the fancy category. The SRS 620 also very much goes into this bucket.
I have a sr620 and I'll never regret it.
I wonder how that small transformer can feed that large baking tray of
ECL.
My 5370A: Well, it's simply old. An array of MAYBE contacts.
But then it had a 10811 oscillator and was really cheap from
a local ham who had gone SK.
regards
Gerhard DK4XP
On 3/13/23 4:38 PM, Bob Camp via time-nuts wrote:
All of this still is based on a “I want to measure 10 MHz” sort of baseline. If 22.48 GHz is the typical
target, that’s a whole different ballpark. Multiple channels (to measure delta’s on 1 pps signals )
also change the target a bit.
The next branch to this thing is the timebase. In a lot of labs, the counter had a TCXO (or XO) in
it. It never / ever ran on that timebase. It always was locked to “something else”. In the modern
day, that might well be a GPSDO. Indeed this does have an impact on your counter purchase.
And a trap I've been caught in is "just because it has an external
reference input, that doesn't mean the output is in anyway locked to
that reference"
Many modern replacements for the 8663 of the 1980s 1990s have this issue
- JPL used tons of 8663s, and developed test setups using the 10 MHz
input to do things like modulate the phase of the output, because it's
directly locked. This is not the case with the modern E8663D, for
instance.
The Keysight 336xx function generators have a 10 MHz input, but it feeds
into a FLL of sorts with the internal oscillator, and all they do is
make sure the internal oscillator is at the same frequency (with some
TBD transfer function, much like a GPSDO). If you have two of them
"locked" to the same source, there's no reason why they will maintain a
fixed phase relationship. This is very unlike the 3325 or similar
function generators, which might have an indeterminate phase shift, but
once you knew what it was, it stayed the same as long as they were
powered up. Instead, you need to use an explicit sync signal to all the
generators.
So like anyone, I'm going to let my personal brand of timenuttery color my
response.
If I lost everything time and frequency related in my lab and was setting
it up again on a limited budget I'd focus on getting a good quality GPSDO
for a frequency/1pps reference first. Probably a trimble thunderbolt if I
could find one, but I'd also consider other options.
From there a lot of options open up. For me, a tapr ticc would be the
highest priority since I tend to be interested in phase differences between
signals. If I was dealing with phase drift of frequencies much above 1Hz,
I'd probably add some sort of stable frequency divider, probably based on
picdiv if the frequency of interest was still low enough.
If I just needed absolute frequency and not a phase I might consider some
other device which would take the 10mhz reference. Depending on the
accuracy needed this might even be some dirt cheap old counter which uses a
traditional "count pulses/cycles between gate triggers". Dividing a
relatively high accuracy 10mhz clock from a GPSDO down to 1hz and using
that as a gate on a suitably big counter would get you to approximately 1
Hz resolution. I'm not a big frequency nut so I don't have a lot of
experience here.
On Mon, Mar 13, 2023, 7:39 PM John Miller via time-nuts <
time-nuts@lists.febo.com> wrote:
Hi Bob,
Lots of interesting info here, for sure. To start, I'll clarify and answer
the first four questions:
-
How good is good? I don't really know - a lot of this depends on how
much I have to spend. I got my Ramsey CT-125 for $30, and it's great, but
can't perform any analysis. How about "trustworthy measurements in the
range of 1-5ns". -
Budget? I'd like to stay under $250, unless an incredible option comes
along for not much more. I'm basing that on two things: 1) what I have seen
5334s and 5335s sell for, and 2) how much I can usually reasonably allocate
to hobbies. -
How soon do I want it? I've been getting progressively deeper into
"TimeNuttery" over the past 3-4 years, so I'm fine waiting 6-12mo for the
right piece of gear to come along - I just want to know what to look for. -
How much effort? I'm willing to put in a lot of effort as long as there
is a light at the end of the tunnel. I have plenty of experience replacing
mundane components in older gear (RTC batteries, tag tantalum caps, carbon
resistors, etc.) so minor work doesn't scare me off. However, the $150
5386A that "just" needs a prescaler? Yeah, I know how that goes - it sits
in a closet for two years and I end up buying another functioning 5386A for
$350.
I am very interested in home brew projects, especially if it's something I
can build myself. I am aware of the TAPR TICC, and similar time interval
counter projects, but I'm also interested in a "general purpose" counter
that can be used to, say, characterize an oscillator in another piece of
equipment.
If I could find a 5334 for $50, I'd probably jump on it right away.
Looking at recently sold on ebay currently places working 5334Bs closer to
the $150 mark, and 5335As around the $250 mark. Prices on old gear have
started to climb again.
John
On Mar 13, 2023, at 5:24 PM, Bob Camp kb8tq@n1k.org wrote:
Hi
This pretty quickly gets into “how good is good?”, “what’s the
budget?”, “how quick do you need it?”,
and “how much effort do you want to sink into this?”.
If you have the time to shop, eBay can and does turn up some “finds”.
When those pop up, they
likely will not hang around all that long. The more common listings at 3
or 10X the magic price will
indeed keep hanging around for a long time.
Indeed HP / Agilent / Keysight isn’t the only game in town. The SRS 620
is still a pretty good beast.
There are various “home brew” projects out there that compete quite well
with a number of the counters
mentioned above.
So, what happens as you move along?
The 5334 / 5335 generation machines came in at a nanosecond or two sort
of resolution. Their competitors
might have pushed a couple more ns into that budget in the same era.
Typically they are big boxes with
GPIB interfaces. The 5345 / 5360 / 5370 go back to the same time frame,
but generally give you more resolution.
Still the same big box / GPIB setup.
How well is something this old likely to work? Those displays are pretty
old and getting harder to find. There
are some unique front end stuff in them that can be tough to repair (
put 5V into the 5335 and there goes the
front end on 1X attenuation / DC coupling ….).
Next up are the 5313x machines. They get you a serial output that should
work for logging. They also are a
bit smaller. Power supplies typically are their weak point. Resolution
is in the 100 to 400 ps range depending
on model and how picky you are.
While it seems crazy, the 5323x generation has been out long enough to
be bouncing around eBay. You add
an ethernet interface to the mix. Resolution goes down into the 10’s of
ps. Don’t count on using the ref out
for anything ….
Price?
The 5334 should be a sub $50 item by now and the 5335 still under $100.
The 5313x generation should come
in below $300. The 5323x generation should be below $1500. Yes, you can
easily find all of these for 5X
those prices.
All that and we haven’t even begun to talk about frequency range, or
what you want to use it for.
Bob
On Mar 13, 2023, at 2:26 PM, John Miller via time-nuts <
time-nuts@lists.febo.com> wrote:
Hey All,
Long ago I reached the point where I really need to get my hands on a
real frequency counter, but I was able to work around with with
cobbled-together solutions. Now I have started a new project and I need
something trustworthy that I can rely on for good measurements. I'm looking
for something "general purpose" that can also do time interval measurements
as well as logging, be it to GPIB, serial, USB, whatever. The ability to
operate off of an external timebase would be nice, too, since I do have a
known-good rubidium oscillator.
The HP 5334B and 5335A are good options, but I have some anxiety about
buying older equipment from ebay that may be in rough shape or questionable
provenance. That said, I suspect that there are other reputable options out
there, and I want to keep my mind open. I'm not biased towards old or new
or any particular brand, but I would like to keep the cost under a couple
hundred dollars.
Anyways, I figured if anyone could get me some recommendations, it
would be you guys! (And of course if anyone here has one they want to sell,
let me know!)
Thanks in advance,
John M.
KC1QLN
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Just curious: Could you elaborate please?
´ due to its unique business model "
Lester B Veenstra K1YCM MØYCM W8YCM 6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)
lester@veenstras.com
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Keyser WV 26726 USA
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-----Original Message-----
From: Richard (Rick) Karlquist via time-nuts [mailto:time-nuts@lists.febo.com]
Sent: Monday, March 13, 2023 6:24 PM
To: Discussion of precise time and frequency measurement
Cc: Richard (Rick) Karlquist
Subject: [time-nuts] Re: Frequency counter recommendation wanted
On 3/13/2023 2:24 PM, Bob Camp via time-nuts wrote:
Indeed HP / Agilent / Keysight isn’t the only game in town. The SRS 620 is still a pretty good beast.
There are various “home brew” projects out there that compete quite well with a number of the counters
mentioned above.
SRS was a formidable competitor to HP/A/K due to its
unique business model. I would seriously consider
anything they make.
Rick
N6RK
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