[ARC5] Drift in BC-453 - more

Sat Dec 16 09:50:24 EST 2017

This thread has taken many meandering twists and turns.It all started when I suggested that BFO stability may be the reason that WSPR cannot be decoded with a commend reciever.Yes, it is a "hobby thing" where I aspire to make a complete 630 meter station from command components.One of the "Ham-mered' transmitters can be re purposed as the transmitter and the BC-453 as the receiver.The transmitter will be controlled by XCO or VCO with PLL.
The computer systems drift ARE NOT the issue with WSPR. It works fine with other rigs.The BC453 LO "seems" to be stable if I leave it on a weak beacon station for a period of time.
I built a 85 Khz fet Colpitts oscillator from some junk box components. I hope it will be more stable than the command set BFO, but 
it may have more phase jitter than I want.  We'll see...It will be used to drive the grid of the existing BFO oscillator disconnected from the set's BFO can. The plate circuit will remain intact .

I haven't had time to do  the drift measurements on the BFO and LO yet, but I will get there eventually. Stay tuned...

    On Friday, December 15, 2017 10:44 PM, Bill Cromwell <wrcromwell at gmail.com> wrote:

 Hi Bob,

The sound card specs (and most other stuff) is "good enough" for my 
purposes. That's why I only guess (and not really even that much effort) 
about my own sound cards. I haven't looked for specs from the 
manufacturers but I have looked at what some others have done to their 
sound cards to spank them with GPS or rubidium standards. They do the 
same things to the oscillators in their radios. Splitting hairs is a 
hobby all unto itself and may be applied to frequency control. In my 
work...the work that provided for my family and me and now pays my 
retirement.. I "transferred standards" all day long every day. I came to 
understand pretty well about not wasting time splitting hairs any finer 
than needed. Unless it is your hobby or you work in a research lab to 
see just how fine hairs can be split. I was looking at microinches. In 
my woodworking hobby I would be laughed right out of the lumber yard 
talking about microinches. I wonder if even 10 ppm would be required for 
the original problem. The goal was WSPR through a command receiver. 
Probably not the best choice. The viable solutions weren't 'practical' 
or 'reasonable' but it *IS* a hobby. So maybe give it a try.

73,

Bill  KU8H

On 12/15/2017 09:13 PM, Bob kb8tq wrote:
> Hi
>
> Either life is a perpetual disaster and there is no solution to any problem *or* one works
> with what is at hand. Indeed there are those who actually *have* bothered to measure
> some of this stuff and who actually pass that information along. The information on the
> sound card crystals is *not* based on guesswork ….
>
> Checking this stuff out is not rocket science. There are a lot of very easy ways to do it.
> The original post could be trouble shot with a source that is “only” in the 10 ppm range
> injected into the IF.
>
> Bob
>
>> On Dec 15, 2017, at 7:45 PM, Bill Cromwell <wrcromwell at gmail.com> wrote:
>>
>> Hi,
>>
>> I couldonly make a wild guess about the stability of the xtal in the sounds card. I have been reading some specs in the past few years (decade or two) for some oscillators spec'ed in terms of parts per billion. What the actual specs are for any given sound card..who knows. If you want to know start by asking the manufacturer and by measuring it yourself. The way I outlined we don't even care about that. Just as we don care about the HFO or the BFO (if used) in the receiver. We are only measuring things against WWV's carrier. We have already ceded that WWV is completely useless. But we don't make it even more useless by adding all the errors in the receiver and the computer and the sound card and whatever is being used for the display. As long as the pips stay on the screen that is all that is required. So there will only be one useless standard and not a half dozen.
>>
>> 73,
>>
>> Bill  KU8H
>>
>> On 12/15/2017 04:44 PM, Bob kb8tq wrote:
>>> Hi
>>>
>>> We’ve gone around a bit on accuracy vs stability vs wander vs
>>> temperature drift. That makes things a bit
>>> confusing. They very much are not the same thing. In some cases they
>>> overlap, but not always the way
>>> you might expect.
>>>
>>> Your typical sound card has a single crystal running it’s timebase. The
>>> stability of the tone in generates
>>> will be roughly what the stability of that crystal is in the computer’s
>>> thermal environment. If the temperature
>>> is fairly constant, it will hold a ppm or three. If the temperature
>>> ramps up and down by 10’s of degrees as
>>> you play your video game ….. it may move around a bit.
>>>
>>> One ppm is one Hz at a MHz. At any of the frequencies involved with a
>>> BC-453, a ppm is a fraction of a Hz.
>>> Expecting the sound card to hold less than a hertz over a few minutes to
>>> a few hours is not unreasonable
>>> in the BC-453 case. That assumes the computer isn’t doing crazy stuff
>>> and your sound card doesn’t have
>>> some really odd parts in it.
>>>
>>> Lots of fun ….
>>>
>>> Bob
>>>
>>>> On Dec 15, 2017, at 2:14 PM, millerke6f at aol.com
>>>> <mailto:millerke6f at aol.com> wrote:
>>>>
>>>> Intersting comments on using the Computer to sort out drift
>>>> parameters.  I often wonder how the various clocks in the computer
>>>> sound card and cpu clocks vote into the calculus?  Granted, some
>>>> correction and validation of the computer's internal clock systems can
>>>> be accomplished using external internet resources, but the question
>>>> remains as to how accurate the computer sound card processes are.
>>>> Perhaps it's just that the calcuations in the computer's sound card
>>>> DSP are done in the audio range that allows for sub  1 Hertz
>>>> calculation?
>>>>
>>>> Cheers
>>>> Bob, KE6F
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Bob kb8tq <kb8tq at n1k.org <mailto:kb8tq at n1k.org>>
>>>> To: Kenneth G. Gordon <kgordon2006 at frontier.com
>>>> <mailto:kgordon2006 at frontier.com>>
>>>> Cc: Arc5 <Arc5 at mailman.qth.net <mailto:Arc5 at mailman.qth.net>>
>>>> Sent: Tue, Dec 12, 2017 12:27 pm
>>>> Subject: Re: [ARC5] Drift in BC-453 - more
>>>>
>>>> Hi If you are running a radio at 400 KHz, and a similar radio at 4,000
>>>> KHz the drift of the second one (in Hz) probably will be 10X the drift
>>>> of the first radio. The same applies if you go to 40 MHz (you now are
>>>> at 100X vs 400 KHz). Yes, there are a bunch of assumptions there about
>>>> radio construction, IF frequencies and various other things. To the
>>>> extent this is “simple”, a 1 Hz drift on a BC-453 would be about the
>>>> same as a 100 Hz drift on a similar radio on 10 meters or a 10 Hz
>>>> drift on 80 meters. Simply put - if you *think* you could listen to
>>>> SSB on 10M with a low IF / single conversion non-crystal based radio
>>>> (ignoring anything but drift as a problem) … you should get about 1 Hz
>>>> drift on the 453. You could compare to comfortably listening to SSB on
>>>> 80 M as well. Of course, you immediately get into “drift over what
>>>> period of time”. Any radio like this that I ever used for SSB stayed
>>>> on pretty much all the time. Use it in the evening and leave it on all
>>>> day while I was busy with other stuff. Starting from dead cold … yikes
>>>> …. that’s a tough test for a tube based radio. If you *do* want to
>>>> test for sub 1Hz sort of stability it’s likely easier to shove a
>>>> stable signal into the radio and let a computer look at the audio
>>>> coming out than to do a bunch of other crazy stuff. The advantage is
>>>> that the result of the test is looking at the same thing the decoder
>>>> software in the computer will be looking at. There are a lot
>>>> reasonably stable oscillators on the auction sites to provide an
>>>> adequate signal. The risk is more spending $20 and getting a dead one
>>>> than anything else. Pretty much anything called an OCXO should do the
>>>> trick. Lots of fun Bob > On Dec 12, 2017, at 2:57 PM, Kenneth G.
>>>> Gordon <kgordon2006 at frontier.com <mailto:kgordon2006 at frontier.com>>
>>>> wrote: > > On 12 Dec 2017 at 14:32, MICHAEL ST ANGELO wrote: > >>
>>>> Bill, >> >> What is this millihertz spec for WSPR? I haven't tried it
>>>> yet but I >> thought frequexcy stavility has to be a couple of hertz
>>>> for the 2 >> minute cycle: >> >>
>>>> <https://groups.google.com/forum/#!topic/2-meter-wspr/-hDK071K1iM> >>
>>>>>> Mike N2MS > > Hi again, Mike. That spec is for 2 meters: it becomes
>>>> far, far more critical at HF and MF. > Yes. Millhertz. > > Since,
>>>> "Many WSJT-X capabilities depend on signal-detection bandwidths no
>>>> more than a > few Hz. Frequency accuracy and stability are therefore
>>>> unusually important." > > See this for details: > >
>>>> http://www.physics.princeton.edu/pulsar/K1JT/wsjtx-doc/wsjtx-main-1.8.0.html#GENERAL
>>>>>> In fact, someone on one of our lists mentioned something like <0.5
>>>> Hz drift in 2 minutes or > less. I can't remember the details now, but
>>>> his post included the link above. As I remember > it, he also told us
>>>> that if the drift exceeded what I mentioned above, that would prevent
>>>>> decoding of the input. > > I know that Bill Cromwell noted enough
>>>> drift from the very slight drift in filament voltage by > line-voltage
>>>> drift to cause very noticable drift. As he says, he decided to simply
>>>> forego > attempts to use those modes. > > Although I am inclined to
>>>> agree with him, I am very curious to learn if it IS possible to use a
>>>>> BC-453 for these modes. I would guess not, but stranger things have
>>>> happened. > > Ken W7EKB > > --- > This email has been checked for
>>>> viruses by Avast antivirus software. > https://www.avast.com/antivirus
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