[ARC5] Drift in BC-453 - more

Bob kb8tq kb8tq at n1k.org
Sun Dec 17 15:46:54 EST 2017 

H

The X version is targeted at VLF (so BC-453 territory). That’s what has made
some of this a bit confusing. Since it’s way more difficult than the other versions
it’s a tough one to evaluate against. Anything that gets propagation or multipath 
into the act … not so much for the slow version. It *does* give you a significant 
improvement in SNR so it’s worth doing if you can. VLF is “easy land” for SDR 
radios. Making them stable enough for this stuff is pretty easy. 

Lots of fun ….

Bob

> On Dec 17, 2017, at 2:23 PM, Bill Cromwell <wrcromwell at gmail.com> wrote:
> 
> Hi Bob,
> 
> Thanks for the info about various flavors of WSPR. I interpreted that (regarding my own use) as bad and worse. I'm a 'forty meter ham' so the X flavor is right out. Since I am most always interested in what other hams are doing - what is the X version of WSPR for? Microwaves or...?
> 
> Sometimes I can pass along information that gives or leads others toward a solution or resolves a piece of the puzzle. So now I know much more about WSPR than I ever wanted to know - just like you said:)
> 
> 73,
> 
> Bill  KU8H
> 
> 
> 
> On 12/17/2017 12:36 PM, Bob kb8tq wrote:
>> Hi
>> 
>> Ok, so just to try to get this back to some sort of solid base:
>> 
>> There are many different things all called WSPR. You have 2.0, 2.1 and
>> X. They
>> share some things in common. They each have very different requirements for
>> stability. In addition software *can* do interesting frequency tracking
>> things with
>> some other modes, but not so much with WSPR.
>> 
>> If you go to Mr Google, he can tell you far more about each type of WSPR
>> than
>> you would ever want to know. There’s also way more about various PSK modes
>> than you would ever need to dig into, unless you are about to take a nap
>> :) ….
>> 
>> So, back to the start of this:
>> 
>> Which WSPR are we talking about? If it’s the 15 minutes  < 0.1 Hz stuff
>> …. not going to
>> happen with a non-crystal based tube set. It also isn’t going to work at
>> normal HF frequencies
>> no matter what the radio (straight off the official web site ….).
>> 
>> So no, this is not some sort of failing of this or that radio. It’s also
>> not anything
>> that changing out a cap or two will fix. The X mode stuff simply is not
>> designed
>> to work with this sort of gear. The other modes …. probably fine.
>> 
>> Bob
>> 
>>> On Dec 17, 2017, at 12:17 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net
>>> <mailto:arc5 at mailman.qth.net>> wrote:
>>> 
>>> It's good to know that you got a narrow digital signal to work on a
>>> command set.
>>> At least I now know it's not a total fools errand on my part...
>>> thanks!
>>> 
>>> 
>>> On Saturday, December 16, 2017 10:23 PM, Bill Cromwell
>>> <wrcromwell at gmail.com <mailto:wrcromwell at gmail.com>> wrote:
>>> 
>>> 
>>> Hi,
>>> 
>>> If it matters..I have used a command receiver for PSK-31. After a warmup
>>> I was able to just sit and copy the mail. I have let my 80 meter command
>>> receiver go but that is the one that I used. I didn't mention it since
>>> the question is about the BC-453. Mine is much more stable and I don't
>>> have to let it run for hours before I can use it. Waterfalls produce
>>> straight lines and most transmitters stay on the same displayed
>>> frequency for hours.
>>> 
>>> Ken said he would try his on WSPR. I would just because I am curious now
>>> but I have abandoned WSPR. I also have too many other things to do. I
>>> would like to know if it can do WSPR and if not, why not.
>>> 
>>> I don't notice any issues with soundcards. I assume whatever bad habits
>>> those xtals in the sound cards may have it doesn't interfere with my
>>> uses. I have read reports from some hams about how they modify the sound
>>> card to stabilize it with rubidium or caesium or gps. I don't recall
>>> them claiming it solved a problem. Just that they wanted to do it. Maybe
>>> Beethoven sounds more mellow or something <evil grin>.
>>> 
>>> 73,
>>> 
>>> Bill  KU8H
>>> 
>>> On 12/16/2017 09:09 PM, Bob kb8tq wrote:
>>> > Hi
>>> >
>>> > You *will* notice 5 Hz a minute on SSB. Most people will notice 5 Hz /
>>> > 10 minutes if the QSO goes on for a while. You also will get a bit
>>> > bothered by it on 170 Hz shift RTTY if pictures or something similar is
>>> > being sent. Net operation is yet another place you will notice it. PSK
>>> > modes tend to be bothered by a few Hz of shift, simply because of the
>>> > narrow bandwidth. That puts pretty much all of them in the category
>>> as well.
>>> >
>>> > Indeed a straight tube radio with no crystals involved will require some
>>> > tuning to stay “on channel” for SSB. How much depends on 80M (not a
>>> > whole lot) vs 10M (quite a bit). Both are normal HF bands that people
>>> > run SSB on.
>>> >
>>> > Back in the day, the BC-453 was commonly used by a lot of us as a tack
>>> > on “super IF” for various radios. I don’t ever remember it being an
>>> > issue for drift compared to the radio that was feeding it. Simply put,
>>> > the drift came from the 4 MHz -> 455 KHz process, not from the 455 -> 85
>>> > KHz conversion.
>>> >
>>> > The debate seems to be 5 Hz per minute vs 5 uHz (or 5 mHz … ) per minute
>>> > as the requirement for HF WSPR.
>>> >
>>> > Bob
>>> >
>>> >
>>> >> On Dec 16, 2017, at 6:24 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net
>>> <mailto:arc5 at mailman.qth.net>
>>> >> <mailto:arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net>>> wrote:
>>> >>
>>> >> Neil,
>>> >>
>>> >> Yup!
>>> >> I did mention 5Hz/minute.
>>> >> The radio works fine for CW because the drift is almost imperceptible
>>> >> to the human ear , but WSPR notices!
>>> >>
>>> >> I guess you haven't worked with waterfalls and these digital modes?
>>> >> The issue is obvious.
>>> >> This stuff requires a whole other level of timing and stability.
>>> >> I also said that I will do a an actual analysis when time permits...
>>> >>
>>> >> My hope was that someone other than myself is attempting to get a
>>> >> command set to receive  WSPR and JTXX modes.
>>> >> Anybody?
>>> >>
>>> >>
>>> >>
>>> >>
>>> >> On Saturday, December 16, 2017 5:53 PM, AKLDGUY .
>>> <neilb0627 at gmail.com <mailto:neilb0627 at gmail.com>
>>> >> <mailto:neilb0627 at gmail.com <mailto:neilb0627 at gmail.com>>> wrote:
>>> >>
>>> >>
>>> >> The thread has meandered around because we haven't been given anything
>>> >> to go on.
>>> >> You have blamed the BFO but haven't mentioned any stability figure.
>>> >>
>>> >> Is the B+ feed to the BFO tube original? Are the resistors good? Have
>>> >> they been
>>> >> replaced by significantly different values? Is the decoupling to it
>>> >> still present? Are the
>>> >> caps bad?
>>> >>
>>> >> Sounds silly, but has a 6SR7 been fitted yet the heater line been
>>> >> rewired for 12V? Are
>>> >> you running 25V on the heater line and a wiring mistake has resulted
>>> >> in 25V on the
>>> >> 12SR7?
>>> >>
>>> >> I hope you've eliminated the painfully obvious.
>>> >>
>>> >> Neil ZL1ANM
>>> >>
>>> >>
>>> >> On Sun, Dec 17, 2017 at 3:50 AM, J Mcvey via ARC5
>>> >> <arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net>
>>> <mailto:arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net>>> wrote:
>>> >>
>>> >>    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...
>>> >>
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>>> bark less - wag more
>>> 
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