[ARC5] Drift in BC-453 - more

J Mcvey ac2eu at yahoo.com
Sun Dec 17 12:17:21 EST 2017 

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> 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>> 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>> 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>> 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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