[ARC5] Drift in BC-453 - more

Peter Gottlieb kb2vtl at gmail.com
Sat Dec 16 18:31:46 EST 2017


That kind of drift can be compensated for in receiving software. Why it isn't is 
a question for the developers.  It's just a form of AFC.


On 12/16/2017 6:24 PM, J Mcvey via ARC5 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> 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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