[ARC5] Drift in BC-453 - more

[Kenneth G. Gordon]

On 12 Dec 2017 at 19:30, Bill Cromwell wrote:

> Hi,
> 
> If the drift in parts per million is the same for the oscillator
> systems in each of those radios then all of that holds up. As soon as
> we do anything to compensate for drift your statements fall apart. But
> generally free running at lower frequencies are more stable than
> higher frequency oscillator systems. Temperature is the biggest bogey
> man in the drift arena and there are well known ways to manage that.
> Hams and professional engineers alike have built some pretty stable
> oscillator systems (heterodyne HFO, BFO, VFO combinations). 

...the Wadley triple-mix system...or doubled like in the AN/FRR-59...

> So we can build a radio to receive WSPR and it's total drift stack
> comes to 1.9 Hz over two minutes. What if the distant TX also drifts a
> mere 2.9 Hz during the same two minutes but drifts the other
> direction? Then add the same kind of atmospheric mayhem that causes
> WWV to be "useless". Again, we do the best we can. 

Indeed. And have fun doing it too.

> I think it was mentioned again that time has to be within a second or
> two at each station. The use of network time standards is indicated.
> My (mis)understanding is that the "esp" modes rely on online databases
> to help sort out what is being sent - to improve the chances of a
> correct guess. So those milliHertz modes seem to depend on outside
> resources to prop up their useability. 

Seems like it, doesn't it?

> All of that for tiny a message that takes all night to get there. Sort
> of like "Kilroy was here". 

Yes. It seems like it is in exercise in....something....but not particularly useful for 
communications purposes...

However, I DO know that experimentation with these modes has resulted in improvements in 
weak-signal detection and display. Maybe that is the main reason for the existence of such 
modes?

> That is not my cup of tea at all. This is not to dismiss WSPR or
> JT(favorite flavor here). Splitting milliHertz seems like a reasonable
> facet of the hobby to me. Other hams seem to be happy with it. We all
> have to control our transmissions. The new MF and LF allocations are
> very narrow slices of spectrum and we need to be aware of what our
> signals are doing and how they can be fitted together in that narrow
> slice. So some degree of splitting hairs is required. I believe
> (perhaps incorrectly) that I can see (not hear) a difference of less
> than one cycle per second. Maybe in my lab it is only deciHertz and
> not milliHertz or microHertz. That will have to be good enough. 

Same here.

> As to the original post..the OP seems to be experiencing a wildly
> excessive amount of drift. 

That is exactly what I thought too. Perhaps we misunderstood? Mac? Care to fill us in or 
correct us?

> I run my command receivers on batteries and when I pipe the audio into
> a sound card and display it on a waterfall display I cannot see *any*
> drift. 

And I run mine on regulated supplies for both HV (which I keep "low") and filaments, and 
**I** don't see *any* drift either. Waterfall lines are pretty much vertical and don't "lean" to 
one side or the other.

I'll dig out my favorite BC-453, hook it up and do some testing, then will report results here.

> That means no net drift for the VFO, BFO, incoming signals, and the
> computer clocks all combined. 

Same here, although I do use "internet time" to keep my computer clock more accurate. 
Even so, drift in my computer's clock is minimal.

> Maybe there is a deciHertz that I am unable to resolve. In *my* radio
> world that is insignificant. Does the OP have truck tire tracks across
> his radio? <evil grin> 

I don't think so, but that IS a thought... :-)

I DID find the BFO coil in one of my hacked-up BC-454s had been burnt somehow. Even so 
the BFO still worked. I replaced that BFO box with a new one. That is the receiver that 
someone had tried to modify to cover 10 meters back in the early 1950s and never finished. 
I finished it and it works surprisingly well. I've never measured the drift though.

Ken W7EKB

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