I can get two tones easily less than one hertz apart by listening to the
beats as long as the two tones are close in amplitude. What you actually
hear is the phase between the two tones gradually changing, not the
frequency of the beat note. In this manner you can get much less than 1
hertz frequency difference. Try it. You will see what I mean.
Carl Moreschi N4PY
121 Little Bell Drive
Bell Mountain
Hays, NC 28635
----- Original Message -----
From: "Robert & Linda McGraw K4TAX" <RMcGraw@Blomand.Net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Monday, January 09, 2006 12:40 PM
Subject: Re: [TenTec] [Orion] O2 versus Orion
> My experience tells me that there is a concernable difference in ones
> ability to audibility and accurately "zero beat" a given signal. Unless
one
> can observe the difference in beat of the two signals via the S-Meter
> fluctuations as the frequency gets very close, it is thus below the audio
> passband of the and certainly below the low frequency hearing of most
folks.
> Less than 30 to 50 Hz for example. Therefore the 1 Hz resolution or ones
> desire to achieve such is of rapidly questionable accuracy.
>
> To this end, I prefer to actually measure the transmitter output or actual
> oscillator frequency with a suitable counter capable of measuring to 0.01
Hz
> at the desired frequency or better. Truthfully, not many hams have access
> to such high accuracy items as their cost is several times that of an
Orion
> II. Thus we do more "referencing" than actually measuring of frequency
> values. In each case, the reference add a percentage of error +/- to the
> resolution method.
>
> I took some time to "practice" various zero beat methods this morning and
> then looked at the actual transmitter frequency. In most cases I was able
> to get within 30 to 50 Hz of the desired frequency but certainly in fact
no
> closer, as the audio passband fell apart below 30 Hz and there was simply
> "nothing to hear" coming out of the receiver. Once I got closer in
> frequency then I was able to detect the swing of the S-Meter and bring
> things in a good bit closer. Still, accuracy of 1 Hz was questionable.
>
> We must remember that these radios are not designed to be frequency meters
> or frequency counters and thus the stability and repeatability is very
> questionable when one gets into the single digit Hz region. Then why do
> they put 1 Hz resolution on radios? To be better than the next fellow and
> to sell radios with features.
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message -----
> From: "Martin AA6E" <martin.ewing@gmail.com>
> To: "Bill Tippett" <btippett@alum.mit.edu> > standard for WWV comparison.
> >
> > Now that I look at the schematics, I see that the CODEC has a separate
> > "14.360 MHz" clock crystal. Maybe that's the problem. It should be
> > generated from the TCXO. Is that the birdie I hear at 14,351.770?
> > (.05% low) This would introduce a minor offset, which is cancelled
> > out if you calibrate against WWV. Or is there more to it?
> >
> > Orion's accuracy and stability are good, but none too high, IMO. This
> > shows up in netting accuracy at the higher freqs. Of course, 95% of
> > rigs out there are worse. The new IC-7000 has a much better spec:
> > +/- 0.5 ppm vs Orion's +/- 3 ppm. Probably cost them a couple of
> > bucks more. The IC-7800 claims +/-.05 ppm 0-50C "after warmup", for a
> > price.
> >
> > It would be nice if the master oscillator was at least upgradeable or
> > syncable to an external reference, for the few folks who are looking
> > for very high precision.
> >
> > 73 Martin AA6E
> > --
>
>
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