[RTTY] About N4II's experiment...

[Joe Subich, W4TV]

> It's not like simple AFSK, where you just need to follow the
> manufacturer's instructions.

Only follow the manufacturers instructions if the manufacturer knows
how to give valid instructions - unlike some PhDs who think they can
increase the speed of light by almost 50% at will.

Manufacturers who skip the chipmaker's recommended regulator for the
sound ADC, who fail to properly decouple (filter) the USB power, who
fail to regulate the V/2 reference for their op-amps and who fail to
adequately decouple their power distribution bus certainly can't be
trusted to know what they're doing when it comes to instructions
about setting AFSK levels.

73,

    ... Joe, W4TV


On 3/15/2014 7:30 AM, Kai wrote:
> You're quite right Chen. At the risk of annoy the moderator with
> off-topic discussions, time-of-flight is not all that needs to be
> measured, but it is necessary to a certain precision. The probe signal
> is quite a bit more sophisticated. The signal bends in three dimensions,
> separates into counter rotating waves of circular polarization that
> travel different paths and at different propagation velocities, possibly
> reflects and diffracts from  the gray line region and Auroral oval
> boundaries. It is subjected to multipath and ISI, and so on. It's a
> digital signal designer's heaven (and a propagation weenie's heaven)!
> Competing theories predict different paths, as well as different
> multipath, and differing propagation velocities. The ionosphere is
> complex, and then you add the Earth magnetic field, and things get
> really interesting in a hurry (think CRT). It's not like simple AFSK,
> where you just need to follow the manufacturer's instructions.
>
> 73,
> Kai, KE4PT
>
>
>
> On 3/15/2014 12:23 AM, Kok Chen wrote:
>> On Mar 14, 2014, at 8:49 PM, Kai wrote:
>>
>>> We do however want to measure the propagation speed of signals in the
>>> ionosphere...
>> There are more unknowns than measurables, Kai, if all you are
>> measuring is the path transit time.  The problem is not the "baud
>> rate" (we know for example that it is easy to measure transit time to
>> much more precise than T, using a pulse whose width is T).
>>
>> Think of a similar experiment where you use total internal reflection
>> of a prism in a reflex light path to measure the speed of a laser
>> beam.  You don't know the size of the prism, nor the distance of the
>> laser to the prism, and you don't know the refractive index of the
>> glass used to construct the prism.  All you can do is to measure the
>> transit time as precisely as possible.  With that alone, you cannot
>> determine the refractive index of the prism.
>>
>> Now imagine the prism to be a simple model of the ionosphere.  (In the
>> case of the ionosphere, the density is not even constant.)
>>
>> 73
>> Chen, W7AY
>>
>>
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