Probably, but my guess is that the rate of change is so slow, and the
increase in signal is so low that the increase in IM distortion is not
noticeable.
On Apr 18, 2005, at 8:59 AM, Gary Schafer wrote:
> But the issue is one of gain "expansion" not of compression. Does
> expansion produce the same kind of distortion that compression does?
>
> 73
> Gary K4FMX
>
>
> Bill Fuqua wrote:
>> I think the real issue is being missed there. The real test of
>> non-linearity is the production of harmonic and intermodulation
>> distortion. This means allows measurements of nonlinearity as small
>> as a very small fraction of a percent. Even to a part per million
>> with very specialized equipment.
>> If there were nonlinear propagation the RF spectra would be
>> unusable. The apparent increase in signal strength could be in
>> perception. Which has to do with your reference. On receive, a
>> signal to noise ratio of 0 db would be unintelligible but a 3 or 6 db
>> increase in signal would provide lots of improvement. And are you
>> measuring signal or signal+noise? It comes down to this. If no
>> harmonics are produced and no intermodulation products produced
>> between the transmitting and receiving sites the propagation path is
>> linear.
>> Now, if you should be unfortunate enough to have a
>> thermonuclear blast between the transmitter and receiver you would
>> have lots of nonlinearity. This is due to the greatly ionized region
>> (large volume of plasma) due to the blast. This scrambles signals and
>> presents all sorts of problems for those trying to use RF
>> communications.
>> If you want to do such an experiment arrange for two stations
>> near by to transmit a KW signal and then look for the intermodulation
>> products at the far end of the path. From that you can calculate the
>> degree of nonlinearity. Don't use stations are close enough that
>> there may be mutual coupling between their antennas and sending a 2
>> tone test will not work either because the degree of nonlinearity
>> that you are looking for will be very very small. But don't forget.
>> There is also nonlinearity in your receiver as well. But all of those
>> sources of nonlinearity are small compared to the nonlinearity that
>> would produce several db increase in receive signal strength over the
>> change transmitter output power.
>> 73
>> Bill wa4lav
>> _______________________________________________
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>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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