[CQ-Contest] Re: NAQP Power and AGC

Barry Kutner w2up at itw.com
Fri Aug 14 11:41:41 EDT 1998

On 14 Aug 98, T A RUSSELL <n4kg at juno.com> wrote:

> On Fri, 14 Aug 1998 01:20:25 +0100 "Barry Kutner" <w2up at mindspring.com>
> writes:
> >
> >On 13 Aug 98,, AD6E at aol.com <AD6E at aol.com> wrote:
> >
> >> 
> >> Hi again Tom,
> >> 
> >> I found a real expert in this field: AE0M works in the hearing aid 
> >industry
> >> and is well versed in the human hearing field.  Tony told me that 
> >for
> >> unrelated voice applications (such as telephones) there probably 
> >needs to be 2
> >> or 3 dB difference to be able to say that one is louder than the 
> >other.
> >> However, for a "trained ear", and that probably includes all of us, 
> >it is very
> >> possible to distinguish strength differences betweens two tones in a 
> >noisy
> >> environment with only a few tenths of a dB difference.  I that means 
> >it really
> >> does makes a difference between running 100W and 150W after all. 
> >Guess I'm
> >> lucky no one took me up on that challange... hi
> >> 
> >> 
> >Al - You are forgetting about the effect of AGC. I presume most, if 
> >not all, of us use the AGC almost all the time. Since this pretty 
> >much equalizes the audio level of what we hear, the small power 
> >differences shouldn't make a difference.
> >73 Barry
> >--
> The AGC will equilaze audio output from different signals ONLY 
> when there is only one signal in the receiver passband.
> When there are several signals in the passband, the STRONGEST
> signal will set the AGC voltage which controls the receiver gain and
> weaker signals will produce less output.  
Yes and no. As a RTTY op, I sometimes notice selective fading between 2 
tones 170 Hz apart emanating from the same station. Here we are 
talking about 2 tones, each coming from a different location, 
propagation path, etc. Do the short term fades equalize the 
small differences? Dunno...
73 Barry
Barry Kutner, W2UP                            Internet: w2up at mindspring.com
Newtown, PA                                   Frankford Radio Club


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