[1000mp] System gain in the 1000MP station

[Tom Rauch]

> > IMO it would be pretty rare condx when 1 S unit would
> > even be noticeable, much less make a difference in bagging a QSO.

Even 1dB makes a very large difference in readability when signals 
are near noise or QRM levels. 
 
> receiver.  Now, 6 dB may not mean much when the band is wide open but
> 6 dB will put you right on top of a pileup when you otherwize were
> just part of the masses.  In fact 1 or 2 dB may do the same. And
> assuming the rest of the system is reasonable (already have a decent
> antenna, decent coax) $600 for 6 dB is a lot of bang for the buck

It sure is! Especially on low bands, where 6dB extra antenna 
performance costs big big dollars in resources!

Even on higher bands, six dB is a tremendous improvement under 
marginal conditions of any type, be it QRM, noise, or just plain 
weak signals.      

I think part of the confusion is people incorrectly assume the 
absolute signal to noise level change reflects directly in a  
readability change of a similar amount. 

It does not work that way, and even amounts *less* than one dB 
can be the difference between making and not making a QSO.

Another possible contribution to the rumor that a few dB makes no 
difference comes from watching S meters, and assuming hey are 
correct. The S meters on our rigs are almost certainly neither  
linear nor accurately calibrated to some sort of a dB standard. So 
what you see might not even come close to what is really 
happening. 

My FT1000D for example, while fairly close around S-7 or higher, is 
about one or two dB per S unit down below S-5. This is a normal 
characteristic of most rigs. My IC751A's, when calibrated 
according to factory alignment, average 4dB per S unit, and are 
around 1dB per S unit below S3. Collins, Drake, and other 
companies shot for around 5dB per S unit, but because of AGC 
characteristics have the same problem with scale non-linearity as 
modern rigs. 

The end result of that is if I see an S-2 station increase to S-3, and 
observe a large difference in readability (which I typically do) I might 
assume it was from a 6dB change in level. In fact, it was probably 
a 2dB or less change in level!

Another myth is an "X" db improvement in transmitting antenna 
gain results in the same improvement in receiving. That isn't true 
either, because when the system limits on external noise or QRM 
only directivity (not gain) improves S/N ratio. A lower gain antenna  
always will improve S/N when it has a better null towards 
interference or noise, even if it has much less gain.

The end result of all of this is once you get past having a 
reasonably decent modest-cost antenna system, the next big bang 
for the buck is more power.
73, Tom W8JI
W8JI@contesting.com