OK
I wouldn't say I am a casual user, but on the other hand, I've never gone
to a lot of trouble to actually measure the signal strengths -- I
consider the S-meter pretty useless for measuring these 1 or 2 db
differences since that isn't what it is designed for, but yes, I will
admit that if you had a clean white noise source some could probably
detect your signal maybe at the 1.5 - 2db level above that. Again,
however, my experience isn't like that -- VHF noise levels move around --
as do HF ones and the original post was that someone would "kill" for 1
db which hardly seems appropriate.
(an aside)
How do you use the volt meter as an accurate measure of the signal above
the noise level? Sounds like a neat trick. Where do you measure it, etc.
Anyway -- as far as I can tell, we all seem to agree that 1 - 2db isn't
much but perhaps some people can realize an advantage to it under certain
circumstances.
Dave
N7UE
On Wed, 2 Apr 1997 km1h@juno.com wrote:
> I certainly do not know what your operating preferences are Dave but by
> your comments I would assume (very bad choice of words to a lawyer, I
> know) that casual operating predominates.
> I am talking from the experiences of an in-the-trenches DXer and
> contester, HF and VHF where 2dB makes the difference at times.
>
> Here is an example of a possible situation. I am in a DX pileup on CW and
> my signal is only 1dB above the din which means I am just part of the
> noise at the other end. If I increase my signal 2dB I will now have a 3dB
> advantage and it should predominate. Theroetical...YES; works all the
> time....NO. There are way too many other factors involved including
> operator skills, antenna angles QSB, etc, etc.
Well -- and this is the point, right? 1 or 2 db of transmitted power
just isn't worth getting all excited about -- now 10db is worth talking
about (or even less)
>
> Also 3dB is readily detectable by anyone with normal hearing; tests have
> proven that as low as 1.5dB can be detected by a few and 2 dB by a
> sizeable number. Find out for yourself the next time you get your hearing
> checked.
In a clean unvarying environment, not contest conditions on 160M
>
> For those who sit on 75 or 20M SSB and chat with S9 ++ signals all the
> time even 10dB probably goes unnoticed unless they are constantly
> watching an S meter.
> For the chap operating weak signal VHF a signal 2dB out of the noise is
> all it takes. The human ear is a wonderful device for detecting a
> coherent signal out of white noise.
>
I will admit that sometimes VHF noise is pretty clean and constant so
this is probably more true here than on HF -- particularly if no one else
is on the band at the time.
> For the DX Contester, a 2 dB advantage (power, antenna or whatever) can
> win or lose a contest. Take a look at the KM1H contest scores from
> 1987-95 if you doubt that. Getting the band edge first on 20M on SSB into
> EU as the band openst is an absolute key strategy. On either mode it
> means you can get the jump on the competition and keep moving up first to
> the next highest band as it opens.
Yes - but how do you know he has a 2 db advantage? We don't know what he
is doing -- maybe he has a big amp? or hardline? or a high antenna? Or
he just did everything right and knows where and when to look for dx?
Getting the band edge may be a tactical advantage, but it says nothing
about your radiated power. Indeed, its probably "worth" more than a
couple of db of radiated power.
> I realize this is an AMP reflector but I sense a very wide diversity
> here. I enjoy amps but put most of my $$$ into antennas. 10 thru 20M have
> 4 high stacks and a 4/4 on 40M. I can pick up many, many more dB by
> switching stack phasing than going from 1200W to 10KW into a single
> antenna.
Definitely!
>
> Detecting a 1dB change requires very expensive equipment; I had to pay
> $25 for my Simpson 260 at a flea market. For the sake of discussion let
> us assume that the signal amplification in Brand X receiver is perfectly
> linear.
>
> Thats my 33 1/2 cents worth for today on THAT subject.
>
> 73...Carl KM1H
> On Tue, 1 Apr 1997 18:50:25 -0800 (PST) "David B. Ritchie"
> <dbr@alumni.caltech.edu> writes:
> >
> >3db is barely detectable by the human ear
> >1-2 db can be measured by expensive instruments
> >2db hardly seems useful on any band (of course, the first 160db may be
> >
> >VERY useful)
> >Dave N7UE
>
David B. Ritchie, Esq.
D'Alessandro & Ritchie, P.C. -- Intellectual Property Lawyers
3521 E. Yorkshire Road, Pasadena, CA 91107-5432
818-683-8800 (TEL) 818-683-8900 (FAX) dbr@alumni.caltech.edu
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|