[ARC5] dB Power and QRP according to HR magazine. [Was dB - Apples& Oranges]

Wed Oct 30 22:38:44 EDT 2013

Nice story carl
I met Sam at arecibo a few months before his death. Was at his house. I returned to Arecibo for a second time just a few weeks after his death. Helped the observatory staff remove the last boxes of radio junk box stuff from his house. I saved a few small items from the dumpster. Funny coincidence. I just looked and handled a few of those items earlier today while looking for something else for the first time in many years

I am very honored to be able to say I met Sam

Bruce. Kj3z

Sent from my iPhone

On Oct 30, 2013, at 4:59 PM, "Geoff" <geoffrey at jeremy.mv.com> wrote:

There were tests done at the Dayton Hamvention a few times over the years using real test equipment such as current model HP and high end transceivers.

Some could tell 1dB in a very controlled enviroment and a few could barely tell 3dB. I fall into around 1.5dB, maybe a hair better if Im rested and ready to concentrate.

It took years of training and my first real exposure at pee weak signals was at the W1BU/W1FZJ 1296 mc EME station in the early 60's. Id walk in and Sam would be copying a CW exchange from the R390 plus 100Hz audio filter and all I heard was noise. The plotter chart showed how "loud" the signal really was. After about a year I could match Sam and he then let me operate various skeds while he was on some HF SSB frequency chatting with the other end.
The 28' Kennedy dish and old schoolbus is still there totally abandoned. Sams son Pat still lives in the house with his family but his ham interests are much different.

Carl

----- Original Message ----- From: "Leslie Smith" <vk2bcu at operamail.com>
To: "ARC-5 List" <arc5 at mailman.qth.net>
Sent: Wednesday, October 30, 2013 2:29 PM
Subject: [ARC5] dB Power and QRP according to HR magazine. [Was dB - Apples& Oranges]

>"I believe it started as saying 1dB is too small of a change for the >human ear to detect and morphed to become
1 dB is the minimum change that the ear can detect.  This sort of morphing is common."  - Bill

Hi Bill
I see you understand the process that barristers (an Australian
high-level lawyer) use in court during cross examination.

Years ago an article appeared in "Ham Radio" magazine relating the
ability of a human ear to detect a change in sound level.

The article was quite interesting - even though the measurements were
done on an informal basis using only uncalibrated equipment that might
be found in a well equipped "ham" shack.. After a half-hearted search I
couldn't find the article, but it was definitely published by "HR".

If my memory is correct the author of that article found the change in
power (i.e. dB) was greater than the figure most have quoted in this
thread, and well above 1 dB.  The article drew the conclusion that under
good conditions a 5 or 10 watt QRP transmitter may make effective DX
contacts - and that a 100W or 400W signal might be heard 'better' but
that QRP was still worth-while.

Some will criticize the method, some will criticize the equipment but I
applaud the idea of doing the work and observing the result.
My observation is this:  "Knowledge gained by personal effort is often
of a better quality than knowledge gained by other means."

73 de Les Smith
vk2bcu at operamail.com

On Thu, Oct 31, 2013, at 2:47, Fuqua, Bill L wrote:
  I believe it started as saying 1dB is too small of a change for the
  human ear to detect and morphed to become
1 dB is the minimum change that the ear can detect.  This sort of
morphing is common. An example, my wife
was told that adding green beans to our dogs diet prevents gas. However,
I am sure that it began as green bean
don't cause gas as some other do. Anyway, she puts green beans into his
dinner bowl, which is OK since he
enjoys eating some "people food".

73
Bill wa4lav

From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on
behalf of Brian Clarke [brianclarke01 at optusnet.com.au]
Sent: Wednesday, October 30, 2013 1:47 AM
To: hwhall at compuserve.com; ARC-5 list
Subject: Re: [ARC5] dB Power Apples and dB Voltage Oranges,     was Re:
Selectivity Ratings...

You may be referring to the work of Fletcher and Munson in the Bell labs
in about 1938. However, their work was based on laboratory experiments
with young listeners.

We now know that the ear's ability to pick up slight differences depends
on, among other things:
 a.. age (presbycusis)
 b.. frequency
 c.. purity of the frequency (bandwidth, distortion within hearing
 range)
 d.. genetic differences
 e.. one ear or both
 f.. history of noise exposure (eg, working around tin bashing shops,
 repairing naval vessels, working on rocket motors)
 g.. history of hearing damage (eg, tinnitus)
 h.. disease of cochlear nerve and other parts of the hearing apparatus
 i.. duration at particular ambient noise levels
 j.. the 'reward' for hearing something.

1 dB is a purely mathematical definition and has nothing whatever to do
with human hearing acuity, consensual or otherwise. WRT your last
sentence, keep wondering.

My own experience from working in sound recording studios is that a 2 dB
difference is about the limit that any reasonably experienced person can
reliably discern.

73 de Brian, VK2GCE.

On Wednesday, October 30, 2013 12:25 PM, Wayne said:

> Good CW operators
> can hear as little as 1.5dB change and oft times even under 1 dB will > bring
> a very marginal signal out of the noise.
>
> I seem to recall that the original 1 dB definition was based on a > consensus of the smallest power change in an audio circuit that could > be discerned by the human ear. I've always wondered how they conducted > the tests to arrive at that, though.
>
> Wayne
> WB4OGM
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