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

Wed Oct 30 16:59:40 EDT 2013

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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