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[K0OD]

"<<Did some research on that question years ago and concluded a single dB added something like 10% to ones CQWW score...>>"

"That is a seriously flawed study and conclusion as anyone who understands such studies would understand."

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Flawed sure. But I couldn't escape concluding that a single dB of power was meaningful and capable of being quantified:

I DID study fairly identical stations. Often the same guy will be QRO in one test and low power in another. There were cases where full bore contest stations with big stacks entered QRP. By looking at the totality of the top`10-20 scores, it was possible to estimate conditions for a specific weekend and attempt to adjust for that.

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If one db makes no difference, but 10 dbs is big (as anyone can see in the results), where does an extra db or two start to matter: Between db 3 and 4, or  around dB 7 and 8?

Note too that I'm talking only about one db of transmitting power. A microscopically better antenna might help on transmitting gain, receiving gain and receiving noise/QRM  reduction via a cleaner pattern...all just a bit, but a meaningful bit, I think. Again, think in terms of running weak JAs on 80.

[W8JI]

A study is either good and has some reasonable connection to what we are trying to determine, or it is not good.

The "study" you did is absolutely meaningless in determining how many contacts per dB someone can get because of power.

We can't even remotely assume a change of ten or more dB in level extrapolates down to 1 dB change even if NOTHING else changes. Any change in power level would be a non-linear threshold effect with QRM or background noise setting the knee of the change.

Making things worse, better more experienced operators generally also run better stations and they have more skill.

Also everyone lives in different locations, has different antennas, has good and bad days, and so on.

It's all rubbish unless the only variable is the power. I can tell you first hand I looked at logs from here when we lost a primary amplifier and dropped back to a small backup amp about 3-4db less power and the rate never noticably changed.

That's because we are over the threshold of being marginal for most people.

They reached the same silly conclusion in the Stew Perry 160 Contest and gave QRP and ten watt stations extra multipliers for low power. The result was for a few years everyone starting running real low power and a 1500 watt staion could never win over a ten watter.

From here on 160, ten watts gives me about one third to half fewer contacts as 1500 watts. 100 watts from 1500 is barely noticable, just a few contacts.

As a matter of fact I looked at leading USA scores one year just now at random and the top high power W's and the top ten watters were within 25% of the same.

It's a threshold effect when the signal gets down in the clutter or noise, not a linear progression.

73 Tom

[K0OD]

"It's a threshold effect when the signal gets down in the clutter or noise, not a linear progression"

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I was talking about a 10% increase in score, not contacts. Getting an extra few very rare mults in the CQWW requires breaking thru a BUNCH of thresholds at various times, on various bands, in different directions, etc. The threshold isn't just noise:  Working rare central Asian mults can involve beating a wall of Japanese callers.  So I'm not sure it can be thought of as merely "breaking the squelch" in an overall sense. Even then, wouldn't there would be ONE CRITICAL DB among the ten?  ("the db that broke the pileup's back")

I'm just throwing out this idea. My study was done so long ago that I'm pretty hazy on the details. But I doubt that many top DX contest stations would be so quick to disrespect a single db or two. Especially not stations here in the Midwest.  

[W8JI]

I know people focus on every fraction of a dB. Focusing on every last dB doesn't actually mean it is a worthwhile thing. It is really just something they can control. People mostly can't change other things that are more important, like locations or operator skill levels.

Tune the band sometime and be attentive to what you hear or notice. What really happens with transmitting signal is people are basically in layers. There are the upper layers all the way down to the very bottom layers. Upper layer stations stand out, even if they are 5db apart from each other. They are only a few dozen of the better stations in better locations. Then there is the vast majority of the crowd. This might be big stations in poorer locations or without good propagation, and the rest mostly high power medium antenna stations.

Then there is a layer of weaker signals, and finally really weak stations with poor locations and low power and small antennas.

There's about 50 dB or more difference between upper layer stations and lowest level stations just from one general area, and the difference of a few dB isn't noticable at all unless someone is near the lower limit of being heard.

The real difference in scores for the same operator at different stations, and you can ask anyone who operates from here, is in receiving. For example I'm about 15 miles from another station with somewhat similar antennas for 40. We can sit here in daylight on 40 meters and run DX stations one after another that the other station close to me can't even hear. We can turn the stack off and drop signal level 3-5db and continue to run stations they can't here.

There is so much difference that a single op here can tie or beat multi-ops using run and assist radios and the cluster.

That difference isn't the transmitted signal. It is the receiver. The difference isn't the gain, it is the directivity and the local noise floor out for miles.

Once you are over the noise floor a reasonable amount you will get nearly every station anyone else will get, IF you can hear the really weak stations. But that really weak station heard in a quiet location, even if he was 3dB better, wouldn't work significantly more people.

Our run rate doesn't slow any noticable amount even when we drop 3-6dB on transmit. The problem is always receiving the really weak guys, like the 5 watt low dipole stations at night or the daytime 4000 mile stuff on 40 meters. That's what makes it or breaks it, and gain doesn't help that. Noise floor and directivity does, but not ERP or gain.

73 Tom


 

   

[W8JI]

By the way, the same is true when people call us.

It isn't the 1dB or even 3 dB that makes a difference. It is the timing, skill, and the luck of the draw of the caller.

One dB isn't squat one way or another. Ten dB is huge, but not one dB. it is meaningless.
73 Tom

[N3OX]

"Ten dB is huge, but not one dB. it is meaningless. "

What about 1dB difference of a noise-level VU4 on 160m?

[W8JI]

If everyone you work is zero dB S/N ratio and there isn't much fading, then 1 dB is huge. With ten dB of fading and nearly all signals several dB or more out of the noise, it's pretty tough to tell.

That's about ten QSO's out of 2000 on 160, and half of them will be W5's using a 40 meter dipole with one watt that take 15 minutes to get the calls. That extra dB means we can get the calls in 5 minutes for the two points. :-)

[K8KAS]

We are really getting carried away guys, first how do you measure 1 DB, I worked for many years on commerical RF antenna test ranges in the automotive sector and it was very very hard to measure 1 DB in that world. Ham receivers forget it, yes there is QSB on the testing done on a test range, you would see signals vary plus/minus 1 Db and this was measured with known testing levels and qualiy receivers made for exact measurements.
From many years of ham work I as well place much more value on timing, audio quality and DX know-how than the 1 db we talk about. I feel 3 DB is the breaking point as to you see it or not and it making any difference at all.

[N3OX]

"first how do you measure 1 DB"

* with * your * ears *  if signals are at the noise floor.  

"I feel 3 DB is the breaking point as to you see it or not and it making any difference at all. "

But if that would catch on as the average "I don't care" threshold, that is, each individual ham would stop working toward some goal once they got within 3dB of it, that would cause an average 6dB path degradation for every QSO.  

If a dB is hard to measure, and hard to hear, it makes a perfect threshold for whether or not a change matters.  That way, two hams get within 2dB of as good as they could have done.


73
Dan

[AC2AZ]

I need to put my 2 cents in.  Someone reported using a 5/8 on 160 meters.  Unless that antenna was 322 feet long, it's not a 5/8 wave.  The gain in a 5/8 wave comes from the actual physical 5/8 length compare to an isotropic, 1/4, or 1/2 wave.  An "electrical" 5/8 is not the same as a physical 5/8.  The 43 foot 5/8 wave from DX and Five-zero can only achieve radiation pattern performance to 13 meters.  This may be one reason many people don't see a difference in performance.  In fact, a 1/4 may perform better if a true 1/4 wave length, only because the radiation pattern is "classical" and not distorted as would a short antenna trying to be 5/8 but physically short, frequency aside.  This is my understanding, that the physical length determines the pattern, and the electrical length determines the impedance, as gleaned from antenna theory books.  My understanding is basic and if incorrect, I would like hear an alternate understanding.

Also, with regards to DX, the higher radiation angle of a 1/4 may be more beneficial to achieve skip than a low radiation angle of a 5/8, which would excel in ground waves.

Bob