[CQ-Contest] How much is a dB worth ?

[Tim Shoppa]

Dave, while those statistics were my personal station, I also looked at
other scores in top-5 or top-10 boxes of the big DX contests. I would
generally say that the #5 NA HP entrants have twice the Q's and 3 times the
score of the #5 NA LP entrant. Tripling the score with 12 dB more power,
works out to 10% more score per dB. (1.10 to the 12th power is a little
more than 3.)

While it is not obvious that a #5 NA LP entrant's antenna system is
identical to a #5 NA HP entrant's antenna system, I think that it's a fair
assumption that they both put in a similar effort and have decent antenna
systems.

Dave, on my home antenna system, I actually do quite well in DX contests on
high bands, but really struggle on high bands in domestic contests. I am
just inside the beltway and have a nice terrain drop off to the NW and N
and by some stretch of imagination a long "14 lane wide concrete valley" to
the NE, that I'm thinking must help radiation at DX angles. Who knows,
maybe all that concrete is conductive or something helping reduce ground
losses too. Look at what Frank was saying about salt marshes, maybe a mile
of 14 lanes of concrete valley pointing to NE, is as good of a conductor as
a mile of salt marsh!

On low bands of course most guys do not have a beam and I do exceptionally
well there, both domestic and DX.

On nearby terrain... I also have the WMAL radial field just a little to my
Northeast, too. They are going to turn that
isolated-by-270-to-beltway-merge triangle into a housing development, hope
some of the ground conductivity stays in place!

Tim N3QE

On Tue, Mar 1, 2016 at 10:18 AM, David Siddall <hhamwv at gmail.com> wrote:

> I would postulate that the worth of a dB is not linear, but rather, there
> is a tipping point.  If Tim was using a beam at 50-70 feet on the high
> bands, I think his results would be more in line with those of N1UR.  With
> a doublet, the first 6dB got him into barefoot & beam range, and over
> general QRM levels.
>
> BTW, Tim, congratulations for the AMAZING scores with that setup.
>
> 73, Dave K3ZJ
>
>
>
> On Tue, Mar 1, 2016 at 9:41 AM, Tim Shoppa <tshoppa at gmail.com> wrote:
>
>> Certainly, Tom! My antenna is a 130-foot doublet, up 75 feet between
>> trees,
>> fed by tuners and ladder line.
>>
>> On 160M the antenna is fed by tying the ladder line together at ground
>> level and feeding it against ground as a "Marconi T". Essentially the
>> ladder line becomes a vertical element and the 130-foot top becomes a
>> tophat.
>>
>> Some pictures of ladder line relay switching and tuners here:
>> http://www.trailing-edge.com/tuners.html
>>
>> I have a couple 160M receive antennas too (a K9AY for NE/SW, and a
>> west-facing pennant.)
>>
>> Tim N3QE
>>
>> On Tue, Mar 1, 2016 at 9:29 AM, Tom Carrubba KA2D <ka2d at arrl.net> wrote:
>>
>> > Hi Tim
>> >
>> > May I ask, what antenna do you use?
>> >
>> > Thanks
>> > Tom KA2D
>> >
>> > -----Original Message----- From: Tim Shoppa Sent: Tuesday, March 01,
>> 2016
>> > 6:40 AM To: cq-contest at contesting.com Subject: Re: [CQ-Contest] How
>> much
>> > is a dB worth ?
>> > My interpolation on CW and RTTY using my personal logs, for 24-34 hour
>> > efforts in 48 hour contests and almost unchanged antenna system, after
>> > adding two different amps.
>> >
>> > Note that my numbers only track transmit power dB, not receive system
>> dB's.
>> > I have improved my receive system on 160M but not on the other bands in
>> > this time.
>> >
>> > Note that for CW tests I was often in the top 10 box for assisted LP but
>> > now am not necessarily in the top 10 box for CW now that I enter
>> assisted
>> > HP. And I actually lump a couple different contests together and apply
>> some
>> > tweaks based on what I feel to be changes in propagation to keep things
>> > comparable to my last year on LP.
>> >
>> > Going from barefoot to AL-811H (8dB) doubled my QSO's and tripled my
>> > scores. With this change I usually get S&P on first call and can often
>> hold
>> > a run frequency for a good time in the biggest CW and RTTY contests.
>> >
>> > Going from AL-811H to AL-1500 (another 4dB) added another 30% to my QSO
>> > numbers and another 50% to my scores. With this change I almost always
>> get
>> > S&P on first call and only rarely get pushed off a run frequency.
>> >
>> > So making a little table, just using ARRL DX CW as an example:
>> >
>> > 100W = 1000Q's
>> > 600W = 2000Q's (8dB more power for 3dB more Q's).
>> > 1500W = 2400Q's (12dB more power for 3.8dB more Q's)
>> >
>> > 100W = 1M points
>> > 600W = 2.7M points (8dB more power for 4.2dB more points).
>> > 1500W = 3.5M points (12dB more power for 5.5dB more points).
>> >
>> > I would say each dB more power, means 7 to 9% more Q's.
>> > And each dB more power, means  more points 11 to 12% more points.
>> >
>> > There is some "compression" to the score expansion (a dB is worth more
>> > moving from 100W to 600W, than a dB moving from 600W to 1500W).
>> >
>> > I think this compression factor would have been less, or not there at
>> all,
>> > if I had improved my receive system as well as my transmit power (i.e.
>> I am
>> > now an alligator, all mouth, no ears).
>> >
>> > If I had chosen WPX, the QSO ratios would be similar, but the point
>> ratios
>> > will be a little larger (WPX mults continue to grow quicker than ARRL
>> DX or
>> > CQ WW mults.)
>> >
>> > Tim N3QE
>>
>>
>