Interesting analysis Dave. Assuming everything is logarithmic, a 33% increase in contacts for a 13 db power increase implies 7% more contacts for 3 dB more power:
10^[(3/13) * log(1.33)] = 1.07 And 100% more contacts for a 25 dB power increase implies 8.7% per 3 dB: 10^[(3/25) * log (2)] = 1.087 However, I think that overstates the advantage of higher power. The higher-power stations also probably had better antennas and other equipment as well. But it does put a useful upper bound on the number. In a non-competitive situation I would expect the difference to be even less. Alan N1AL On Tue, 2011-06-07 at 12:20 -0500, dave wrote: > To try to put some meaningful numbers on the value of a few extra dB I > looked at some recent contest scores. Actually not at the scores > themselves but the number of Q's made. There is of course wide > variability in this. A lot appears to depend on whether it is > primarily a NA contest or international. But it might give some clue > about the value of additional power. > > To hopefully remove some of the many variables, I looked only at the > top few stations. The assumption is that these guys have good stations > with good antennas in good locations. Have to believe that they put in > nearly equal effort, i.e. approx the same number of hours. Implicit > also is the assumption they are approx equally good operators. > > In the 2010 ARRL 160m contest these power levels made this many Q's: > > 1st 2nd > QRP 805 718 > LP 1078 1038 > HP 1989 1776 > > In 2010, with the low sunspot numbers, this was basically a NA > contest. Not much in the way of DX activity. > > Assuming other things are equal - which may or may not be the case - > it looks like 13 dB (5w to 100w) is worth about a 33% increase in Q's. > And 25 dB (5w to 1500w) will yield somewhat more than double. > > In the 2010 ARRL Sweepstakes: > > 1st 2nd > QRP 982 835 > LP 1257 1244 > HP 1466 1453 > > This is a NA contest. > > Here 13 dB was again about a 33% increase and 25 dB something less > than double. Indeed having a KW was not much help here. > > But if we look at longer distance and check the 2010 ARRL > International DX contest (looking at stations in NA, not EU or other > continents): > > 1st 2nd > QRP 1021 912 > LP 2872 2738 > HP 4362 4474 > > Here 13 dB gives nearly 3x as many contacts. 25 dB gives about 4.5x as > many. > > It looks like a few extra dB may be valuable on longer paths, but not > worth much within NA, which is about what you would expect. > > This does not address the question of what 3 dB is worth. A little > hard to figure. Within NA 13 dB yields about 33%. So what would 3 dB > yield? Dunno, but my guess is not much. > > How much is 3 dB worth on longer paths? Again hard to say but there is > probably some threshold, or minimum required, to work the DX. Is that > threshold 3 dB, i.e. 10w? Honestly probably not. Somewhere between 5w > and 100w, but unknown. > > Maybe some enterprising souls could get together, a few run 5w, a few > run 10w, a few 25w, and a few 50w. Compare results when it is over. > > > 73 de dave > ab9ca/4 > > > > > > On 6/7/11 7:23 AM, drewko wrote: > > There is another way of looking at it-- how many additional contacts > > would potentially be available by utilizing an increase of just 3db? > > > > I don't know the answer but there is a somewhat analogous situation in > > astronomy having to do with the brightness of stars. They are also > > measured on a logarithmic scale, called magnitude, each magnitude > > representing twice or half the brightness level of the following or > > preceding magnitude. A difference of one magnitude does not appear > > very large to the eye, yet the ability to see one magnitude fainter > > can yield three times as many stars. I imagine some similar effect > > might pertain to radio waves. > > > > BTW, I'm not asking for more power in the KX3; would be quite content > > with 10 watts, same as my K3. > > > > 73, > > Drew > > AF2Z > > > > > > On Mon, 06 Jun 2011 08:56:48 -0700, Alan N1AL wrote: > > > >> On Mon, 2011-06-06 at 08:10 -0700, juergen wrote: > >> > >>> However from a communications effectiveness point of 20 watts is a > >>> much more realistic power level, especially for SSB QSO's. > >> > >> The difference between 10 and 20 watts is only 3 dB, half an S-unit. > >> Compared to the 20-30 dB of QSB you often find on the HF bands, you > >> would hardly even notice such a small difference. I think it is quite > >> rare that 3 dB would be the difference between making a contact or not. > >> > >> Alan N1AL > >> > > > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[email protected] > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
