Posted by
Dave-7 on
Jun 07, 2011; 5:20pm
URL: http://elecraft.85.s1.nabble.com/KX3-vs-K3-and-other-rigs-tp6443819p6450573.html
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
>>
>
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