Posted by
Bill VanAlstyne W5WVO on
Oct 31, 2010; 7:47pm
URL: http://elecraft.85.s1.nabble.com/K3-APF-Adjustable-Q-tp5688670p5692057.html
So yes, there are a BUNCH of variables that determine whether the DX station
is going to hear your signal.
My approach -- though this has been confined to 6 meters up until recently,
when I got back on HF CW and digital modes with a VERY small footprint --
has always been to do whatever I can to make sure the other guy CAN hear me.
That means the best antennas and the most power I can put together, in
combination of course with the smartest operating practices I can learn and
master. The QRO part of that, well, that's just me. A lot of guys love the
thrill of beating their heads against a brick wall -- sorry, I mean, the
thrill of working DX with QRP and small antennas. :-)
Notwithstanding big differences in things like power and antennas, however,
I think the two principle reasons for assuming the DX station will
eventually be able to copy you are:
(1) Their locations are probably quieter than yours -- sometimes (as in an
island DXpedition location) a LOT quieter, maybe as much as 10 dB or more
quieter.
(2) Guys who run DXpeditions or who run their home stations from rare
entities are usually very, very good operators -- probably better than you
are, for sure better than I am.
Since I've been back on HF CW chasing DX with my puny little sloper and 100
watts, I've seen many, many DX stations go to extreme efforts to pull
through a complete QSO with a weak W/K station (like me) that they
absolutely do NOT need to work for any pragmatic reason, other than personal
pride in operating skills. And some of these guys' skills are just amazing.
Bill W5WVO
-----Original Message-----
From: Kok Chen
Sent: Sunday, October 31, 2010 18:44
To: Elecraft Reflector
Subject: Re: [Elecraft] K3 APF Adjustable Q
On Oct 31, 2010, at 10/31 10:05 AM, Byron Servies wrote:
> Naieve newbie question, because im missing something here: if the
> signal you want is that hard to receive, what are the chances the
> other station will be able to hear your reply?
Since I use simple antennas, and even though I always run barefooted,
I *always* assume a DXpedition to an isolated island can copy me when
I can barely copy them above the noise.
Although Reciprocity Theory states that if both of you use the same
power, the received power at the two antenna terminals will be the
same independent of what antennas are at each end, other things
determine if he can copy you better than you can copy him.
The obvious factor that influence whether he can copy you is therefore
obviously the amount of power that you use compared to the amount of
power that he uses.
However, another factor, arguably more important, is the antennas'
directivity and where the directivity are aimed at. If his antenna is
more directive than yours by 3 dB, all else being equal, he has a 3 dB
of SNR advantage. If the arrival angle of his signal at your antenna
is 10 dB below where your antenna actually peaks, while your signal
arrives at his antenna where the response of his antenna peaks, you
have yet another 10 dB disadvantage, etc.
The same SNR argument applies to how noisy his local RF environment is
compared to your environment.
And of course, how optimal and easy to use the filtering at his end is
to pull your signal out of the noise, which is what the APF is all
about for CW (and correspondingly, the use of matched filters for
digital modes).
73
Chen, W7AY
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