[RTTY] DJ3IW and NAQP (long)

[Kok Chen]

On Monday, July 22, 2002, at 04:17 AM, DJ3IW Goetz wrote:

> 2) Their receive capabilities are not on par with their TX power
>    (Chen mentioned 25kW) and multielement stacked Yagis at great height?

HI HI, Goetz, I had made that comment completely jokingly :-)

And, if they had bigger antennas, it would actually help them,
since they have a better S/QRM ratio when receiving you...

BUT

...only if they are beamed to you!

If you are, say, 10 dB down from an angle with where they are beaming,
they may have 10 dB *lower* S/N ratio than you have.  Because their
main lobe has 10 dB more gain, pointed right at sky noise.

This could happen too if their elevation pattern [wave angle, take-off
angle, whatever you want to call "that"]  peak is not optimal in your 
direction.
Now, in that case it is especially true if their antenna is too high and
peak wave angle is really at 18 degrees.  (Wait, Goetz, it is you
who said bigger and higher antennas are better? Nicht wahr? HI HI)

This is even true when they have comparable antennas to yours.
It is quite easy to be 6 to 10 dB down just 30 or 40 degrees to the
side of where you are pointing.  The signal strength is only down that
much, but the sky noise is more or less constant as you swing the
beam a little (at least my guess is sky noise is omni-direction to
the first order :-).

There are two things which govern if you can hear someone.  The first
is if they are above your local system noise, and the other is if they 
are
over the sky noise (mostly the case on HF, even during "quiet" periods).

Take the case that I mentioned above.  If they are just above sky noise 
for
you, you may be 10 dB deep inside the noise for them.  They won't even
know you are there on the headphones (which some RTTY'ers use.
I can't stand to use headphones myself, but Trey told me that even he
used headphones for RTTY at VP8THU).

The "one directional" propagation happens to me quite often.  I would 
call
someone that I can print over and over and get no response.  Even
happened with AA5AU during NAQP this time.  And very often I would
receive comments like "sri, you were at the back of my beam."  Since
I could print them very loudly from the back of their beam, I suspect
a contribution to why they can't tell I was there is the SNR phenomenon.

I have a suspicion, too, that during these high noise periods, that it
is more critical to use a filter matched to the passband of the RTTY
signal.

73
Chen, W7AY