On Jun 14, 2010, at 6/14 4:39 AM, Stephen/Marilyn Haines wrote:
> The difference between 45 and 75
> baud pushes me from "yes it's hard but I enjoy it" to "It's impossible
> -- why bother." Is there anyone else on the list with a truly weak
> signal that had the same reaction?
Steve,
Since you mentioned the power that you are using, I assume the
diffculty is because you are not heard by others, and not because you
can't copy the others, correct? Do you get a lot of AGN, AGN when you
call them?
One does lose a couple of dB in SNR when demodulating 75 baud versus
45.45 baud. Most big guns that are heard in a contest are way, way
over the threshold of decodability however (perhaps not from ZP,
though), so losing a couple of dB usually means that a previously
decodable big gun signal is still perfectly decodable at 75 baud.
Copy should only become difficult for the marginal signals -- ones
that are just barely over the noise floor of the receiving system
before. I.e., people who used to throw an error or two at 45.45 baud
would now, at 75 baud be fully garbled.
If others can no longer copy you at 75 baud, your signal might be
right at the edge of copy for most people even when you were using
45.45 baud.
One experiment you can perform is by lowering your RF power from 40
watts to between 24 and 25 watts during the next contest and then try
to work people at 45.45 baud. Do you have the same difficulty as
using 40 watts at 75 baud? If you do have the same problem being
heard, then yes, short of raising your RF output or adding some gain
to your antenna system, it is a problem that is going to be hard to
fix (other people would need better modems or their antennas need to
point your way, etc).
Now, on the other hand, if the problem is due to your not being able
to copy the other folks cleanly, it is probably some setup thing (for
example, using I.F. filters that are too narrow for 75 baud) that can
be fixed.
73
Chen, W7AY
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