[Elecraft] question for psk users

[Ian White GM3SEK]

Jim Brown wrote:
>> Because with the close spacing of signals in the various PSK  sub-bands, a
>> signal of more than about 50watts will completely annihilate all the other
>> PSK signals and make that sub-band unusable for everyone else.
>
>This is urban myth that keeps getting propagated and eventually 
>everyone believes it as gospel.
[...]

The reason why a strong signal will "annihilate all the other PSK 
signals" is that most users are trying to receive an entire 2.5kHz 
bandwidth in one gulp. This means that even one strong signal within 
that bandwidth will activate the AGC and drive all the other signals 
down.

Regrettably most PSK users don't understand what is happening, so they 
have to rationalize it into simpler terms like "It's a crime to be 
loud."

>There are MANY factors that contribute to signal strength, including 
>antenna efficiency and gain, antenna pattern, propagation, and yes, 
>transmit power.  Of those factors, transmit power is the SMALLEST.

And propagation is by far the BIGGEST factor in making someone's signal 
loud, for the most innocent of reasons.

>What is FAR, FAR more important to prevent interference is making sure 
>that your signal is CLEAN -- no sidebands produced by audio distortion, 
>or by distortion in a poorly adjusted rig or power amp.

IMD is certainly another important factor. Naturally, IMD will show far 
more clearly on a strong signal than a weak one so once again this gets 
rationalized into "strong = IMD".

But PSK's big, unacknowledged 'elephant in the room' will always be the 
habit of receiving in a 2.5kHz bandwidth. Unfortunately this is deeply 
engrained in the PSK culture.



-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek