[Top] [All Lists]

Re: [RTTY] Yaesu RTTY power

To: RTTY Reflector <rtty@contesting.com>
Subject: Re: [RTTY] Yaesu RTTY power
From: Kok Chen <chen@mac.com>
Date: Sun, 16 Jan 2011 10:39:24 -0800
List-post: <rtty@contesting.com">mailto:rtty@contesting.com>
On Jan 16, 2011, at 10:21 AM, Ktfrog007@aol.com wrote:

> For rag chewing, which is mostly  on PSK, I run 30-40W.  

Remember that PSK31 works under a different "rule."

PSK31 is, through the genius of Peter G3PLX, not simply PSK modulation but also 
is amplitude waveshaped.  If not for the amplitude waveshaping, PSK will have 
the same wide keying sidebands that you see on FSK signals.  

Instead, when you look at an idle PSK signal, all you see are just two 
carriers, 31.25 Hz from one another (unless the transmitter has poor IMD, when 
you will see more keying components).

However, this waveshaping also creates a crest factor of 3 dB.  If your 
transmitter clips at 100 watts, you should not set the average RF power, under 
the idle PSK31 modulation, to any greater than 50 watts.

This peak power to average power ratio is not such a big deal to hams.  But to 
professionals, crest factor matter since peak transmit power is sometimes a 
constraint in the design.  Because of that, PSK31 is probably not as useful to 
them, but the waveshaping of PSK31 a going to be a godsend when the sunspots 
come back again to face many more digital mode stations.

Chen, W7AY

RTTY mailing list

<Prev in Thread] Current Thread [Next in Thread>